Overview of the LHCb results
Overview of the ATLAS results
Overview of the CMS results
High-energy proton-proton (pp) collisions at large final state particle multiplicities exhibit heavy ion-like behaviors. Among many others, one of the peculiar feature of heavy ions is partonic energy loss (aka jet quenching) in the produced Quark-Gluon Plasma. The search for jet quenching effects also in small collision systems (such as pp) is warranted. To date no evidence of jet quenching...
Studying the quenching of high momentum particles in collision systems of various shapes and sizes provides crucial insights on the initial conditions and the transport properties of the QGP. Such insights can be obtained via investigations of the high transverse momentum ($p_T$) anisotropy harmonics and their collision energy and system-size dependence. We present the beam-energy and...
A crucial open question is why many models of expanding systems exhibit an apparent simplification in their description while gradients in the system are still large and hydrodynamics is not expected to apply. We discuss a new conceptual approach to understand the pre-equilibrium bulk evolution of a system in terms of a reduced set of slow modes. We propose that the emergent dominance of these...
Spin alignment of vector mesons produced in non-central heavy-ion collisions could occur due to the large angular momentum and intense magnetic field expected in the initial stages of these collisions. Experimentally, vector meson polarization is observed from the angular distribution of the decay daughters with respect to a quantization axis. The study of the angular distribution of the decay...
The sPHENIX detector at BNL’s Relativistic Heavy Ion Collider (RHIC) will measure a suite of unique jet and Upsilon observables with unprecedented statistics and kinematic reach at RHIC energies. A MAPS-based vertex detector upgrade to sPHENIX, the MVTX, will provide a precise determination of the impact parameter of tracks relative to the primary vertex in high multiplicity heavy ion...
In the present investigation we use $^3P_0$ model to calculate the partial decay width of Y(4008) state decaying to $D\bar{D}$ pairs in hot and dense nuclear medium. The impact of nuclear density and temperature is inculcated through the mass modification of pseudoscalar $D$ meson, calculated using chiral hadronic SU(3) plus QCD sum rule approach. The results of the present work will prove as...
In heavy-ion collisions, the observed non-zero second-order azimuthal anisotropy coefficient, $v_{2}$, for particles with high transverse momenta $\it{p}_{\rm T}$ is driven by the path-length dependent energy loss of hard partons travelling in the QGP, known as the jet quenching effect. Recent measurements show also a non-zero $v_{2}$ values for high $\it{p}_{\rm T}$ charged particles at high...
Measurements of two-particle correlations in $pp$ collisions show the presence of
long-range correlations along $\Delta\eta$ that are strikingly similar to
those seen in heavy-ion collisions.
In heavy-ion collisions, the long-range correlations are known to arise from the
collective dynamics of the produced quark-gluon plasma (QGP).
The similarity between the $pp$ and heavy-ion...
In 1974, J. L. Anderson and H. R. Witting proposed the Relaxation Time Approximation (RTA) to the relativistic Boltzmann equation [1], following all the development already made in the non-relativistic case by Bhatnagar, Gross and Krook [2]. This approximation is used in several fields of physics and has been recently employed to study the hydrodynamization of the matter produced in...
Direct photons are a powerful tool to study the properties of QCD matter in nuclear collisions. We investigate the contribution of pre-equilibrium photons before hydrodynamization in addition to those of conventional prompt and thermal photons to obtain a comprehensive picture of direct photon emission in the hybrid model based on relativistic hydrodynamics [1]. Numerical simulations at an LHC...
Probing the quark gluon plasma in small system is a hot topic nowadays. By combining the thermal and hard parts, with the Cooper-Frye freeze-out, quark coalescence and hard parton fragmentation hadronization mechanisms, we investigate the $p_T$-spectra, the differential elliptic flow and the number of constituent quark (NCQ) scaling of pions, kaons and protons of high multiplicity p+ Pb...
The exploration of the fundamental structures of nucleon and nucleus has always thrived on the complementarity of lepton scattering and purely hadronic probes. With the Electron Ion Collider (EIC) on the horizon, it becomes more urgent than ever to complete key measurements in this regard with high precision in hadonic $p$+$p$ and $p$+Au collisions during the final years of RHIC running. When...
Quarkonia are considered a distinguished tool to study the strongly-interacting medium formed in ultra-relativistic heavy-ion collisions. However, their production is also sensitive to initial state effects such as the modifications of the parton distribution functions (PDF) in the nucleus or the gluon saturation at low Bjorken-x. These phenomena are typically studied using proton-nucleus...
The chiral imbalance along with the magnetic field produced during heavy-ion collisions may cause a charge separation in the magnetic field direction, a phenomenon known as the chiral magnetic effect (CME). A new technique, the sliding dumbbell method (SDM), is designed to study the CME-like charge separation. In the SDM, the whole azimuthal plane is scanned for each event by sliding the...
We present our calculation of electromagnetic effects, induced by the spectator charge on Feynman-xF distributions of charged pions in peripheral Pb+Pb collisions at CERN SPS energies, including realistic initial space-time-momentum conditions for pion emission. The calculation is performed in the framework of our simplified implementation of the fire-streak model, adapted to the production of...
One of the most important discoveries at the LHC is the observation of collective-like behavior and strangeness enhancement in small collision systems (e.g. pp and p-Pb collisions). They effects are strikingly similar to those observed in heavy-ion collisions, where they are attributed to the production of a deconfined hot and dense medium, known as strongly interacting Quark-Gluon Plasma. In...
The properties of QCD matter produced in ultrarelativistic heavy ion collisions can be determined in a global analysis of LHC and RHIC observables. Bayesian analysis [1] has provided meaningful credibility ranges for the ratio of shear viscosity to entropy density $\eta/s$, as well as for key parameters describing the initial state, essentially confirming earlier results like those obtained...
Measurements of elliptic flow in relativistic nuclear collisions are known to be sensitive to the quadrupole deformation of the colliding nuclear species. We explore the possibilities offered by high-precision data collected in Ru+Ru and Zr+Zr collisions at RHIC for studies of nuclear deformation at high energy. By exploiting the fact that isobaric systems share the same hydrodynamic...
The axial-vector form factors of the decuplet baryons are investigated in the chiral constituent quark model using their explicit quark spin polarizations. The ``quark sea'' arises from the chiral symmetry breaking which results in the Goldstone bosons mediating the interaction between constituent quarks. The axial-vector form factors which have some physical significance corresponding to...
During the large hadron collider long shutdown 2 (LHC-LS2), the Muon Spectrometer of the ATLAS experiment known a major upgrade in the region 1.0 <η< 1.3. motivated by the improving of the high-Pt measurement within the trigger system, where the old monitored drift tube chambers will be replaced by new ones in which an additional trigger detector RPC (resistive plate chambers) will be...
