The LHC heavy-ion physics program aims at investigating the properties of strongly-interacting matter in extreme conditions of temperature and energy density, where the formation of the Quark-Gluon Plasma (QGP) is expected. Heavy quarks (charm and beauty) are regarded as unique probes of the properties of the QGP as they are created on a very short time scale in initial hard scattering...
Charm quarks are a powerful probe of the Quark-Gluon Plasma (QGP) formed in high-energy heavy-ion collisions. Produced in hard scattering processes on a timescale shorter than the QGP formation time, they experience the whole evolution of the medium interacting with its constituents. The measurements of charm-hadron production allow testing the mechanisms of in-medium parton energy loss....
Short-lived resonances are powerful probes to understand the hadronic phase in ultra-relativistic heavy-ion collisions, due to their lifetimes of $\sim$10 fm/c, comparable to the time span between chemical and kinetic freeze-out. The measurements of short-lived resonances in small collision systems provide the baseline for heavy-ion collision measurements as well as exploration of cold nuclear...
Jets produced in high energy heavy ion collisions are quenched by the production of the quark gluon plasma. Measurements of these jets are influenced by the methods used to suppress and subtract the large, fluctuating background and the assumptions inherent in these methods. We compare measurements of the background by the ALICE collaboration [1] to PYTHIA Angantyr simulations of Pb-Pb...
The sPHENIX detector at BNL’s Relativistic Heavy Ion Collider (RHIC) will quantify the properties of quark-gluon plasma created in relativistic heavy ions collisions with a focus on the measurements of jets and Upsilon states. A crucial component to the sPHENIX detector design for jet measurements is the hadronic calorimeter (HCal) which is located outside of the solenoid magnet and composed...
The ALICE experiment at the LHC is designed to investigate the properties of the Quark-Gluon Plasma by studying high-energy A--A collisions. Medium effects like parton energy loss can be examined by measuring the production of charged particles at high transverse momentum ($\textit{p}_{\text{T}}$). In particular, the correlation between $\textit{p}_{\text{T}}$ spectra and event multiplicity of...
The sPHENIX detector at BNL’s Relativistic Heavy Ion Collider (RHIC) will enable a spectrum of new or improved cold QCD measurements, enhancing our understanding of the initial state for nuclear collisions. sPHENIX measurements in proton-proton and proton-nucleus collisions will reveal more about how partons behave in a nuclear environment, inform our understanding of the initial state in...
Nuclear parton distribution functions (nPDFs) of quarks and antiquarks affect the production of electroweak bosons in proton-lead (pPb) collisions. In this presentation, a new measurement of the Drell-Yan (DY) process is presented in pPb collision at the center of mass energy of 8.16 TeV with the CMS detector. The rapidity dependence of this process is particularly sensitive to nPDFs, but...
The ALICE experiment is devoted to study the Quark Gluon Plasma (QGP), which is the high-density state of matter, obtained in high-energy heavy-ion collisions, where quarks and gluons are deconfined. Since heavy quarks (charm, beauty) are created mostly with hard scatterings during the first stages of the collisions and their abundances remain constant while the system evolves, they can be...
Charm quarks are ideal probes of the Quark-Gluon Plasma (QGP). Due to their large mass they are produced in the early stages of ultra-relativistic heavy-ion collisions in hard-scattering processes.
D$^{0}$-tagged jets are valuable tools to investigate the charm interaction with the QGP. Furthermore, charmed jets can provide information to study the mass-dependent energy loss by analysing...
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 strong 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...
Jets recoiling from a direct-photon have long been seen as a golden probe of the quark gluon plasma created in relativistic heavy ion collisions, due to the ability to tightly constrain the initial hard scattering kinematics. Until recently, the ability to measure this channel and the ensuing observables at RHIC were largely statistics-limited, owing to the small cross-section of direct photon...
At RHIC energies high pT direct photons are mainly produced by the
quark-gluon Compton scattering process. Being not disturbed by fragmentation
processes, they provide access to initial condition of partonic collisions.
Direct photon production in pp collisions serves an ideal probe for gluon
parton distribution functions (PDF), whereas quark PDFs are well constrained
by deeply inelastic...
