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Recent observations of long-range multi-particle azimuthal correlations in p-Pb and high multiplicity pp collisions provided new insights into collision dynamics and opened a possibility to study collective effects in these small systems.
In this talk, we present new measurements of $p_{\text{T}}$-differential elliptic flow coefficient $v_2$ for a variety of identified charged hadrons from pp...
We study the critical properties of net-baryon-number fluctuations at the chiral restoration transition in a medium at finite temperature and net baryon density. The chiral dynamics of QCD is modeled by the Polykov-loop-extended Quark-Meson Lagrangian with the coupling of quarks to vector mesons. The Functional Renormalization Group is employed to properly account for the scaling properties...
Exclusive photoproduction of Upsilon(nS) meson states off protons is measured in ultraperipheral pPb collisions at a center-of-mass energy per nucleon pair of 5.02 TeV. The measurement is carried out in the $\Upsilon (nS)\to\mu^+\mu^-$ decay modes, with data collected by the CMS experiment corresponding to an integrated luminosity of $32.6$~nb$^{-1}$. Differential cross sections, as a function...
Quarkonia, i.e. bound states of $b\bar{b}$ and $c\bar{c}$ quarks, are powerful observables to study the properties of nuclear matter under extreme conditions. The formation of a Quark-Gluon Plasma (QGP), which is predicted by lattice calculations at high temperatures as reached at LHC energies, has a strong influence on the production and behavior of quarkonia. A suppression, due to the color...
Experimental evidence suggests that collectivity in asymmetric small systems ($p$, $d$, $^{3}$He+A) is directly related to the initial collision geometry. Therefore, a compelling question is whether the same argument can be extended to p+p, and even $e^+e^-$ collisions. We have modified A-Multiphase-Transport-Model (AMPT) to include the constituent quark structure of the proton. We find with...
We present a novel formulation of the IP-Glasma initial state model in 3+1D, where the 2D boost invariant IP-Glasma is generalized to 3D through JIMWLK rapidity evolution of the pre-collision Wilson lines [1]. By breaking boost invariance, the 3D model no longer trivially satisfies Gauss' law at the initial time, and we now enforce it locally. We compare the time evolution of the...
The fluctuations of conserved charges - such as electric charge, strangeness, or baryon number - in ultrarelativistic heavy-ion collisions provide insights into the properties of the hot and dense matter produced as well as the QCD phase diagram. They can be related to the moments of the multiplicity distributions of identified particles. We extend the previous and ongoing measurements of the...
In recent years data from small collision systems at LHC and RHIC have revealed
evidence for collective behavior of the produced hadrons. Collective behavior in
small systems clearly points towards a strongly coupled system being formed in
these collisions. If so, the matter formed must also radiate thermal or low
momentum direct photons. PHENIX is ideally positioned to search for any...
The experimentally observed dissociation and regeneration of bound quarkonium states in heavy-ion collisions provide a powerful tool to probe the dynamics of the hot, dense plasma. These measurements are sensitive to the effects of color screening, color recombination, or other, new suppression mechanisms. In the large-statistics Run 2 lead-lead and proton-lead collision data, these phenomena...
We present a lattice calculation on the cross-correlations of conserved charges
(baryon number, electric charge and strangeness) near the transition
temperature. We extrapolate to small baryo-chemical potentials, and thus we
cover typical STAR energies. We confront our finding to the latest STAR date
set on cross-correlations. In this work we use continuum lattice results with
resolution up to Nt=16.
In this talk, we present a systematic study of direct soft photon observables from the RHIC Beam Energy Scan (BES) to the LHC energies. We utilize the power of photons as clean and penetrating probes of the strongly-coupled nuclear matter created in relativistic heavy-ion collisions, together with the fact that the rapidly expanding Quark-Gluon Plasma (QGP) imprints its evolution on the photon...
Proton-nucleus collisions play an important role as a control system for
interpreting hot nuclear matter effects in $A+A$ collisions. Yet, there is a large amount of data from both RHIC and the LHC that indicate that collective effects are also present in such small systems. Understanding the origin of these effects is still incomplete, since a variety of models with very different underlying...
In the high-energy limit of heavy-ion collisions, the system right after a collision is described as an over-occupied gluon plasma expanding in the beam direction. Its space-time evolution can be studied by means of real-time lattice gauge theory simulation techniques with dynamical quarks. To find observable consequences of such nonequilibrium evolution, the understanding of quark dynamics is...
Heavy quarkonium related observables are very useful to obtain information about the medium created in relativistic heavy ion collisions. In recent years the theoretical description of quarkonium in a medium has moved towards a more dynamical picture in which decay and recombination processes are very important. In this talk we will discuss the equations that describe the evolution of the...
At the LHC, in ultra-peripheral heavy-ion collisions the highly boosted electromagnetic field of the Pb ions represents a source of quasi-real photon. Vector meson photo-production measurements in p-Pb (Pb-Pb) collisions are sensitive to the gluon parton distribution functions in the proton
(nucleus). LHCb results on charmonium production in ultra-peripheral p-Pb and Pb-Pb collisions will be...
We develop, within a canonical formulation of statistical mechanics, a systematic procedure to evaluate fluctuations of conserved quantities, such as baryon number, measured within an experimental acceptance. In nearly all experiments the baryon number fluctuations are approximated by the corresponding signals for net-proton measurements. We will discuss the validity and, in particular, the...
Measurements of long-range azimuthal correlations involving heavy-flavor quarks provide a powerful tool in unraveling the origin of collectivity observed in small collision systems. With data collected by the CMS experiment at the LHC in 2016, elliptic azimuthal anisotropy ($v_2$) of prompt $D^{0}$ meson at mid-rapidity in 8.16 TeV pPb collisions is presented from long-range two-particle...
In this study, we investigate the real-time evolution of quarkonium bound states
in a quark-gluon plasma in an improved QCD based stochastic potential model. This
model describes the quarkonium dynamics in terms of a Schrödinger equation with
an in-medium potential and two noise terms encoding the residual interaction
between the heavy quarks and the medium. The time evolution described by...
Understanding experimental results on nuclear modification factors of heavy quarkonia as well as open heavy mesons is complicated due to the interplay between the cold and hot medium effects. In order to disentangle these two effects it is crucial to have a good understanding of thermal behavior of quarkonia and heavy quarks in the hot medium. The quarkonium spectral function is of the most...
The relevance of subnucleonic degrees of freedom and their fluctuations in the description of multiple experimental observations in small collision systems (flow harmonics, diffractive phenomena, hollowness effect...) has been recently established.
A representative example is the first measurement of symmetric cumulants, SC(n,m), performed by the CMS Collaboration in the three collision...
We present an overview of recent results on in-medium spectral functions and transport coefficients of hadrons using the Functional Renormalization Group approach. Our method is based on a recently developed analytic continuation procedure that allows to calculate real-time quantities like spectral functions at finite temperature and chemical potential. Results for the quark, the sigma and the...
Measurements of dijet production and photo-nuclear interactions in heavy-ion collisions probe several nuclear mechanisms. In particular, dijet measurements in pPb collisions have been shown to be one of the most important tools for constraining the gluon nuclear parton distribution functions (PDFs) at large Bjorken-x. Dijet production in pp and pPb collisions at a nucleon-nucleon centre-of-...
We propose that rapidity dependent momentum correlations can be used to extract the shear relaxation time $\tau_\pi$ of the medium formed in high energy nuclear collisions. The stress-energy tensor in an equilibrium quark-gluon plasma is isotropic, but in nuclear collisions it is likely very far from this state. The relaxation time $\tau_\pi$ characterizes the rate of isotropization and is a...
In ultrarelativistic heavy-ion collisions, correlations of particles with opposite quantum numbers provide insight into charge creation mechanisms, the time scales of quark production, collective motion of the QGP, and re-scattering in the hadronic phase. The longitudinal and azimuthal widths of general charge balance functions for pions, kaons, and protons are used to examine the two-wave...
The electromagnetic field of relativistic heavy ions can be described by a flux of virtual photons. In ultraperipheral collisions (UPC), where the impact parameter is larger than the sum of nuclei radii, the interaction of these photons with the nucleus can provide insight into its structure and allow us to probe nuclear shadowing via photoproduction of charmonia.
Extensive efforts on this...
The production of low-mass dielectrons is one of the most promising tools for the understanding of the chiral symmetry restoration and of the thermodynamical properties of the Quark-Gluon plasma (QGP) created in heavy-ion collisions. At low invariant mass, the dielectron production is sensitive to the properties of vector mesons in the medium and modifications related to the chiral symmetry...
One of the key results of the LHC Run 1 was the observation of an enhanced production of strange particles in high multiplicity pp and p-Pb collisions at 7 and 5.02 TeV, respectively. A smooth increase of strange particles relative to the non-strange ones with event multiplicity has been observed in such systems. Results from Run 2 at the top LHC energy are extended exploiting a dedicated high...
Quarkonia breaking in nucleus-nucleus collisions is a powerful tool to probe
density and temperature of the medium created in heavy ion collisions. Forward rapidity measurements in $p(d)$+Au collisions are essential to understand how quarkonia states are affected by initial state effects, formation time, and local particle multiplicity. Earlier measurements in Au+Au collisions showed a...
We report recent ALICE results on primary charged particle and neutral meson production in pp (2.76, 5.02, 7 and 8 TeV), p-Pb (5.02 TeV), Pb-Pb (2.76 and 5.02 TeV) and Xe-Xe (5.44 TeV) collisions. The transverse momentum ($p_{\rm T}$) spectra of charged hadrons used in the analysis were measured in the kinematic range of $0.15 < p_{\rm T} < 50$ GeV/$c$ and $ |\eta|< 0.8$. The charged hadron...
Since its startup in 2009, the Large Hadron Collider at CERN has spent about 3 months of its operating time providing nucleus-nucleus (Pb-Pb) collisions. Peak Pb-Pb luminosity is now over 3 times design and integrated luminosity is expected to attain the initial design goal of 1 nb-1 in the 4th Pb-Pb run in late 2018. Following the demonstration of their feasibility in 2012, two...
The matter created in non-central heavy-ion collisions is expected to possess a significant fraction of the initial angular momentum carried by the two colliding nuclei. This angular momentum can lead to vorticity of the system and be partially transferred to the spin of produced particles due to the spin-orbit coupling, leading to the phenomenon of global polarization. The STAR Collaboration...
Anisotropic flow is a key observable to characterize the system created in heavy-ion collisions, as it is sensitive to its initial state, transport properties, the equation of state and freeze-out conditions. In this presentation, we present the anisotropic flow coefficients of inclusive charged particles in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 and 5.02 TeV, and Xe-Xe collisions at...
The equation of state (EoS) in $2+1$ flavor QCD has recently been established in the continuum limit at the physical quark masses in ab initio lattice QCD calculations. The HotQCD collaboration result provides the EoS in the temperature range from $130$ to $400$ MeV. We extend the HotQCD equation of state to higher temperatures. We utilize the Highly Improved Staggered Quarks (HISQ) action. We...
The spectra of charged particles in XeXe and PbPb collisions at $\sqrt{s_{NN}} = 5.44$ TeV and $\sqrt{s_{NN}} = 5.02$ TeV, respectively, are presented in six ranges of collision centrality. The PbPb nuclear modification factor is constructed with a measured pp reference, and the XeXe nuclear modification factor is formed with an extrapolated pp reference. Both are found to be heavily...
We study spatial isovector meson correlators in $n_f=2$ QCD with dynamical domain-wall fermions on $32^3\times 8$ lattices at temperatures $T=220-380$ MeV. We measure the correlators of all spin-one ($J=1$) isovector operators. We observe an approximate degeneracy of all considered correlators with increasing temperature. This approximate degeneracy suggests emergent $SU(2)_{CS}$ and...
Large magnetic field and large angular momentum are expected to be present in the initial stages of high-energy heavy-ion collisions. One of the physics interests of the heavy-ion program using the ALICE detector at the LHC is to look for signatures of these effects. This can be achieved by studying the angular distributions of the decay daughters of hyperons and vector mesons.
We present new...
The ALICE Collaboration will undertake a major upgrade of the detector apparatus during the second LHC long shutdown (LS2, 2019-20) in view of the Runs 3 and 4 (2021 to 2029). The objective of the upgrade is two-fold: i) an improvement of the tracking precision and efficiency, in particular in the low-momentum range; ii) an improvement of the readout capabilities of the experiment, in order to...
The measurement of charge particle production in heavy ion collisions, when compared with $pp$ data, provides insight into the properties of the hot and dense quark-gluon plasma. The ATLAS detector at the LHC recorded 0.49 nb$^{-1}$ of Pb+Pb collisions, 25 nb$^{-1}$ of $p$+Pb collisions and 4.2 pb$^{-1}$ of $pp$ collisions, all at the center-of-mass energy $\sqrt{s_{NN}}=\sqrt{s}=5.02$ TeV....
Understanding the properties of strong interaction matter with its physical
spectrum of light and strange quarks near the pseudo-critical temperature
of (2+1)-flavor QCD is one of the central goals of high energy nuclear
physics. It generally is expected that the analytic crossover transition in
QCD is sensitive to properties of the true chiral PHASE transition at
vanishing quark masses [1,2]....
The elliptic and higher-order azimuthal anisotropy Fourier harmonics ($v_n$) are obtained for pPb collisions at $\sqrt{s_{NN}} = 8.16$ TeV over a wide range of event multiplicities based on multiparticle correlations. The data were collected by the CMS experiment during the 2016 LHC run. A sample of peripheral PbPb collisions at $\sqrt{s_{NN}} = 5.02$ TeV covering a similar range of event...
In hydrodynamic picture of heavy ion collisions, local thermal vorticity of the QGP fluid leads to polarization of nonzero spin hadrons produced out of it [1]. The nonzero polarization of $\Lambda$ hyperons has been recently discovered by STAR in non-central Au-Au collisions in RHIC Beam Energy Scan program [2].
We further study the predictions of the hydrodynamic model for different...
ALICE is the experiment specifically designed for the study of the
Quark-Gluon Plasma in heavy-ion collisions at the CERN LHC. The ALICE detector
will be upgraded during the LHC Long Shutdown 2, planned for 2019-2020,
in order to cope with the maximum interaction rate of 50 kHz of Pb-Pb foreseen
for Runs 3 and 4.
The ambitious programme of high-precision measurements, expected for the
muon...