Interfacing the initial stage with fluid dynamics
Quarkonia are considered a distinguished tool to study the strongly-interacting medium formed in ultrarelativistic heavy-ion collisions and they are sensitive to the dense gluonic system at low-x in the initial state of heavy-ion collisions. This can be investigated in photonuclear or proton-nuclear collisions. Furthermore a modification of the quarkonium vector states polarization in...
Heavy quarks (charm and beauty) are primarily produced in hard-scattering processes with large momentum transfer due to their large masses. They are effective probes to study cold-nuclear-matter (CNM) effects such as gluon saturation, shadowing, $k_{\rm T}$ broadening and energy loss in CNM in p-Pb collisions. In recent years, effects ascribed to the collective expansion of the deconfined...
The leading order result of single inclusive gluon production in high energy pA collisions has been calculated by various approaches for more than two decades . The first saturation correction to the leading order result, terms that are enhanced by $\alpha_s^2 A^{1/3}$ with $\alpha_s$ the strong coupling constant and $A$ the atomic number of nucleus, was only analytically attempted recently...
In high-energy heavy-ion collisions the standard procedure to turn the measured hard-process yields into centrality dependent cross sections is to use normalization factors calculated with the Monte-Carlo Glauber model. Canonically it is assumed that a necessary input, the inelastic nucleon-nucleon cross section, is unmodified wrt. the measured cross section in proton-proton collisions. At the...
In small colliding systems and near the QCD critical point, the effects due to hydrodynamic fluctuations can be significant. The effective field theory of fluctuating hydrodynamics has recently been formulated on the closed time path (Schwinger-Keldysh formalism) [1]. Such formulation allows for a systematic treatment of non-linear interaction among energy-momentum densities and hydrodynamics...
Measurements of open heavy-flavor hadron and quarkonium
in heavy-ion collisions provide a powerful tool
to study both initial-state effects on heavy-quark production and final-state interactions
between heavy quarks and the quark-gluon plasma (QGP).
Recent ATLAS measurements of azimuthal anisotropy of muons from heavy-flavor decays in pp and Pb+Pb collisions are presented.
Muons with...
We present a framework to simulate the dynamics of hard probes such as heavy quarks or jets in a hot, strongly-coupled quark-gluon plasma (QGP) on a quantum computer [1]. Hard probes in the QGP can be treated as open quantum systems governed in the Markovian limit by the Lindblad equation. However, due to large computational costs, most current phenomenological calculations of hard probes...
Initial state geometry is a key quantitative component of theoretical descriptions of relativistic heavy-ion collisions. Phenomenological models of the initial state are typically designed to reproduce one-body observables, e.g. charged hadron multiplicity and coefficients of the spatial Fourier decomposition, 𝑣𝑛. However, these models may not simultaneously describe many-body observables such...
The ultra-peripheral collisions (UPCs) of relativistic heavy ion beams lead to a diverse set of photon-nucleus interactions. The measurements of particles and their interaction produced in photo-nuclear reactions can shed light on the QCD dynamics of novel, extremely asymmetric colliding systems, with energies between those available at RHIC and the LHC. Understanding the hadronic fluctuation...
One of the main goals of the second phase of the Beam Energy Scan program at RHIC is to search for the QCD critical point. In order to study the thermodynamic effects of the presence of a critical point, we constructed a family of equations of state using a model that couples Lattice QCD results to a parameterized critical point from the 3D Ising model universality class. The mapping of the...
Quarkonium suppression in heavy ion collisions has been used as a probe of the quark-gluon plasma (QGP) for decades. The intuitive picture of sequential suppression based on the Debye screening of the heavy quark potential is obscured by other in-medium processes such as dissociation and recombination. A natural question to ask is what we can learn about the QGP from measurements of quarkonium...
Heavy quarks are produced by hard scattering in relativistic heavy-ion collisions. Since heavy quarks are created early in time, those could be used as effective probes for the lead ions and the QGP. In this parallel talk, new results on beauty and charm meson spectra based on the CMS data collected in Run 2 are presented. Those spectra depend on the nuclear parton distribution functions of...
We present predictions for proton and nuclear structure functions using numerical solutions to the Balistky-Kovchegov equation with the collinearly improved kernel and including the impact-parameter dependence. Two different approaches to the nuclear case are studied: a solution obtained using a newly proposed type of initial condition which represent the given nucleus and the solutions based...
In this talk we explain how the novel first-order approach proposed by Bemfica, Disconzi, Noronha [1], and Kovtun [2] naturally solved the long-standing problems of causality, stability, and well-posedness of relativistic Navier-Stokes theory. We discuss the differences between this new approach and Israel-Stewart theory, emphasizing how such distinctions could affect our current understanding...
Recently, in the context of the effective kinetic theory developed by Arnold, Moore and Yaffe [1], Berges and Mazeliauskas [2] have shown that the quark-gluon plasma after a sufficiently energetic heavy-ion collision exhibits prescaling, i.e., that the distribution function can be characterized by a scaling distribution plus three dynamical exponents that converge to the universal scaling...
In recent years there has been a great effort to search for collectivity in small collision systems. Ultra-peripheral pPb events offer the possibility to study photon-proton collisions at center of mass energies of several hundred GeV, and provide a new arena for the search of collectivity at very small systems. The CMS experiment has collected a large dataset of photon-proton collisions by...
We present a way to construct 3D initial conditions for relativistic heavy-ion collisions based on the Glauber collision geometry [1]. Local energy and momentum conservation conditions are imposed to set non-trivial constraints on our longitudinal profiles’ parameterizations for the system’s initial energy density and flow velocity. We show that the $\sqrt{T_A T_B}$ scaling of initial energy...
We introduce the Trajectum framework, a new heavy ion code which incorporates many of the necessary components to perform a heavy ion collision simulation in one executable. We use Trajectum to study a generalization of the TRENTo initial conditions, namely varying the free streaming velocity $v_\text{fs}$. In addition, we show the results of a Bayesian analysis performed with this...
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 strong interactions after their creation.
A measurement of the thermal radiation from the QGP in the mass region between the $\phi$ and the $\rm J/\psi$ allows to estimate the medium temperature. In this...
Relativistic heavy-ion beams are accompanied by a large flux of equivalent photons, giving rise to a set of photon-induced processes. These ultra-peripheral collisions (UPCs) can lead to photon-photon interactions. This poster presents a new measurement of exclusive dimuon production, which provides detailed constraints on the nuclear photon flux and its dependence on impact parameter and...
By describing the initial stage of heavy ion collisions in terms of freely-evolving classical fields, we perform a first-principles calculation of the energy density one- and two-point correlation functions at finite proper time. Our approach allows us to systematically resum the contributions of high momentum modes that would make a power series expansion in proper time divergent. In order to...