Jet modification is an essential probe of the quark-gluon plasma produced in heavy-ion collisions. However, current jet modification measurements compare proton-proton and heavy-ion jets that had different properties when they were produced. Extracting the essential modification of jets by the quark-gluon plasma from these measurements requires an in-depth understanding of how jet observables...
We have studied the effect of strong magnetic field on the interplay
of coefficients related to the transports of momentum, heat and
charge of a hot QCD matter by shear ($\eta$) and bulk ($\zeta$)
viscosities, thermal ($\kappa$) and electrical ($\sigma_{\rm el}$)
conductivities, and some derived coefficients,
{\em viz.} $\frac{\eta}{s}$, $\frac{\zeta}{s}$, Lorenz (L), Knudsen
($\Omega$),...
High energy partons are known to lose energy when passing through the hot and dense medium produced in heavy-ion collisions. This results in a modification to the transverse momentum distributions of jets. It has been previously shown in Pb+Pb collisions at $\sqrt{s_{NN}} = 2.76$~TeV that parton energy loss within the Quark Gluon Plasma results in significant modifications to the transverse...
In 2018, LHCb recorded ~210 microbarn^{-1} integrated luminosity of PbPb collisions at sqrt(s_NN) = 5.02 TeV.
Although limited to peripheral hadronic collisions, this new dataset offers unique opportunities to study simultaneously open and close heavy flavor production, at forward rapidity down to zero pT, at the LHC.
Moreover, with an increase of the luminosity by a factor 20 compared to...
Experimental results from RHIC and LHC show an indication of a mass ordering
on the quark energy loss when crossing the hot and dense medium formed in
A+A collisions. The ordering is more evident at low $p_T$ region, where the
quark mass is more relevant for the energy loss mechanisms. However, this
final-state quark energy loss competes with other effects such as nuclear
shadowing and...
It is predicted that for the noncentral events in
ultrarelativistic heavy-ion collisions (URHICs),
a strong magnetic field is generated at the very early
stages of the collisions. However, as we know
the quarkonia, the physical resonances of $Q \bar Q$
states, are formed in the plasma frame at a time,
$t_F$ (=$\gamma \tau_F$), which is order of 1-2 fm,
depending on the resonances and...
Many prior studies of in-medium quarkonium suppression have implicitly made use of an adiabatic approximation in which it was assumed that the heavy quark potential is a slowly varying function of time. In the adiabatic limit, one can separately determine the in-medium breakup rate and the medium time evolution, folding these together only at the end of the calculation. In this paper, we...
Rivet (Robust Independent Validation of Experiment and Theory) is a valuable framework for the comparison of data and simulations. Since features required for heavy ion analyses were only recently available, there is a backlog of analyses which need to be implemented. We discuss implementation of heavy ion analyses in Rivet by undergraduates in a Course-Based Undergraduate Research Experience...
When an energetic parton propagates in a hot QCD medium it loses energy by emitting radiation induced by the parton scattering in the medium. The emission spectrum for such processes is typically split into either a regime dominated by a single hard scattering (GLV) or by a regime dominated by multiple low momentum transfers (BDMPS-Z). Both these regimes admit a close analytic treatment. Only...
We propose a set of correlation and fluctuation observables that, taken together, could indicate the level of equilibration of the matter produced in relativistic nuclear collisions. Theoretical models of the expansion and cooling of QGP used to estimate properties like viscosity and the shear relaxation time generally assume that the QGP reaches local thermal equilibrium. However, it is not...
The recent experimental observations of azimuthally anisotropic flow in small systems at RHIC and LHC energies has stimulated a big interest in these collisions, traditionally regarded only as control measurements for heavy-ion collisions and now becoming a new study area for the formation and evolution of the quark-gluon plasma. In the early stage of proton-nucleus collisions extremely...
Proton-ion collisions have been included in runs at the LHC and RHIC in addition to proton-proton and heavy ion collisions as a means of studying cold nuclear matter (CNM) effects. These asymmetric systems have yielded some unexpected trends, notably in measurements of nuclear modification factors at different centralities. Detectors at forward/backward rapidity have been used as a proxy for...
Two particle correlations which use a high momentum trigger particle are a
useful probe for exploring energy loss in the quark gluon plasma,
particularly in the high multiplicity environment of heavy ion collisions.