Relativistic thermodynamics with spin provided the polarization 4-vector to characterize the spin alignment in rotating systems. Based on a Yang-Mills flux-tube initial state and a high-resolution, (3+1)D particle-in-cell relativistic (PICR) hydrodynamics simulation, we numerically obtain the polarization vector for $\Lambda$ hyperons at NICA and FAIR energies, and find that the $y$ component...
Precise measurements of higher-order coefficients of anisotropic flow ($v_n$, $n>3$) are now available in Pb+Pb data collected at the Large Hadron Collider. Higher-order coefficients are interesting because they do not simply originate as a response of the medium to its initial geometry, but rather from an intricate nonlinear coupling of harmonics of lower order. Hence, they serve as a...
The second phase of the Beam Energy Scan at RHIC, BES-II, is scheduled for 2019-2020 and will explore with precision measurements the high baryon density region of the QCD phase diagram. Some of the key measurements at center-of-mass energies at 19.6 GeV to 7.7 GeV in collider mode and 7.7 GeV to 3.0 GeV are: the kurtosis of net-protons that could pinpoint the position of a critical point, the...
We present charged particle spectra at midrapidity measured in lead-lead collisions at a center-of-mass energy per nucleon pair of 5.02 TeV with ALICE, in twenty centrality classes ranging from most central (0-5%) to very peripheral (95-100%) collisions. At high transverse momentum ($8 < p_{\rm T} <30$ GeV/$c$), the average nuclear modification factor ($R_{\rm AA}$) is found to increase from...
The sPHENIX experiment at RHIC will collect high statistics proton-proton, proton-nucleus and nucleus-nucleus data, starting in the early 2020's. The sPHENIX capabilities enable state-of-the-art studies of jet modification, upsilon suppression and open heavy flavor production to probe the microscopic nature of the strongly-coupled Quark Gluon Plasma, and will allow a broad range of cold QCD...
A new framework for relativistic hydrodynamics with spin is proposed. It is based on the conservation laws for charge, energy, momentum, and angular momentum. The conservation laws lead to hydrodynamic equations for the charge density, local temperature, and fluid velocity, as well as for the spin polarization tensor. The resulting set of differential equations extends the standard picture of...
Understanding the microscopic properties of the hot and dense QCD matter produced at RHIC and the LHC is a critical task for heavy-ion physics. Toward this end, we have developed a non-perturbative microscopic approach to study the bulk, transport and spectral properties of the quark-gluon plasma (QGP) [1-2], treating light, heavy and static partons in a unified framework. Starting from a...
The measurement of D-meson production in jets can provide important insights into the interactions of heavy-flavour quarks with the quark-gluon plasma created in heavy ion collisions. In particular, the role of gluon splitting processes in the production of heavy flavour, which is fundamental for a complete understanding of the quenching mechanisms for both light and heavy quarks, can be...
We establish a set of equations for moments of the distribution function. On the one hand, these equations generalize the fluid dynamics to the out-of-equilibrium evolution of boost invariant plasmas. On the other hand, they systematically generalize the theoretical framework of viscous hydrodynamics to arbitrary orders. These moments quantify details of the momentum anisotropies of...
Using the extraordinary versatility of RHIC in selecting different colliding
species, the PHENIX experiment has collected data in p+Al, p+Au, d+Au, and $^{3}$He$+$Au at 200 GeV center-of-mass energy and conducted a comprehensive set of anisotropic flow measurements. These geometry-controlled experiments provide a unique testing ground for theoretical models that produce azimuthal particle...
At very small fractional momentum of the nucleon, the increase of the gluon density is expected to saturate, but no experimental measurements have yet shown this saturation effect without ambiguity. Measurements of prompt photon production at forward rapidity in p-Pb collisions represent suitable tests for the onset of the gluon saturation.
The LHCb experiment is well suited for prompt photon...
Measurements of quarkonium production play an important role in understanding the properties of the Quark-Gluon Plasma (QGP) created in relativistic heavy-ion collisions. Quarkonium suppression in the medium due to the color screening effect has been proposed as a direct signature of the QGP formation. However, other effects, such as cold nuclear matter (CNM) effects and regeneration, add...
We present new symmetric cumulant measurements, as well as two-, four- and six-particle $v_n$ measurements (and their ratios) for charged and particle identified hadrons. These measurements will be presented for a broad range of transverse momenta and centrality intervals in U+U collisions at $\sqrt{s_{NN}}$= 193 GeV and Au+Au, Cu+Au, Cu+Cu, d+Au and p+Au collisions at $\sqrt{s_{NN}}$=200 GeV....
Recently, near-side azimuthal angular correlations across a large pesudorapidity gap, commonly called as long-range ridge-like correlations, have been observed in small collision systems. It opens up opportunities to explore the multiparton dynamics of QCD and the limitation of fluid dynamics description of the matter created in these collisions. We report the STAR measurement of azimuthal...
The experimental data collected by the ATLAS experiment during the 2015 Pb+Pb and 2017 Xe+Xe LHC runs offer new opportunities to study charged particle azimuthal anisotropy. The high-statistics Pb+Pb sample allows for a detailed study of the azimuthal anisotropy of produced particles. This should improve the understanding of initial conditions of nuclear collisions, hydrodynamical behavior of...
Heavy quarks (charm and beauty) are produced in hard parton scatterings in the early stages of hadronic collisions. Therefore, they are ideal probes to investigate the properties of the Quark-Gluon Plasma (QGP) produced in ultra-relativistic heavy-ion collisions. The study of angular correlations between heavy-flavour particles and charged particles allows us to characterize the heavy-quark...
The production cross sections of the $\Upsilon(1S)$, $\Upsilon(2S)$, and $\Upsilon(3S)$ states were measured separately using the CMS experimental apparatus, in pp, pPb, and PbPb collisions at 5.02 TeV. New results on the production of the three upsilon states in pPb are reported, including cross sections as a function of transverse momentum (p$_T$) and rapidity ($y$). The data show a stronger...
Bottomonium suppression has long been discussed as a probe for the quark-gluon plasma generated in ultra-relativistic heavy ion collisions. The use of a realistic hydrodynamic background which is anisotropic in momentum space has shown to reproduce experimental data for various windows across each experiment. We have recently expanded our model to incorporate a realistic lattice-vetted...
The azimuthal anisotropies of particle spectra measured in proton-nucleus (pA) and nucleus-nucleus (AA) collisions play a key role in constraining QCD matter properties like the shear viscosity over entropy density ratio eta/s. We compare calculations of v_n’s from viscous fluid dynamics and from kinetic transport which start both from the same initial conditions and which implement the same...
Measurements of four-particle flow cumulants $c_{n}\{4\}=\langle v_n^4\rangle -2\langle v_n^2\rangle^2$ for $n=2$ and 3, and symmetric cumulants $SC(n,m)=\langle v_n^2 v_m^2\rangle-\langle v_n^2\rangle\langle v_m^2\rangle$ for $(n,m)=(2,3)$ and $(2,4)$ are presented in $pp$, $p$+Pb and peripheral Pb+Pb collisions at various collision energies, aiming to probe the long-range collective nature...
Ultra-peripheral heavy ion collisions occur when the nuclei have large impact parameter and interact through photon-induced reactions. These include processes in which an energetic photon emitted by one nucleus resolves the partonic structure of the other and stimulates jet production. Much like deep inelastic scattering, such processes provide a clean probe of the nuclear parton...
The nuclear modification of groomed jet splitting in relativistic heavy-ion collisions at RHIC and the LHC energies is studied [1] based on the higher twist formalism. Assuming coherent energy loss for the two splitted subjets, a non-monotonic jet energy dependence is found for the nuclear modification of jet splitting function: strongest modification at intermediate jet energies whereas...
We present calculations of hadron production from gluon dominated non-equilibrium matter in various small collision systems using the IP-Glasma model combined with a state-of-the-art fragmentation prescription based on the Lund model. We study bulk observables such as particle spectra, nuclear modification factors (R_{pA}), proton-to-pion ratios and multi-particle azimuthal angular...
First results on two-particle angular correlations for charged particles emitted in $e^+e^-$ collisions using 730 $pb^{-1}$ of data collected between 91 and 209 GeV with the ALEPH detector at LEP are presented. With the archived data, the correlation functions are studied over a broad range of pseudorapidity $\eta$ (rapidity $y$) and azimuthal angle $\phi$ with respect to the electron-positron...
New measurements of collective flow in XeXe collisions at a center-of-mass energy of 5.44 TeV per nucleon pair, collected by the CMS experiment at the LHC, are presented. The $v_{2}$, $v_{3}$ and $v_{4}$ Fourier coefficients of the anisotropic azimuthal distribution are obtained employing three different analysis techniques: two-particle correlations, scalar product method and multiparticle...
Quarkonium production in high-energy hadronic collisions provides a fundamental test of QCD. Its modification in a nuclear medium is a sensitive probe of the space-time temperature profile and transport properties of the QGP, yielding constraints complementary to the ones obtained form the quenching of light and heavy flavor. We will present new results for the suppression of high transverse...
Hard splittings in the evolution of a jet may be modified by the presence of a dense strongly interacting medium. Grooming procedures can be used to isolate such hard components of a jet and allows one to focus on the two subjets resulting from a sufficiently hard partonic splitting. The modification of these splittings in medium could highlight the role of jet induced medium response as well...
Nearly collinear pairs of partons are sensitive to potential novel coherence effects in the parton energy loss process, which can be observed through measurements of jet substructure. This analysis presents a new measurement of jets containing a gluon that splits into a heavy quark pair, i.e., a heavy-quark antenna. Such jets are identified by analyzing the groomed substructure of double...
We calculate isolated photon production at forward rapidities in proton-nucleus collisions in the Color Glass Condensate framework [1]. Our calculation uses dipole cross sections solved from the running coupling Balitsky-Kovchegov equation with an initial condition fit to deep inelastic scattering data and extended to nuclei with an optical Glauber procedure that introduces no additional...
The heavy-quark potential is a highly versatile theoretical tool. It allows one to summarize many aspects of the intricate interactions between a QQbar bound state and its surrounding medium in a single complex valued quantity. It is systematically defined from QCD [1,2] and at the same time provides an intuitive understanding of the physics of in-medium quarkonium modification. I.e. it offers...
Many observables which are used as a signature of collective effects in heavy-ion collisions when measured in high multiplicity pp and pA interactions reveal a very similar behaviour. We present first measurements of different order flow coefficients and their magnitude correlations using the Symmetric Cumulants for data collected by ALICE during the LHC Run 2 operation. The data sample...
Reaching next-to-leading order (NLO) accuracy in perturbative calculations of particle production in QCD at high energy is essential for reliable phenomenological applications. In recent years, the Color Glass Condensate effective theory (the natural framework for such calculations) has indeed been promoted to NLO accuracy. However, the first NLO calculations met with unexpected difficulties,...
New results on quarkonia production in proton-lead collisions at LHCb at 8.16 TeV nucleon-nucleon center-of-mass energy will be presented. Measurements include J/psi and psi', where the prompt and from-b-decay components can be disentangled, and the 1-- bottomonia states. The large data sample allows the determination of nuclear modification factors with high accuracy.
LHCb has the unique...
Correlations of electroweak probes, jets, and charged particles are a powerful tool to study medium modifications of the parton shower. One can impose constraints on jet quenching mechanisms in heavy ion collisions by measuring jet substructure observables, such as fragmentation functions or jet momentum density profiles. Tagging jets with an associated photon helps to constrain the associated...
The measurement of the decorrelation of flow harmonics, $v_n$, and event plane angles, $\Psi_n$, (or flow vector, $V_n\equiv v_ne^{in\Psi_n}$) in the longitudinal direction explores the non-boost-invariant nature of the initial collision geometry and final state collective dynamics. The decorrelations were first observed at the LHC, but are predicted by several (3+1)D hydrodynamic models to be...
We analyze the recent STAR collaboration results on net-kaon fluctuations in the framework of the Hadron Resonance Gas (HRG) model and lattice QCD. In the latter, the kaon contribution is isolated using the Boltzmann approximation [1]. Our purpose is to extract the freeze-out temperature and chemical potential as functions of the collision energy. In our HRG model, we use the complete hadron...
We present a novel approach to the treatment of thermal fluctuations in the (3+1)-D viscous hydrodynamic simulation MUSIC. We investigate the phenomenological impact of thermal fluctuations on hadronic and electromagnetic observables using the state-of-the-art IP-Glasma + hydrodynamics + hadronic cascade hybrid approach [1]. In particular, we show that these thermal fluctuations influence the...
the study of charm production in heavy-ion collisions is considered an excellent probe to study the properties of the hot and dense medium created in heavy-ion collisions. Measurements of D- meson nuclear modification, elliptic and triangular flow in PbPb collisions can provide strong constraints into the mechanisms of in-medium energy loss and charm flow in the medium. The measurement of...
Recent observations at RHIC and the LHC of two- and multi-particle correlations
in high multiplicity relativistic proton-proton and proton-ion collisions and similarity of the results to those observed in central heavy-ion collisions are often interpreted as an evidence for collective particle production in small collision systems. These results motivate a study in even smaller systems, such...
A novel equation of state with the surface tension induced by particles’ interactions was generalized to describe the properties of the neutron stars. In this equation the interaction between particles occurs via the hard core repulsion by taking into account the proper volumes of particles. Recently, this model was successfully applied to the description of the properties of nuclear and...
We investigate the relative importance of initial and final state effects on azimuthal correlations in low and high multiplicity p+Pb collisions at LHC energies. By matching the classical Yang-Mills dynamics of pre-equilibrium gluon fields (IP-GLASMA) to a perturbative QCD based parton cascade for the final state evolution (BAMPS) on an event-by-event basis, we find that signatures of both the...
At energies below $\sqrt{s_{NN}}\approx2.55$ GeV, strange quarks can not be produced in binary nucleon-nucleon collisions because of the higher production threshold of the lightest hadrons carrying strangeness. Hence, the investigation of sub-threshold strangeness production in heavy-ion collision is one of the most promising probes, to access the properties of the created system, as the...
Multi-particle flow correlations in Pb+Pb collisions provide unique insight into the nature of event-by-event fluctuations of the initial eccentricity as well as final state dynamics in the transverse and longitudinal directions. This talk presents a detailed study of transverse flow fluctuations using 4 and 6-particle cumulants $v_n\{4\}$ and $v_n\{6\}$ for $n=1, 2, 3$, and 4. This includes...