Collective phenomena in heavy-ion collisions are very sensitive to initial geometry including nuclei deformation effects. Recent hydrodynamic model calculations suggest that such deformation effects can be probed by studying event-by-event mean $p_T$ ($\left \langle p_T \right \rangle$) fluctuation and the correlation between mean $p_T$ and harmonic flow. In particular, due to prolate shape of...
We study the thermal equilibration and properties of the matter produced at the Beam Energy Scan (BES) program by employing the Parton-Hadron-String Dynamics (PHSD) transport approach which consistently describes the whole non-equilibrium dynamics of heavy-ion collisions, from the early nucleon hard scatterings, to the partonic phase based on the effective propagators and couplings from the...
No existing model for the initial stages of a heavy-ion collision, when used as initial conditions for hydrodynamics simulations, can provide a satisfactory description of flow in ultra-central collisions. It is therefore useful to understand what properties the initial stages must have in order to be compatible with experimental data. To this end, we parameterize the early-time energy density...
We exploit the concept of hydrodynamic attractors to establish a macroscopic description of the early time out-of-equilibrium dynamics of high energy heavy-ion collisions. One direct consequence is a general relation between the initial state energy and the produced particle multiplicities measured in experiments. When combined with an ab initio model of energy deposition, the entropy...
By measuring the momentum correlations of pions created in heavy-ion collisions we can gain information about the space-time geometry of the particle emitting source. Recent experimental results from multiple different collaborations demonstrated that to properly describe the shape of the measured correlation functions, one needs to go beyond the Gaussian approximation. Some studies suggest...
We present the results of the second-order Fourier coefficients (v2), which characterizes the azimuthal anisotropy, in p+p, p+Au, and d+Au collisions at sqrt(sNN) = 200 GeV. The v2 values are calculated via the two-particle correlation method. To investigate the role of initial geometry effects, the measured v2 is extracted by two different kinematic selections. The two results are compared...
Over the last years, Machine Learning (ML) tools have been successfully applied to a wealth of problems in high-energy physics. Supervised ML methods allow for significant improvements in classification problems by taking into account correlations among observables and by learning the optimal selection from prepared samples. In this talk, we will discuss the application of ML for the...
Studies of longitudinal decorrelation of anisotropic flow provide unique constraints on the initial conditions and dynamical evolution of the quark- gluon-plasma in heavy-ion collisions. With data collected by the STAR experiment at RHIC, the factorization ratio for flow harmonics, rn(η, ηref )(n = 2,3), are obtained over a wide η range for 27, 54.4 and 200 GeV Au+Au collisions as a function...
Multiparticle correlation techniques have been used to study the nature of long-range collectivity in small collision systems. The subevent cumulant method was shown to significantly reduce the nonflow contributions compared to the standard cumulant method. However, a jet could fall across the boundary between two neighboring subevents and residual nonflow exists in this method. Requiring an...
When two heavy ions collide at ultrarelativistic energies a very rich and non-trivial sequence of stages emerges in the evolution of the produced fireball. An important ongoing program in the field is the development of new observables and analysis techniques for anisotropic flow measurements, which would be sensitive only to one particular stage at a time in the heavy-ion evolution (e.g. only...
Jet quenching is a possible consequence of the formation of a quark-gluon plasma (QGP) in collision systems, but to date no significant jet quenching has been observed in small systems. At the same time final states of pp and pPb collisions with large underlying event activity exhibit collective behavior that resembles hydrodynamic evolution. It is believed that observed level of the...
In heavy-ion collisions a strong magnetic field is created ($\sim$ 10$^{15}$ T), which together with the presence of a non-zero electric and axial charge density, leads to vector and axial currents called the Chiral Magnetic Effect (CME) and Chiral Separation Effect (CSE), respectively. Their coupling gives rise to a collective excitation in the quark-gluon plasma (QGP) called the Chiral...
Studies of the production of light-flavor hadrons in different collision systems are of prominent importance to investigate the hadronisation process. Recently, the ALICE Collaboration has presented results from pp, pA and AA collisions, exploiting its detector's excellent tracking and PID capabilities down to low transverse momentum. Pions, kaons, protons and (multi-)strange hadrons have been...
We study exclusive quarkonium production in the dipole picture at next-to-leading order (NLO) accuracy, using the non-relativistic expansion for the quarkonium wavefunction. This process offers one of the best ways to obtain information about gluon distributions at small x, in ultraperipheral heavy ion collisions and in deep inelastic scattering. The quarkonium light cone wave functions needed...
In this contribution we will present the latest results on two-particle number and transverse momentum correlations from the ALICE Collaboration in order to study the initial stages and dynamic evolution of nucleus-nucleus collisions from small to large systems.
In pp and p-Pb collisions, the physical origin of long-range flow-like correlations remains an open question, with implications...
The Color Glass Condensate (CGC) effective field theory (EFT) at leading order describes well the Deep Inelastic Scattering (DIS) inclusive cross section data at small-x as measured by the HERA experiments [1-3]. Recently the inclusive DIS impact factors have been calculated in Next-to-Leading Order (NLO) accuracy in CGC EFT [4-6], and the soft gluon divergence present at NLO has been...
Early time dynamics of heavy-ion collisions represents an important quest to connect the initial conditions with the hydrodynamic evolution and to understand thermalisation in general. Directly sensitive measurements have remained elusive so far. Electromagnetic radiation is a sensitive probe to study QCD systems throughout the full time evolution including the very early stages. In this...
Heavy quarks (charm and beauty) are produced in abundance during the early stage of ultrarelativistic heavy-ion collisions. They therefore experience the full evolution of the quark-gluon plasma (QGP). This makes them unique probes of the initial conditions and of the collective behaviour of the medium as it expands and cools.
The elliptic flow ($v_2$) is an observable that reflects the...
We present the forward rapidity gap spectra from proton-lead collisions for both pomeron-lead and pomeron-proton topologies measured at CMS. The analysis is performed over 10.4 units of pseudorapidity at a center-of-mass energy of $\sqrt{s}_{NN}=8.16$ TeV, i.e. almost 300 times higher than previous measurements of diffractive production in proton-nucleus collisions. For the pomeron-lead...
We present the time resolved evolutions of the anisotropic flow coefficient $v_n$ with consideration of both the linear and non-linear dependence on the initial eccentricities $\epsilon_m$. The relativistic Boltzmann equation is utilized in the few collision regime in order to model the evolution of the phase space distribution.
Our analytically calculated time-dependent flow harmonics are...
Within the Color Glass Condensate effective theory, most observables are computed by adopting the eikonal approximation. At asymptotic energies, this corresponds to treating the dense target as an infinitely thin shockwave. However, finite longitudinal width corrections to the shockwave approximation might be important at realistic energies. In such a case, the propagation of a parton through...
Measurements of two-particle correlations in $pp$ collisions show features that are strikingly similar to those seen in heavy-ion collisions, suggesting that a tiny droplet of the QGP is produced even in such collisions. In the $pp$ collisions models that attribute the correlations to semi-hard processes can also qualitatively reproduce the measurements. In this talk, we report on a series of...
