Ultra-peripheral collisions (UPC) of heavy nuclei provide the opportunity to study interactions between high energy photons induced from the electromagnetic field of ultrarelativistic nuclei and the nuclei from the other beam. The photon fluctuates to a quark-antiquark dipole which then elastically scatters off the nucleus, emerging as vector meson and opposite-charge pseudoscalar meson...
Photonuclear interactions are studied in ultra-peripheral p-Pb collisions with the ALICE experiment, where the photon radiated by a Pb nucleus probes the gluon density of the proton at low Bjorken-x. The exclusive $\rm{J/\psi}$ photoproduction cross section $\rm{\sigma(\gamma + p \rightarrow J/\psi + p)}$ is expected to follow a power law trend as $x$ decreases, but it should deviate from this...
The classical field approximation to Color Glass Condensate for two colliding nuclei has been solved in the literature using numerical methods and recursive analytic solution. In the weak field limit, analytic solutions in transverse momentum space have also been known for some time. Based on the latter, we derive expressions for the space-time dependence of classical gluon 2-point functions...
We developed a formalism to study momentum anisotropy, in particular, the collective flow $v_2$, in the ultra-relativistic onium-onium scattering. We derived the impact-parameter dependent cross section up to the next-to-leading order in the eikonal approximation. With this formalism, we are able to interpret the origin and behavior of $v_2$ in the dilute limit, by investigating the elementary...
During the last years, there has been an increasing interest in how the quark mass affects the jet quenching phenomena and dynamics of heavy flavor in HIC. Here, we will present a new effect, which consists in anisotropic broadening and gluon radiation sourced by the background flow, transverse to the parton momentum, and sensitive to the quark mass. This effect appears due to a modification...
Correlation functions of energy flow operators have been recently proposed as a tool to identify the onset of colour coherence within the jets. As a promising exploration avenue to unveil the scales of the Quark-Gluon Plasma, it has yet to be demonstrated how the medium back-reaction to the jet propagation will blur such identification. In this work, by using a perturbative prescription to...
Recent measurements by the CMS and ATLAS experiments reveal a deficit of charged particles in pp collisions with excited Υ(nS) states compared to the Υ(1S) ground state. This observation is suggested to be a manifestation of excited bottomonia suppression in pp interactions. The analysis presented in this talk is an independent approach, complementary to the CMS and ATLAS analyses, based on...
This project aims the application of non-extensive statistics, more specifically that proposed by C. Tsallis, in the study of the transverse momentum distribution of mesons composed of charm quarks produced in collisions between heavy ions at relativistic energies. Non-extensive statistics has been very successful in the description of transverse momentum spectra of particles produced in...
Particle correlations are a powerful tool to study the bulk properties in relativistic heavy ion collisions. The momentum correlations between identical particles originating from the same particle-emitting source, referred to as the Bose-Einstein correlations, measure scales that are related to the geometrical size of the source. The two particle azimuthal angular correlations measure the...
Distinguishing between the modification of quark- and gluon-initiated jets in the quark-gluon plasma (QGP) remains an unresolved challenge without a definitive answer from experiment. We demonstrate that a fully data-driven technique, known as topic modeling, may be used to study the separate modification of quark and gluon jets experimentally. Our proof-of-concept study is based on...
The measurement of the dijet production cross-section in p+Pb collisions is of great interest to the understanding of initial state effects. The analysis of this channel can provide input to the parameterization of the modification of parton distribution functions (PDFs) in nuclei and to search for the onset of non-linear QCD effects or gluon saturation at low Bjorken-x. In 2016, the ATLAS...
We present calculations of dielectron anisotropic flow in heavy-ion collisions at HADES beam energies from a hadronic transport approach. The collectivity of the electromagnetic radiation produced during the evolution of these collisions has recently been dubbed as a barometer, serving as a probe for the flow velocity of the underlying hadronic matter. In particular, we study the elliptic flow...
Keywords : Heavy-ion Collisions, Event generator, EPOS, PHSD, EPOSi+PHSDe, Quark-Gluon
Plasma
Ultrarelativistic heavy-ion collisions at RHIC and the LHC provide a hot and ultra-dense form of matter composed of deconfined quarks and gluons, named QGP. Different models like EPOS and PHSD allow to study the space-time evolution of such heavy-ion collisions. Their dynamics is complicated;...
The electromagnetic fields produced by non-central heavy ion collisions are extremely powerful and give rise to a plethora of fascinating subjects in the strongly interacting matter. Their evolution is a significant and unresolved issue.