In relativistic heavy-ion collisions, event-by-event fluctuations in the transverse plane in the initial states of quark-gluon plasma (QGP) could lead to anisotropic flows of the final hardons, which has been successfully described by relativistic hydrodynamics simulation. On the other hand, the initial states fluctuations in the longitudinal direction could lead to the fluctuations and...
We report on recent progress in understanding multi-particle correlations in $pA$ collisions from the initial state. We consider a proof of principle model of eikonal quarks from the projectile proton multiple-scattering off of a dense nuclear target. With this model, we find that many of the features observed in light-heavy ion collisions at RHIC and the LHC which are often ascribed to...
Previous calculations of the shear viscosity to entropy density ratio in the hadron gas have failed to reach a consensus, with $\eta/s$ predictions differing by almost an order of magnitude. This work addresses and solves this discrepancy by providing an independent extraction of this coefficient using the newly-developed SMASH (Simulating Many Accelerated Strongly interacting Hadrons)...
We study the propagation of charm and bottom quarks in the quark-gluon plasma (QGP) by means of a relativistic Boltzmann transport approach that in the large M/T limit recovers the standard Langevin dynamics. The non-perturbative interaction between heavy quarks and light quarks is described by means of a quasi-particle approach in which light partons are dressed with thermal masses. The last...
The large sample of high quality data taken in pp collisions at $\sqrt{s} = 7$ TeV and 13 TeV, together with smaller data sets at 900 GeV and 2.76 TeV, and in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV at the LHC with the ALICE detector allows for a systematic study of the light (anti-)nuclei production in these collision systems.
The excellent performance of the Inner Tracking...
Recent measurements of correlations between two particles separated in pseudorapidity and azimuthal angles have shown striking similarities between results obtained in $pp$, $p$+A and A+A collision systems. In the $pp$ collision system, unlike in $p$+A and A+A collisions, the strength of the correlations, quantified by the anisotropy parameter $v_2$, shows little dependence on the observed...
Heavy flavor quarks are unique tools for studying the properties of the Quark Gluon Plasma (QGP) produced in high-energy nuclear collisions. In this talk we will present measurements of various charm hadrons ($\Lambda^{\pm}_{c}$, $D^{\pm}_{s}$, $D^{*\pm}$, $D^{\pm}$ and $D^0$ ($\bar{D}^0$), as well as open bottom production through displaced decay daughters ($B\rightarrow J/\psi$, $D^0$, $e$),...
Detailed measurements of collectivity in Au+Au collisions at RHIC provide a key
connection between the initial geometry of the deposited energy and the
hydrodynamic evolution of the medium. Utilizing the PHENIX silicon detectors, we present new measurements of flow coefficients extending over a wide range in pseudorapidity $-3 < \eta < 3 $ and to higher $p_T$. Over a broad range in...
We present a measurement of the hyper-triton lifetime with the ALICE detector at the LHC, aiming at shedding light on the hyper-triton lifetime puzzle. During the LHC Run 2, the ALICE experiment recorded Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV that complement the Pb-Pb datasets acquired at $\sqrt{s_{\rm NN}}$ = 2.76 TeV from Run 1. These datasets allow for a systematic study of...
The observation of collective effects in small systems, such as strangeness enhancement and the appearance of a ridge, have posed a challenge to conventional models for multiparton interactions and hadronization underlying general purpose MC event generators.
In this talk I will present the microscopic model for collective effects recently implemented in the Pythia8 and DIPSY event...
Longitudinal harmonic flow decorrelation (the "torque" effect [1,2]) is a sensitive probe of the early dynamics of ultra-relativistic nuclear collisions. We propose new decorrelation measures of flow magnitude and event-plane angles and apply them to Pb+Pb collisions at the LHC, modeled via event-by-event hydrodynamic simulations. The basic purpose is to verify a generic feature, namely, that...
The data from RHIC Beam Energy Scan phase I (BES-I) have shown interesting results below $\sqrt{s_{NN}}<$ 19.6 GeV in identified hadron anisotropy ($v_1$, $v_2$, $v_3$), kaon over pion ratios, and net-proton higher moments. These interesting features continue to the lowest energy, $\sqrt{s_{NN}}$ = 7.7 GeV, and motivate the investigation to even lower energy collisions. The STAR fixed-target...
In a quantum field theory, apparent thermalization can be a consequence of entanglement as opposed to scatterings. I will discuss how this can help to explain open puzzles such as the success of thermal models in electron-positron collisions. It turns out that an expanding relativistic string described by the Schwinger model (which also underlies the Lund model) has at early times an...
Simulations of relativistic heavy-ion collisions based on viscous hydrodynamics provide an accurate description of the bulk observables measured at RHIC and LHC beam energies, including identified particle yields, mean $p_T$ and multiparticle correlations. The success of the hydrodynamic framework, however, is naturally expected to break down in the dilute limit where discrete particle degrees...
In high energy collisions nuclei are practically transparent to each other but produce very hot, nearly baryon-free, matter in the central rapidity region. Where do the baryons go? We calculate the energy loss of the nuclei using the color glass condensate model. Using a space-time picture of the collision we calculate the baryon and energy densities of the receding baryonic fireballs. For...
Beauty quark production in heavy-ion collisions is considered to be one of the key measurements to address the flavour-dependence of in-medium energy loss in heavy-ion collisions. On the other hand, the measurement of the production of strange beauty mesons can provide fundamental insights into the relevance of mechanisms of beauty recombination in the quark-gluon plasma. In this talk, we will...
In relativistic high energy collisions, hard scattered partons can fragment into two back-to-back jets. These jets can be used as hard probes to study properties of the Quark Gluon Plasma created in nucleus-nucleus collisions. Di-hadron correlations with respect to high $p_T$ trigger particles are a useful tool to study the interactions between jets and the medium in high-energy heavy-ion...
The multiplicity dependent results of identified particle production allowed the discovery of collective-like behavior in pp collisions at the LHC. Good understanding of the effects attributed to well-understood physics, like multiple hard scatterings, is required to establish the origin of the new phenomena. Experimentally, those effects can be controlled using event shapes, like transverse...
The measurement of strange and resonance particle production in relativistic heavy ions collisions is of great interest to investigate the properties of the hadronic matter under extreme conditions. The enhanced production of strange and multi-strange hadrons with respect to non-strange ones was
historically considered as one of the signatures of the formation of a partonic phase during the...
Heavy quarks serve as valuable probes of the QGP properties as well as the mass hierarchy of parton energy loss. Experimental data at the LHC indicate significant nuclear modification of heavy flavor ($D$ & $B$) meson production that is comparable to light flavor hadrons, which seem contradictory to one’s earlier expectation of $\Delta E_g > \Delta E_q > \Delta E_c > \Delta E_b$. We extended...
Recently there has been rapid progress in understanding in-medium dynamics of a quarkonium based on the framework of open quantum system [1-5]. The stochastic potential model [5] introduces thermal fluctuations on Debye screened potential and hence incorporates wave function decoherence. This model however lacks quantum dissipation, which has so far limited its application to early times and...
Heavy flavoured jets are important in many of today's studies both as tests of QCD and as probes of hot and dense medium created shortly after the hard scattering. We notice that recently $b\bar{b}$ dijet correlations in proton-proton collisions have been measured by the CMS and ATLAS collaborations at the LHC, NLO+PS p+p baseline could give a rather perfect description of the experimental...
Presented is a feasibility study of hypernuclei mesurments for the upcoming NICA/MPD Project. The DCM-LAQGSM model was used as well as the full realistic MPD reconstruction chain. Presented here are invaraint mass spectra for three decay modes. A good resolution with 3 MeV/c$^{2}$ was achieved.
The relativistic heavy ion collisions undergo extremely hot and dense phases, which are postulated to resemble parts of the cosmological early stages. This suggests that the collisions could provide a QCD laboratory, in which phenomena of strong interactions are studied. The investigations of colour interactions in the collisions are made in a Monte-Carlo computational model which implements...
A charge-sensitive in-event correlator ($R(\Delta S)$) is proposed and tested for its efficacy to detect and characterize charge separation associated with the Chiral Magnetic Effect (CME) in heavy ion collisions~[1]. For CME-driven charge separation, the correlator gives a concave response relative to the second-order event plane ($\Psi_2$), and a null response relative to the third-order...
The NA61/SHINE experiment at the CERN SPS experiment is planning to upgrade the detector and extend the heavy-ion programme after 2020 to allow precise measurements of particles with short lifetime (charmed particles in particular).
The study of heavy flavour production is a sensitive tool for new detailed investigations of the properties of hot and dense matter formed in nucleus-nucleus...
DIRC-like Time-of-Flight detector (DTOF) is an innovative TOF utilizing internally reflected Cherenkov light for high energy charged particle identification. It achieves a high level of performance at the extreme data taking conditions under high luminosity and high backgrounds. The basic structure of DTOF is composed of a Fused Silica radiator connected to fast photomultiplier (MCP-PMT or...
THERMINATOR model [1] is a Monte Carlo event generator invented to study the statistical production of particles created in relativistic heavy-ion collisions. Its current description allows one to study the highest collision energies achieved by LHC and RHIC colliders. However it is possible to adapt THERMINATOR model to the lower energy spectrum as is used in Beam Energy Scan (BES) program at...
We compute the suppression, angular, and rapidity distribution of single open heavy flavour and the momentum, angular, and rapidity correlations for pairs of open heavy flavour in pA and AA collisions at RHIC and LHC from an AdS/CFT-based energy loss model. We quantitatively compare the strongly-coupled QGP predictions for AA collisions to the weakly-coupled QGP predictions of Nahrgang et al....
The initial conditions and particle emission in proton-proton collisions is much better constrained than in heavy-ion collisions. This allows for a precise investigation of the interaction between pairs of produced baryons such as proton-$\Lambda$ and $\Lambda$-$\Lambda$ in this system.
In this analysis femtoscopic correlations of proton-proton, proton-$\Lambda$ and $\Lambda$-$\Lambda$ pairs...
Supervised learning with a deep convolutional neural network (CNN) is used to identify the QCD equation of state (EoS) employed in event-by-event (2+1)-D relativistic viscous hydrodynamics coupled to a hadronic cascade ``afterburner" simulations of heavy-ion collisions from the simulated final-state pion spectra $\rho(p_T, \phi)$. High-level correlations of $\rho(p_T,\phi)$ are learned by the...
The chiral magnetic effect (CME) and the chiral magnetic wave (CMW) have been predicted to arise from the coupling of domains with quark chirality imbalances in the quark-gluon plasma (QGP) and the strong magnetic field produced by energetic spectator protons. Searches for these quark chirality effects in nucleus-nucleus collisions have been performed at RHIC and the LHC as major scientific...
More than 15 years ago a longitudinal effective string rope model was proposed [1] to construct nucleus-nucleus collision Initial State (IS) for realistic 3+1D relativistic fluid dynamical models. This model reflected correctly not only the energy-momentum, but also angular momentum conservation, initial shear flow, and local vorticity [2]. Recent experimental and theoretical developments...
Energetic heavy quarks passing through the hot and dense medium of a quark-gluon plasma (QGP), represented by the resulting mesons, are viewed as a suitable probe for the interactions inside of the QGP, in particular the mechanisms of energy loss, as they are less likely to thermalize within the medium and are mostly created at early stages of the medium evolution.
However, models of both,...
Due to the different energy scales involved in the production of charmonium states in proton-proton collisions, they provide important testing grounds for the theory of Quantum Chromo-Dynamics (QCD). The initial charm-quark pairs are produced in large-$Q^2$ processes that allow for a perturbative treatment while the hadronization into a bound system is non-perturbative.
Different effective...
The angular correlation function (CF) refers to the correlation of particles in the relative pseudorapidity ($\Delta\eta$) and relative azimuthal angle ($\Delta\phi$). CF is influenced by various physical phenomena such as conservation laws, collective particle flow, resonance decays, final state interactions, or particle production mechanism - e.g., correlation of particles within the single...
Anisotropic flow plays a crucial role to characterize the momentum anisotropy of the final state particles. In order to probe the properties of the system created in high multiplicity pp collisions at LHC energies, we study within the percolation color sources, the effects of initial state geometry, profile distribution, size and eccentricity fluctuations in pp collisions at the LHC energies....
Anisotropic flow at SPS energies was measured by the NA49 Collaboration more than 10 years ago. Recently new data for Pb-Pb collisions were collected by the NA61/SHINE experiment during the Pb-ion beam energy scan program at the SPS. This motivated a new analysis of the available NA49 data, based on modern flow measurement techniques that will also utilize the spectator fragments for ...
Anisotropic flow plays a critical role in understanding the properties of the quark- gluon plasma. In this poster we present the elliptic and triangular flow of multi-strange particles in Pb--Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV. The measurements are presented at mid-rapidity for a wide range of particle transverse momenta. The results are compared to those for elliptic and...
J/$\psi$ mesons and other hadrons containing a charm or a beauty quark are
excellent probes to study the Quark-Gluon Plasma (QGP) produced under
extreme temperature and energy density conditions in heavy-ion collisions. Because of their large mass,
heavy quarks are produced in hard parton-scattering processes at the
beginning of the collisions and they are therefore present in the QGP
during...
Averaged jet charge characterizes the electric charge distribution inside jets, and provides a powerfull tool to distinguish quark jets from gluon jets. In this talk, we give the first prediction for the medium nodification of averaged jet charge in heavy-ion collision at the LHC energy, where the jet productions in $pp$ collisions are simulated by pythia6+FastJet, and parton energy loss...
The ALICE experiment at the Large Hadron Collider (LHC) is dedicated to study the properties of the Quark-Gluon Plasma (QGP), a de-confined state of strongly-interacting partons formed in relativistic heavy-ion collisions. Heavy quarks, produced by parton-parton hard scatterings in the early stages of such collisions, stand out as unique probe to study the QGP, as they are expected to...
In the first part of the talk we shall investigate how the averaging
over a large number of events influences the shape of the observed
correlation function. We demonstrate that a shape characterised by Levy
distribution may result from an average over Gaussian sources with
varying sizes and orientations. We then propose to sort the events
according to their similarity and investigate...
To understand the dynamics of cluster formation, starting from homogeneous distribution, we set up classical molecular dynamics simulation of the baryon motion, supplemented by a Langevin equation to model the effect of a meson heat bath. Quantum mechanical kinetic energy is included via an effective potential, tuned to reproduce known properties of nuclear matter. We then modify the...
Interaction cross-sections for baryon pairs are of fundamental interest
and they are actively investigated theoretically. They are known well for
pairs of common (anti-)baryons, however there is a lack of precise
data for heavier baryons, including the ones carrying strangeness. The
so-called kaonic atoms are also investigated theoretically and their
properties crucially depend on the...