In this talk, we report on phenomenological studies using the recently developed 3-D IP-Glasma initial state. Our 3-D formulation generalizes the boost invariant formulation by including both the rapidity evolution (JIMWLK) and the temporal evolution (Classical Yang-Mills) in the longitudinal direction. Special attention is paid to the local realization of Gauss law in a 3D+1 environment....
We present new results on photon production in heavy ion collisions, including prompt, pre-equilibrium, and thermal photon production from quark gluon plasma and hadron gas phases. We use a model consisting of IP-Glasma initial condition, KoMPoST pre-equilibrium evolution, MUSIC hydrodynamics, and UrQMD transport to both describe hadron production and provide input for the calculation of...
The ridge phenomena observed in small size systems such as high multiplicity pp and pA collisions triggered a lot of activity to study the two particle correlations from the initial state point of view. In this talk, we will discuss the multiplicity and mean transverse momentum dependence of v2 by adopting CGC-based calculations in pA collisions. More precisely, we apply CGC techniques to...
For various centrality selections, we will present $v_{2}$ and $v_{3}$ measurements as a function of particle species and transverse momentum for several beam energies and system size. The longitudinal flow decorrelation $r_n(\eta,\eta_{ref} )$ $(n=2, 3)$ will be also presented at three different collision energies.
Investigating the beam-energy and collision-system size dependence of the...
Two-particle azimuthal correlation has been proposed to be one of the most direct and sensitive channels to access the underlying nonlinear gluon dynamics.
In hadron collisions at RHIC, forward particle production probes gluons at small x where the gluon density rises sharply.
During the 2015 RHIC run, STAR has collected data for measuring azimuthal correlations of neutral pions detected...
In this presentation, measurements of $v_2$ and $v_3$, in the p/d/$^3$He+Au collisions at 200 GeV will be shown as a function of $p_{T}$ and multiplicity from STAR. The non-flow is studied with several different methods using p+p collision as a reference. It has been found that non-flow subtracted $v_{n}$ signals are not sensitive to these methods. The $v_2$ signals are also extracted using...
Fluctuations of event-wise average transverse momentum ($[p_\mathrm{T}]$) and the harmonic flow ($v_n$) carry important information about initial-state geometry. Collisions of nuclei with large quadrupole deformation are predicted to produce an initial state with enhanced shape and size fluctuations, and result in a non-trivial correlation between $v_n$ and $[p_\mathrm{T}]$ in the final state....
Momentum anisotropies caused by collective flow phenomena in HICs have been known to convey a rich amount of information on the collision geometry. In pp and pA collisions the system size is too small for the hydrodynamic description of these anisotropies to be applicable. Instead, a microscopic description of the non-equilibrium dynamics has to be employed. Indeed, kinetic theory simulations...
Charged particle multiplicity spectra and hadron entropies are measured using the H1 detector at HERA, where positrons of energy 27.6 GeV collided with protons of energy 920 GeV. For the analysis, data on deep-inelastic scattering in the momentum transfer range $5< Q^2< 100$ GeV$^2$ and inelasticity range $0.0375< y< 0.6$ are used. The observed multiplicity spectra of charged hadrons are...
Particle production at forward rapidities in proton-nucleus collisions provides access to the target structure at very small momentum fraction x, where non-linear QCD dynamics is expect to play an important role. Recently, the CASTOR calorimeter at CMS [1], covering pseudodapidity region -6.6 < eta < -5.2, has released first jet spectra measurements in proton-lead collisions, probing nuclear...
We have compared four models of initial conditions of a fluid dynamic description of high energy heavy ion collisions, focusing on the expectation values and event-by-event fluctuations in the initial transverse energy density profiles from Pb-Pb collisions. Specifically, introducing a Fourier-Bessel mode expansion for fluctuations, we determine expectation values and two-mode correlation...
We present the computation of exclusive and inclusive dijet production in electron-proton and electron- nucleus collisions at small-x within the Color Glass Condensate effective field theory. We compute the cross- sections differentially in mean dijet momentum and momentum imbalance, as well as its corresponding elliptic anisotropy. For exclusive dijet production, we employ a dipole model with...
Fluctuations of event-wise average transverse momentum ($[p_\mathrm{T}]$)
and the harmonic flow ($v_n$) carry important information
about initial-state geometry.
Collisions of nuclei with large quadrapole deformation are predicted
to produce an initial state with enhanced shape and size fluctuations,
and result in non-trivial correlation between $v_n$ and $[p_\mathrm{T}]$
...
Strongly intensive observables can be used to measure forward-backward (FB) correlations between charged particles produced in hadronic collisions in two separate pseudorapidity intervals. Within the model of independent statistically identical particle sources, these observables do not depend on the mean value and fluctuations in the number of the sources, therefore the deviation from the...
Heavy quarks, which are produced at the earliest stage of relativistic heavy-ion collisions, probe the entire history of the quark-gluon plasma that is created in the collision. Initially the plasma is populated with chromodynamic fields which can be treated as classical. In the talk transport of heavy quarks interacting with such long-wavelength chromodynamic fields will be discussed. The...
We calculate eccentricities in dilute-dense limit of pA collisions, by calculating correlations functions of the energy density field of the Glasma immediately after the collision event at proper time $\tau = 0^{+}$. The proton is treated as a collection of a finite number of hot spots of Gaussianly distributed color charges, as in the IPGlasma setup. The correlations of its color charges are...
In the present work, we study the effect of mass-modifications of kaons ($K$) and antikaons ($\bar{K}$) on the experimental observables relevant for nucleus-nucleus collisions. The in-medium masses of $K$ and $\bar{K}$ mesons evaluated using effective hadronic chiral SU(3) mean field model are implemented in A Multi-Phase Transport (AMPT) model to calculate different experimental...
We study the kinematics of nuclei after a collision at close to the speed of light. The nuclei are treated as sources of color-glass condensate that form gluon fields between the nuclei after the collision. We consider this field to be the driving force in the subsequent deceleration and transverse motion of the nuclei. We solve this problem for early times in the general situation, and we...
A new model denoted ICCING (Initial Conserved Charges in Nuclear Geometry) reconstructs the initial conditions of BSQ conserved charges in the QGP by sampling the ($g \rightarrow q\bar{q}$) splitting function over the initial energy density. I will discuss the new open source C++ version of ICCING, coupled to TRENTO. We find that even at top LHC energies that the initial conditions due to...
The ultra-peripheral Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV performed at the ATLAS experiment are used to
study a rare light-by-light scattering process, $\gamma\gamma\rightarrow\gamma\gamma$, allowed in Quantum Electrodynamics via a loop diagram.
The poster summarises recent light-by-light measurements conducted using a combination of 2015 and 2018 datasets recorded by...
