Electroweak bosons produced in lead-lead (Pb+Pb) collisions are an excellent tool to constrain initial-state effects which affect the rates of hard-scattering processes in nucleus-nucleus interactions. The production yields of massive electroweak bosons, observed via their leptonic decay channels, offer a high-precision test of the binary collision scaling expected in Pb+Pb and a way to...
Evidence for the production of top quarks in heavy ion collisions is reported in a data sample of lead-lead collisions recorded in 2018 by the CMS experiment at a nucleon-nucleon center-of-mass energy of $\sqrt{\smash[b]{s_{_{\mathrm{NN}}}}} = 5.02$ TeV, corresponding to an integrated luminosity of $1.7\pm0.1\,\text{nb}^{-1}$. Top quark pair ($\mathrm{t\bar{t}}$) production is measured in...
High energy partons are known to lose energy when passing through the hot and dense medium produced in heavy-ion collision. This results in a modification to the transverse momentum distributions of both charged hadrons and 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...
We model relativistic heavy-ion collisions with a hydrid dynamical approach which consists of an IP-Glasma initial state followed by a phase modeled by an effective QCD kinetic theory [1]. This then leads into viscous hydrodynamics and finally transport theory (MUSIC + UrQMD) [2]. The system's complete energy-momentum tensor -- including the shear and bulk viscous components -- is followed...
The STAR Collaboration at RHIC reports the measurements of both charged and fully-reconstructed inclusive jet production in central (0-10\%) and peripheral (60-80\%) Au+Au collisions at $\sqrt{s_{\scriptsize{\textrm{NN}}}}$ = 200 GeV. The charged jet analysis utilizes a dataset corresponding to 70 $\mu\mathrm{b}^{-1}$ recorded in 2011, while the new fully-reconstructed jet analysis utilizes a...
Evidence for collectivity and effects beyond nPDF modifications and energy loss in small systems has been observed in recent years. In high-multiplicity pPb events, J/$\psi$ is found to show a surprisingly large long-range elliptic anisotropy signal, comparable to that for light and open-heavy flavor hadrons. In addition, results on prompt J/$\psi$ and $\psi(2S)$ production in pPb data at 5.02...
Deep inelastic scattering (DIS) total cross section data at small-x as measured by the HERA experiments is well described by Balitsky-Kovchegov (BK) evolution in the leading order dipole picture [1-3]. Recently the full Next-to-Leading Order (NLO) dipole picture total cross sections have become available for DIS [4-6], and a working factorization scheme has been deviced which substracts the...
Heavy flavours are effective probes of the hot and dense matter, the Quark-Gluon plasma (QGP), produced in ultra-relativistic heavy-ion collisions. Due to the very short time scale characterising their production, they experience the whole evolution of the system. In particular, measurements of heavy-flavour production in Pb-Pb collisions at the LHC energies, including nuclear modification...
We investigate photon emission at the hadronization stage of high-energy heavy-ion collisions.
According to coalescence/recombination models for hadronization from a quark-gluon plasma (QGP),
quarks and antiquarks closely locating in the phase space are assumed to suddenly form a hadron.
Transition from free quark/antiquark states to hadrons (bound states of quarks or antiquarks) is,...
The Colour Glass Condensate effective field theory is a useful framework for studying heavy ion collisions at ultrarelativistic energies, such as those reached at the Large Hadron Collider at CERN. 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...
New measurements of jet quenching observables at RHIC and at the LHC, such as jet substructure observables, demand an increased precision in the theory calculations describing medium-induced radiation of gluons. Closed expressions for the gluon spectrum including a full resummation of multiple scatterings have been known for the past 20 years, but have only been evaluated in specific limits...
Within the two p-Pb data samples collected by the LHCb detector at sqrt(s_NN) = 5 and 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 performances in particle reconstruction and identification, these charm states are studied down to zero pT with...
Quarkonia are excellent probes for studying the properties of quark-gluon plasma formed in relativistic heavy-ion collisions at RHIC. In order to fully understand the observed suppression of quarkonium production in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV, it is essential to understand well the cold nuclear matter (CNM) effects on the quarkonium production. Collisions of p+Au at...
Isolated photon production in pp collisions is one of the most clear tests of hard QCD processes and proton structure functions. Their measurement in pA collisions provides the possiblity to check initial geometrical scaling and possible modifications of the nucleon structure function in nuclei. Furthermore, the isolated photons constrain the kinematics of scattered partons and therefore, the...