Recent years have seen significant theoretical progress in the transport description of open heavy flavor in QCD matter -- a number of models are now able to simultaneously describe a subset of the most important heavy flavor observables -- a simultaneous description of a comprehensive set of observables at all available collision energies still poses a challenge. A global analysis...
The study of the Quark-Gluon Plasma created in ultrarelativistic heavy-ion collisions at the CERN-LHC is complemented by reference measurements in proton-lead (p--Pb) and proton-proton (pp) collisions, where the effects of multiple-parton interactions and hadronization beyond independent string fragmentation can be investigated.
In this poster, we present a Bayesian unfolding procedure
to...
We present new differential measurements of charge separation relative to the second- ($\Psi_2$), third- ($\Psi_3$) and fourth-order ($\Psi_4$) event planes for Au+Au collisions at $\sqrt{s_{NN}}$= 200, 39, 27 and 19.6~GeV, U+U at $\sqrt{s_{NN}}$= 193 GeV and Cu+Au, Cu+Cu, d+Au and p+Au at $\sqrt{s_{NN}}$=200 GeV. The measurements are performed with a charge-sensitive correlator $R(\Delta S)$...
Studies of collisions of highly accelerated ions are the key to understand the creation of quark matter. Experimental physicists put considerable effort in collecting information characterizing the various processes occurring during such collisions. In order to describe such scenarios, complex models have been constructed, one of them being the EPOS approach. It applies Parton-based...
Heavy quarks are unique probes to study the medium created in heavy-ion collisions. Detailed measurements of the production of bottom hadrons can supply information crucial to understanding the properties of the strongly interacting QCD matter and the flavor dependence of parton energy loss. In this poster, the measurement of transverse momentum spectra of $D^0$ from beauty-hadron decays in pp...
Cross sections for direct photon production in hadronic scattering processes have been calculated according to an effective chiral field theory following Turbide et al. For $\ \pi + \rho \rightarrow \pi + \gamma$ and $\ \pi + \pi \rightarrow \rho + \gamma$ processes, these cross sections have been implemented into a novel hadronic transport approach (SMASH), which is suitable for collisions at...
We present a model of the dynamical evolution of relativistic heavy ion collisions, which combines second-order viscous hydrodynamics and microscopic transport. In particular, we present a hybrid approach with MUSIC hydrodynamics, particlization with improved treatment of resonance masses based on spectral functions, and SMASH (Simulating Many Accelerated Strongly-interacting Hadrons)...
We study the interplay of the fugacity expansion for the Grand Canonical Partition Function, and the Taylor and virial expansion for the number density. We compare results from the Vladivostok group lattice QCD study [1], and from a toy model of QCD with the predictions of a Cluster Model Expansion. We outline different strategies for the search of singularities in the complex chemical...
Dissipative relativistic fluid dynamics is not always causal. We discuss the causality structure of high energy nuclear collisions. When the fluid evolution equations are hyperbolic, one can bring them to a characteristic form describing the radial expansion of the fireball. This dynamics is causal if the characteristic velocities are smaller than the speed of light such that the domain of...
Due to their large masses, heavy quarks are considered to be an excellent probe to study the properties of the quark gluon plasma through their interactions with the medium. In this presentation, we report on improved measurements, achieved by using supervised machine learning technique, of $D^0$-meson and $D^{\pm}$-meson transverse momentum ($p_{\rm T}$) spectra at mid-rapidity ($|y|<$1) in...
The goal of relativistic heavy ion collider experiments is to explore the properties of the strongly interacting matter produced with very high temperature and energy density, conditions under which the formation of a Quark-Gluon Plasma (QGP) is expected. Heavy quarks, i.e. charm and beauty are sensitive probes of the QGP as they are produced in the initial stages of the collision and witness...
The ALICE experiment at the LHC is designed to investigate the properties of the Quark-Gluon Plasma by studying high-energy pp, p-Pb, Pb-Pb and also in the recently for the first time recorded Xe-Xe collisions. Medium effects like parton energy loss can be examined by measuring the production of charged particles and their nuclear modification factor at high transverse momentum...
The Event Plane Detector (EPD) is an upgrade to the STAR experiment that will significantly improve event plane resolution and provide a measure of collision centrality at forward rapidity ($2.1<|\eta|<5.1$). The complete detector, composed of two scintillator wheels at $\pm\eta$ and 2.1$<$$|\eta|$$<$5.1, will be operational in the 2018 run, but in 2017, a quarter of one wheel was...
We present for cluster produced with the new combined PHQMD+FRIGA model for Nuclotron and NICA energies. PHQMD is a new n-body approach to simulate heavy ion collisions starting from FAIR/NICA energies. The FRIGA clusterisation algorithm, which can be applied to n-body transport approaches, is based on the simulated annealing technique to obtain the most bound configuration of fragments and...
We present the first out-off-equilibirum analysis of relativistic collision dynamics in the vicinity of a critical point. Using holography, we study the collision of ultra-relativistic lumps of energy in a strongly coupled gauge theory with a non-trivial phase diagram which includes a critical point. Choosing collision energies in the vicinity of the critical point, we explore the distribution...
In high-energy nuclear collisions, light nuclei provide a unique tool to explore the QCD phase structure. The production of light nuclei is sensitive to the temperature and phase-space density of the system at freeze-out. In addition, phase transition will lead to large baryon density fluctuations, which will be reflected in the light nuclei production. For example, the ratio of proton...
The mass dependence of anisotropic flow as a function of $p_T$ in small systems
observed at both RHIC and the LHC provided strong evidence of collective
behavior and suggests the formation of the smallest QGP droplets in these systems. If the cause of this mass dependence is indeed radial flow, this should be reflected in the spectral shapes at low $p_T$. Further, one would expect hard...
Correlated electron-positron pairs produced in heavy-ion collisions provide an excellent probe of the hot and dense strongly-interacting medium, i.e. the Quark-Gluon Plasma (QGP), created in such systems. They are produced at all stages of the collision without significant final-state interactions. Moreover, thermal radiation from the medium, both during the partonic and the hadronic phase,...
The equation of state is one of the fundamental properties of the QCD matter created in relativistic nuclear collisions. Lattice QCD simulations now provide a realistic equation of state at vanishing density, but it may differ from what we should see in the experiments because heavy-ion systems may be out of chemical equilibrium, in strong magnetic fields and affected by finite size effects....
One of the main goals of Beam Energy Scan program of Relativistic Heavy-ion collision experiment is to map the QCD phase diagram. Measurement of higher order cumulants of net-proton and net-charge distributions are regarded as one of the potential tools to locate the QCD critical point in the phase diagram. Knowing the probability distributions of net-proton are useful for quark-meson (QM)...
Construction and beam test results of the new prototype of electromagnetic calorimeter (EMCal) module for the sPHENIX detector are presented. sPHENIX will collect high statistics proton-proton, proton-nucleus and nucleus-nucleus data at the Relativistic Heavy Ion Collider (RHIC) from the early 2020's. The sPHENIX capabilities will enable investigations of jet modification, upsilon suppression...
The Event Plane Detector (EPD) is an upgrade to the STAR experiment. It is similar to the Beam Beam Counter (BBC) which has been a part of the STAR experiment since the beginning, but will provide more pseudorapidity coverage ($2.2<|\eta|<5.1$ compared to $3.3<|\eta|<5.0$) and higher granularity (744 distinct channels compared to 32), leading to an increase in first-order event plane...
Freezeout in relativistic collisions occurs as a result of competition between interaction of the fireball constituents and fireball expansion. The magnitude of interaction of the fireball constituents is expected to go down as we go from nucleus-nucleus (A-A) to proton-nucleus (p-A) to proton-proton (pp) collisions which should show up in the thermal model fits of the hadron yields. However,...
Multi-particle azimuthal correlations have recently been measured in proton/deuteron-nucleus collisions at RHIC and at the LHC, and call for theoretical explanations. In particular, whether they originate from the initial or final state interaction is a matter of intense debate. We propose a new, initial-state mechanism to generate multiple correlations like $c_2\{4 \}$ from the combined...
Following our earlier finding based on RHIC data about the dominant jet production from nucleus corona region, we reconsider this effect in nucleus-nucleus collisions at LHC energy. Our hypothesis was based on the experimental data, which raised the idea of a finite formation time for the produced medium. At RHIC energy and in low density corona region this time reaches about 2~fm/c. In the...
Coulomb effects on charged pion transverse momentum spectra produced in Au-Au collisions at RHIC-BES energies are investigated. From these spectra the negative-to-positive pion ratios as a function of transverse momentum are obtained and used to analyze the Coulomb final state interaction between the charged pions and the positive net-charge of the particle source. The „Coulomb kick” (a...
One of the goals of heavy-ion collisions is to search for the Quark-Gluon Plasma (QGP) and study its properties. Due to their large masses, heavy quarks are mainly produced in the initial hard scatterings during the early stage of heavy-ion collisions and experience the entire space-time evolution of the system. At the STAR experiment, utilizing high-precision secondary vertex reconstruction...
The ALICE experiment studies Pb-Pb collisions at the LHC in order to investigate the properties of the hot and dense QCD matter at extreme energy densities. Heavy quarks are sensitive probes to test the medium properties, since they are formed at a shorter time scale with respect to the deconfined state. In particular, the elliptic flow parameter $v_2$ of D mesons is sensitive to the degree of...
Multiplicity and event-shape variables like spherocity can be used to select events according to their topology. They provide a powerful tool to study soft-QCD processes (low Q$^{2}$), such as multiple parton interactions (MPI) and colour reconnection (CR) mechanisms which are expected to produce more isotropic events with respect to events dominated by jet production.
At the Large Hadron...
The heavy-flavour production in proton--nucleus collisions is sensitive to Cold Nuclear Matter effects (CNM), related to the presence of nuclei in the colliding system such as the modification of the parton distribution functions of nuclei (e.g. shadowing or saturation effects), and parton energy loss in cold nuclear matter. These effects can induce a modification of the heavy-flavour...
A recent result from the STAR experiment shows that in 10-40% central Au+Au collisions at the top RHIC energy the elliptic flow ($v_2$) of the $D^0$-meson follows the Number-of-Constituent-Quark scaling in the same way as it does for light flavor hadrons. This suggests that charm quarks have gained sufficiently large collectivity through their interactions with the Quark-Gluon Plasma (QGP). It...
In the early stage of relativistic heavy-ion collisions, coherent and anisotropic classical Yang-Mills field emerges.
This field, referred to as glasma, has several instabilities from the anisotropy, so small fluctuations in glasma grow exponentially.
Glasma is also known to have chaoticity, which make the field configuration complex and produces the entropy.
Instability and chaoticity of...
Electron-positron pairs are an excellent probe to investigate the properties of the Quark-Gluon Plasma (QGP) created in ultra-relativistic heavy-ion collisions. Because they are produced at all stages of the collision and do not interact strongly with the medium, their spectra reflect the entire space-time evolution of the system. At low invariant mass ($m_{\textrm{ee}} < 1.2 \textrm{...
Dileptons are a prime probe of the deconfined state of strongly-interacting matter, the Quark-Gluon Plasma (QGP), produced in high-energy heavy-ion collisions, as they are not affected by final-state interactions and produced at all stages of the collision. A measurement of the thermal radiation from the QGP in the dielectron intermediate-mass region gives information on the medium...
Low-mass dielectrons are an important probe for the hot and dense medium which is created in ultra-relativistic heavy-ion collisions. Since leptons do not interact strongly and are produced throughout the whole collision process, they carry information from all collision stages with negligible final-state interaction.
The ALICE detector is well-suited to perform this measurement due to its...
We present the first calculations of all the diffusion transport coefficients related to the baryon, electric and strangeness charge for a hot and dense hadron resonance gas and for a simplified kinetic model of the quark-gluon plasma[ [arXiv:1711.08680]][1]. We demonstrate that the diffusion currents do not only depend on gradients of their corresponding charge density. Instead, there...
Dijet, dihadron and hadron-jet angular correlations as well as dijet transverse momentum asymmetry have been reckoned as important probes of the transverse momentum broadening effects in relativistic nuclear collisions [1,2]. Dijets become de-correlated due to the vacuum soft gluon radiation associated with the Sudakov logarithms and the medium-induced transverse momentum broadening.
We...
As electromagnetic probes dileptons open a window to the in-medium properties of vector mesons. In this talk, medium effects to vector mesons are discussed for heavy ion collisions in the low kinetic energy regime of $1 - 3A$ GeV, where the dielectron emission is accessed by the HADES experiment at GSI. A new hadronic transport approach named SMASH (Simulating Many Accelerated...
Dileptons ($l^+l^-$) are produced throughout all stages of heavy-ion collisions (HIC) through various production mechanisms. Since leptons have a small interaction cross section with the strongly interacting medium, they carry information about the medium from the early stages to the final state of the system. For this reason, dileptons provide an essential tool for studying the properties of...
In Ultra-relativistic Heavy-Ion Collision (HIC) very strong initial electro-magnetic (e.m.) fields are created inducing a vorticity in the reaction plane that is odd under charge exchange, allowing to distinguish it from the large vorticity of the bulk matter due to the initial angular momentum conservation. Conjointly thanks to its mass, $M_{b,c}>>\Lambda_{QCD}$, there should be no mixing...
Measurements of low $p_{\rm T}$ direct photon production at midrapidity in pp collisions at $\sqrt{s}=2.76$ and 8 TeV, as well as in p-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV were carried out by the ALICE experiment at the LHC. Photons were detected with either of the two electromagnetic calorimeters, EMCal and PHOS, and via reconstruction of $e^+e^-$ pairs from conversions in the ALICE...
Dielectrons produced in ultra-relativistic heavy-ion collisions provide a unique probe of the system evolution as they are unperturbed by final-state interactions. Among the different physics sources of dielectrons, thermal radiation in the form of real and virtual photons is of particular interest as it carries information about the temperature of the hot and dense system created in such...
The medium modification of jets continues to be studied in greater and greater detail, ranging from their absolute yields to substructure measurements. A key problem has always been to accurately determine the jet energy calibration in order to establish the influence of the hot QCD medium on the observed jet properties. A way to circumvent this ambiguity is the measurement of direct...
Despite of a generally very successful description of the elliptic and higher harmonic flow in heavy-ion collisions by theoretical models, there is no single model that explains the dependence of the directed flow on pseudorapidity, collision energy, system size, and the particle type. This indicates that an important piece in our picture of ultrarelativistic heavy-ion collisions is still...