In this talk, firstly, I will show the electromagnetic evolution in the pre-equilibrium stages which is a gluon-dominated and far-from-equilibrium system...
The hotspot model has proven to be an efficient tool to study coherent and incoherent diffraction HERA data by modelling the initial state fluctuations of the gluon density of the proton. The hotspot model in its original form is a non-perturbative model applicable for low momentum transfer and underestimates the incoherent cross section in orders of magnitude when extended for large momentum...
Bayesian inference provides a powerful approach to constrain jet quenching model parameters using experimental measurements. It remains an open question, however, which jet observables provide complementary information in this approach, and in turn which observables the community should focus on measuring and calculating. In this talk we report a first, exploratory study which incorporates jet...
In this work, we assess the impact of the expansion of the medium on angular distribution of gluons at different kinematical scales in a medium-induced cascade . Firstly, we study the scaling of the gluon spectra at low$-x$ between expanding and static medium profiles and apply them to obtain the transverse momentum broadened spectra. The numerical solutions for the in-medium cascades are...
In the context of jet-medium interaction, we consider the response of QCD-like plasma to energy/momentum disturbance as a function of the gradient. For both N=4 super-Yang Mills theory in strong coupling limit and kinetic theory under relaxation time approximation, we find that hydrodynamic modes continue dominating medium's response even in the region where Knudsen number is large. However,...
Heavy quarks, like charm quarks, are produced early in the relativistic heavy-ion collisions and probe all stages of the evolution of the created medium – the Quark Gluons Plasma. Two-particle correlations at low relative momentum (the femtoscopic correlations) are sensitive to the interactions in the final state and the extent of the region from which correlated particles are emitted...
The LHCb experiment has recently undergone a series of major upgrades: the entire tracking system has been replaced with higher-granularity sensors, the readout electronics have been upgraded, and all hardware triggers have been replaced with a new state-of-the-art streaming readout system. In addition, the gaseous target SMOG system has been upgraded with a dedicated storage cell to greatly...
The ALICE experiment has been upgraded over the last years during the LHC Long Shutdown 2.
With the new and upgraded detectors ALICE is now capable of reading out the data of the collisions in a continuous way. With a data acquisition rate 100 times larger than before, an integrated luminosity of more than 10 nb$^{-1}$ is expected to be collected for Pb--Pb collisions during the Run 3...
Constraining the initial condition of the QGP using experimental observables is one of the most important challenges in our field. Recent studies show that the Pearson Correlation Coefficient (PCC) between $v_n$ and event-wise mean transverse momentum $[p_\mathrm{T}]$, $\rho_n(v_n, [p_\mathrm{T}])$, and $[p_\mathrm{T}]$ fluctuations can probe several ingredients of the initial state. This talk...
Measurements of jet substructure in ultra-relativistic heavy ion collisions suggest that the jet showering process is modified by the interaction with quark gluon plasma. Modifications of the hard substructure of jets can be explored with modern data-driven techniques. In this study, a machine learning approach to the identification of quenched jets is designed. Jet showering processes are...
We have studied the influence of realistic modeling of the medium formed in
Relativistic Heavy-Ion collisions on Jet Quenching phenomena. We used JEWEL to
simulate the medium modified parton shower and coupled it with vUSP-hydro$+\rm
T_RENTo$ models. We have studied the influence of these combination of models on jet observables
such as $R_{AA}$, jet mass, $x_J$ and subjet...
Understanding the apparent absence of the modification of high-$p_T$ partons in small colliding systems has become critical. A major avenue of investigation that remains largely unexplored is the identification of observables that are experimentally more robust in small colliding systems than the traditional $R_{AA}$. In recent years the study of jet substructure observables in heavy-ion...
Heavy flavor jets are powerful tools to gain insight into the in-medium partonic energy loss mechanisms and the transport properties of the quark-gluon plasma (QGP) in high-energy nuclear collisions. In this work, we present the first theoretical study of the longitudinal momentum fraction $z_{||}$ carried by $\rm{D^0}$ meson in jets in Pb+Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV. The...
The ALICE experiment at the LHC investigates the properties of the hot and dense nuclear matter created in heavy-ion collisions. By comparing the particle production in pp and p--Pb collisions, possible nuclear initial state effects can be isolated. Measurements of the $\omega$ meson $p_\text{T}$-spectra in pp and p--Pb collisions not only allow for a determination of the nuclear modification...
Measurements of neutral mesons in small collision systems can serve as a baseline to understand modifications in heavy-ion collisions, where a QGP is formed.
These measurements can also be used to test pQCD predictions and to constrain fragmentation functions as well as parton distribution functions.