Previous direct photon-hadron correlation measurements in PHENIX have
demonstrated the energy loss observed as the suppression of high momentum
particles is redistributed 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 the...
Analytic solutions of a nonlinear boson diffusion equation (NBDE) with schematic initial conditions account for the fast local equilibration of gluons in relativistic heavy-ion collisions. The exact solutions are achieved through a nonlinear transformation that was proposed in Ref. [1], but in addition, include the singularity at $\epsilon=\mu<0$, and boundary conditions at the singularity. ...
ATLAS measurements of longitudinal flow decorrelation using two- and four-particle correlations for harmonics n=2 and 3 in Xe+Xe and $p$+Pb collisions covering a wide range of transverse momenta and collision centrality are presented and compared with Pb+Pb collisions. The measurements are performed using data from Xe+Xe collisions at 5.44 TeV, Pb+Pb collisions at 5.02 TeV, and $p$+Pb...
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 ALICE detector at the Large Hadron Collider (LHC) has been optimized for studying the strongly-interacting matter - the Quark-Gluon Plasma (QGP) at extremely high densities created in heavy-ion collisions. Charm quarks are produced in initial hard scattering processes, transport through the whole evolution of the system, and interact with the QGP constituents. Therefore, they are powerful...
The precise measurement of the neutral meson production in pp collisions can be used as a constrain for fragmentation functions and parton density functions needed by pQCD calculations. Additionally, those measurements can be used as an input for direct photon analyses. Moreover, the dependence of the neutral meson cross section on the event particle multiplicity and on the event sphericity...
Jet quenching refers to interaction of the jet shower with the QCD medium (QGP) generated in relativistic heavy ion collisions, which can have multiple phenomenological consequences: jet energy loss; modification of jet substructure; and induced acoplanarity. In this poster we report a measurement of the fragmentation of jets in central and peripheral Au+Au collisions at...
Measurements of the jet substructure in Pb+Pb collisions provide information about the mechanism of jet quenching in the hot and dense QCD medium created in these collisions, over a wide range of energy scales. This poster presents the 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 and...
ALICE is a dedicated heavy-ion experiment and focusses on the properties of the Quark-Gluon Plasma (QGP), a state of strongly interacting matter expected to be formed in heavy-ion collisions.
When performing proton-proton collisions, the energy densities reached are in principle not sufficient to form this medium and hence measurements in this system serve as a baseline to understand the...
In recent years jet substructure observables have been used at the LHC as instruments to search for new physics as well as to test perturbative and probe non-perturbative processes in QCD. One such observable, the generalized jet angularity, is of particular interest due its infrared and collinear (IRC) safety and thus calculability from first principles. Its general form has two continuous...
Jet quenching is one of the main signals used to investigate the properties of a strongly interacting quark-gluon plasma (QGP). Jet quenching can manifest as more than just energy loss, it can also be seen in the modification of jet substructure. This work focuses on measuring the substructure observable $z_{g}$, a byproduct of softdrop grooming, which probes the physics of the first hard...
We calculate charmonium production in Ultrarelativistic Heavy-Ion Collisions (URHICs) within a semiclassical Boltzmann transport approach for the dissociation and regeneration of charmonium where open charm diffusion is explicitly accounted for. The diffusion of charm quarks is simulated using Langevin dynamics yielding time-dependent quark spectra which serve as input into the regeneration...
Renewed interest in the question of QGP formation in small systems (pp, pA) has revived investigations into whether there is jet modification associated with these collision systems. One such modification of interest is broadening of jet acoplanarity, which is attributed to jet broadening in the medium. While this broadening has not been observed in minimum bias events at the LHC, ALICE data...
The similarities between pp, p-A and A-A collisions have not been fully understood. One issue when comparing e.g. transverse momentum ($p_{\rm T}$) distributions for different colliding systems at similar mid-rapidity multiplicity, is that selection biases and autocorrelations may play different roles. Recently, the use of the correlation between relatively high-$p_{\rm T}$ tracks ($p_{\rm...
Forward-backward multiplicity correlations have been studied in different colliding system, for all them, the difference with experimental results reveals physical phenomenon not well understood. In this work we present a study of forward backward multiplicity correlations on jets produced in proton-proton collisions using the PYTHIA event generator from UA5 to LHC energías. The analysis is...
