Charm quarks are mainly created in hard processes at the beginning of the heavy-ion collisions and can be used as a tool to study properties of the Quark-Gluon Plasma (QGP). The modification to D-meson production in heavy-ion collision is sensitive to the energy loss of charm quarks in the QGP. The Heavy Flavor Tracker was installed at the STAR experiment in 2014 and enables the topological...
The study of short-lived hadronic resonances in heavy-ion collisions
provides information about strangeness production and the hadronic phase of the
system. Resonance measurements in pp collisions set the baseline to which heavy-ion collisions are compared as well as contribute to the understanding of particle
production mechanisms through comparison with different model predictions. At the...
Heavy quarks (charm and beauty) are effective probes of the QCD matter formed in high-energy nuclear collisions. They are produced in hard partonic scattering processes occurring in the initial stage of the collisions, propagate through the medium and interact with its constituents. Therefore, they probe the entire evolution of the system.
The study of their production in pp collisions...
Understanding $J/\psi$ meson hadroproduction has been a long-term effort both experimentally and theoretically. However, none of the existing theoretical models can successfully describe both $J/\psi$ transverse momentum ($p_{T}$) spectrum and the polarization. Furthermore, the composition of inclusive $J/\psi$ is complicated, including direct production via gluon fusion, parton...
In the early stages of collisions, hard-scattering of the quarks and gluons from incoming nuclei results in the production of high momentum partons which fragment into collimated sprays of hadrons called ``jets". At lower transverse momenta where the event-by-event reconstruction of jets becomes difficult, their event averaged effect generates observable correlations, which have been studied...
In view of the LHC Run3 starting in 2021, the ALICE experiment is preparing a major upgrade including the construction of an entirely new inner silicon tracker (the Inner Tracking System) and a complete renewal of its Online and Offline systems.
During its Run3, LHC will deliver Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.5 TeV with a peak luminosity $L=6\times10^{27}\,cm^{-2}\,s^{-1}$...
sPHENIX is the next generation detector at the Relativistic Heavy Ion Collider (RHIC) designed to explore the properties of the quark-gluon plasma through measurements of jet properties and upsilon spectroscopy The detector consists of a 1.5T superconducting solenoid, tracking, electromagnetic and hadronic calorimeter with a high speed data acquisition system. The calorimeters use a common...
Heavy flavor quarks are dominantly produced from initial hard partonic scattering processes in high-energy nuclear collisions. Their interactions with nuclear medium are sensitive to the medium properties. The Heavy Flavor Tracker (HFT) has been successfully integrated into the STAR experiment at RHIC since early 2014. Based on the state-of-the-art Monolithic Active Pixel Sensor (MAPS)...
Relativistic hydrodynamic simulations play a key role in exploring the QGP bulk property and the QCD phase transition from analyses of high-energy heavy-ion collisions at RHIC and LHC. From the intensive study based on relativistic viscous hydrodynamic models with event-by-event initial fluctuations, we can extract detailed information of the bulk feature of the QGP such as transport...
The proposed sPHENIX experiment is designed to reconstruct jets in heavy-ion collisions at RHIC. A crucial component to reconstructing the energy of jets is the sPHENIX calorimeter system which includes electromagnetic and hadronic calorimeters. The hadronic calorimeter (HCal) is a sampling calorimeter with alternating layers of steel absorber and scintillating tiles. There is an inner and...
We construct a blast wave model with viscous corrections by calculating the viscous stress tensor from the parameterized flow field in the Navier Stokes approximation. We then use statistical Bayesian analysis tools to extract the shear viscosity over entropy ratio at the kinetic freeze-out temperature T=T_fo from experimental data. Note that this approach is complementary to the existing...
Heavy ion collisions at extremely high energy, such as the top
energy at RHIC and the typical energy at LHC, exhibit the property of
transparency where there is a clear separation between the almost
net-baryon-free central rapidity region and the net-baryon-rich
fragmentation region. We calculate the net-baryon rapidity loss and
the nuclear excitation energy using the energy-momentum tensor...
We compute the suppression, angular, and rapidity distribution of single open heavy flavor and the momentum, angular, and rapidity correlations for pairs of open heavy flavor at RHIC and LHC from an AdS/CFT-based energy loss model. We quantitatively compare these strongly-coupled QGP predictions to the weakly-coupled QGP predictions of Nahrgang et al., PRC90 (2014) [arXiv:1305.3823]. In the...
The powerful photon fluxes of relativistic nuclei provide a possibility
to study photonuclear and two-photon interactions in ultra-peripheral collisions (UPC)
where the nuclei do not overlap and no strong nuclear interactions occur.
Within Vector-meson Dominance Model (VDM), $\rho^0$ contribution prevails in QCD photon structure
function and gamma+A -> $\rho^0$ +A process in heavy-ion UPC...
Effects related to the angular momentum of the mid-rapidity source created in a heavy ion collision are under intense study. While the angular momentum of the collision is completely determined by the impact parameter and the beam direction, the angular momentum of the mid-rapidity source may fluctuate event to event. We study these fluctuations in a Glauber calculation and with the UrQMD...
Longitudinal multiplicity correlations and longitudinal asymmetry studies in heavy-ion collisions have suggested a hint of some asymmetry in the initial geometry and its effects in the final state particle fluctuations. In addition to the expansion of the medium in the transverse direction, commonly quantified using Fourier coefficients ($v_{n}$), the initial geometry and resulting...
Azimuthally differential HBT is a powerful tool for investigating the source shape at freeze out.
In heavy ion collisions, radial and anisotropic flow of the expanding medium have been observed.
These hydrodynamic expansions result in the deformation of the initial geometry.
Studying the deformation of the source shape is important for investigating the dynamics of the system evolution.
In...
The study of beauty production in heavy-ion collisions is considered one of the key measurement to address the flavour-dependence of in-medium energy loss in PbPb collisions. In pPb collisions, studies of b-quark production can also provide insights into the relevance of cold nuclear matter effects in the heavy-flavour sector. The CMS experiment has excellent capabilities for measuring b-quark...
Jets initiating from a B-quark (B-jet) are sensitive to the collisional energy loss of the quark when traversing through Quark Gluon Plasma (QGP). Among the light jet background, the rare B-jets can be identified by utilizing some characteristic B-hadron decay properties, such as its long lifetime and semi-leptonic decay modes. With the proposed sPHENIX detector at RHIC, we study a variety of...
Jet-hadron and di-hadron correlations are sensitive to the low momentum and large angle modifications induced by interactions with the medium and allow higher precision measurements than jet-by-jet measurements because the background can be determined by averaging over several jets. However, the combinatorial background has limited the precision of these measurements. The Zero Yield At...
The string melting version of a Multi-Phase Transport (AMPT) model
can reasonably describe the $dN/dy$ yields, $p_{T}$ spectra and
anistropic flows of pions and kaons at low $p_{T}$ in heavy ion
collisions at RHIC and LHC energies [1,2].
However, it failed to reproduce the $dN/dy$ and $p_{T}$ spectra of
baryons [2,3]. For example, it overestimates the proton yield at
mid-rapidity but...
Femtoscopy studies of protons and Lambda hyperons have been carried out in pp collisions at 7 TeV, as measured by the ALICE collaboration. Contrary to the more complex situation in heavy-ion collisions, the Lambda-proton femtoscopy measurement in pp collisions allows us to investigate the scattering parameters for the hyperon-nucleon pair as the source that characterises the emission of the...
We present recent STAR measurements of the anisotropic flow coefficients $v_n$ ($n = 1-6$) in Au+Au, Cu+Cu, Cu+Au collisions at $\sqrt{s_{NN}} = 200$~GeV and U+U collisions at $\sqrt{s_{NN}} = 193$~GeV and for Au+Au collisions spanning the full range of the first beam energy scan ($7 - 200$~GeV: BES-I). For a given beam energy, the differential $v_n$ measurements indicate acoustic scaling...
We propose a novel technique, using the expansion of the effective potential in a base of harmonic functions, to study the Functional Renormalization Group (FRG) method at
finite chemical potential. Within this theoretical framework we determined the equation of state and the phase diagram of a simple model of massless fermions coupled to scalars through Yukawa-coupling at the zero-temperature...
The determination of transport coefficients plays a central role in characterizing hot and dense nuclear matter. In the present work we calculate the electric conductivity of hot hadronic matter by extracting it from the rho-meson spectral function, as its zero-energy limit at vanishing momentum. Recent calculations of the electric conductivity in hot nuclear matter have been performed in...
ALICE at the LHC is designed to explore the quark-gluon plasma (QGP) state resulting from high energy heavy-ion collisions. The ALICE Electromagnetic Calorimeter (EMCal) can be used to measure hard probes of the initial collision, including jets, high $p_T$ photons, neutral mesons ($\pi^0$, $\eta$, $\omega$), and electrons. For LHC Run 2 (2015-2018) an additional detector was installed on the...