Furthermore, a precise knowledge of the $\omega$-meson production improves the measurement...
Recent results of charmed baryon production in $pp$ collisions showed a significant enhancement of the baryon-to-meson ratio compared with the expectation based on $e^{+}e^{-}$ collisions. This indicates that the charm fragmentation into hadrons is not an universal process among different collision systems, and different mechanisms may play a role in the hadronic collisions with respect to...
Jets can be copiously produced in heavy-ion collisions at the LHC energies. Their calibration is crucial for precise measurements of various processes, such as top-quark pair production. The poster presents the measurement of jet energy scale and resolution in proton-lead collisions collected at 8.16 TeV in 2016. The balance between Z boson and jet transverse momenta is explored for jet...
The precise measurement of the neutral meson production in pp collisions can be used to constrain fragmentation functions and parton density functions needed by pQCD calculations. Additionally, those measurements serve as input for direct photon analyses.
Moreover, the dependence of the neutral meson cross section on the event charged-particle multiplicity could give further insight into...
Measurements of the production of hadrons containing heavy quarks (charm and beauty) allow a study of cold nuclear matter (CNM) effects such as gluon saturation, shadowing and energy loss in p-Pb collisions. Understanding these effects is important for the proper interpretation of results in Pb-Pb collisions. In addition, the measurements provide the possibility to investigate the...
We present a new high-statistics measurement of inclusive $J/\psi$ production versus event multiplicity in $p$+$p$ collisions at $\sqrt{s} = 500$ GeV with the STAR experiment at RHIC. At mid-rapidity, calorimeter-triggered events are selected for candidate $J/\psi$ detection in the dielectron decay channel. Existing measurements at both $\sqrt{s} = 200$ GeV from STAR and $\sqrt{s} = 7$ TeV...
Jet fragmentation allows us to explore the evolution process of the QCD jets. It can be studied using the transverse momentum ($j_\mathrm{T}$) and longitudinal momentum fraction ($z$) of constituent particles. The $j_\mathrm{T}$ distributions of jet fragments have been measured in pp and p—Pb collisions at $\sqrt{s}$, $\sqrt{s_{NN}}$ = 5.02 TeV with ALICE, and various parton-shower models...
The differences in hadron chemistry observed at $e^{+}e^{-}$ machines versus hadron colliders may indicate that the mechanisms by which partons evolve into visible matter are not universal. In particular, the influence of the underlying event in hadron collisions requires further study. With full particle ID, precision vertexing, and a high rate DAQ, the LHCb detector is uniquely well suited...
Measurements of jet properties in small systems provide insights into perturbative and non-perturbative QCD aspects of jet structure and cold nuclear matter effects. Additionally, recent studies of high-multiplicity final states in small collision systems exhibit signatures of collective effects that are conventionally associated with the formation of hot and dense, color-deconfined QCD...
Partonic scatterings with high momentum transfer occur before the formation of the quark-gluon plasma (QGP) in heavy-ion (A+A) collisions and result in collimated collections of hadrons called jets. The modification of the parton shower in the QGP compared to that in proton-proton (p+p) collisions offers insight into the nature of the medium's interaction with colored probes. Typically, this...
Nuclear parton distribution functions (nPDFs) are an essential part in predictions of heavy-ion collisions. nPDFs have been determined via "global QCD analysis" in which nPDF-dependent prediction of a given process compares with its actual measurement. The challenging part of nPDF extraction is the uncertainty estimation. The most common approach for this purpose is Hessian method which has...
Production measurements of heavy quark pairs in pp collisions are a known tool to test perturbative quantum chromodynamics calculations. In addition, they provide a reference for the corresponding studies in nuclear collisions. Indeed, in Pb-Pb collisions, the heavy quarks are produced at the early stages of the collision and can then experience full medium evolution. Open heavy flavor hadrons...
Two-particle azimuthal correlations are a powerful tool to investigate the details of the mechanisms of jet quenching and hadron production. Suitable candidates for these studies are strange mesons ($\mathrm{K^{0}_{S}}$) and baryons ($\Lambda/\overline{\Lambda}$), as their relative production rates differ for jets originating from quark or gluon. Measurements of near- and away-side hadron...
The production of prompt photons in association with jets is a very sensitive probe of the gluon distribution in light and heavy nuclei as well as of the properties of the quark-gluon plasma. We present a new calculation of prompt photon production with up to three jets at next-to-leading order of (NLO) QCD matched to parton showers with the POWHEG method. As applications, we examine...