Fluctuations in the multiplicity of particles produced in relativistic nuclear collisions influence many multi-particle correlation measurements. In each nuclear collision, the number of produced particles fluctuates because the number of particle sources fluctuates and the number of particles emerging from each source also fluctuates. Further, we expect that jet and thermal source models of...
The observation of anisotropic collective flow in the small systems produced by proton-proton and proton-nucleus collisions at the Relativistic Heavy-Ion Collider and the Large Hadron Collider has led theorists to the hypothesis that hydrodynamics can occur without thermal equilibration. Viscous hydrodynamic flow has the effect of smoothing out fluctuations in particle momenta, but conversely...
The observation of multiparticle correlations in heavy ion collisions are usually associated to collective behavior in the formed medium. Recent results at RHIC provide strong arguments for QGP formation in smaller systems.
In this poster, I present the status of the neutral pion second harmonic coefficient v2 as a function of transverse momentum at low and high pT for very central d+Au...
A longstanding interest in the heavy-ion physics community has been the measurement of jets associated with high $p_{\rm T}$ photons. At leading order, these photons are produced back-to-back with a jet (usually a quark jet), with balanced transverse momentum, during the early stages of the collision. As photons do not interact strongly with the quark-gluon medium, they do not lose energy and...
In high energy nucleus-nucleus collisions a novel state of nuclear matter, the Quark Gluon Plasma (QGP) is created. Hard partonic scatterings which happen inside the bulk of this nuclear matter serve as an important probe of QGP properties through their energy loss. An important observable for studying the extent of this partonic energy loss is the jet fragmentation function. Previous studies...
High transverse momentum direct photons are penetrating probes in
relativistic heavy ion collisions. Once produced, they leave the collision
region virtually unaffected, even if a hot, dense partonic medium was
formed. This is also the reason why direct photons are immune to the
suppression observed for high pT hadrons and jets in heavy ion collisions,
but can probe the initial state...
Jets in $A+A$ collisions are modified both in terms of their particle yield and that they appear broader when compared to their counterparts in $p+p$ collisions. This modification stems from the energy loss of hard-scattered partons traversing the Quark Gluon Plasma (QGP) before fragmenting into jets. Examining the jet modification allows us to study how the jet...
An outstanding puzzle in heavy ion physics is the mechanism that generates
collective motion of heavy quarks (charm and bottom) in large collision
systems. The measured azimuthal anisotropy coefficient $v_2$ of electrons
from heavy quarks closely resemble those of light quarks, despite the
several orders of magnitude differences in quark mass. In order to further
understand the quark mass...
Different types of high energy hard probes are used to extract the jet transport properties of the Quark-Gluon Plasma created in heavy-ion collisions, of which the heavy boson tagged jets are undoubtedly the most sophisticated due to its clean decay signature and production mechanism. In this study, we used the resummation improved pQCD approach with high order correction in the hard factor to...
The collective flow and the possible formation of the Quark-Gluon Plasma (QGP) in the small colliding systems are hot research topics in the heavy-ion community. Recently, ALICE, ATLAS and CMS collaborations have measured the elliptic flow and the related number of constituent quark (NCQ) scaling of identified hadrons in p+Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV, which are important...
Heavy quarks are ideal probes of the QGP matter. To consistently describe the medium evolution and heavy-quark-medium interaction, we improve the linear Boltzmann Transport (LBT) model [Phys. Lett. B777 (2018) 255-259] by modeling QGP as a collection of quasi-particles with equation of state (EOS) fitted to the lattice QCD data. We call this QLBT model, in which the in-medium scatterings of...
In PbPb collisions at the LHC, heavy-flavor (charm and bottom) quarks are predominantly produced at the initial stages of the collision via hard scattering, and they evolve with the whole system. The $D^0$ mesons provide insights on the heavy-quarks and details about the system at initial stages, for example, the potential effects of strong electromagnetic (EM) fields created by collision...
The sPHENIX detector at BNL’s Relativistic Heavy Ion Collider (RHIC) benefits from the extensive detector advances driven by LHC and Electron-Ion Collider (EIC) detector R&D. The combination of electromagnetic calorimetry, hadronic calorimetry, precision tracking, and the ability to record data at a very high rates enables measurements of jets, jet substructure, and jet
correlations at RHIC...