We develop a framework to simulate the 3+1D dynamics of the initial energy deposition in heavy-ion collisions by taking into account the finite longitudinal extent of the colliding nuclei in the Color-Glass Condensate framework. Based on a simple model for the color charge distributions of the colliding nuclei, we demonstrate how the boost-invariant limit is recovered at high energies along...
ATLAS measurements of dimuons produced via $\gamma\gamma$ scattering processes in inelastic, non-ultra-peripheral Pb+Pb collisions at 5.02 TeV are presented using an integrated luminosity of 1.9 nb$^{−1}$. The $\gamma\gamma \rightarrow \mu^{+}\mu^{-}$ pairs are identified via selections on pair momentum asymmetry and acoplanarity, and the contribution from the heavy flavor decay background is...
Abstract: J/ψ-meson is a bound state of charm and anti-charm (c ̄c) quark pair, whereas the heavy (anti)charm quarks are produced in the initial stages of ultrarelativistic heavy-ion collisions. The J/ψ production is sensitive to the presence of the deconfined state of quarks and gluons, quark-gluon plasma, which is expected to form in the nuclear collisions. Prompt J/ψ-mesons are produced at...
Neutron structure and skin thickness in nuclei have been traditionally measured by low-energy scatterings where the nuclei are only gently disturbed. Their precisions have been limited by theoretical uncertainties in modeling the nuclear force. Here, we propose an unconventional approach to probe the neutron skin by smashing isobar nuclei completely apart at relativistic energies to compare...
The deconfined state of matter created in hot and dense medium at ultra relativistic heavy-ion collision causes back-to-back charge separation along the direction of magnetic field produced due to energetic spectator protons, a
phenomena known as the chiral magnetic effect (CME). A new technique, the Sliding Dumbbell Method (SDM), is developed to search for back-to-back charge separation on...
Measurements made recently by the STAR collaboration show that the Lambda hyperons produced in relativistic heavy-ion collisions are subject to global spin polarization with respect to an axis coincident with the axis of rotation of the produced matter. Recently formulated formalism of relativistic hydrodynamics with spin, which is a generalization of the standard hydrodynamics, is a natural...
The system created in relativistic nucleus-nucleus collisions may possess large orbital angular momentum leading to the particle global polarization perpendicular to the reaction plane. The local asymmetries in the velocity fields due to anisotropic flow can generate vorticity and particle polarization along the beam direction. In parity violating weak decays of hyperons, the momentum...
Preliminary STAR-BNL data shows Pearson coefficient ($\rho\left(v_{n}\{2\}^{2},\left[p_{\mathrm{T}}\right]\right)$) could be an intriguing observable to probe the shape deformation in atomic nuclei. Using a well-built and popular multi-phase transport calculation (AMPT), millions of collision events are produced from initial stages to final hadrons comparing with limited statistics from...
We show that high-$p_\perp$ $R_{AA}$ and $v_2$ are way more sensitive to the QGP thermalization time, $\tau_0$, than the distributions of low-$p_\perp$ particles, and that the high-$p_\perp$ observables prefer relatively late thermalization at $\tau_0$ ∼ 1 fm/c. To calculate high-$p_\perp$ $R_{AA}$ and $v_2$, we employ our newly developed DREENA-A formalism, which combines state-of-the-art...
The seeds of jets are highly energetic partons, which are produced from hard scatterings in heavy ion collisions. As such, they might be affected by the precursor state of the quark-gluon plasma, the so-called glasma, via strong classical color fields. Starting from the glasma initial conditions, the Yang-Mills equations are solved analytically to leading order within the...
The last decade of hadron spectroscopy has unveiled a wealth of states that do not have the properties expected of particles composed of 2 or 3 valence quarks.
Among the most intriguing of these exotics is the X(3872), which various models attempt to describe as a hadronic molecule, a compact tetraquark, an unexpected charmonium state, or their mixtures. Production in heavy ion collisions,...
Medium induced parton energy loss is not conclusively established neither in very peripheral heavy-ion collisions nor in proton-ion collisions. However, the standard interpretation of azimuthal momentum anisotropies in theses systems implies some partonic rescattering. The upcoming light-ion runs at the LHC provide a unique opportunity to search for parton energy loss in different systems of...
Recent work by [Kajantie, McLerran, and Paatelainen][1] studies, in a completely classical setting, the gluon bremsstrahlung produced when a sheet of colored glass interacts with a color-charged point particle. Remarkably, the radiation spectrum thus calculated is in qualitative agreement with experiment. I will present here the results of our [paper][2], where we extend these results to...
Exclusive vector meson production is a powerful process to probe the gluonic structure of protons and nuclei at small Bjorken-$x$, and it also makes it possible to study the geometry of the nuclei in the transverse plane. An accurate description of the process requires us to use a vector meson light front wave function that correctly represents the meson. Currently, the light front wave...
Particle production at LHC energies results from the interplay of hard- and soft-QCD processes and is sensitive to non-linear QCD evolution in the initial state. In particular, for p-Pb collisions, one can use the proton to probe the low-$x$ dense gluonic fields of the Pb nuclei. The multiplicity and rapidity dependence of charged- and neutral-particle production, therefore, provides important...
Relativistic heavy-ion beams are accompanied by a large flux of equivalent photons, giving rise to a set of photon-induced processes. These can lead to photon-photon interactions in both ultraperipheral collisions, where the nuclei do not overlap, as well as in hadronic processes accompanied by the production of hot, dense matter. The latter provides a potentially sensitive electromagnetic...
We present the recent results of J/$\psi$-jet correlation and the cross-sections Y(nS) states in heavy-ion collisions, using the data collected by the CMS experiment at $\sqrt{s_{\rm{NN}}}=5.02$~TeV.
J/$\psi$ production has long been known to be modified in heavy-ion collisions, via, among many, the Debye screening effect. Indirect evidence of, in particular, the non-vanishing $v_{2}$ of...
We investigate the measurement of Hanbury Brown-Twiss (HBT) photon correlations [1] as an experimental tool to discriminate different sources of photon production. To showcase that HBT correlations can distinguish between such sources, we consider two different scenarios in which we enhance the yields from standard hydrodynamical simulations. In the first, additional photons are produced from...
The Colour Glass Condensate effective field theory is a useful framework for studying heavy ion collisions at ultra-relativistic energies, such as those reached at the Large Hadron Collider. In this framework, we study the rapidity evolution of Wilson lines that appear explicitly in cross section expressions. The next-to-leading order BK (Balitsky-Kovchegov) equation for the 2-point Wilson...
Using Bayesian inference, we present state-of-the-art quantifications of initial conditions as well as pre-hydrodynamic and hydrodynamic transport properties of quark-gluon plasma based on hadronic observables from both the Relativistic Heavy Ion Collider and the Large Hadron Collider [1,2]. Estimations of initial state properties are performed by marginalizing over the theoretical...