Heavy quarks are produced through initial hard scatterings in heavy-ion collisions, and are affected by the hot and dense medium throughout its evolution when propagating in the medium. Several models have predicted that fluctuations in the initial conditions, together with frequent interactions with the QGP medium could lead to a finite triangular flow $v_3$ for the $D^0$ meson.
We present...
Jets are modified in relativistic heavy-ion collisions due to jet-medium interactions. Measurements of jet medium modifications have so far been obscured because of the large underlying anisotropic flow background. In this analysis we devise a method to subtract all orders of the flow background using data themselves. The flow background subtracted away-side jet correlation shape and width...
Metastable domains of topological charges in QCD can cause chirality
imbalance and, under the strong magnetic field present in heavy-ion
collisions, result in charge separation along the magnetic field, a
phenomenon called the Chiral Magnetic Effect (CME) [1]. Charge
separation can also be caused by intrinsic particle correlations coupled
with elliptic flow anisotropy, a major background for...
We present the analysis of the transverse momentum ($\textit{p}_\text{T}$) spectra for primary charged particles as well as the nuclear modification factor ($\text{R}_\text{AA}$) in Pb--Pb collisions at $\sqrt{s_\text{NN}}=5.02\,\text{TeV}$, using the data collected in November 2015 by ALICE at the LHC. In addition, a new analysis of data at $\sqrt{s_\text{NN}}=2.76\,\text{TeV}$ will be...
Using the 5.02 TeV collision-energy per nucleon pair PbPb and pp LHC data of 2015, CMS measured the spectra of charged particles in the $0.5 < p_{T} < 400$ GeV (pp) and $0.7 < p_{T} < 400$ GeV (PbPb) transverse momentum ranges for central rapidities. The corresponding nuclear modification factors, $R_{AA}$, are measured is several bins of centrality, from the most central 0-5% to the...
Azimuthal anisotropy $v_2$ is a useful tool for the study of the properties of the quark-gluon plasma (QGP). Recent studies with parton transport models suggest, however, that the majority of light quark $v_2$ comes from the anisotropic escape of partons, not hydrodynamic flow [1-4]. Heavy quarks, produced by hard scatterings at early times in relativistic heavy ion collisions, are regarded as...
Charmonium production is among the promising signatures for quark-gluon plasma
formation in relativistic heavy-ion collisions. Here we investigate hot-medium effects on the suppression of the $J/\Psi$ yields in Pb$+$Pb and p$+$Pb at $\sqrt{s_{NN}} = 5.02$ TeV in a model that encompasses screening of the real part of the potential, damping of the $c\bar{c}$ binding through the imaginary part,...
Dileptons ($l^{+}l^{-}$) are produced in all the stages of the heavy-ion collisions, and escape with minimum interaction with the strongly interacting medium. Thus, $l^{+}l^{-}$ pair measurements play an essential role in the study of hot and dense nuclear matter, created in heavy-ion collisions. Recently, a significant excess of $J/\psi$ yield at very low transverse momentum ($p_{T}<0.3$...
COLD NUCLEAR MATTER EFFECTS ON NON-PHOTONIC ELECTRON PRODUCTION MEASURED IN p+Au COLLISIONS BY THE STAR EXPERIMENT
Zachariah Miller (UIC)
Due to their large masses, heavy flavor quarks are dominantly produced in initial hard parton scattering processes in high-energy heavy-ion collisions. They experience the full evolution of the strongly interacting Quark-Gluon Plasma (QGP) created in...
Chirality is the only fundamental symmetry in the nuclear matter. The study of the vorticity and possible chiral vortical effect allows us to access this fundamental property of the hot and dense nuclear matter created in high-energy nuclear collisions, especially at the high baryon density region. Global polarization parameters of identified particles can be extracted from the azimuthal...
The RHIC beam energy scan program allows us to investigate the phase-diagram of QCD matter. The nature of the quark-hadron transition can be studied through analyzing the space-time structure of the hadron emission source. One of the best tools to gain information about the source is the measurement of Bose-Einstein or HBT correlations of identical bosons. In our latest measurements, we...
Field-complexification approaches to the sign problems in chiral models at finite chemical potential are examined analytically and numerically.
We apply the thimble integration method to the 1-dimensional Thirring model at finite chemical potential to show that the multi-thimble contributions with alternating signs are important to reproduce the crossover behavior. We also use the complex...
Confinement and chiral phase transitions are remarkable nonperturbative phenomena emerging from QCD and QCD-like theories. A theoretical understanding of these transitions and their interrelations is of fundamental importance. While it is widely perceived that their dynamics arises from nontrivial topological configurations in Yang-Mills theories, a concrete and sophisticated realization of...
Although it was demonstrated more than 13 years ago that the
increase in midrapidity $dN_{\rm ch}/d\eta$ with increasing centrality
of Au+Au collisions at RHIC was linearly proportional to the number
of constituent quark participants ($N_{qp}$) in the collision,
it was only in the last few years that generating the spatial positions of the
three quarks in a nucleon according to the...
The planned sPHENIX experiment is a major initiative and a key part of the future of heavy ion physics in the US. One of the key pillars of the planned physics program is detailed measurements of jets, which requires hadronic calorimetry over a large solid angle. The sPHENIX hadronic calorimeter (HCal) is a sampling calorimeter comprising alternating layers of steel absorber and plastic...
Heavy quarks are widely used in measurements in ultra-relativistic heavy-ion collisions to provide information on the Quark-Gluon Plasma (QGP) properties. This is the case for all particles produced in hard scattering processes, that can be reconstructed in jets, since they are mainly produced before the complete medium formation and can interact with the plasma during its early stages and its...
Particle correlations in azimuth ($\varphi$) and pseudorapidity ($\eta$) difference are a powerful tool, widely used in all collision systems to study numerous sources of correlations. Examples include the collective behaviour of the QGP medium, jets, quantum statistics or Coulomb effects, conservation laws, and decays of resonances. In this talk, we report such measurements from ALICE with...
The measurement of heavy flavour production is a powerful tool to study the properties of the high-density QCD medium created in heavy-ion collisions as heavy quarks are sensitive to the transport properties of the medium and may interact with the QCD matter differently from light quarks. In particular, the comparison between the nuclear modification factors of light- and heavy-flavour...
Heavy quarks are mainly produced by hard processes during the early stage of heavy-ion collisions and before the formation of the quark-gluon plasma (QGP). As most of the heavy quarks are expected to propagate through the medium during its evaluation, they can encode information on different stages of the medium. The D$^0$ meson is the lightest meson containing a charm quark. Measurement of...
Heavy-flavour production in p--Pb collisions is sensitive to Cold Nuclear Matter (CNM) effects such as the modification of the nuclear Parton Distribution Functions (PDFs), initial-stage radiation or energy loss, and multiple scattering of partons in the nucleus. These initial-state effects can induce a significant modification of the heavy-flavour production at low momentum and their...
Heavy charm quarks are produced dominantly in the initial stage of high-energy heavy-ion collisions. They take part in the whole evolution of the medium, interact with the produced Quark-Gluon Plasma (QGP) and lose energy due to collisional and radiative processes. Therefore, they serve as unique probes of the QGP transport properties. Charm quarks can be studied by measuring D mesons that...
The ALICE experiment at the LHC is designed to investigate the properties of the Quark-Gluon Plasma by studying high energy pp, p-Pb and Pb-Pb collisions. The parton energy loss in the medium can be examined by measuring the production of charged particles and their nuclear modification factor at high transverse momentum. In ALICE, charged particles are measured with the Time Projection...
The two-wave quark production scenario can be investigated experimentally by measurements of balance functions of identified particle pairs [1]. In this scenario, quark-antiquark pairs produced in the earlier stages of the collision are pulled apart due to collective effects, while pairs produced during hadronization are unlikely to separate. We present the measurements of such balance...
The sPHENIX Collaboration at RHIC is planning a major upgrade to the PHENIX experiment by constructing an entirely new spectrometer based on the former BaBar solenoid magnet that will enable a comprehensive study of jets and heavy quarkonia in relativistic heavy ion collisions. The calorimeter system of the sPHENIX experiment will cover an acceptance of ±1.1 units in pseudorapidity and full...
The latest results on jets and heavy flavor by the LHC experiments demonstrate the need to explore complementary measurements at RHIC, providing lower energies and lower initial virtualities. The proposed sPHENIX detector at RHIC will explore the quark-gluon plasma by measuring jets, b-tagged jets, jet correlations and the three upsilon states. The sPHENIX detector will cover full azimuth and...