The equations of relativistic hydrodynamics can be obtained from
the Boltzmann equation via the Chapman-Enskog (CE) procedure and
Grad’s 14 moments approximation. These approaches give different
results for the transport coefficients, which reduce to the same
expressions in the non-relativistic limit.
In this contribution, the propagation of a harmonic longitudinal
wave is considered in...
Relativistic hydrodynamics has played a key role in our understanding of the novel properties of quark-gluon plasma. However, the validity of hydrodynamical models in describing the extreme conditions produced in heavy ion collisions has still not been properly justified theoretically. Even more, the gradient expansion, commonly used to derive hydrodynamics from microscopic theory, has been...
We study effects of dynamical initialization with a core-corona picture in hydrodynamic description of small colliding systems at RHIC and the LHC energies. We previously proposed an idea of dynamically initializing hydrodynamic fields by utilizing source terms in hydrodynamic equations [1]: Instead of setting initial conditions at a fixed hydrodynamic initial time, we make initially produced...
In this work, we extend the resummation of multiple medium-induced emissions to apply to dynamically expanding media. This is done by recasting the quenching weight as the solution of a rate equation with medium-induced partonic splitting functions that are sensitive to the expansion. We perform the calculations in the framework of Baier-Dokshitzer-Mueller-Peigne-Schiff-Zakharov (BDMPSZ)...
Understanding the early out-of-equilibrium dynamics of heavy-ion collisions (HIC) remains one
of the biggest theory challenges. So far, there are no first principle calculations for the equilibration
process of the quark gluon plasma and the dynamics close to the phase transition. In particular
describing the behavior close to the conjectured critical point, where critical slowing down...
We present first numerical applications of a recently formulated framework of perfect fluid hydrodynamics with spin [1] to model the space-time evolution of polarization in heavy-ion collisions. We consider various initial conditions for the hydrodynamic evolution and different forms of the spin tensor to study consequences of various physical assumptions for the time evolution of the system's...
The aim of the ongoing relativistic heavy-ion collision experiments is to explore the possible hot and dense deconfined state of QCD matter produced in such high energy collisions, the so called Quark-Gluon-Plasma (QGP). High energy partons (gluons, light quarks as well as heavy quarks) are produced in initial partonic sub-processes in the collisions between two heavy nuclei. Heavy quarks are...
The experimental measurement of the direct photon $v_2$ and the theoretical prediction for the same differ by a large margin both at RHIC and at the LHC energies. This is known as the ``direct photon puzzle". We investigate the effect of initial conditions on the production and elliptic flow of photons from relativistic heavy ion collisions in detail.
It is well known that the inclusion of...
The accuracy of astrophysical observations regarding compact stars are
ahead of a big evolution jump thanks to instruments like NICER [1],
which will increase the accuracy of the measurements. The discovery of
gravitational waves originating from merging neutron stars in this year
(GW170817 [2]) is the first step to use gravitational waves as a probe
for extremely dense nuclear...
The QCD equation of state at zero baryon chemical potential is the only element of the standard dynamical framework to describe heavy ion collisions that can be directly determined from first principles. Continuum extrapolated lattice QCD equations of state have been computed using 2+1 quark flavors (up/down and strange) as well as 2+1+1 flavors to investigate the effect of thermalized charm...
Recent STAR results on net-proton cumulant ratio $C_{4}/C_{2}=\kappa\sigma^{2}$ show a non-monotonic behavior as a function of beam energy [1], which has been interpreted as a signature of the QCD critical end point. However, all previous STAR results were obtained with a binomial assumption for the efficiency correction. Unfolding of net-proton distributions is necessary in order to correct...
We develop a macroscopic description of the space-time evolution of the energy momentum tensor during the pre-equilibrium stage of a high-energy heavy-ion collision. Based on a weak coupling effective kinetic description of the microscopic equilibration process (a la ``bottom-up"), we calculate the non-equilibrium evolution of the local background energy-momentum tensor as well as the...
We investigate the effect of composite pions on the behaviour of the chiral condensate at finite temperature within the Polyakov-loop improved NJL model.
To this end we treat quark-antiquark correlations in the pion channel (bound states and scattering continuum) within a Beth-Uhlenbeck approach that uses medium-dependent phase shifts.
A striking medium effect is the Mott transition which...
The STAR experiment has published the energy dependence of the directed flow (v1) of identified particles, such as proton, charged kaons and pions [1]. A clear sign change is observed in excitation function of the proton v1 slope, which could be an indication of the softening of the equation of state (EoS) due to 1st order phase transition. The v1 slope for produced particles, such as charged...
The study of modification of boson-tagged jet and dijet in high energy heavy ion collision can provide physical insight of jet-medium interactions. In this study, we use the Linear Boltzmann Transport(LBT) model to simulate the propagation of the shower partons generated from pythia or sherpa Monte Carlo simulations in the hot quark gluon plasma. We first calculate the $p_{T}$ distribution of...
We extend the S-matrix framework to the Delta-type resonances (spin 3/2, isospin 3/2) in elastic pion-nucleon scatterings up to 1.8 GeV mass. We evaluate not only Deltas, but also rho, f_0, K* and K_0 meson properties using the S-matrix framework, and implement them in the hydrodynamical description of Pb+Pb collisions at LHC.
We show that the proper treatment of resonances modifies the...
The Transition Radiation Detector (TRD) of the ALICE detector at the LHC provides electron identification and an online trigger on high-$p_{\rm T}$ tracks of electron candidates, to significantly enrich samples of electrons originating from open heavy-flavour and heavy quarkonia decays.
The TRD consists of 522 chambers arranged in 6 layers. Each chamber comprises a radiator and a MWPC with pad...
Starting from the investigation on the measurements of elliptic flows for charmed hadrons, we study charmonium state elliptic flows formed from coalescence of charm and anti-charm quark elliptic flows in the quark-gluon plasma. We find that the elliptic flow of the J/ψ meson is larger than that of the ψ(2S) meson in the intermediate transverse momentum region, and show that the elliptic flows...
An experimental observation of a first order phase transition, the critical end point and the restoration of spontaneously broken chiral symmetry is the milestone in our understanding of the phase structure of strongly interacting matter. Herewith, electromagnetic probes (dileptons) play a unique role. An unprecedented interaction rate of the Compressed Baryonic Matter (CBM) experiment at FAIR...
In this talk we present a comprehensive set of measurements on hadronic resonance production with ALICE, including new results from the LHC Run II . Transverse momentum spectra, integrated yields, mean transverse momenta, particle ratios and nuclear modification factors will be presented for $\rho(770)^{0}$, $K^*(892)^{0}$, $\phi(1020)$, $\Sigma(1385)^{\pm}$, $\Lambda(1520)$ and...
The lifetimes of short-lived hadronic resonances are comparable to the lifetime of the hadronic phase in high-energy heavy-ion collisions. These resonances are sensitive to re-scattering and regeneration processes in the time interval between the chemical and kinetic freeze-out, which might affect the resonance yields. Thus, such resonances can be very useful to probe the medium. Measurements...
Hadronic resonances are unique tools to investigate the interplay of re-scattering and regeneration effects in the hadronic phase of heavy-ion collisions. As the $\phi$ meson has a longer lifetime compared to other resonances, it is expected that its production will not be affected by regeneration and re-scattering processes. Measurements in small collision systems such as proton-proton (pp)...
In late 2015 the ALICE collaboration recorded Pb--Pb and pp collisions at $\sqrt{s_{\rm NN}}$ ($\sqrt{s}$) = 5.02 TeV.
The availability of data at the highest energy ever achieved in laboratory for heavy-ion collisions together with a pp reference at the same energy opens up the possibility for a detailed study of the nuclear modification factors ($R_{\rm AA}$) of identified particles.
The...
The measurement of conserved charge distributions have generated considerable interest in understanding the cumulants of conserved quantum numbers in the QCD phase diagram, in particular the behavior near a possible critical end point and hadronization near chemical freeze-out line. Net-protons have been used as a proxy for net-baryons. In this poster, we show a first measurement of the...
We present the analysis of transverse momentum ($\textit{p}_\text{T}$) spectra of primary charged particles in Pb-Pb collisions at $\sqrt{s_\text{NN}}=5.02\,\text{TeV}$ and $\sqrt{s_\text{NN}}=2.76\,\text{TeV}$.
For both data sets, we employ improved analysis methods that result in a significant reduction of systematic uncertainties with respect to previous analyses.
We discuss the evolution...
Particle production at high energies is often described as a result of the interplay of perturbative (hard) and non-perturbative (soft) QCD processes. Therefore, the measurements of transverse momentum spectra in pp collisions are important to provide a baseline for perturbative QCD and constraints for a better tuning of models and event generators. In addition, they constitute a valuable...
Asymmetric p+A collisions serve as a baseline for the understanding of the nucleus-nucleus collisions. Traditionally, they have been employed to observe the differences between the elementary and heavy-ion collision experiments. The heavy flavor production in p+A collision is well explained by cold nuclear matter effects in earlier experiments such as SPS and RHIC. The recent observation of...
Currently, one of the major investigations in heavy ion physics concerns the search for the QCD high temperature critical
point associated with the chiral transition, which has stimulated tremendous effort from both theory and experiment. On the theory side, a major role in the analysis of experimental results is played by hydrodynamical simulations of heavy ion collisions, which need as an...
The equilibration of a finite Bose system is modelled using a gradient expansion of the collision integral in the bosonic Boltzmann equation that leads to a nonlinear transport equation. Employing a method that had been proposed earlier for the analytical solution of the equilibration problem in a finite fermion system [1], the basic equation for bosons and in particular, gluons, is solved in...
This poster presents a study of an estimation of the background for the measurement of photon-hadron correlations in 5.02 TeV proton-lead collisions. Photon-hadron correlations measure the fragmentation function, which may be modified by energy loss in the QGP. The energy of the photon is not affected by the QGP, so it gives information about the energy of the parton prior to interaction with...
We report a comprehensive study on the initial-state partonic eccentricity fluctuation and final-state anisotropic flow fluctuation in Au + Au collisions at 200 GeV using a multiphase transport model. Event-by-event eccentricity and flow anisotropy are characterized by multi-particle cumulants up to fourth order harmonic. Experimental results of azimuthal anisotropy fluctuation by means of...
The evolution of strongly interacting matter created at the FAIR-NICA energies characterized by high net baryon densities and moderate temperatures is expected to occur near the boundary of the first order phase transition and probable in vicinity of the critical QCD point. A large event-by-event fluctuations of hadronic observables are expected to be the signatures of this critical point. In...
With the help of a master equation we study the evolution of the
multiplicity distribution. Particularly we focus on the third and fourth
factorial moments from which all other kinds of moments can be
calculated. Among them we also determine the skewness and the kurtosis.
We first study how the third and the fourth moments thermalise when the
kinetic temperature is fixed. Then we study...
The Bjorken formula [1] is very useful for estimating the initial energy density in relativistic heavy ion collisions, once an initial time $\tau_0$ is specified. However, it is well known that the formula is only valid at very high energies [2], where $\tau_0$ is much bigger than the time it takes for the two nuclei to cross each other. Therefore, the Bjorken formula cannot be trusted at...
Studies of integral and differential correlation functions of elementary particles produced in high-energy nucleus-nucleus collisions provide invaluable information on the particle production dynamics, the collision system evolution, and might also enable the determination of fundamental properties of the quark matter produced in these collisions. Extensive measurements of general balance...
Quantum Chromodynamics (QCD) predicts that heavy quarks lose less energy than light quarks in the Quark-Gluon Plasma (QGP) created in relativistic heavy-ion collisions. However, recent measurements of the nuclear modification factor ($R_{AA}$) and elliptic flow ($v_2$) for open charm mesons at RHIC show results comparable in magnitude to those of light hadrons, suggesting that charm quarks...
We report on a preliminary study of the production of f$_{0}$(980)$\rightarrow \pi^{+}\pi^{-}$ at mid-rapidity ($\vert y \vert$ < 0.5) performed with the ALICE detector at the LHC in minimum bias pp collisions at centre-of-mass energy $\sqrt{\mathit{s}}$ = 5.02 TeV. The f$_{0}$(980) signal extraction is challenging due to the large background from correlated $\pi^{+}\pi^{-}$ pairs from...
The flow coefficients $v_n$ are commonly extracted from multi-particle distributions where the properties of one or several particles are averaged over a large range in pseudorapidity $\eta$ or transverse momentum $p_{\text{T}}$.
Such approaches assume that the observed multi-particle distributions can be factorized into a product of single-particle distributions.
However, it is known that...
We employ the AdS/CFT correspondence and numerical relativity techniques to investigate the far-from-equilibrium dynamics of a strongly coupled non-Abelian plasma with a critical point [1] in the temperature and chemical potential phase diagram. In the case of an out-of-equilibrium homogeneous medium [2], isotropization happens before the system thermalizes and the behavior of the pressure...
Ever since the discovery of the quark-gluon plasma the understanding of its fas thermalization has been a topic of intense research. We use the gauge/gravity duality to model the out-of-equilibrium first stage of a heavy ion collision through the collision of gravitational shockwaves in numerical relativity. This investigation of collisions of sheets of energy density in a non-conformal...
Two-particle Bose-Einstein femtoscopic correlations are measured with the data from the LHC Run II collected by CMS in proton-proton collisions at 13 TeV. The analysis is performed over a wide range in event multiplicity, especially reaching the multiplicity regime in which long-range collective correlations were observed. This extension to high multiplicity events represents an important...
Femptoscopic measurements allow access to the spatio-temporal characteristics of the systems produced in relativistic heavy-ion collisions. This poster presents new measurements of the two-pion HBT radii $\mathrm{R_{out}}$, $\mathrm{R_{side}}$ and $\mathrm{R_{long}}$ have been made for shape-engineered events by the STAR experiment. Shape selection was accomplished via cuts on the...
Hanbury Brown and Twiss (HBT) radii are measured as a function of centrality, transverse momentum, rapidity, and azimuthal angle with respect to the second-order event plane in central $p$+Pb collisions at $\sqrt{s_{NN}} = 5.02$ TeV with the ATLAS detector at the LHC. A total integrated luminosity of 28 nb$^{-1}$ is sampled. The radii are presented as a function of the local density...