Color charge correlations in the proton at moderately small x
are extracted from its light-cone wave function. The charge
fluctuations are far from Gaussian. Correlators are described by
n-body GPDs which exhibit interesting dependence on impact parameter
as well as on the relative transverse momentum (or distance) of the
gluon probes.
This analysis provides initial conditions for...
The pre-hydrodynamic evolution of a heavy-ion collision can have important effects on final state observables, and has received significant renewed interest. Here, we utilize a state-of-the-art simulation chain of heavy ion collisions to extend our previous investigation on the effects of pre-hydrodynamic evolution on final-state observables to small systems. Our simulations include different...
Interesting features in the production of strange hadrons have been revealed in heavy-ion collisions. Observations include: the development, with centrality, of a peak in the $\Lambda/K^0_S$ ratio at intermediate $p_{\rm T}$; and the enhanced yield of strange and multi-strange baryons, compared to minimum bias pp collisions. These features have been further investigated by studying pp...
The LHCb collaboration has recently measured cross sections for the simultaneous production of two charmed-particles in p-p [1] and p-Pb [2] collisions. These include opposite-sign and same-sign D-meson pairs offering, for the first time, a chance to study the interplay of single-parton (SPS) and double-parton scattering (DPS) across different collision systems.
In this talk, we discuss our...
We present the elliptic azimuthal anisotropy coefficient ($v_2$) of the identified strange hadrons ($K_{S}^{0}$ and $\Lambda$) in pPb and PbPb collisions at 5.02 TeV, and the heavy-flavor hadrons ( J/psi, D$^0$) in pPb at 8.16 TeV and high-multiplicity pp at 13 TeV, using data collected by the CMS experiment at the LHC.
The $v_2$ values of identified strange hadrons were measured for the...
Dileptons and photons are unique tools to study the space-time evolution of the hot and dense matter created in ultrarelativistic heavy-ion collisions. They are produced continuously by a variety of sources, in particular prompt and thermal photons and semi-leptonic heavy-flavour hadron decays, during the entire history of the collision and traverse the medium with negligible final state...
Using the ALICE Zero Degree Calorimeters (ZDC) it is possible to study the very forward charged and neutral energy in pp and p-Pb collisions. By correlating these measurements with the midrapidity particle production, one obtains new direct insights into the initial stages of the collisions. New results on the energy detected in neutron and proton ALICE ZDC in pp collisions at $\sqrt{s}$ = 13...
Heavy-ion collisions at ultra-relativistic energies at the LHC provide a unique opportunity to study the strongly interacting quark-gluon plasma (QGP). Anisotropic flow phenomena provide valuable information on the initial conditions of heavy-ion collisions, the transport coefficients, and the dynamic evolution of the created QGP. In this talk, we present investigations of the...
The CMS Collaboration reports on new differential measurements of $\gamma\gamma \rightarrow \mu^{+}\mu^{-}$ production in ultra-peripheral PbPb collisions at $\sqrt{s_{\rm NN}}$ = 5.02~TeV, using data collected during the 2018 LHC run with an integrated luminosity of 1.5~nb$^{-1}$. Photon-photon interactions have been observed in hadronic heavy-ion collisions by STAR and ALTAS experiments at...
At Relativistic Heavy Ion Collider (RHIC) Beam Energy Scan (BES) energies, the dynamics of the pre-hydrodynamic stage and the effects from a nonzero net baryon current become essential components of the dynamical evolution of the collision fireball. We develop a (3+1)-dimensional initial stage model for both energy-momentum and the net baryon current, as dynamical initial conditions for a...
Multiparticle azimuthal correlations have proved their usefulness to study and constrain the properties of the quark-gluon plasma (QGP) produced in ultrarelativistic heavy-ion collisions. Recently, the event-by-event correlated fluctuations between two different flow amplitudes have been measured using Symmetric Cumulants. These results exhibit a better sensitivity to the transport properties...
In ultrarelativistic heavy-ion collisions, strong electromagnetic fields arising from the Lorentz-contraction of highly charged nuclei generate a large flux of quasi-real photons. STAR measurements of the Breit-Wheeler photon-photon fusion process in Ultra-Peripheral Collisions (UPC) have recently demonstrated that the colliding photons are linearly polarized and that the linear polarization...
In ultrarelativistic heavy-ion collisions a quark-gluon plasma is created. Its pre-equilibrium evolution includes some fascinating phenomena of QCD. Focusing on the regime when gluonic occupation numbers are large, which can be achieved in the high energy and weak coupling limit, classical-statistical lattice simulations can be used to extract nonperturbative information on the dynamics. In...
Within the p-Pb data sample collected by the LHCb detector at sqrt(s_NN) = 8.16 TeV, a rich set of open charm hadrons is observed with abundant statistics.
Thanks to the LHCb forward acceptance that is complementary to general purpose detectors, with excellent performance in particle reconstruction and identification,these charm states are studied down to zero pT with overwhelming precision....
In this presentation, we show measurements of the second Fourier coefficient of the azimuthal distribution (elliptic flow, v2) of prompt D0 and D0bar mesons using the four-particle cumulants technique at midrapidity (|y| < 1). These measurements are performed using data from PbPb collisions at 5.02 TeV collected by the CMS detector at the LHC in 2018. The v2 of prompt D0 and D0bar mesons are...
Direct photons are emitted unscathed from all the stages of the relativistic heavy ion collisions and therefore are an excellent probe to study the properties of Quark Gluon Plasma (QGP) as they do not interact strongly with the medium. PHENIX has already measured a direct photon excess in Au+Au collisions at 200 GeV in the low momentum region with respect to p+p collisions. With the results...
Building upon Ref. [1], we present an improved three-dimensional dynamical initialization model for heavy-ion collisions, implementing local energy-momentum conservation and baryon charge fluctuations at string junctions [2]. These improvements lead to an excellent description of the charged hadron and net proton rapidity distributions in Au+Au collisions from 7.7 to 200 GeV. Based on these...
The intense electromagnetic fields produced by ultra-relativistic heavy nuclei have been proposed as a source of quasi-real photons i.e. in the Weizsacker-Williams equivalent photon method. A photon from one nucleus can fluctuate into a quark antiquark pair and interact directly with the other nucleus to produce a vector meson (e.g. $\rho^0$). Recent STAR measurements of the Breit-Wheeler...
We propose a new parameterization of the three-dimensional initial condition for the application of the hydrodynamic model to relativistic heavy-ion collisions. In particular, we implement different average-energy production scaling behaviors for different rapidity regions in this proposed ansatz. Near mid-rapidity, the energy deposition is given by the well-tested TRENTo model, with and...
It is well established that high multiplicity pp and p-Pb collisions exhibit many of the signatures associated with the formation of a sQGP in heavy-ion collisions. If final-state interactions are responsible for this, one would also expect some amount of jet modification.