The ALICE detector is designed for study of Quark-Gluon Plasma in heavy ion collisions at the LHC. Major upgrades of the detector are planned before the LHC run 3 from 2021. Along with a much higher rate capability to fully utilize the luminosity to be delivered, ALICE will also have enhanced physics capabilities with new addition of detector components.
The Muon Forward Tracker (MFT) is...
Di-hadron correlations in relative azimuthal angle and over large pseudorapidity separations ($\Delta\eta$) recently revealed evidence for collectivity in the small collision systems of pp and p--Pb.
In this analysis we investigate the correlations between tracks in the Inner Tracking System and energy deposition in the Forward Multiplicity Detector (FMD) ($1.7<\eta<5$,...
Jets and their modifications due to partonic energy loss provide a powerful tool to study the properties of the QGP created in
ultrarelativistic heavy-ion collisions. For anti-$k_t$ jets with a resolution parameter $R=0.4$, previous
measurements of the di-jet asymmetry $A_J$ at STAR [1] indicate that the observed imbalance of an initial ``hard-core" di-jet selection with ...
Jet imbalance is a known signature of jet energy loss in the hot, dense medium produced in heavy ion collisions. New measurements of the dijet asymmetry at ATLAS are presented using the 2011 Pb+Pb data from the LHC at $\sqrt{s_{NN}}=2.76\mbox{TeV}$ using jets reconstructed with the anti-k_t algorithm with parameters R=0.3 and 0.4. While previous measurements demonstrated a significant effect...
The Compressed Baryonic Matter (CBM) experiment at FAIR is designed to explore the QCD phase diagram in the region of large baryochemical potentials. One of the important experimental observables are dileptons, which probe the properties of the matter in the fireball from the first stage of the collision until freezeout. Dileptons will be produced over a wide range of invariant mass region...
Direct Photon Simulations with POWHEG BOX
Direct photons provide particular insight into nuclear collisions. Since they give immediate access to the energy scale of a hard scattering, direct photons allow further constraints of (nuclear) parton distribution functions, especially on the poorly known distribution of initial state gluons. Direct photons have, moreover, the potential to yield...
The suppression of the quarkonium states in AA collisions, observed by the STAR and PHENIX collaborations at RHIC and by the CMS and ALICE collaborations at LHC, is one of the most convincing evidence for the creation of the Quark Gluon Plasma (QGP). The precise survival of excited states vs ground states could even allow to measure the highest temperature reached in those collisions,...
I will discuss the dynamics of the hadronic phase in ultrarelativistic nuclear collisions in the context of the UrQMD transport model.
I will present results on the hadronic phase effects on final state observables like hadron multiplicity and collective flow. These results show that especially hadron resonance properties and multiplicities, which are very sensitive probes of the hadronic...
Hadron yields obtained from elementary collisions up to heavy-ions
have been successfully described by
thermal models with a few parameters such as temperature and baryon
chemical potential [1, 2].
However, the LHC$/$ALICE experiment has recently found that the proton
and antiproton yields are a factor of 2 too low compared to thermal
description [3]. This has been shown to arise...
Very strong magnetic fields can arise in non-central heavy-ion collisions at ultrarelativistic energies, which may not decay quickly due to induced currents in the conducting plasma. Presence of very strong magnetic fields in the plasma (of order $10^{15}$ Tesla) during early stages in RHICE has been explored extensively recently primarily in connection with the so called chiral magnetic...
We study the influence of the finite width of rho meson on the pion momentum distributions and anisotropies. We evaluate the rho-meson properties in the S-matrix framework, and implement them in the hydrodynamical description of the expansion dynamics.
We show that the proper treatment of rho mesons modifies the spectrum of daughter particles, and thus the final observable distributions [1]....
Transport coefficients of hot hadron and QGP matter characterize their behavior upon external perturbations. Although this can be interesting by itself, they are important input for many phenomenological models that explain data for heavy-ion collisions. In this talk, we present our recent results from kinetic theory for the electric conductivity in a hot hadron gas (see Phys.Rev.D 93...
A central goal of heavy ion experiments at the RHIC and LHC Collider is to characterize the properties of the strongly couple Quark Gluon Plasma (sQGP) and the QCD phase diagram. Harmonic Flow measurements of identified particles play an essential role for such studies since they can give insight on the transport coefficients of the sQGP. In this poster we report on the measurements of...
The particle species dependence of elliptic flow ($v_{2}$ ) at intermediate
transverse momentum ($p_{T}$ ) provide a mean to investigate the hadronization mechanism
of the dense medium formed in heavy ion collisions. At intermediate
$p_{T}$ (> 2 GeV/c), $v_{2}$ of different particles exhibit an interesting scaling behaviour when
divided by their constituent number of quarks (NCQ-scaling). At...
Understanding the properties of extreme phases of nuclear matter created in relativistic heavy ion collisions is one of the major challenges in theoretical physics. A question that is central to the understanding of the very early stages of such collisions near the cross-over temperature of QCD is: How do non-conformal properties affect the resulting plasma? In this presentation we address...
In heavy-ion collisions, strong interactions occur between hard scattered partons and the Quark Gluon Plasma.
Dihadron azimuthal correlations with high $p_T$ trigger particles are a valuable tool to study the interactions between jets and the medium.
Previously, it was shown that dihadron azimuthal correlations are expected to depend on the azimuthal angle of trigger particle relative to the...
Event-by-event fluctuations contain information on the dynamics and correlations in pp and heavy-ion collisions. In nuclear collisions event-by-event fluctuations of the mean transverse momentum ($p_{\rm T}$) are used to study collective phenomena. To contribute to the understanding of the collective effects in pp collisions which have been recently shown by experiments at the LHC, and to...
Event-by-event measurement of anisotropic flow is crucial to understand the initial state conditions and particle production in heavy-ion collisions. Uranium nuclei provide a unique opportunity to study this, owing to its intrinsic prolate shape and the presence of different overlap configurations in the central collisions like body-body and tip-tip. We present the measurement of the...
Kharzeev et al. [1] proposed strong P and CP violation in the hot dense matter created in non-central heavy-ion collisions. The strong magnetic field (B $\sim 10^{15}$ T) induces a separation of electric charge along the direction of the magnetic field resulting in the Chiral Magnetic Effect (CME). This effect has been experimentally observed by the ALICE experiment for Pb-Pb collisions at...
High energy heavy ion collisions are found to be excellent factories for producing heavy hadrons and composite particles including light (anti)nuclei. With upgraded detectors, we are now able to measure hadrons beyond ground states. Thus, heavy ion collisions provide new ways of studying exotic hadrons, which are the primary interests in hadron physics, as many experiments other than heavy ion...
Jets are a fundamental feature of high-energy particle interactions.
They result from the fragmentation of hard-scattered partons,
a key process of Quantum Chromodynamics (QCD).
The study of the charm content of jets is interesting because up to now
it has eluded a precise quantitative understanding in the framework of perturbative
QCD (pQCD). This is in contrast with other hard processes...
In heavy-ion collisions, measurements of short-lived hadronic resonances can constrain properties of the late hadronic phase, including its lifetime. Along with stable hadrons, resonances are also used to study the flavor dependence of parton energy loss at high transverse momentum and anomalous baryon-to-meson ratios at intermediate momentum. The ALICE detector, which provides excellent...
It is widely expected that the growth of parton densities at low x predicted from linear QCD evolution cannot continue indefinitely, and that non-linear effects will lead to gluon saturation. We propose the measurement of forward(3.5 < y < 5) direct photons in a new region of low x(∼ 10 −6 ) in proton-nucleus collisions at the LHC as a decisive probe of gluon saturation. In order to...
A strong suppression of hadron yields in d+Au collision has been seen at forward rapidities at RHIC, which would be a sign for the onset of gluon saturation in the heavy Au nucleus.
Direct photons provide complementary insight towards the physical nature of the suppression of hadron yields since they are directly sensitive to the gluon density at forward rapidities (through gluon Compton...
Forward-backward (FB) correlations are usually measured between observables obtained in an event-by-event analysis in two separated pseudorapidity intervals.
The conventional observable for the FB correlations analysis is the charged particle multiplicity.
In the present study, instead of the multiplicity, we took an intensive observable, namely the event-averaged transverse momentum of...
Azimuthal anisotropies of particle production in high energy heavy ion collisions have proven to be an excellent tool for investigating the initial geometry and the bulk properties of the Quark Gluon Plasma (QGP). Azimuthal anisotropy, measured through Fourier coefficients v_n, have been measured at mid-rapidity and are used to constrain the initial geometry and viscosity-over-entropy ratio...
The system created in non-central nucleus-nucleus collisions possesses
large orbital angular momentum. Due to this, particles produced in such
a system can become globally polarized along the direction of the
system's angular momentum. We present global polarization measurements
for $\Lambda$ and $\bar\Lambda$ hyperons in Pb-Pb collisions at
$\sqrt{s_{\rm NN}}=2.76$ GeV performed with the...