Studies of the fluctuations of conserved charges (baryon number, electric charge, strangeness, etc.) can be used to chart the phases of strongly interacting QCD matter, as well as to locate the critical end-point (CEP) in the associated QCD phase diagram. The cumulants (and cumulant ratios) of the multiplicity distributions for conserved charges, which are linked to susceptibilities and their...
The study of strange hadronic resonances in pp collisions contributes to the study of strangeness production in small systems. Measurements in pp collisions constitute a reference for the study in larger colliding systems and provide constraints for tuning QCD-inspired event generators. Since the lifetimes of short-lived resonances such as $\rm K^{*}(892)^{\pm}$ ($\tau \sim 4$ fm/$\textit{c}$)...
Initial state partonic energy loss is an important benchmark of the nuclear medium properties in fixed target and heavy ion collision experiments, yet remains imprecisely determined up to now. The E906/SeaQuest experiment at Fermilab primarily measures Drell-Yan and J/psi production for p+A collisions with fixed targets H, D, C, Fe, and W. The experiment provides an ideal configuration for...
Dihadron angular correlations in forward $pA$ collisions have been considered as one of the most sensitive observables to the gluon saturation effects. In general, both parton shower effects and saturation effects are responsible for the back-to-back dihadron angular de-correlations. Recent developments have allowed to incorporate the so-called parton shower effect, namely the Sudakov effect,...
Two additions to the forward instrumentation of ALICE will be described: the new Fast Interaction Trigger (FIT) and the Forward Calorimeter (FoCal). The former will be installed during the Long Shutdown 2 (2019/2020), while the latter is proposed for Long Shutdown 3 (2024-2026).
The FIT detector provides a fast trigger, a precise collision time measurement for time-of-flight based particle...
A Forward Calorimeter (FoCal) is proposed as an addition to the ALICE experiment to be installed during Long Shutdown 3 (2024-2026).
The main goal of the FoCal proposal is to measure forward (3.5 < y < 5) direct photons in pp and p-Pb collisions to obtain unique experimental constraints on proton and nuclear PDFs in a new region of low x $(10^{-5} - 10^{-6})$. It provides measurements of...
Heavy flavor and quarkonia productions are important hard probes to test Quantum Chromodynamics (QCD) and study the properties of the Quark Gluon Plasma (QGP) created in high energy heavy ion collisions. The energy loss of quarks and gluons in the QGP is expected to have flavor/mass dependence. The Forward Silicon Vertex Tracker (FVTX), installed in the PHENIX detector in 2012, enables the...
Functional continuum methods provide ab-initio access to the non-perturbative regime of quantum chromodynamics. In particular, they allow accessing non-zero temperatures and densities, making them an ideal tool to access QCD's phase diagram. The functional QCD collaboration [1] aims to map out the phase diagram in a systematic manner. Within the functional renomalization group (FRG) approach,...
We provide an analytical calculation of the covariance of the energy-momentum tensor of the glasma in heavy ion collisions at tau=0+. This is done in the McLerran-Venugopalan model. We then implement its proper time evolution, providing the initial conditions for the subsequent hydrodynamical evolution of the system. Quantities such as the initial viscosity of the Quark Gluon Plasma can also...
In non-central relativistic heavy ion collisions, the created matter possesses a large initial orbital angular momentum. Particles produced in the collisions could be polarized globally in the direction of the orbital angular momentum due to spin-orbit coupling. Recently, the STAR experiment has presented the polarization signals for Λ hyperons and possible spin alignment signals for phi...
We study the thermodynamics of hadronic matter using the hadron
resonance gas model where the repulsive interactions between baryons
are modeled using the mean field approach.
We have shown [1] that repulsive interactions are especially important
when considering the higher order fluctuations. We now extend the
treatment of [1] to cover not only ground state baryons but heavier
resonances...
One of the most spectacular observations in heavy ion physics has been that thermalization may occur in small system collisions. For example, harmonic flow coefficients vn(pT) measured in high multiplicity p+A reactions are well reproduced by viscous hydrodynamics calculations. Small system collisions in fact serve as good tests of hydrodynamics because they should be more difficult to...
Heavy flavour probes provide important information about the in-medium properties of the quark gluon plasma produced in heavy-ion collisions. In this work, we investigate the effects of (2+1)d event-by-event fluctuating hydrodynamic backgrounds on the nuclear suppression factor and momentum anisotropies of heavy flavour mesons and non-photonic electrons [1,2]. Using the state-of-the-art D and...
Heavy flavor $R_\text{AA}$ and $v_n\{m\}$ have been previously calculated in an event-by-event framework at mid-rapidity [1,2]. Those results showed that exploring new observables in the heavy flavor sector can lead to further constraints on the properties of the QGP. Furthermore, longitudinal dependence of the heavy flavor observables has not yet been explored. In this work we expand the...
Heavy quarks produced in relativistic heavy-ion collisions have proven to be sensitive to the properties of quark-gluon plasma (QGP) through which they propagate. Current measurements of open charm in heavy-ion collisions show unexpectedly large momentum anisotropies and small nuclear modification factors, posing a challenge for the theoretical understanding of the nature of coupling between...
The high luminosity (HiLumi) upgrade of the Large Hadron Collider will
enable us for more detailed, high-precision experimental analysis of
the heavy ion collisions. Testing both the new theoretical models and
performing high-statistics simulations require novel, easy-to-use,
fast, extendable generators.
The recently developed HIJING++ version is based on the latest version
of PYTHIA8 and...
In this presentation we make comparisons between hydrodynamic behavior in UrQMD/CASCADE [1], UrQMD/HYDRO, AMPT and Chaos Many-Body Engine [2] Au+Au simulated events at CBM-FAIR energies. We analyze the properties of different flow streams classes [1] and of the Fourier coefficients in the mentioned interaction models as a function of incident energy, rapidity and impact parameter.
[1] Danut...
Recent studies of hydrodynamic fluctuations in rapidly expanding fluids suggest the existence of a universal renormalization which characterizes the long time behaviour of the equilibrium correlators of energy and momentum and transport coefficients. These results were obtained by assuming zero densities of conserved charges. In this work we study the effects of hydrodynamic fluctuations when...
We perform a principal component analysis (PCA) of $v_n(p_T)$ in event-by-event hydrodynamic simulations of Pb+Pb collisions at the Large Hadron Collider. PCA is a statistical technique for extracting the dominant components in fluctuating data. It was suggested to apply it to relativistic collisions [1] in order to extract the information from event-by-event fluctuations from the...
Identification of charged kaons can be carried out using kink topology based on the two-body decay mode ($K\rightarrow \mu +\nu_\mu$) inside the volume of TPC detector. For the first time for Pb-Pb collisions, the transverse momentum spectra of charged kaons are measured from their decay daughters using kink topology with the new Run 2 data at $\sqrt{\it{s}_{NN}} = 5.02$ TeV for different...
The CMS measurement of the dijet pseudorapidity and transverse momentum distributions in pPb versus pp collisions at 5.02 TeV provides a direct constraint on nuclear gluon PDFs in a wide range of $x$ and $Q^2$ [CMS-PAS-HIN-16-003]. We report on the impact of these data on the EPPS16 nuclear PDFs [Eur.Phys.J. C77, 163]. For this, we have devised a non-quadratic extension of the Hessian PDF...
Many great efforts have been made to investigate the Chiral Magnetic Effect (CME), which replies on the existence of extremely large electromagnetic fields in relativistic heavy-ion collisions. However, the recent CMS measurements in small systems challenge the traditional CME interpretation, indicating that the dominant contribution to the CME observable of charge azimuthal correlation...
Gravitational wave observations of GW170817 placed bounds on the tidal deformabilities of compact stars allowing one to probe equations of state for matter at supranuclear densities. Here we design new parametrizations for hybrid hadron-quark equations of state and test them against GW170817. We find that GW170817 is consistent with the coalescence of a binary hybrid star-neutron star. We also...
Quantum Chromodynamics in the presence of intense magnetic field reveals exotic phenomena
like chiral magnetic effect, magnetic catalysis, inverse magnetic catalysis, vacuum
superconductivity etc. Such a strong magnetic field is expected to be produced in non-central
relativistic heavy ion collision experiments at RHIC and LHC. So, the study of ``strongly"
interacting hot and/or dense...
Measurements of the yield and structure of jets in heavy-ion collisions at different collision energies and kinematic ranges can be used to constrain jet energy loss models, and in turn give information about the structure of the quark-gluon plasma itself. ALICE reconstructs ''full'' jets with high-precision tracking of charged particles combined with calorimetric detection of neutral...
Quarkonia are produced in the initial hard scatterings and are useful probes to study the microscopic properties of the matter produced in the ultra relativistic heavy-ion collisions. The experimental results show that in nucleus-nucleus collisions, the charmonium yields are modified compared to the expectations based on the yields measured in proton proton interactions, scaled by the number...
Initial- and final-state radiation are important processes for the physical interpretation of high-energy collisions at the Large Hadron Collider. Calculations of these perturbative QCD corrections are, however, limited to probabilistic approximations using parton shower approaches in event generators. Although this Monte-Carlo DGLAP description is nowadays state-of-the-art, there still exist...
Our presentation will be based on our recent paper [1].
We construct a new, simple model of the heavy ion collision, local in the impact parameter plane. This model can be regarded as a new realization of the ``fire-streak'' approach, originally applied to studies of lower energy nucleus-nucleus reactions.
Starting from local energy and momentum conservation, we provide a full description of...
Spectral functions of quarkonia hold many information on bound states and their in-medium modifications as well as on transport properties. Determining spectral functions is subject of many calculations, in lattice QCD as well as in perturbation theory.
We compare continuum extrapolated lattice results [1] to a perturbatively determined spectral function obtained by interpolating between...
We investigate the hydrodynamic medium response to jets in the quark gluon plasma (QGP) fluid in dijet events, in particular focusing on the interference effect between the flows induced by a back-to-back pair of jets. In high-energy heavy-ion collisions, jets deposit their energy and momentum into the QGP medium fluid via the successive interactions with the medium constituents during their...
The search for experimental signatures of the critical point (CP) of strongly interacting matter is one of the main objectives of the NA61/SHINE experiment at the CERN SPS. In the course of the experiment, an energy (beam momentum 13A – 150/158A GeV/c) and system size (p+p, p+Pb, Be+Be, Ar+Sc, Xe+La) scan is performed. Proposed observables include non-monotonic fluctuations of integrated...
Understanding the energy loss of partons traversing the strongly interacting matter created in heavy ion collisions is one of key goals of the heavy ion physics program. In this talk we present results of phenomenological analyses of various recent jet quenching data. The core of the model used in these analyses is based on the shift formalism which allows for an extraction of the magnitude of...
The two-prong substructure of the leading subjets inside a reconstructed jet opens new windows on precision constraints on the in-medium modification of parton showers. We present the first resumed calculation of the groomed soft-dropped subjet momentum sharing distribution in heavy ion collisions, and demonstrate that both the STAR data at RHIC and the CMS results at LHC can be understood in...
We investigate the applicability of fluid dynamics (FD) in relativistic heavy-ion collisions by comparing its solutions to those of the relativistic Boltzmann equation (BE) [1]. The latter can be solved numerically [2] and its FD limit is well known [3]. We consider various (2+1)-dimensional boost-invariant scenarios, with realistic initial transverse profiles of energy and particle density....
A large excess in the yield of $\mathrm{J/\psi}$ at very low transverse momentum (${p}_\mathrm{T}<\mathrm{300\ MeV/}c$) and forward rapidity (2.5< $y$ <4.0) was recently reported by ALICE using the LHC Run-1 data, in Pb-Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 2.76 TeV. This is suggestive of coherent $\mathrm{J/\psi}$ photo-production, similar to measurements in ultra-peripheral collisions...
The extent to which J/psi mesons are accompanied by other particles within the same jet provides information about how the J/psi is formed, which is still not completely understood. The details of J/psi production may have important consequences for their interaction with the quark-gluon plasma. We present a study of jets containing a J/psi in pp collisions at 5 TeV with the CMS experiment....
Polarization is a key observable to determine the quarkonium production mechanism in hadronic elementary collisions. Its very small value measured at the LHC has been challenging the commonly-used theoretical models and it still represents a major standing issue in the field.
On the other hand, phenomenological studies have shown that primordial quarkonium in AA interaction can be polarized by...
In high-energy pp collisions, there can be a substantial contribution from Multi-Parton Interactions (MPI) in particle production mechanisms. In this case, several interactions at the partonic level occur in a single pp collision and this implies a correlation between the particle production and the total event multiplicity. At the LHC energies, MPI might occur at hard momentum scales, thus...
The quarkonium production as a function of multiplicity in proton-proton and proton-lead collisions is considered as an interesting observable to comprehend multi-parton interactions and to seek out the presence of collectiveness in the small systems. The multiplicity dependence of J/$\psi$ production has been studied in pp collisions at $\sqrt{s} = 7$ and 13 TeV and p-Pb collisions at...
Relativistic heavy-ion collisions are the unique tool to study the properties of the deconfined state of quarks and gluons, Quark-Gluon Plasma (QGP). Dissociation of J/$\psi$ is thought as one of the strong evidences of QGP formation. At LHC energy, regeneration of J/$\psi$ from thermalized charm quarks is also expected to be pronounced.
In order to discuss the QGP effects in relativistic...
High multiplicity events of small colliding systems at high c.m.s. energies show similar collective features as those observed in events
of heavy ion collisions with comparable multiplicities, such as long-range near-side correlations and v_n coefficients [1,2]. Whether this behaviour may be attributed to the presence of a deconfined state in small systems is an open question.
Recent analyses...
Measurements of jet substructure are useful tools for the understanding of the mechanism of jet quenching. Using those multi-scale probes, the results of jet fragmentation functions, jet shape and jet spectra could be used to search for possible medium response and to quantify the properties of the Quark-Gluon Plasma within the theoretical models. In this poster, jet reconstruction, background...
Resonances are useful tools to study the properties of the hadronic medium produced in high energy heavy-ion collisions, due to their short lifetime. They are good candidates to probe the interplay of particle re-scattering and regeneration in the hadronic phase. In particular, the K$^{*}(892)^{\pm}$ resonances are important because of their very short lifetimes ($\sim$ 4 fm/$\it c$) which are...
We present the first preliminary results on direct and elliptic flow of particles with strange content ($K^0_s$ and $K^+$) in Au+Au collisions at $1.23\,\mathrm{A GeV}$ measured with HADES. The study of strange particle flow in heavy-ion collision is according to the theory sensitive to in-medium hadron modifications. Kaon flow was seldom measured at such low center-of-mass energy region...