Here, we present the search for jet quenching effects by studying the yield of charged particles associated with high...
Understanding the relation between QCD evolution in the Bjorken limit and the Regge limit is crucial to achieve a complete and smooth picture of proton and nuclear structure. The hope in the small x regime, where gluon density is expected to reach saturation and the naif partonic picture is expected to break down, was that by computing higher-order corrections to small x evolution (BK...
In ultrarelativistic heavy-ion collisions, two-particle transverse momentum correlations provide information on the system dynamics and properties. Recently published results by ALICE on the two-particle transverse momentum correlator $G_{2}$ in Pb-Pb collisions demonstrate a narrowing of the correlation function in the azimuthal direction from peripheral to central collisions, which has...
There exist simple and direct relations between the state of the system at early times, and final-state observables. For example, the final elliptic flow is approximately proportional to the initial eccentricity, which represents the leading term in a cumulant expansion of the initial density. This expansion is a systematic method written in terms of length scales that contains the global...
Going beyond the simplified gluonic cascades, we have introduced full flavor treatment by including both gluon and quark degrees of freedom for partonic cascades inside
the medium. We then solve the set of coupled evolution equations with splitting kernels calculated analytically for exponentially expanding and Bjorken media to arrive at
medium-modified parton spectra for quark and gluon...
It is well established that the spatial asymmetries of the overlap region in the initial state of a heavy ion collision, together with their fluctuations, are quite faithfully translated into final-state momentum anisotropies by a fluid-dynamical evolution. We investigate the relationship between initial-state eccentricities and final-state anisotropic flow harmonics for a simplified...
It is a long standing puzzle that hydrodynamic calculations give larger
elliptic flow for ultra-central Pb+Pb events than experiments. One explanation
is that sampling from a single particle distribution in Glauber model generates
too much shape fluctuation, which can be expected to be modified by NN
correlations. We study the fluctuation of shape-deformation as currently
implemented...
The study of jets in heavy ion collisions provides important information about the interaction of partons with the quark-gluon plasma. Originating from hard scatterings among partons of the colliding nuclei, jets are affected by the entire space-time evolution of the medium, including the pre-equilibrium stage. I report on our numerical lattice simulations of jets traversing the...
We present a new Monte Carlo that generates events based on statistics
specified with any 1-point and 2-point function, including arbitrary
correlations.
Such a code can be useful for quickly generating events when
analytic formulas are known (for example from recent derivations of CGC
fluctuations), and for use in Bayesian analyses, where the initial state can
be characterized by...
Jets are powerful tools for probing the properties of quark-gluon plasma (QGP) formed in high-energy nucleus-nucleus (AA) collisions. Recent results in high-multiplicity pp collisions suggest that QGP is also formed in such collisions since they show similar features to those that are associated with QGP production in AA collisions. Measurement of jet properties in pp collisions as a function...
The out-of-equilibrium quark-gluon plasma and how it equilibrates in the pre-equilibrium stage of ultrarelativistic heavy-ion collision is of decent interest. Based on effective kinetic QCD theory including both gluon and all light quark/antiquark degrees of freedom, we investigate the pre-equilibrium dynamics of the quark-gluon plasma and how it connects to near-equilibrium viscous...
In the recent past the STAR collaboration reported the measurement of Λ hyperon in non-central AuAu collisions. The origin of this polarization was successfully modeled as the vorticity present in the QGP fluid due to the non-zero angular momentum in non-central collisions. Other phenomena may generate vorticity in a fluid. A fast parton crossing the QGP transfers momentum and energy to it and...
We present a systematic study of the pre-equilibrium dynamics of relativistic heavy-ion collisions using the microscopic transport model SMASH. We focus on the time evolution of the distributions of energy-momentum currents and three types of conserved charges, produced by string excitation and fragmentation at intermediate and high energies. We address their dependence on the system size and...
The properties of the strongly intensive variable Σ [1] characterizing correlations between the number of particles produced in two observation windows separated by a rapidity interval in pp interactions at LHC energies are studied in the framework of the string fusion approach [2,3]. The analytical calculations are supplemented by the MC simulations permitting to take into account the...
Measurements of jet suppression and modification in heavy-ion collisions provide powerful and broad information on the dynamics of the hot, dense plasma formed in relativistic nucleus-nucleus collisions.
In this talk at the Initial Stages conference, we present measurements of jet energy loss and modification which are sensitive to the initial transverse geometry of Pb+Pb collisions.
The...
Recently, jet substructure observables have been widely used in the study of jets. Some observables are sensitive to the wide angle soft particles within the jet, for example, the Lund plane distribution with different jet radii and soft drop parameters. As the jet loses energy and momentum during its evolution inside the quark-gluon plasma (QGP), the “lost" energy and momentum is deposited in...
Momentum anisotropy, quantified by the coefficients of anisotropic flow, $v_n$, is observed in the final states of both small and large nuclear collision systems. In large A-A systems, anisotropy is of geometric origin, and determined by a hydrodynamic response to the initial spatial anisotropy of the system. In smaller systems, such as p-A, d-A or peripheral A-A collisions, a range of...
A colliding system of ultra-relativistic heavy-ions is commonly simulated with phenomenological models, which include relativistic hydrodynamics and a hadronic cascade afterburner. Typically, any model of heavy-ion collisions must include some estimate of the initial conditions, whose properties are a subject of intense research. Also, many of the common approaches used in the field have no...
The parton distribution functions of nuclei are not well constrained for most of the kinematic domain probed with heavy-ion collisions at the LHC. Direct photons in proton-nucleus, W and Z boson production in proton-nucleus and nucleus-nucleus collisions at the LHC can be used to constrain the nuclear parton distribution functions. In this contribution, we present recent results on W- and...
In the initial stages of heavy-ion collisions, topological QCD vacuum fluctuations can induce local parity and charge-parity violations, evincing charge separation in the presence of strong magnetic field, a phenomenon known as the chiral magnetic effect (CME). The CME-driven charge separation is along the magnetic field direction, mainly produced by the spectator protons in relativistic...
The sPHENIX experiment at RHIC is currently under construction and on
schedule for first data in early 2023. Built around the excellent
BaBar superconducting solenoid, the central detector consists of a
silicon pixel vertexer adapted from the ALICE ITS design, a silicon
strip detector with single event timing resolution, a compact TPC,
novel EM calorimetry, and two layers of hadronic...
Initial conditions for relativistic heavy-ion collisions may be far-from-equilibrium but it is expected that on very short time scales the dynamics converge to a universal attractor that defines hydrodynamic behavior. We investigate how far-from-equilibrium effects may influence experimentally driven searches for the Quantum Chromodynamic critical point at RHIC. We find that the path to the...