We study the equilbriation for gluons far from thermal equilibrium in relativistic kinetic theory with Color Glass Condensate (CGC) inspired initial distribution. Using a partonic cascade approach BAMPS with newly developed stochastic scheme for implementing the quantum statistics, we now simulate here a static gluonic matter with elastic collisions. We show that under such a elastic...
Collisions of ultrarelativistic heavy ions provide an opportunity to investigate strongly interacting matter under extreme energy densities and temperatures. Interaction of hard scattered partons with the hot and dense medium leads to a suppression of the observed jet yields, known as jet quenching. Along with other experimental approaches, studies of the jet substructure have the prospects of...
We study the behavior of the real and the imaginary parts of the static
potential between a heavy quark and its anti-quark,
which are in relative motion with respect to the QGP medium. The heavy
quark-antiquark complex potential is obtained by correcting both the
Coulombic and the linear terms in the Cornell potential
through the dielectric function in real-time formalism using the hard...
Both open and hidden heavy-flavor physics in nuclear collisions is entering a new and exciting stage towards reaching a clearer understanding of the new experimental results with the possibility to link them directly to the advancement in lattice QCD.
Recent results from experiments and theoretical developments regarding open and hidden heavy-flavor dynamics have been debated at the Lorentz...
Heavy quarks (charm and beauty) are unique probes used to understand the properties of the QCD medium produced in ultra-relativistic heavy-ion collisions. Due to their large masses, they are created in the early stages of the collisions and experience the full evolution of Quark-Gluon Plasma (QGP). They interact with its consitutents and lose energy as they travel through the medium. Heavy...
Both the energy and momentum transfer dependence of vector meson photoproduction off the proton are promising signatures of gluon saturation. In this talk, the momentum dependence of exclusive vector mesons such as $\rho^{0}$ and $\Upsilon$ photoproduction will be presented. The $\rho^{0}$ cross section measurement will be presented for $t$ values above 0.5 GeV for the first time, which was...
We use an improved version of the $SU(3)$ flavour parity doublet quark-hadron model to investigate the baryon number susceptibilities near the de-confinement and nuclear liquid-gas transition. The parity doublet model has been improved by adding the six-point interaction of the $\sigma$ (and $\zeta$) meson in the effective mean field Lagrangian, resulting in a good description of nuclear...
Results with the new HIJING++ will be presented here for hadron production in high-energy heavy ion collisions. The recently developed HIJING++ version based on the latest version of PYTHIA8 and contains all the nuclear effects has been included in the HIJING2.1. We also included an improved version of the shadowing parametrization and jet quenching. Here we summarize the mayor changes of the...
Events that started with very similar initial conditions should also evolve similarly and produce similar single-particle distributions of hadrons. This is natural consequence of hydrodynamic description of a collision. We present a novel method for data analysis. It compares the histograms of azimuthal hadron distributions from each event and organizes the events in such a way that those with...
Hydrodynamic or local thermal fluctuations are an important source of event-by-event fluctuations in relativistic heavy-ion collisions. It is a challenge to identify and investigate their effects on experimental observables. Application of the theory of hydrodynamic fluctuations to the boost-invariant (Bjorken) flow has shown that
long-range (rapidity) two-particle correlations are induced by...
In order to test the applicability of hydrodynamics to small systems, we simulate p+p collisions at $\sqrt{s}=7\text{ TeV}$ and p+Pb collisions at $\sqrt{s}=5.02\text{ TeV}$ using the superSONIC package, which consists of AdS/CFT pre-equilibrium flow, 2+1-dimensional viscous hydrodynamics, and a hadron cascade stage. The initial conditions for hydrodynamics are generated using a Glauber-type...
The flavor dependence of jet quenching in the QGP is an important tool to study radiative and collisional energy loss in the medium using probes of different mass scales. B-tagged jet nuclear modification measured at LHC has not shown a parton flavor dependence at high $p_T$, where the quark mass is much smaller than the $p_T$ scale. The proposed sPHENIX experiment at RHIC will measure...
I will discuss recent progress in the determination of the quark matter equation of state (EoS) and its applications to the phenomenology of neutron stars (NSs). The current state-of-the-art matched QCD EoS comes from the work of Kurkela el al. (2014), in which the authors matched chiral effective theory (cEFT) at low densities to pQCD at high densities. Since then, the $T=0$,...
PHENIX has studied the production of muons from the semi-leptonic decay
of heavy-flavor mesons in the forward rapidity region 1.2<|eta|<2.2. The
measurement of heavy quark production in p+p collisions is important as
a baseline for studying hot and cold matter effects in heavy-ion
collisions, and is a test of pQCD theory. In p+Au collisions, we can
study cold-nuclear-matter (CNM) effects on...
Nuclear modification factors ($R_{AA}$ or $R_{CP}$) of charged hadrons and
identified particles for heavy-ion
collisions at RHIC and LHC have been used to quantitatively study
the interplay of the partonic collectivity and hadronic
suppression. The outward pressure of strongly interacting partonic
medium in the early stage of the collision creates radial boost, which
is the key factor for...
The modified number of constituent quark (NCQ) scaling
$v_{n}/n_{q}^{n/2} \sim KE_{T}/n_{q}$ for mesons and baryons and the
scaling relation $v_{n} \sim v_{2}^{n/2}$ for higher-order
anisotropic flows, which were observed experimentally, have been
investigated at the top energy of Relativistic Heavy-Ion Collider. It has been found that the modified
NCQ scaling can not be obtained from the...
The production of charmonium states (for instance J/$\psi$ and $\psi(2S)$) is one of the probes studied to investigate the properties of the Quark-Gluon Plasma (QGP) formed in high-energy heavy-ion collisions. Indeed, the presence of a deconfined medium should modify the charmonium production yield, due to a competition of the color screening of the charm quark anti-quark potential and the...
A large excess in the yield of J/ψ at very low transverse momentum compared to the expectations from the nuclear overlap region was recently reported by ALICE in peripheral Pb-Pb collisions at √sNN=2.76 TeV. The observation, made at forward rapidity (2.5<y<4.0) for pT<300 MeV/c using the muon spectrometer, is suggestive of coherent J/ψ photo-production, similar to the measurements done in...
In this work, we explore the interplay between soft (low-$p_T$) and hard (high-$p_T$) particles
in the hadronic phase
of Pb+Pb collisions with $\sqrt{s_{NN}} = 5.02\,\textrm{TeV}$
and $\sqrt{s_{NN}} = 2.76\,\textrm{TeV}$ at the LHC.
The partonic jet energy loss is handled by MARTINI in our simulations,
given that the bulk dynamics of the QCD medium is calculated
with the IP-Glasma...
ATLAS uses a jet reconstruction algorithm in heavy ion collisions that takes as input calorimeter towers of size 0.1x0.1 in $\Delta\eta$ x $\Delta\phi$ and iteratively determines the underlying event background. This algorithm, which is different from the standard jet reconstruction used in ATLAS, is also used in the proton-proton collisions used as reference data for the Pb+Pb and p+Pb. ...
Jet energy loss in the Quark Gluon Plasma (QGP) is an active area of research, with many different measurement techniques attempting to determine its properties. One technique is to measure the azimuthal correlations of a trigger jet and the associated hadrons in the event. These measurements, known as jet-hadron correlations, are expected to be sensitive to broadening and softening of an...
Femtoscopy allows us to measure the space-time characteristics of the system
at the moment of particle emission using two-particle correlations. In comparison to the most abundant pions, kaons provide a cleaner probe as they are less affected by resonance decays. Since kaons contain strange
quarks and have smaller cross section with hadronic matter than pions, they
may be sensitive to...
We present results from a femtoscopic analysis of Lambda-Kaon correlations in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV by the ALICE experiment at the LHC. All pair combinations of $\Lambda$ and $\bar{\Lambda}$ with K$^{+}$, K$^{-}$ and K$^{0}_{S}$ are analyzed. The femtoscopic correlations are the result of strong final-state interactions, and are fit with a parametrization based on a...
Correlations measurements as a function of the azimuthal angle and rapidity are very useful for investigating particle productions in high-energy nucleus- nucleus collisions.
Long range, near side angular correlations have been observed in high multiplicity $pp$ and $p$-Pb collisions at the LHC energies.
Possible explanations of the long range correlations in high multiplicity $pp$ and $p$-Pb...
Direct photons, which are produced during all stages of a heavy-ion collision, directly probe the conditions of their production environment. The large yield and large anisotropy of low momentum direct photons observed in 200 GeV Au+Au collisions poses a significant
challenge to theoretical models. Measurements at a lower collision energy may provide
new insight on the origin of the low...