The first measurement of isospin fluctuations in the kaon sector is reported in Pb-Pb collisions at $\sqrt{s_{NN}}=$ 2.76 TeV, recorded with the ALICE detector. A robust statistical observable $\nu_{dyn}$ was used to extract the novel isospin fluctuations from the distributions of neutral and charged kaons as a function of collision centrality. The results show a significant variation in the...
Relativistic hydrodynamics is one of the fundamental tools used to interpret the data measured in heavy-ion collision experiments at RHIC and the LHC. Despite the success of second order viscous hydrodynamics in reproducing physical observables, there exist still theoretical problems that may question validity of this approach for description of heavy-ion collisions. The main source of the...
We have investigated the properties of quarkonia in a hot QCD medium in the presence of strong magnetic field, which may be produced in the non-central events at RHIC and LHC and then studied its quasi-free dissociation due to the Landau-damping mechanism. Using the Schwinger propagator in the lowest Landau level, we have calculated the real and imaginary parts of the retarded gluon...
A Muon Chamber (MUCH) system comprising of alternating layers of segmented absorbers and detector triplets will perform the task of dimuon detection at CBM experiment at FAIR. Unprecedented interaction rates (~10 MHz) of Au+Au collisions and a high radiation environment in CBM impose severe constraints on the detector design. For the first two stations of MUCH where the particle rates reach...
The study of hard jets and their interactions with the traversed medium provides a very improtant tool to probe the quark-gluon plasma produced in relativistic heavy-ion collisions. In this work [1], we study both light and heavy flavor jet quenching on the same footing utilizing a Boltzmann transport model including both elastic and inelastic parton-medium interactions within perturbative...
We calculate energy deposition and axial charge production from color flux tubes at early times in a heavy-ion collision. Based on analytic expressions for the space-time dependent fluctuations of the axial charge and energy density distributions in terms of the unpolarized and linearly polarized gluon distributions of the nuclei, we develop a phenomenological model for the initial state,...
Heavy flavour quarks (charm and beauty) are of special interest for the study of the Quark-Gluon Plasma as they are predominantly produced in the initial hard-scattering processes and participate in the entire evolution of the system. Moreover, heavy flavour production is well under control of perturbative QCD. Thus, heavy flavours are an excellent probe to study pQCD in small systems as well...
We use the gauge/gravity duality to map thermodynamic fluctuations of black holes onto fluctuations of baryon charge in a hot and baryon dense Quark-Gluon Plasma (QGP). Our approach gives results that are in quantitative agreement with state-of-the-art lattice simulations for the QCD equation of state at finite baryon density and the moments of fluctuations of baryon charge, while...
Direct photons are unique probes to study both the thermal and collective properties of the Quark Gluon Plasma (QGP). PHENIX has discovered a large excess of the direct photon yield as well as a large azimuthal anisotropy at the low $p_{T}$ region in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV$/c^{2}$. The two observations of large yield and anisotropy are quite challenging for the current...
A very promising probe to study the quark-gluon plasma, a deconfined state of
quarks and gluons predicted by lattice quantum chromodynamics calculations
in ultra-relativistic heavy-ion collisions, are correlated dielectron pairs.
Electrons reach the detector without significant final state
interactions. In addition, the low-mass dielectron spectrum comes from various
sources, i.e. Dalitz and...
Low-mass dimuon production, including light neutral mesons $\eta,~\rho,~\omega,~\phi$, provides key information on the hot and dense state of strongly interacting matter produced in ultra-relativistic heavy-ion collisions. The proper baseline for these observations is provided by the measurements of low-mass dimuons in pp collisions, which also allows for the tuning of light particle...
We study the relativistic hydrodynamics with chiral anomaly and dynamical electromagnetic fields. This theory is called the chiral magnetohydrodynamics (MHD) [1]. It is a framework that can evolve the system of QGP fluids and electromagnetic fields consistently, and it will play an important role in quantifying anomaly-induced effects in heavy-ion collisions. We formulate the chiral MHD as a...
Heavy flavour quarks (charm and beauty) offer a unique opportunity to study the strongly-interacting medium, known as the Quark-Gluon Plasma (QGP), created in ultra-relativistic heavy-ion collisions. They are produced in the early stages of the collision, in hard scattering processes, allowing the heavy quarks to interact with the QGP throughout its entire evolution. The measurement of the...
Measurements of production and azimuthal anisotropy of prompt charm mesons ($D^0$ and $D^*$) are presented using $p$+Pb data at $\sqrt{s_{NN}}=8.16$ TeV collected in 2016 by ATLAS. Prompt charmed meson production is measured in minimum bias $p$+Pb data, and is reconstructed via two decay channels: $D^0\rightarrow K+\pi$ and $D^*\rightarrow D^0+\pi\rightarrow K+\pi+\pi$. The measured charm...
A measurement of $Z$ boson production is performed via leptonic decay channels using data samples from the 2015 LHC run obtained at the center-of-mass energy of $\sqrt{s_{_{\rm{NN}}}} = 5.02$ TeV with a total integrated luminosity of 0.49 nb$^{-1}$ and 25.3 pb$^{-1}$ in Pb+Pb and $pp$, respectively. Integrated and differential cross sections are measured for both electron and muon channels in...
The collisions of heavy ions at ultrarelativistic energies provide an excellent
way to study the phase transition from hadronic matter to a deconfined state
of quarks and gluons, the Quark-Gluon Plasma (QGP). The ALICE (A Large
Ion Collider Experiment) detector at the LHC is designed for the study of the
QGP properties. Heavy quarks (charm and beauty), having a large mass, are
produced in the...
Jet is the collection of concentrated final state hadrons produced from the fragmentation of hard scattered parton in high energy hadronic, leptonic or heavy-ion collision. In proton-proton (pp) collisions, measurement of jet production cross-sections and jet properties provide validation for perturbative Quantum Chromo Dynamics (pQCD) and gives detailed insight of parton to jet fragmentation....
Heavy quarks (charm and beauty) are produced via hard parton scatterings in the initial stage of the collision. Thus, they are ideal probes of the Quark-Gluon Plasma (QGP) created in ultra-relativistic heavy-ion collisions at the LHC. Two-particle angular correlation studies in heavy-ion collisions have provided deep insight into the the in-medium partonic energy loss and its dependence on the...
Heavy quarks (charm and beauty) are sensitive probes to study the properties of the Quark-Gluon Plasma (QGP), the hot and dense medium formed in high-energy heavy-ion collisions. Due to their large masses, heavy quarks are produced in hard partonic scattering processes in the initial stages of the collision. Their abundance is not expected to be modified through the evolution of the system....
Heavy quarks (charm and beauty) are a valuable probe to study the properties of the Quark-Gluon Plasma created in Pb--Pb collisions. In order to distinguish the hot nuclear matter effects in Pb--Pb collisions from possible Cold Nuclear Matter effects (CNM), measurements in p--Pb collisions are crucial.
Possible CNM effects, such as $k_{\rm{T}}$-broadening, shadowing and parton energy loss in...
Heavy quarks (charm and beauty) are sensitive probes to study the properties of the Quark-Gluon Plasma (QGP) produced in high-energy heavy-ion collisions. Due to their large masses, charm and beauty quarks are produced in the initial stages of the collisions in hard-scattering processes and they explore the entire evolution of the system
The measurement of charm production in pp collisions is...
Heavy quarks (charm or beauty) are powerful probes to study and characterise the properties of the deconfined medium created in high-energy heavy-ion collisions, the Quark-Gluon Plasma (QGP). Because of their large masses, heavy quarks are produced in initial hard-scattering processes, and they subsequently experience the whole system evolution, interacting with the medium constituents. The...
In high energy hadron collisions, direct photons can be produced at different stages and are of particular interest to study the hot QCD medium since they escape it without being affected.
At high transverse momentum ($p_{\text{T}}$), these photons may come from hard scattering processes (prompt photons) and from high $p_{\text{T}}$ parton fragmentation. Their measurement in proton-proton...
Quarkonium production mechanism in elementary collisions has not been fully understood. Experimental data on the $J/\psi$ cross section in p+p collisions can be described relatively well by several models that are currently available on the market. However, these models differ in their predictions for the $J/\psi$ polarization. Therefore precise measurements of $J/\psi$ polarization can...
The measurement of the fragmentation functions of jets into charged particles in heavy ion collisions can provide insight into the mechanism of the modification of the parton shower in the hot, dense QCD medium created in these collisions. Additionally, a study of the jet fragmentation in $p$+Pb collisions, where a large volume of hot QCD matter is not expected to be created, can provide...
The yield ratios of strange anti-baryons to baryons have been measured in heavy-ion collisions and exhibit a trend that is getting closer to unity with increasing number of valence strange quarks. This ratio has, however, never been measured for charm baryons, and it will be important to establish if they exhibit a similar amount of baryon-to-anti-baryon enhancement as strange baryons....
The ALICE detector at the Large Hadron Collider (LHC) has been optimised for the studies of the Quark-Gluon Plasma (QGP) created in heavy-ion collisions. Charm quarks are one of the probes that has been extensively used to elucidate the properties of the QGP. They are dominantly produced at the initial stage of the collisions and experience the whole evolution of the system.
While most of...
Due to their high masses ($m_{\text{c}}\approx 1.5\text{ GeV}/c^2$, $m_{\text{b}}\approx 4.8\text{ GeV}/c^2$), charm and beauty quarks are mostly produced in the initial hard scattering processes, happening immediately after the lead nuclei collide. This process has typical time scales shorter than the Quark-Gluon Plasma formation time, therefore by studying the kinematic properties of...
Electron-positron pairs are a unique experimental tool to investigate the hot and dense medium created in ultra-relativistic heavy-ion collisions. Such pairs are produced during all stages of the collision and do not interact strongly. Therefore, they carry information about the medium properties and the whole space-time evolution of the system.
Measurements of dielectron production in...
Hadronic resonances are interesting probes of the hot and dense matter created in heavy-ion collisions. Due to their short lifetime, resonances are useful tools to understand the mechanism of particle production and properties of the hadronic phase. If the time interval between the chemical and kinetic freeze-out (hadronic phase) is comparable with the lifetime of the resonance, the yield of...
Neutral meson production in proton-proton collisions is described by pQCD in a large kinematic range. Parameters of theoretical models in both perturbative (NLO, NNLO) and non-perturbative (structure function, fragmentation function) regimes are constrained by neutral pion and $\eta$ meson spectra. The ratio of $\eta$ to $\pi^0$ spectra tests $m_{\rm T}$ scaling violation in the low $p_{\rm...
ALICE has measured the invariant cross sections for the production of $\pi^{0}$ and $\eta$ mesons in proton-proton collisions at center of mass energies of $\sqrt{s}$ = 0.9 TeV, 2.76 TeV, 7 TeV and most recently 8 TeV.
Neutral mesons are reconstructed via their two photon decay channels by means of an invariant mass analysis.
Photons are detected with three different systems; using the...
Measurements of neutral meson spectra in pp collisions provide a good opportunity to test pQCD calculations at high ${p}_{T}$.
The ratio $\eta$ to $\pi^0$ allows to study phenomenological principles like $\rm{m}_{T}$ scaling at low ${p}_{T}$. Furthermore, $\pi^0$ and $\eta$ spectra in pp collisions provide a reference to understand the mechanisms appearing in p-Pb and Pb-Pb collisions at the...
The production of heavy quarks in proton-proton (pp) is described in the framework of perturbative Quantum Chromo-Dynamics (pQCD) via the leading order process ${\rm gg\, (q\bar{q})} \rightarrow {\rm Q\bar{Q}}$. Among higher-order processes, gluon splitting ${\rm gg\, (q\bar{q})} \rightarrow {\rm gg} \rightarrow \rm gc\bar{c}$ is known to account for a large fraction of the charm produced at...
In heavy-ion collision experiments, the study of event-by-event fluctuations is a powerful tool to characterize the thermodynamic properties of the hot and dense QCD matter. According to the Lattice QCD calculations, an analytic cross-over exists at small $\mu_{B}$ regions but there is no experimental evidence for the location of predicted cross-over. Experimentally, it is thought that up to...
The substructure of inclusive jets in lead-lead and proton-proton collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV is reported using the ATLAS Run 2 data at the LHC. Jet substructure observables have been recently developed to access the internal structure of jets produced in proton-proton collisions. These observables are sensitive to the angular and momentum correlations of the jet...
Large In LHC RUN 2, the Large Hadron Collider restarted with a centre-of-mass energy increase of around 60% with respect to the end of the LHC RUN 1, in which the highest energy of pp collision is 7 TeV. At this new energy, 13 TeV in pp collision, it is absolutely essential to restudy the general features of the pp interaction, in particular the soft or semi-hard bulk of particles that form...
In meaurements of bulk charged-particle production, the kinematic characteristics of produced hadrons and correlation between them in the presence of the hard scattering signatures is a very interesting topic for understanding the physics processes relevant in small collision systems. Extensive data samples have been accumulated by the LHC experiments experiments to conduct these studies in...
In heavy ion collisions, the intense electromagentic fields result in a high rate of photon-photon collisions. The cross section for the process $\gamma\gamma\rightarrow \mu^{+}\mu^{-}$ involves the equivalent photon fluxes from the nuclei and elementary cross sections calculated in QED. These fluxes also arise in the calculation of exclusive vector meson production and ultra-peripheral jet...
Heavy quarks (charm and beauty) are powerful probes to investigate the properties of the Quark-Gluon Plasma (QGP), the hot and dense medium produced in ultra-relativistic heavy-ion collisions. Heavy quarks are produced in hard-scattering processes on a time scale shorter than the QGP formation time; therefore, they experience the whole evolution of the produced system of strongly-interacting...
Charm quarks possess large masses, and thus can serve as penetrating probes to study the intrinsic properties of the hot medium created in heavy-ion collisions. However, Cold Nuclear Matter (CNM) effects, such as the change in the parton distribution function between a free nucleon and a nucleus, also affect the charm quark production in nuclear collisions with respect to p+p collisions. These...
In relativistic heavy-ion collisions, heavy quarks (charm and beauty) are ideal probes to investigate the properties of the hot and dense colour-deconfined QCD matter, so called Quark-Gluon-Plasma (QGP). Heavy quarks are produced in initial hard partonic interactions, and they propagate through the QGP.A strong suppression of heavy-flavour hadron production has been observed in the most...