The proposed high-luminosity high-energy Electron-Ion Collider (EIC) will explore the proton/nuclear structure, search for gluon saturation and precisely determine the nuclear parton distribution functions (nPDFs) in a wide x-$Q^{2}$ phase space. Heavy flavor and jet measurements at the future EIC will allow us to better constrain the nPDFs within the poorly constrained high Bjorken-x region,...
The production of heavy quarkonia states in p+A collisions is sensitive to a range of initial- and final-state effects that must be quantified in order to fully understand the dynamics of heavy quarks in the QCD medium. One way to disentangle the various effects is by measuring charmonia production in different rapidity and momentum regions, using various beam species. Here we present...
In 2018, LHCb recorded ~210 microbarn^{-1} integrated luminosity of PbPb
collisions at sqrt(s_NN) = 5.02 TeV. With an increase of the luminosity by a
factor 20 compared to the previous 2015 PbPb dataset, precise measurements on
photo-produced charmonia in ultra-peripheral collisions are foreseen. Moreover,
the great momentum resolution of the detector allows to study photo-produced
J/psi...
The STAR Collaboration has performed several detector upgrades in the last few years, including the replacement of the inner chambers of the Time Projection Chamber (iTPC, with pseudorapidity $0 < |\eta| < 1.5$), the Event Plane Detector (EPD, $2.1 < |\eta| < 5.1$) and the Endcap Time of Flight (eTOF, $-1.5 < \eta < -1.0$) that are commissioned and fully operational since 2019. A full suite of...
Nuclear deformation is a ubiqutous phenomenon for most atomic nuclei, reflecting collective motion induced by interaction between valance nucleons and shell structure. In most cases, the deformation has a quadrupole shape $\beta$ that is axially and refection symmetric, either prolate $\beta>0$ or oblate $\beta<0$. Collisions of deformed nucleus lead to large shape and size fluctuations in the...
Photon-induced reactions in ultra-peripheral collisions (UPCs) of Pb-emphasized textPb nuclei at the LHC have been studied using the ALICE detector for several years. The ALICE detector can measure the photoproduction cross section for vector mesons at various rapidities, centre-of-mass energies and collision systems. This process allows us to study the energy evolution of the gluon content of...
Measurements of $W^{\pm}$, $Z$, and charged-hadron production in Pb+Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV
are presented using data recorded by the ATLAS experiment at the LHC in 2015 corresponding to a total integrated luminosity of 0.49\,nb${}^{-1}$.
The the electro-weak (EW) bosons are reconstructed in both the electron and muon decay channels.
The EW boson yields measured in Pb+Pb...
In this talk, the prospects and the physics goals of a new fixed-target experiment, NA60+, which has been proposed for taking data with heavy-ion collisions at the CERN SPS in the next years, will be presented. The competitiveness and complementarity of the NA60+ physics program in the landscape of the experiments foreseen at other facilities in the next decade will also be discussed.
The...
The measured charge distribution of a nucleus is often used to sample
positions of nucleons within the nucleus. However, since nucleons
have finite size, the resulting charge distribution is different from
the sampled distribution. We show that this can have significant
observable effects: Not only does it increase the size of the
nucleus, but also changes the surface diffusiveness. ...
We calculate the energy loss and angular radiation distribution for heavy quark propagating through the quark-gluon plasma at the LHC in the framework of the QCD extended Moller theory i.e. BDMPS formalism plus large Coulomb logarithms. We study the role of Coulomb Logarithms in heavy quark propagation. We calculate the energy loss and estimate the Quenching Weights both including the phase...
Within the dipole picture for electron-nucleus ($eA$) deep inelastic scattering (DIS) at small Bjorken $x$, we consider special, ``aligned jet", configurations, which are very asymmetric: one of the quarks from the dipole fluctuation of the virtual photon carries most of the longitudinal momentum of its parent. We argue that such configurations correspond to relatively large dipole sizes and...
The electroweak process is often used to probe the parton distribution functions (PDFs) in a proton and the nuclear parton distribution functions (nPDFs) in heavy ions. In this presentation, the measurements of the Drell-Yan process in pPb collisions at 8.16 TeV and of Z bosons decaying to pairs of leptons in PbPb collisions using data collected at 5.02 TeV from the CMS experiment at the LHC...
Studies of the phase diagram of the strongly interacting matter is one of the hottest topics in high energy physics. While the transition from hadronic matter to Quark-Gluon Plasma (onset of deconfinement) is now rather uncontroversial, the difficulties in obtaining a unique and quantitative prediction of the QGP signal within the QCD theoretical framework remain and the scientific community...
We will present the design and physics performance of a high-granularity Forward Calorimeter (FoCal) upgrade for ALICE. The main goal of the FoCal detector is to measure isolated direct photon production to constrain the low-x gluon density in the proton and nuclei and to look for deviations from linear QCD evolution in the high gluon-density regime. In addition, correlation measurements using...
ATLAS measurements of dimuons produced via $\gamma\gamma$ scattering processes in inelastic, non-ultra-peripheral Pb+Pb collisions at 5.02 TeV are presented using an integrated luminosity of 1.9 nb$^{−1}$. The $\gamma\gamma \rightarrow \mu^{+}\mu^{-}$ pairs are identified via selections on pair momentum asymmetry and acoplanarity, and the contribution from the heavy flavor decay background is...
The last decade of hadron spectroscopy has unveiled a wealth of states that do not have the properties expected of particles composed of 2 or 3 valence quarks.
Among the most intriguing of these exotics is the X(3872), which various models attempt to describe as a hadronic molecule, a compact tetraquark, an unexpected charmonium state, or their mixtures. Production in heavy ion collisions, as...
We present a new Monte Carlo that generates events based on statistics specified with any 1-point and 2-point function, including arbitrary correlations. Such a code can be useful for quickly generating events when analytic formulas are known (for example from recent derivations of CGC fluctuations), and for use in Bayesian analyses, where the initial state can be characterized by...
We develop a framework to simulate the 3+1D dynamics of the initial energy deposition in heavy-ion collisions by taking into account the finite longitudinal extent of the colliding nuclei in the Color-Glass Condensate framework. Based on a simple model for the color charge distributions of the colliding nuclei, we demonstrate how the boost-invariant limit is recovered at high energies along...
In 1974, J. L. Anderson and H. R. Witting proposed the Relaxation Time Approximation (RTA) to the relativistic Boltzmann equation [1], following all the development already made in the non-relativistic case by Bhatnagar, Gross and Krook [2]. This approximation is used in several fields of physics and has been recently employed to study the hydrodynamization of the matter produced in...
The ALICE experiment, located at the CERN LHC, is dedicated to study the physics of ultra-relativistic heavy-ion collisions. In order to operate the ALICE Time Projection Chamber (TPC) in continuous mode, recording the full minimum-bias interaction rate of 50 kHz in Pb − Pb collisions, as anticipated at the LHC in Run 3 and beyond, the gated Multi Wire Proportional Chambers (MWPCs) were...