One of the major goals in heavy ion physics is to study the property of Quark Gluon Plasma (QGP). Direct photons turn out to be golden probes due to their small interaction with the medium. Direct photons are also produced in every known or conjectured stages of the collision hence carrying information of the entire evolution of the system. PHENIX has discovered a large excess of thermal...
Results from non-perturbative QCD indicate that chiral symmetry may be restored in the hot and dense matter produced in relativistic heavy ion collisions. This restoration would affect the vector meson mass spectrum and could be examined with the ALICE detector at the LHC. One of the most promising probes to study these effects are dileptons ($μ^{+}μ^{-}$ and $e^{+}e^{-}$) from ρ meson decays...
We study the impact of baryon-antibaryon annihilation into three mesons on heavy-ion collisions. The reactions are based on the quark rearrangement model in the light and strange sector. Box simulations with periodic boundary conditions confirm that our implementation of these reactions fulfills the detailed balance relation on a channel by channel basis. We implement these reactions into the...
While the study of charmonium production provides a unique opportunity to access basic QCD dynamics, the exact production mechanisms are not yet fully understood. Many different models can adequately describe the cross-section and transverse momentum ($p_T$) distribution of charmonium produced in proton-proton collisions, but predict different polarization. Thus, charmonium polarization...
The first measurement of the $\Lambda$(1520) baryonic resonance in pp collisions at $\sqrt{s}=13~$TeV, performed using the ALICE detector at the LHC, is presented. The analysis details for invariant mass reconstruction in the hadronic decay channel $\Lambda$(1520) $\rightarrow$ pK$^{-}$ are discussed. The invariant mass distributions for various $p_{\rm T}$ intervals are obtained from 0 <...
Produced in hard-scattering processes in the initial stage of the collision, heavy quarks probe the whole evolution of the deconfined system (Quark-Gluon Plasma) formed in ultra-relativistic heavy-ion collisions. The measurement of the azimuthal anisotropy of D-meson production is crucial to understand charm quark in-medium energy loss and its coupling to the system. ALICE measured a positive...
The production of Upsilon in p+Pb collisions is a key ingredient for understanding ‘cold’ nuclear effects, relevant both for nuclear PDF studies as well as ‘hot’ nuclear matter studies. The ATLAS experiment has measures the Upsilon in its ground and excited states via the dimuon decay channel using 28 nb-1 of p+Pb data at the center-of-mass energy of 5.02 TeV, and 25 pb-1 of pp data. The...
Low-mass dielectrons are a unique experimental tool to investigate the hot and dense medium created in ultra-relativistic heavy-ion collisions. Since they are created during all stages of the collision and do not interact strongly, they carry information about the medium properties unperturbed by strong final-state effects allowing us to probe the whole space-time evolution of the...
Neutral mesons can provide important information on the energy loss of partons traversing the hot and dense state of matter, which is created in high energy heavy-ion collisions.
Furthermore, they constitute the largest background contribution for direct photons, which are also a very important tool to study the properties of the Quark Gluon Plasma.
In the ALICE experiment, neutral mesons can...
Neutral mesons such as $\pi^{0}$ and $\eta$ that decay into two photons are suitable to study parton energy loss in the QGP, since they can be identified, using a fine-segmented electromagnetic calorimeter, in a wide transverse momentum range.
The Photon Spectrometer (PHOS) in ALICE is an electromagnetic calorimeter which is located at 4.6 m from the interaction point.
PHOS consists of 12,544...
Neutral meson production in pp collisions is described by pQCD in a limited kinematic range. Both $\pi^0$ and $\eta$ meson spectra
constrain parameters of theoretical models in both perturbative (NLO, NNLO) and non-perturbative regimes (structure function, fragmentation function). Neutral meson spectra in pp are used as a reference for Pb-Pb and p-Pb measurements at the same per nucleon...
ALICE has measured the invariant cross sections for the production of neutral pion and eta mesons in proton-proton collisions at $\sqrt{s}$ = 8 TeV.
Neutral mesons have been reconstructed by means of three different detection systems; using the central barrel tracking detectors of ALICE in order to reconstruct photon conversions (PCM) and the two available calorimeters in the experiment,...
Measurement of neutral mesons, such as $¥pi^{0}$ and $¥eta$ plays an important role to study parton energy loss in the Quark-Gluon Plasma created in high-energy heavy-ion collisions. Such measurement in pp collisions at $¥sqrt{s}$ = 5.02 TeV provides a good reference for understanding the mechanisms appearing in p-Pb and Pb-Pb collisions at the same collision energy.
In ALICE, we measure...
The in-medium suppression of J/ψ production in heavy-ion collisions, with respect to pp collisions, serves as a sensitive probe for studying the quark gluon plasma. A full assessment of the suppression requires understanding effects present in the hot and dense medium in the Pb+Pb collisions as well as cold nuclear effects in the small p+Pb collision. Based on Pb+Pb collision data collected in...
Open heavy-flavor mesons (particles made of a heavy quark, i.e. charm or beauty, and a light quark) are a unique tool to study and characterize the properties of the Quark-Gluon Plasma (QGP). Heavy quarks are produced in the initial stages of the collisions, and they experience the whole system evolution, interacting with the medium constituents. Since charm and beauty quarks have different...
Heavy charm and bottom quarks are excellent probes to study the mechanisms by which colored objects lose energy in the QGP. In particular, given their different masses, the differential suppression of charm and bottom can provide important constraints on models describing energy loss mechanisms. The PHENIX experiment has previously used the micro-vertexing capabilities of its silicon vertex...
J/$\psi$ measurements at $\sqrt{s_{\rm NN}}$ = 2.76 TeV Pb$-$Pb collisions clearly show a smaller suppression than the one expected from color screening, when compared to binary-scaled pp collisions. An answer to this behavior is presented by models containing a regeneration component. In these models a possible (re)combination of (un)correlated c$\overline{\rm{c}}$-quarks enhances the...
Longitudinal dynamics has recently become a topic of great interest in the study of ultra-relativistic heavy ion collisions. Measurement of the longitudinal fluctuations of the flow harmonic coefficients $v_n$ and event-plane angles $Psi_n$ can provide a more complete picture of space-time evolution of the hot, dense medium formed in heavy ion collisions. Longitudinal flow decorrelations can...
Heavy quarks (charm and beauty) are produced primarily in the initial hard partonic interactions in heavy-ion collisions.
Since they propagate through and interact with the hot and dense QCD matter,
measurements of the heavy-flavour production provide relevant information on the early stage of the collisions and parton-medium interaction.
A strong suppression of heavy-flavour hadron production...
Cumulants of conserved quantities is one of the powerful tools to study the QCD phase structure.
According to the Lattice Gauge Theory calculation, at small $\mu_{B}$ a "smooth cross-over" for the transition from QGP to hadronic system occurs in heavy-ion collisions [1].
Experimentally, however, there is still no evidence for the predicted "smooth cross-over".
One of the possible ways to test...
Measuring balance functions of different hadronic species holds the prospect of providing a quantitative insight into the chemical evolution of the Quark Gluon Plasma created in ultra-relativistic heavy ion collisions$[1]$. Balance functions have been measured for identified charged-pion pairs and for identified charged-kaon pairs in Pb-Pb collisions at $\sqrt{s_{NN}}=$ 2.76 TeV by the ALICE...
Measurements of the nuclear modification factor for charged hadrons is an indirect way to understand the jet energy loss mechanism. Charged hadron spectra were measured in Pb+Pb, p+Pb and pp collisions at sqrt(s), sqrt(s_NN)=5.02 TeV. The higher statistical significance of the Pb+Pb data sample with the total integrated luminosity of 0.49nb^-1, p+Pb sample of 25nb^-1 and pp sample of 25pb^-1...
Jets originate from hard scattered partons at the initial stage of collisions. In heavy ion collisions, jets are sensitive to medium effects on the partons traversing the QGP and probe the properties of the hot and dense strongly interacting matter. Measurements of the jet nuclear modification factor ($R_{AA}$) and its centrality dependence with different choices of the jet resolution...
Heavy flavor quarks are suggested as excellent probes to study the strongly interacting Quark-Gluon Plasma (QGP) discovered in high-energy heavy-ion collisions. Due to their large masses, charm and bottom quarks are produced dominantly during initial hard partonic scatterings, and thus experience the entire evolution of the QGP. Measurements of heavy flavor production have advanced our...
Charm quarks are created in the early stages of heavy-ion collisions in hard-scattering processes. Therefore, they are ideal probes of the Quark-Gluon Plasma (QGP). The fragmentation of charm quarks can produce D mesons.
Jets containing a D meson as one of their constituents can be identified as originating from heavy-quark fragmentation. D-tagged jets are a valuable tool to characterize the...