A strong enhancement of Λc/D0 ratio compared to the fragmentation baseline is observed in Au+Au collisions at the top energy of the RHIC. This also suggests that Λc may be an important component for the total charm cross section. Precision measurements of charm baryons over a broad momentum range are needed for a detailed understanding of hadronization and...
The sPHENIX detector at BNL’s Relativistic Heavy Ion Collider (RHIC) is designed to accurately study proton-proton, proton-nucleus, and nucleus-nucleus collision systems. The design of sPHENIX, including full azimuthal calorimeter coverage, will allow it to precisely study properties of the Quark Gluon Plasma through open heavy flavor production, jet modification, and Upsilon measurements. ...
The sPHENIX detector at BNL’s Relativistic Heavy Ion Collider (RHIC) will probe the strongly interacting Quark-Gluon Plasma (QGP) with jets, heavy flavor tagged jets and Upsilon production. The sPHENIX electromagnetic calorimeter (EMCal) detector is essential for these measurements. The Chinese sPHENIX EMCal Consortium includes groups from Fudan, PKU and CIAE, and the consortium is planning to...
The sPHENIX MVTX detector will be a state-of-the-art monolithic active pixel (MAPS) vertex detector, used by the sPHENIX collaboration, which will allow the study of heavy flavor physics within heavy ion collisions at RHIC. The detector is at an advanced stage of testing with several test beam activities having taken place through 2019. Three test beams have been performed since 2018 to...
The suppression of heavy quarkonia states in heavy-ion collisions is a phenomenon understood as a consequence of QGP formation in the hot, dense system produced in high
energy heavy ion collisions. A full assessment of the physics scenario requires a detailed study of effects present in Pb+Pb, in comparison to $pp$ collisions. In this poster, we present the results from the studies of prompt...
A Time Projection Chamber (TPC) will be the central tracking detector in the sPHENIX experiment. Its main task is to provide a high tracking efficiency and excellent momentum resolution for precise upsilon spectroscopy and jet measurements. The TPC will cover the full azimuth and a pseudorapidity range of up to $\pm$ 1.1.
A small scale prototype TPC with a radial extension of 40 cm and a...
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...
The energy range covered by the CERN SPS is unique for the investigation of the region of the QCD phase diagram corresponding to finite $\mu_B$. In this talk we will describe the studies for a new fixed target experiment, NA60+, aimed at a precision study of heavy quark and thermal dimuons in Pb-Pb collisions via an energy scan in the interval of incident beam energy 20-160 GeV/nucleon. High...
Jets initiated by the fragmentation of heavy flavor quarks (HF-jet) are sensitive to collisional energy loss of the high energy parton when traversing through Quark Gluon Plasma. Using the state-of-the-art jet detector at RHIC, sPHENIX, we will perform the first HF-jet measurement at RHIC, which includes the nuclear modification and flow of b-jets, and the momentum balance in di-b-jet pairs. A...
The sPHENIX detector at BNL’s Relativistic Heavy Ion Collider (RHIC) will study QGP properties with heavy bottom quark jets (B-jets) produced in high-energy heavy ion collisions. B-jets are expected to offer a unique set of observables due to the large bottom quark mass, but need to be measured across an unexplored kinematic regime, particularly at low pT where the expected mass-dependence...
Recent data from RHIC and LHC show that RAA and v2 of charm hadrons are very similar to that of light and strangeness hadrons. The RAA of bottom decay daughters at low pT seems to be less suppressed than that of light and charm hadrons, suggesting a mass suppression hierarchy. Precision open bottom measurements over a broad momentum range are...
Recently, two scenarios have been proposed to resolve the discrepancy between photon yield and the flow coefficients measured in nuclear collisions at RHIC and the LHC. In the first, additional photons are produced from the early pre-equilibrium stage computed from the "bottom-up" thermalization scenario [1-3]. In the second, the thermal rates are enhanced close to the pseudo-critical...
The quark-gluon plasma is formed in high energy heavy ion collisions such as those at RHIC and LHC, where parton interactions greatly affect many final state observables. Both elastic and inelastic parton cascade models have been constructed, such as ZPC, MPC and BAMPS. Recent studies from a multi-phase transport (AMPT) model, which includes the ZPC elastic parton cascade, have shown that even...