We present unquenched correlator data and corresponding reconstructed spectral functions for quarkonium in both pseudoscalar and vector channels. Correlators are obtained using clover-improved Wilson fermions on $N_f=2+1$ HISQ lattices. To be on the constant line of physics bare quark masses are tuned to reproduce the mass spectrum of quarkonium by comparing the mass spectrum obtained from the...
Quarkonium measurements in hadronic collisions can provide insights into quantum chromodynamics (QCD). The quarkonium formation involves both the perturbative and non-perturbative regimes of QCD and the mechanisms at play are not yet fully understood. In order to get new insights and help constraining model calculations, ALICE has measured several quarkonium observables in proton-proton (pp)...
We have studied the shear ($\eta$) and bulk ($\zeta$) viscosities of hot QCD medium in a weak magnetic field. These viscosities are calculated by using the relaxation time approximation of kinetic theory in weak magnetic field limit, where temperature scale dominates over the energy scale related to magnetic field. It is found that the weak magnetic field reduces both $\eta$ and $\zeta$,...
Direct computations of QCD real-time observables like transport coefficients are very difficult due to the infamous sign problem. The complex Langevin (CL) method is a promising approach to overcome it by using a real-time formulation of QCD on a complex time contour. Studying SU($N_c$) gauge theories with CL, we find that current stabilization techniques are insufficient to obtain correct...
Measurements of the jet substructure in Pb+Pb collisions provide information on the jet quenching in the quark-gluon plasma (QGP) created in these collisions, over a wide range of energy scales. This poster presents ATLAS measurement of the suppression of yields of large-radius jets and its dependence on the jet substructure, characterized by the presence of sub-jets. This measurement is...
Measurements of the lightest open-charm baryon, $\Lambda_{\rm{c}}^{+}$, production can provide important information about the quark coalescence process of hadronization in the quark-gluon plasma (QGP). With strange quark yields being enhanced in the presence of the QGP medium, the production of $\rm{D}^{+}_{\rm{s}}$ is expected to be enhanced in heavy ion collisions if recombination plays an...
The production of quarkonia in high-energy heavy-ion collisions has been studied extensively to understand their production mechanisms and properties of Quark-Gluon Plasma (QGP). PHENIX has the capability to measure $J/\psi$ with muon arms at forward and backward rapidity ($1.2<|y|<2.2$) and charged particle multiplicity with silicon trackers at various acceptance ranges. The recent PHENIX...
Groomed jet substructure measurements, the momentum splitting fraction $z_g$ and the groomed jet radius $R_g$, for inclusive, D$^0$-tagged and B$^0$-tagged jets in $pp$ and central Pb+Pb collisions at $\sqrt{s}=5.02$ TeV are investigated. Theoretical results for light-quark initiated and gluon initiated jets are provided as references though experimentally indistinguishable for now. Charged...
We study the suppression of leading two hadrons within jets and the modifications of their flavor correlations in heavy ion collisions. The di-hadron system is robust against the underlying event background therefore allows its precision measurements. Their suppression is sensitive to any partonic energy loss mechanism and can be used to cleanly test the onset of jet quenching in the...
In Spring 2023, the sPHENIX detector at BNL’s Relativistic Heavy Ion Collider (RHIC) will begin measuring a suite of unique jet and heavy flavor observables with unprecedented statistics and kinematic reach at the RHIC energies.
The combination of electromagnetic calorimetry, hadronic calorimetry, precision tracking, and the ability to record data at a very high rates enables measurements of...
In early stage of high energy nuclear collisions, the Lorentz contracted colliding nuclei nuclei fly near the light cone, with large-x partons acting as static sources of small-x modes that constitute the Color-Glass Condensate (CGC) fields. By interacting CGC fields, the chromoelectric and chromomagnetic fields are formed, they are the glasma fields. The glasma fields serve as initial...
We present a full set of the Boltzmann Equation in Diffusion Approximation (BEDA) for studying thermal equilibration of quarks and gluons. Using BEDA, we first analyse thermalization and quark production of spatially homogeneous systems initially made of pure gluons. We observe that soft partons, dominantly produced via medium-induced radiation, rapidly fill a thermal distribution with an...
Dielectrons are an exceptional tool to study the evolution of the medium created in heavy-ion collisions. In central collisions, the energy densities are sufficient to create a quark-gluon plasma (QGP). Thermal e$^{+}$e$^{-}$ pairs with invariant mass ($m_{ee}$) around 1.5 GeV/$c^{2}$ can be used to estimate the temperature of the QGP.
At LHC energies, the cross section of heavy-flavour (HF)...