Produced in a hard scattering at the early stage of the collision a highly energetic parton is first expected to lose energy in the medium before fragmenting into a hadronic spray of particles called jet. A detailed study of the modification of the jet structure and of its fragmentation pattern in vacuum and in medium should provide insights into the QGP properties.
The jet fragmentation...
Study of event-by-event fluctuations of conserved charges, i.e. susceptibilities of conserved charges is a powerful tool to understand and characterize the thermodynamic properties of the hot and dense QCD matter. The ratios of 2nd order off-diagonal to diagonal susceptibilities such as $\chi^{1,1}_{B,S}/\chi^{2}_{S}$, $\chi^{1,1}_{Q,B}/\chi^{2}_{B}$, and $\chi^{1,1}_{Q,S}/\chi^{2}_{S}$, are...
Upsilons provide an excellent probe for studying the screening length in the Quark Gluon Plasma through simultaneous observation of the Υ(1S), Υ(2S) and Υ(3S), using pp, pA and AA collisions. Unlike the charmonium states, the Υ yield in AA collisions due to coalescence of bottom quarks produced in unrelated hard processes is expected to be small at both RHIC and LHC energies. Comparison of the...
We present an effective model for low-energy QCD thermodynamics which provides a
microscopic interpretation of the transition from a gas of hadron resonances to the quark-gluon plasma by Mott dissociation of hadrons and compare results with data from lattice QCD simulations. We consider the thermodynamics of the Polyakov-loop extended
Nambu–Jona-Lasinio (PNJL) model within the self consistent...
We present a new approach to compute the probability for emission of an arbitrary number of gluons radiated from a high-pT probe of the QGP. Our work is an extension of the maximal helicity violating (MHV) method in which the usual soft-collinear factor is classified according to its symmetry under gluon permutations.
For the purposes of illustration, we show the explicit form of the result...
The measurement of particle production in p-Pb collisions at $\sqrt{s_{\rm NN}}=$ 5.02 TeV allows the study of fundamental QCD properties at low parton momentum fraction $x$ and high gluon densities.
Moreover, it is important as reference for heavy-ion collisions. It can show whether the initial state of the colliding nuclei plays a role in the observed suppression of hadron production at...
Advanced analysis of pp collisions at $\sqrt{s}=7$ TeV collected by the photon spectrometer PHOS of the ALICE experiment
is presented. The 2010 dataset with integrated luminosity $L_{\rm int} = 7,7~\mbox{nb}^{-1}$ has been analysed. Improved energy and timing calibration allow to reconstruct the spectrum of inclusive neutral pions production at midrapidity in the transverse momentum range $0.8...
Measurement of neutral pion production in $pp$ collisions is useful to test the QCD predictions at high $p_{\rm T}$ (> 4 GeV/$c$). At low $p_{\rm T}$, perturbative QCD cannot be applied to predict the particle production and therefore, only phenomenological models can be used. To put constraints on these models, the measurement in a very wide $p_{\rm T}$ region is very important. Furthermore,...
High-energy nuclear collisions are often classified in terms of centrality. Theoretically, the centrality binning is determined by Glauber models which take the nuclear density as an input. The nuclear density is traditionally parametrized by the Woods-Saxon form and is taken to be the same for protons and neutrons. However, according to the theoretical expectations and experimental...
Heavy flavour (beauty and charm) quarks 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 created in heavy-ion collisions. Thus, heavy flavours are an excellent probe to study in-medium energy loss (mechanisms) in nuclear collisions by measuring, for...
We study the evolution of the one-dimensional, non-boost-invariant evolution of a hot dense system, in similar conditions to the ones found in Quark Gluon Plasma created in heavy-ion experiments. We neglect transverse dynamic, but we relax the assupmption of longitudinal boost invariance and rapidity independence.
We compare the results obtained from several formulations of viscous hydrodynics...
A Multi-Phase Transport (AMPT) model has been shown to describe experimental data well, including the particle spectra and azimuthal anisotropies ($v_n$) of pions and kaons below $p_T$ of ~1.5 GeV/c in heavy ion collisions [1] as well as small system collisions [2]. By following the parton collision history in AMPT, we have found that the opacity in AMPT is relatively small and the parton...
Dijet momentum balance in both p+p and Pb+Pb collisions at 2.76 TeV is studied within a multi-phase transport (AMPT) model. We analyze projection \ptslash{} of transverse momentum p_T of all particles onto leading jet axis, and obtain overall momentum balance in dijet events, which qualitatively fits CMS data for p+p and Pb+Pb collisions. Against the contribution to \ptslash{} in leading jet...
Heavy nuclei colliding at ultra-relativistic energies at the Large Hadron Collider (LHC) produce a hot and dense state of matter filled with deconfined quarks and gluons. Particles produced by hard-scatterings interact with the hot and dense medium as they propagate through it, in a process known as jet quenching.
The medium-induced modification of the jet-like particle yield can be...
Relativistic hydrodynamics, which successfully describes the quark-gluon plasma created in heavy-ion collisions, is formulated based on the assumption that systems are almost in local thermal equilibrium. However, a quantum field theoretical way to handle such a locally thermalized matter has not been clearly clarified.
In this study, we develop imaginary-time formalism for relativistic...
The peak rate of interactions in high luminosity heavy ion runs in 2015 and 2016 was well above the ATLAS maximum recording rate of around 1kHz. Therefore an active trigger selection is applied relying partly on algorithms used for selection during pp data taking and a set of algorithms dedicated solely for heavy ions. They are used to collect enhanced samples of high multiplicity,...
QCD inspired models predict that a saturated gluon state, so called Color Glass Condensate (CGC) is produced in the nucleon and nucleus at very high energy such as at the Large Hadron Collider (LHC). One of the most sensitive and cleanest probes of CGC effect is the
production of isolated photon in the forward region ($3 < \eta < 5$) at intermediate $p_{T}$ (few $GeV/c$).
The ALICE-FoCal...
A Large Ion Collider Experiment (ALICE) is a major experiment at the Large Hadron Collider (LHC) at CERN. It is specifically designed to investigate the Quark-Gluon Plasma (QGP), a state of matter in which quarks and gluons are momentarily deconfined. The QGP is short-lived, and must therefore be studied indirectly by identifying the final-state particles produced in heavy-ion collisions. The...
The data of di-hadron azimuthal correlations at different centralities for Au+Au collisions at 200 A$\,$GeV were presented by the PHENIX Collaboration.
It was observed that the away-side correlation evolves from double- to single-peak structure when the centrality decreases. In this work, we show, in terms of the peripheral tube model, that the observed features naturally appear due to an...
Measurements of the charged particle multiplicity as a function of pseudorapidity help constrain our understanding of collision dynamics and particle production mechanisms. In 2016, RHIC operations included d+Au collisions at 200, 62.4, 39, and 19.6 GeV. This poster presents the current status of analysis of charged particle multiplicities in the 2016 d+Au beam energy scan.
Recent results from small collision systems at RHIC and LHC indicate that many of the signatures of collective behavior observed in AA collisions are also present in small systems in high-multiplicity events. The PHENIX experiment has performed comprehensive studies of long-range particle correlations and anisotropic flow in p/d/He3+Au collisions. Mass ordering has been observed in the pt...
Bose-Einstein correlations of identical hadrons reveal information about hadron
creation from the sQGP formed in ultrarelativistic heavy ion collisions. The
measurement of three particle correlations may in particular shed light on
hadron creation mechanisms beyond thermal/chaotic emission. In this poster we
show the status of PHENIX measurements of three pion correlations as a function of...
We make phenomenological predictions for particle spectra and flow in heavy-ion col- lisions using 3+1d anisotropic hydrodynamics (aHydro) including the effects of both bulk and shear viscosities. The dynamical equations necessary are derived by taking moments of Boltzmann equation allowing for three distinct momentum-space anisotropy parameters. The formulation is based on relaxation-time...
The production of φ mesons provides key information on the hot and dense state of the strongly interacting matter produced in high-energy heavy-ion collisions. They are sensitive to enhanced strangeness production in the medium. Measurements in different nucleus-nucleus collisions allow us to perform a systematic study of the nuclear medium effects on phi meson production. In addition to...
Nature of QCD phase transitions in high energy collisions can be pinned down by studying the
behaviour of thermodynamic response functions with respect to $T$ and $\mu_B$.
A first order phase transition is signalled by the divergence of
specific heat ($c_v$), whereas for a second order
or continuous transition, isothermal compressibility
($k_T$) diverges.
$c_v$ is estimated at the kinetic...
We investigate the response of the QCD ground state at finite temperatures to an anti-parallel electric and magnetic field. Due to the electromagnetic triangle anomaly, both neutral and charged pion condensations are created in the presence of non-vanishing ($E\cdot B$).