Recent RHIC and LHC results show that the nuclear modification factors of open charm hadrons at high transverse momenta as well as their elliptic flow are similar to those of light flavor hadrons, indicating that charm quarks also interact very strongly with the Quark Gluon Plasma (QGP). During interactions, charm quarks suffer from substantial energy loss and gain significant elliptic flow....
In ultra-relativistic heavy-ion collisions, creation of a novel state of matter, the quark-gluon plasma (QGP), has been observed. This hot, dense, and short-lived medium of deconfined quarks and gluons is experimentally very challenging to study. Suppressed production of heavy quarkonia, caused by colour screening of the binding force, has been viewed as a direct evidence of the QGP formation....
Jet-medium interaction has two important aspects: jet energy loss and the medium response to the lost energy/momentum. The study of jet energy loss has been very successful in the explanation of the suppression of high $p_T$ hadron and jet productions as well as the nuclear modification of dihadron, dijet, photo-jet and hadron-jet correlations. The search for the signal of the medium response...
A potential upgrade with forward instrumentation of the proposed sPHENIX detector at the Relativistic Heavy Ion Collider (RHIC), together with RHIC’s unique capabilities to collide polarized protons and heavy nuclei, will open the door to exciting new measurements to enhance our understanding of quantum chromodynamics (QCD). These measurements will reveal more about how partons behave in a...
Expansion of a locally equilibrated fluid is considered in an anisotropic space-time given by Bianchi type I metric. Starting from an isotropic equilibrium phase-space distribution function in the local rest frame, we obtain expressions for thermodynamic quantities such as number density, energy density and pressure components. In the case of an axis-symmetric Bianchi type I metric, we show...
The SU(3) flavor parity-doublet quark-hadron model is used to investigate the phase diagram of QCD matter. The quark sector of the model is tuned to the $\mu_B=0$ lattice QCD data on trace anomaly. The structure of the baryon number susceptibilities in the temperature/chemical potential plane is studied in some detail.
The model predicts three phase transitions - nuclear first-order liquid-gas...
With a view to understanding and analyzing the recent available data on momentum- and energy dependence of J/Psi suppression, We compute suppression rate within a hydrodynamical model. For this, we consider an ellipsoidal flow and use an ansatz for temperature profile function which accounts for time and three dimensional space evolution of the quark-gluon plasma. A satisfactory agreement with...
The transition from a hydrodynamical modeling to a particle-based approach is a crucial element of the description of heavy-ion collisions at high energies. Assuming this "freeze out" happens instantaneously at each point of the expanding medium, we show that the local phase-space distribution of the emitted particles is asymmetric in momentum space. This suggests the relevance of anisotropic...
At high temperature, Lattice Quantum Chromodynamics (LQCD) predicts the existence of dense and hot nuclear matter which behaves as a deconfined medium of quarks and gluons. Inside such medium, quarkonia are suppressed due to the color-screeening effect. However, at LHC energies an enhancement in the production of $J/\psi$ has been observed. This enhancement effect is more prominent at lower...
Recent observations of long-range correlations in small systems, such as p+p or p+A, challenge our understanding of the collectivity in the strongly coupling syetems. It has been shown that a multiphase transport (AMPT) model can naturally reproduce the long-range two-particle correlation in p+Pb collisions and in a good agreement with the experimental data [1]. A new subevent cumulant method...
The usage of multiparticle correlation techniques for the study of genuine three-body and even higher-order interactions between hyperons and nucleons, which are relevant for instance for the description of equation of state of a neutron star, is plagued by difficulties in estimating consistently the background contribution to all terms (which are in general of different order) in the...
Ultra-relativistic heavy-ion collisions allow the investigation of the Quark-Gluon Plasma (QGP), a colour-deconfined state of strongly-interacting matter produced in such collisions. Heavy quarks (charm and beauty) are important probes to understand the properties of this QCD medium, since they are produced in the early stages of the collisions and thus experience the whole evolution of the...
Recent measurements performed in high-multiplicity proton-proton and proton-lead collisions at the LHC have shown features that are reminiscent of those observed in lead-lead collisions. Results on (multi-)strange hadron production in proton-proton collisions at $\sqrt{s}$= 5.02 TeV will be shown, based on the analysis of a data sample collected in 2015 with the ALICE detector. This sample is...
In this contribution, we report on the multiplicity dependence of the pseudorapidity density distribution of charged particles in proton-proton (pp) collisions at $\sqrt{s} =$ 5, 7 and at 13 TeV with the ALICE experiment.
The measurements rely on track segments reconstructed with the Silicon Pixel Detector in the kinematic region $|\eta| < 1.8$. Results are presented for three different event...
Heavy quarks (charm and beauty), produced in the initial stages of hadronic collisions in hard scattering processes, provide an important testing ground for perturbative QCD calculations. Measurements of their production as a function of the charged-particle multiplicity in pp and p-Pb collisions have recently gained interest for investigating the interplay between hard and soft mechanisms of...
The measurement of e$^{+}$e$^{-}$ pair production in ultra-relativistic heavy-ion collisions offers a way to investigate the temperature of the quark-gluon plasma created in such systems and to study the effect of the hot medium and the predicted restoration of chiral symmetry. The dominant background in ALICE originates from tracks produced via photon conversions in the detector material....
The Gyulassy-Lévay-Vitev jet quenching [1] has been implemented for Monte Carlo particle event generators, especially for the HIJING$^{++}$[2]. With this new extension, one is able to perform calculations taking into account the geometry and opacity of the colliding nuclei.
We analyzed the old and recent heavy ion data from RHIC to LHC in comparison of the opacity parameter values extracted...
The proposed sPHENIX detector at RHIC will allow state-of-the-art measurements of jets and jet correlations, making using of recent technological and conceptual advances. The kinematic reach of these measurements will overlap with those made at the LHC by taking advantage of the increased luminosity due to accelerator upgrades and the sPHENIX acceptance and rate capability. Particle jets,...
Attractors for relativistic hydrodynamics have been found recently in weakly and strong coupling physical systems. The existence of hydrodynamical attractor provides a firm theoretical foundation for the applicability of hydrodynamics in far-from-equilibrium conditions. In this work we explain how the non-equilibrium attractors of systems undergoing Gubser flow within relativistic kinetic...
We present the correct form of the nonequilibrium viscous correction to the phase space density in the relaxation time approximation that properly takes into account the space-time dependence of the thermal mass. We also investigate the impact the correction has on the bulk viscosity. This correction automatically satisfies the Landau matching condition and energy-momentum conservation. It...
Transport coefficients, such as the temperature-dependent shear and bulk viscosities, are essential QCD ingredients in the hydrodynamical description of relativistic heavy-ion collisions. While the equation of state by now is known with high precision from lattice simulations, the extraction of the transport coefficients from Euclidean simulations is extremely challenging. In particular, the...
The so-called wounded-quark model (WQM) of particle production in heavy-ion collisions extends the monte-carlo Glauber approach to sub-nucleonic degrees of freedom. In the current work, a monte-carlo model, which is conceptually similar to the WQM, is presented. The main difference from the WQM is that each parton from the projectile nucleus can interact with only one parton inside the target...
Identified particle spectra provide an important tool for understanding the particle production mechanism and the dynamical evolution of the medium created in relativistic heavy ion collisions. Studies involving strange and multi-strange hadrons, such as $K^0_S$, $\Lambda$, $\Xi^-$, and $\Omega^-$, carry additional information since there is no net strangeness content in the initial colliding...
The first observation of top quark production in proton-nucleus collisions is reported using proton-lead data collected by the CMS experiment at the CERN LHC at a nucleon-nucleon center-of-mass energy of $\sqrt{s_\text{NN}}$ = 8.16 TeV. The measurement is performed using events with exactly one isolated electron or muon candidate and at least four jets. The data sample corresponds to an...
Event-by-event fluctuations of conserved quantities have been extensively used to study the thermodynamic properties around phase transition region of QCD matter. According to lattice QCD calculation, the off-diagonal cumulants of net-charge ($Q$), net-baryon ($B$) and net-strangeness ($S$) and their ratios to diagonal cumulants are sensitive to the evolution of the system and to constrain the...
There are several theoretical models for initial conditions, which intend to describe the matter created in ultrarelativistic heavy-ion collisions. In this work, we will perform hydrodynamics computations using different initial conditions, as Wood-Saxon, Glauber, Mckln, Nexus and Gubser [1], and calculate several observables, as for instance, anisotropic flows $v_n$ [2], eccentricities...
Dedicated Time-of-Flight detectors are used for particle identification in ALICE, HADES, PHENIX, and STAR. New TOF detectors for Belle II, BESIII, LHCb, MPD, Panda, and SoLID are in various stages of development and implementation. Heavy ion detector experiments using TOF observe an anomalous early-late asymmetry in the time of flight distribution for particles of a given narrow momentum...
The electromagnetic processes of annihilation of $(e^+ e^-)$ pairs, produced
in high-energy nucleus-nucleus collisions, into heavy lepton pairs are
theoretically studied in the one-photon approximation, using the technique of
helicity amplitudes . For the process $e^+e^- \rightarrow \mu^+\mu^-$, it is
shown that -- in the case of the unpolarized electron and positron -- the final
muons...
Recent data from RHIC and LHC show that $R_{AA}$ and $v_{2}$ of charm hadrons are very similar to that of light and strange hadrons. At the same time, the $R_{AA}$ of bottom decay daughters at low $p_{T}$ seems to be less suppressed compared to light and charm hadrons, suggesting a mass suppression hierarchy. Precision open bottom measurements over a broad momentum range are needed for detail...
The density distributions of large nuclei are typically modeled with a Woods-Saxon distribution characterized by a radius $R_{0}$ and skin depth $a$. Deformation parameters $\beta$ are then introduced to describe non-spherical nuclei using an expansion in spherical harmonics $R_{0}(1+\beta_2Y^0_2+\beta_4Y^0_4)$. But when a nucleus is non-spherical, the $R_{0}$ and $a$ inferred from electron...
The study of event-by-event fluctuations requires excellent particle identification (PID) over as large as possible phase space volume. Identification of charged hadrons is achieved at momenta 0.1 − 3 GeV/c. Results of hadron identification and preliminary possibility estimation of the study of event-by-event fluctuations in MPD are presented for the current PID phase space coverage |η| ≤ 1.6.
Two-particle correlations as a function of pseudorapidity difference, $\Delta\eta$, and azimuthal angle difference, $\Delta\varphi$, are used to study a wide range of physical phenomena and provide access to the underlying physics mechanisms of particle production in collisions of both protons and heavy ions. Examples include the collective behaviour of the QGP medium, jets, quantum statistics...
Ultra-relativistic heavy-ion collisions at the LHC produce a hot and dense medium, which is a deconfined state of quarks and gluons. Jets are produced from hard processes in the initial stages of the collision and interact with the medium while propagating through it. Angular correlation analyses of hadron pairs are a convenient method to observe jets and their interaction with the medium...
The Compressed Baryonic Matter (CBM) experiment will be installed at the SIS100 accelerator at FAIR and is currently in construction. It is devoted to precision measurements of QCD matter at high net-baryon densities. With heavy-ion interaction rates up to $10\;\textrm{MHz}$, rare probes like, e.g., multi-strange hyperons will be accessible. In-medium mass distributions of vector mesons can be...
The Nuclotron-based Ion Collider fAcility (NICA) is a new accelerator complex being constructed at the Joint Institute for Nuclear Research (JINR). The general goal of the project is to study the hot and dense baryonic matter in heavy ion collisions in the energy range up to $\sqrt{s_{NN}}$ = 11 GeV and average luminosity of $L = 10^{27}$ cm$^{-2}$s$^{-1}$ for Au+Au collisions. Anisotropic...
The measurement of heavy-flavor tagged jets in relativistic heavy ion collisions is an important tool to study the properties of the hot and dense QCD medium. While the flavor dependence of jet quenching has been attributed to several physics mechanisms, such as collisional and radiative energy losses of hard-scattered partons, previous measurements at the LHC have not shown a strong flavor...
The Time-Of-Flight detector of ALICE has set a new record in the realm of large-area highly-segmented gaseous timing detectors. The apparatus covers the ALICE central barrel with high-performance MRPC strip detectors for a total active area of 140 square metres segmented into about 150000 readout channels, delivering crucial particle-identification information and contributing to a diverse...
Modern RICH detectors often employ Multianode Photomultiplier tubes (MAPMTs), providing excellent timing properties, good quantum efficiency, fine granularity and low dark noise. The CBM RICH detector, as well as the upgraded HADES RICH detector, will both use, actually even share, Hamamatsu H12700 MAPMTs for spacially resolved Cherenkov photon detection. A new FPGA-TDC based electronic...
The Beam Energy Scan (BES) program at the Relativistic Heavy-Ion Collider has shown hints of a critical point and first order phase transition at the BES energies. Key measurements for locating the critical point and determining the first order phase transition are limited by poor event plane resolution, limited statistics and a TPC-only centrality determination. A new event plane and...
The Compressed Baryonic Matter experiment (CBM) at FAIR aims to study the area of the QCD phase diagram at high net baryon densities and moderate temperatures using collisions of heavy ions at center-of-mass energies of a few GeV per nucleon. Anisotropic transverse flow is among the key observables to study the properties of matter created in such collisions.
The CBM...
Heavy quarkonia in high-energy collisions is a sensitive probe of Quantum Chromo Dynamics (QCD) due to its large scale provided by the heavy quark mass relative to the hadronization scale. The angular distribution of decay leptons from heavy quark bound state is a key observable to test heavy quarkonia production mechanisms and bound state formation. Charmonium, in particlular, is an essential...
Bound states of heavy quarks produced in collisions of large nuclei have been the object of intense experimental and theoretical interest for decades, but precise quantification of the various mechanisms affecting their production from p+A collisions to A+A collisions is still not totally understood. One advantage of the RHIC accelerator complex is the flexibility of beam species available...
Heavy quarks are important probes of the properties of the Quark Gluon Plasma (QGP) produced in heavy ion collisions. At RHIC energies charm and bottom quarks are valuable as they are produced primarily in the initial collision, and not through the thermalization of the QGP. PHENIX has previously published, and shown, the invariant yields of bottom and charm quarks in Au-Au collisions at...
Recent measurements at both RHIC and the LHC continue to indicate that particles produced in small collision systems exhibit collective behavior similar to those observed in large collision systems. The PHENIX experiment has measured substantial elliptic ($v_2$) flow coefficients for charged hadrons at midrapidity in a suite of small collision systems over a range of collision energies. We...