In the frame of the proper-time Schwinger formalism, we addressed the oscillation obstacle because of the electric field...
Despite the success of modern nuclear parton distribution functions (nPDFs) in describing nuclear hard-process data, they still suffer from large uncertainties. One of the shortcomings is the lack of data which would constrain the nuclear effects of all parton flavours simultaneously without any a priori assumptions. For example, it has been customary to assume that nuclear modifications for...
Classical Yang-Mills theory calculations are frequently used to study nonequilibrium phenomena in nonperturbative overoccupied systems, especially in the context of ultrarelativistic heavy-ion collisions. We study the limits of the quasiparticle picture of the classical Yang-Mills fields by determining the plasmon mass of the system using 3 different methods. We also demonstrate an algorithm...
We compute the suppression of the bottomonia states $\Upsilon(1S)$, $\Upsilon(2S)$, $\Upsilon(3S)$, $\chi_{b}(1P)$, $\chi_{b}(2P)$, and $\chi_{b}(3P)$ states in LHC $\sqrt{s_{NN}} = 5.023$ TeV Pb-Pb collisions. For the background evolution we use 3+1d anisotropic hydrodynamics with conditions extrapolated from $\sqrt{s_{NN}} = 2.76$ TeV and self-consistently compute bottomonia decay rates...
The electromagnetic field pattern created by spectators in relativistic heavy-ion collisions plants a seed of positive (negative) magnetic helicity in the hemisphere above (below) the reaction plane. Owing to the chiral anomaly, the magnetic helicity interacts with the fermionic helicity of the collision system and causes photons emitted in upper and lower hemispheres to have different...
The measurement of resonances in ultra-relativistic heavy-ion collisions allows one to study the properties of the hadronic medium. Resonances with short lifetimes compared to the duration of the hadronic phase are good candidates to probe the interplay of particle re-scattering and regeneration in the hadronic phase, which result in a modification of the measured yield of resonances.
...
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 fully exploit
the large integrated luminosity that will be provided by the LHC in Run~3 and Run~4.
The Muon Forward Tracker (MFT), an internal tracker added in the...
Anisotropic flow is one of the key observables in heavy-ion collisions and puts constraints on the QGP equation of state. In particular, the pseudorapidity ($\eta$) dependence of anisotropic flow coefficients provides information on the hydrodynamical response of the system in the context of variations in the particle density.
The ALICE detector provides unprecedented angular coverage at the...
We study quark and gluon production from an expanding strong color electric flux tube. Firstly, we derive a set of linear equations for quantum fluctuations by employing a mean-field approximation on top of the strong color electric flux tube, which describes the particle production and its backreaction on the flux tube. Second, we carry out numerical simulations and discuss how the flux...
We calculate the quark self-energy in a quark-gluon plasma that possesses an ellipsoidal momentum-space anisotropy in the local rest frame. By introducing additional transverse momentum anisotropy parameters into the parton distribution functions, we generalize previous results which were obtained for the case of a spheroidal anisotropy. Our results demonstrate that the presence of...
Studies of the production of heavy quarkonium states are crucial to improve our understanding of QCD and hadron formation. Large data samples of S-wave quarkonium states decaying in the dimuon channel have been collected by CMS in pp collisions at 7, 8 and 13 TeV, profiting from a very selective trigger and the record-level energy and luminosity provided by the LHC. This allowed the CMS...
Quarkonia are mesons formed of either a charm and anti-charm quark pair (J/Psi, Psi(2S)), or a beauty and anti-beauty quark pair (Upsilon(1S), (2S) and (3S)). In high-energy hadronic collisions such as those delivered by the LHC between 2010 and 2015, quarkonium production results from the hard scattering of two gluons in a process which occurs very early in the collision followed by the...
We use quasiparticle anisotropic hydrodynamics to study an azimuthally-symmetric boost-invariant quark-gluon plasma including the effects of both shear and bulk viscosities. In quasiparticle anisotropic hydrodynamics, a single finite-temperature quasiparticle mass is introduced and fit to the lattice data in order to implement a realistic equation of state (EoS). We compare results obtained...
Increases in luminosity and collision energy at the LHC challenge the radiation hardness of detectors located along the beamline. This problem is especially acute for the ATLAS Zero Degree Calorimeters (ZDCs), which are exposed to about 10^10 rad/yr, rendering the current version of the detector unusable during p+p running. To address this shortcoming and allow for important triggers and...
The forces that drive the nuclear collision system towards local thermal equilibrium leave few observable traces. We show that measurements of the rapidity dependence of transverse momentum correlations can be used to determine the characteristic time $\tau_\pi$ that dictates the rate of isotropization of the stress energy tensor, as well as the shear viscosity $\nu=\eta/sT$. We formulate...
The high collision energies reached at the LHC enable significant production rates of light (anti-)nuclei in proton-proton (pp), proton-lead (p-Pb) and in lead-lead (Pb-Pb) collisions.
The excellent particle identification capabilities of the ALICE detector, based on the specific energy loss in the time projection chamber and the velocity information from the time-of-flight detector, are...
In heavy-ion collisions, the study of recoil jets tagged by high transverse-momentum "direct photons" ($\gamma_{dir}$) should provide a measurement of the partonic energy loss in the hot, dense medium produced in such collisions\footnote{X.-N. Wang, Z. Huang, and I. Sarcevic, Phys. Rev. Lett. 77, 231 (1996)}. Since a $\gamma_{dir}$ does not interact strongly with the medium, it closely...
One of the main purposes of the physics program of the future heavy ion experiment CBM (FAIR, Germany) is to understand the properties of strongly interacting matter at very high baryonic densities and to study the possibility of a phase transition to a deconfined and chirally restored phase of quark matter. The experiment will operate at high interaction rates up to 10 MHz, that requires a...
We computed excited state masses of singly heavy $\Lambda_b^{0}$ baryon in the framework of Hypercentral Constituent Quark Model. We use hyper coloumb plus power potential, varying ($\nu$) from S.R.(1/2) to quadratic(2.0), in the calculation of ground and radial excited state masses. After that, orbital excited states are also determine for linear($\nu$=1.0) potential. We also introduced first...
Starting from the Boltzmann equation in the relaxation time approximation and employing a Chapman-Enskog like expansion for the distribution function close to equilibrium, we derive second-order evolution equations for the shear stress tensor and the dissipative charge current for a system of massless quarks and gluons. The transport coefficients are obtained exactly using quantum statistics...
Within the context of a hybrid strong/weak coupling model of jet quenching, we study the consequences of the fact that the plasma produced in a heavy ion collision cannot resolve the substructure of a collimated parton shower within it to arbitrary resolution.
We introduce a screening length parameter, $L_{Res}$, proportional to the inverse of the local temperature in the plasma, estimating...
The response functions of a particular medium is a basic tool to understand the properties
of the medium. In the same spirit, Chromo-electric/magnetic response functions (such as
Dielectric permittivity , refractive index , etc.,) can be used to understand the medium
properties of hot QCD/QGP medium. We first obtain the gluon polarisation tensor in a hot
QCD medium which is described in terms...
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 secondary hard interactions.
A measurement of the thermal radiation from the QGP in the dielectron intermediate mass region allows to estimate the medium temperature. In this region the main component of the...
The Time Projection Chamber (TPC) is the main tracking and particle identification detector of the ALICE experiment at the CERN LHC. With the advent of high luminosity data of LHC RUN 2, unexpectedly large local distortions of the drift paths of ionization electrons are observed at the edges of specific readout chambers. These distortions are caused by ions which leak from the amplification...
The sPHENIX experiments will explore the properties of the quark gluon plasma via measurements of jets and upsilons. sPHENIX will feature a state of the art tracking system which consists of a highly granular MAPS silicon pixel detector, a silicon strip detector (INTT) and a time projection chamber (TPC).
The tracking system will work in continuous read out at high data collection rates,...
sPHENIX is an upgrade to the PHENIX detector proposed to explored the quark-gluon plasma formed in heavy ion collisions through measurements of jets and upsilons at RHIC in the 2020's. The experiment will feature a 1.5 Tesla superconducting solenoid magnet which was formerly used by the BaBar experiment. A charged particle tracking system will be placed together with an electromagnetic and...
We present the first calculations of the momentum sharing and angular separation distributions between the leading subjets inside a reconstructed jet, as well as the jet mass distribution modification in heavy ion collisions. These observables are sensitive to the early and late stages of the in-medium parton shower evolution and allow us to probe the quark-gluon plasma across a wide range of...
The Compact Muon Solenoid (CMS) observed the strong suppression of excited bottomonia states $\Upsilon(2S)$ and $\Upsilon(3S)$ in PbPb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV. The analysis was done by comparing the excited state yield to the ground state yield, and then comparing the results in PbPb and pp. For $\Upsilon(2S)$ state of the 0-5% centrality and $\Upsilon(3S)$ states of...
Using generalized quark number susceptibilities we obtain continuum extrapolated
lattice QCD results for the free energy in various strangeness sectors and compare it with the expectations from the
hadron resonance gas model. We use these findings to disambiguate between various spectrum tables. Thus we constrain
the abundance of strange mesons and baryons using finite temperature data. This...
Heavy flavor quarks are an important probe of the initial state of the Quark Gluon Plasma formed in heavy-ion collisions.
Bottom and charm quarks are produced early in the collision, primarily through hard interactions, and experience the full time evolution of the medium.
Understanding bottom quark production in $p+p$ collisions gives a baseline reference for studying larger collision...
The study of asymmetric systems like d+Au is considered useful for distinguishing initial state cold nuclear matter effects from final state QGP effects. Two-particle correlations in highly asymmetric collisions can access jet physics at high $p_T$, possible collective effects at low $p_T$, and the interplay of the two. This poster presents the status of the measurement of $\pi^0 - h^{\pm}$...
ATLAS measurements of multi-particle azimuthal correlations for produced charged particles in small collision systems (5.02 and 13 TeV $pp$, 5.02 TeV $p$+Pb and low-multiplicity 2.76 TeV Pb+Pb collisions) are presented. The correlations are expressed in terms of cumulants $c_n$, which can be directly related to Fourier harmonics $v_n$. A comparison across different collision systems is...
A key topic of interest in studies of jets in heavy ion physics is the path-length dependence of jet-medium interactions. In this contribution, Monte Carlo event simulators are used to estimate the path-length traversed by the recoil jet, under a varying range of trigger conditions. These simulations are then used to make predictions for studies of jet-hadron correlations, where a high pT...
The dimuon mass spectrum, unlike-sign as well as like-sign, is a unique
probe to directly access the different stages of a heavy-ion collision.
The unlike-sign intermediate ($1< m_{\mu^+\mu^-}<3$ GeV/$c^2$) and high
($4< m_{\mu^+\mu^-}<8$ GeV/$c^2$) mass regions are dominated by semi-leptonic
decays of open charm and bottom, and therefore provide information about
the heavy flavor dynamics....
The observation of the modification of hadronic resonance production in heavy-ion collisions allows one to infer the presence of a prolonged hadronic phase after hadronisation. The decay daughters of short-lived resonances suffer re-scattering in the dense hadronic medium, which modifies their correlations and hence the experimentally measured yields. New results on the production of Λ(1520)...
Currently at the Beam Energy Scan at RHIC experimental efforts are being made to find the QCD critical point. On the theoretical side, the behavior of higher-order susceptibilities of the net-baryon charge from Lattice QCD may allows us to estimate its position via Taylor expansion of the density of states at $\mu_B=0$. However, even if the series expansion continues to higher-orders, there is...
The CBM experiment aims at exploring the QCD phase diagram at large baryon densities in the beam energy range from 2 A GeV to 11 (35) A GeV at the SIS100 (SIS300) accelerator of FAIR/GSI. For charged particle identification that is required by many observables that are sensitive to the phase structure like collective flow, phase space population of rare hyperons, fluctuations of conserved...
The dipole flow originates from the asymmetry in the initial density distributions either due to projectile-target asymmetry (Cu+Au collisions) or due to the event-by-event fluctuations. Unlike the conventional directed flow that is rapidity-odd in symmetric collisions, the dipole flow is rapidity-even and has weak dependence on the pseudorapidity. The dipole flow has a characteristic of zero...
The intense magnetic fields produced at the early stages of a heavy ion reaction make it possible to produce photons from processes otherwise not allowed, for instance, the fusion of gluons. In addition, magnetic fields naturally produce an asymmetry in the emission of electromagnetic radiation, hence they can be considered as a source of the large strength of the coefficient $v_2$.
In this...
The upcoming upgrade of the CERN LHC injectors during 2019-20 will boost the luminosity and the collision rate beyond the design parameters for several of the key ALICE detectors including the forward trigger detectors. The nominal Pb-Pb interaction and readout rate for ALICE after LS2 will be of 50 kHz. To remedy this problem the Fast Interaction Trigger (FIT)Êis being designed and...
The recently established sPHENIX Collaboration at RHIC is upgrading
the PHENIX detector in a way that will enable a comprehensive
measurement of jets in relativistic heavy ion collisions. The upgrade
will give the experiment full azimuthal coverage within a
pseudorapidity range of $-1.1 < \eta < 1.1$. In addition to measuring
heavy-ion collisions, the new apparatus will provide enhanced...
The CBM fixed-target experiment at FAIR will investigate highly compressed baryonic matter at moderate temperatures in heavy-ion collisions with 2-11 AGeV beam energy for heaviest nuclei at the SIS100 accelerator at FAIR starting in 2022. The CBM experiment aims at understanding and characterizing nuclear matter at high net-baryon densities but moderate temperatures focussing on the...
The Silicon Tracking System is the central detector in the CBM experiment at FAIR. Operating in the 1 Tm dipole magnetic field, the STS will enable pile-up free detection and momentum measurement of the charged-particles originating from beam-target nuclear interactions at rates between 100 kHz and 10 MHz. It will also allow identifying particle decays occurring within the aperture.
The STS...
The spinodal instability, i.e. the self-amplified deviation from the equilibrium state during a first order phase transition, of the baryonic rich quark matter is studied by both using the linear response theory and solving the Boltzmann equations with the test particle method. The former approach includes the quantum effect but only works near equilibrium, while the second one is...
The first RHIC Beam Energy Scan (BES-I) provided an initial survey of
the QCD phase diagram by acquiring data from Au+Au collisions from
$\sqrt(s_{NN})$ = 7.7 to 62.4 GeV. Based on those results, a second
phase of the BES program, BES-II, has been developed and is scheduled to
run in 2019 and 2020. One of the proposed upgrades to STAR for BES-II
will be the addition of an end-cap...
A prerequisite for producing the Quark Gluon Plasma in heavy-ion collisions is to have a sufficient local energy density, which, traditionally, is estimated via measurements of the produced particle transverse energy ($E_{\mathrm T}$). In hadronic collisions the $E_{\mathrm T}$ is determined by the initial scattering of the partonic constituents of the incoming nuclei as well as...
The new multiparticle observables, which are called "Symmetric 2-harmonic 4-particle cumulants"(SC), were recently reported in [1]. These quantify the correlation between the event-by-event fluctuations of two different flow harmonics. Because the correlation between different order flow harmonics responds differently to the initial conditions or(and) $\eta/s$, SC provide a strong constraint...
Particle production at collider energies is a result of the interplay of perturbative (hard) and non-perturbative (soft) QCD processes. Hence, the measurements of transverse momentum spectra in pp collisions provide baseline tests of perturbative QCD and constraints for a better tuning of models and event generators. In addition, they constitute a valuable reference to study nuclear effects in...
Bottomonium are produced in the heavy ion collisions and their production is modified compared with elementary collisions. This modification in the production of bottomonia happens due to the presence of hot and dense QCD matter, named as quark-gluon plasma (QGP) formed in ultra relativistic heavy ion collisions. We present here a comprehensive model based on color screening, collisional...
An extension of the ideal non-interacting hadron resonance gas (HRG) model
is constructed
which includes
the attractive and repulsive van der Waals (VDW) interactions between baryons.
This VDW-HRG model yields the nuclear liquid-gas transition at low temperatures and high baryon densities.
The VDW parameters $a$ and $b$
are fixed by the ground state properties of nuclear matter,
and the...
Photons emitted in heavy-ion collisions are sensitive to the entire history of the system evolution as they are emitted in all stages of the collision. As such they are excellent probes of the out-of-equilibrium nature of a fast evolving system. The degree of
out-of-equilibrium is encoded in the transport coefficients (the shear and bulk viscosities) and the so-called $\delta f$ corrections to...
Weak decay of beauty baryons in quark-diquark
model
The weak decays of $\Lambda_{b}$ provide valuable information of the
CKM parameter Vcb, fragmentation and hadronisation within the
framework of quantum chromodynamics. Recently, LHCb has reported
Branching ratios for non-leptonic decay $\Lambda_b^0\to\Lambda_c^+
\pi^-$$ = 4.3\pm 0.51 \times 10^{-3} $. This
experimental measurement...
In heavy-ion collision experiments, the study of event-by-event fluctuations provides a powerful tool to characterize and understand the thermodynamic
properties of the hot and dense QCD matter.
The fluctuations of conserved quantities in a finite phase space rapidity window ($\Delta\eta$), like the net-charge, are predicted to be one of the most sensitive signals of the QGP formation and...