Partons are colored probes that interact with the quark-gluon plasma (QGP). By studying jets, the observable final state product of partons, we can improve our understanding of the interaction mechanism between partons and the QGP. Jet nuclear modification factor (RAA) is a simple yet profound observable that measures the amount of suppression with respect to a reference of proton-proton...
This talk presents ATLAS measurements of the azimuthal anisotropy for charged particles in 8.16 TeV $p$+Pb collisions up to a $p_T$ of 50 GeV. The measurements are performed via the two-particle correlation method and the statistics are enhanced at high-$p_T$ by selecting events triggered by a high-$p_T$ jet. Restrictions on other particles are imposed to suppress the contribution from jets....
Relativistic heavy-ion experiments have observed similar quenching effects for (prompt) $D$ mesons compared to charged hadrons for transverse momenta larger than 6-8 GeV, which remains a mystery since heavy quarks typically lose less energies in quark-gluon plasma than light quarks and gluons. Recent measurements of the nuclear modification factors of $B$ mesons and $B$-decayed $D$ mesons by...
We present the semi-inclusive distribution of charged jets recoiling from a trigger hadron in pp and Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV. This technique provides a precise data-driven subtraction of the large uncorrelated background contaminating the measurement. It uniquely enables the exploration of medium-induced modification of jet production and acoplanarity over a...
Three are the mechanisms that influence quarkonium suppression in a medium: screening, thermal decay, and recombination. In recent years, a framework that can treat them consistently at the same time has been put forward, the open quantum system approach. In this talk, we will discuss how the combination of open quantum system and Effective Field Theory techniques are useful to understand...
Understanding heavy-flavor transport properties and energy loss inside a quark-gluon plasma (QGP) is a major interest of the heavy-ion phenomenology. In this work, we combine both open-heavy and heavy-flavor jet observables to study the average heavy quark energy loss as well as its fluctuations. Low-momentum heavy quark interacts with QGP mainly through elastic collisions; for high-momentum...
Heavy ion collisions at high energies can be used as an interesting way to recreate and study the medium of the quark-gluon plasma (QGP). We particularly investigate the jets produced in hard binary collisions and their interactions with a tentative medium. These jets were obtained numerically from the Monte-Carlo simulations of hard collisions using the KATIE-framework [1], where...
We investigate the scattering of a quark jet on a high-energy heavy nucleus using the time-dependent light-front Hamiltonian approach. We present the real-time evolution of the quark-jet in a strong classical color field of the incoming nucleus described by the Color Glass Condensate effective theory. We calculate the cross section, the differential cross section, and the quark jet...
The yields of bound quarkonium states in heavy-ion collisions provide a powerful tool to probe the dynamics of the hot, dense plasma. These measurements are sensitive to the effects of color screening, color recombination, and possibly to other, new phenomena affecting dynamics of heavy quarks in the QCD medium. In this talk, the ATLAS results on bottomonium nuclear modification factor and...
We present a study of the impact of the expansion of deconfined medium on single-gluon emission spectra and the jet suppression factor ($Q_{AA}$) within the BDMPS-Z formalism. These quantities are calculated for three types of media (static medium, exponentially decaying medium and Bjorken expanding medium). The distribution of medium-induced gluons and the jet $Q_{AA}$ are calculated using...
Energy loss of quarks in the hot and dense medium has been studied for
decades. Both the experimental and theoretical efforts hinted that the
energy loss is quark mass dependent (the yield of heavier quarks will be
less suppressed). It was found that the electrons from heavy quarks (charm,
and bottom) are less or similarly suppressed compared to that of light
hadrons. The mass ordering of...
Heavy quarks are produced in the earliest stages of a nucleus-nucleus collision and therefore are an important tool to study the subsequent high energy-density medium formed in relativistic heavy-ion collisions. Over the last few decades major efforts have been undertaken in order to understand the properties of the quark-gluon plasma (QGP) using quarkonia. The extent of medium modification...
Studies of jet energy loss and momentum broadening with photon-jet momentum and angular correlations will be presented, with PbPb data at 5.02 TeV collected by the CMS detector. Photon-jet events provide a means of probing in-medium jet energy loss with good constraints on the initial parton kinematics and flavor. Studies of momentum and angular correlations in photon-jet events can enable...
The production of heavy quarkonium in heavy ion collisions has been used as an important probe of the quark-gluon plasma. To describe the in-medium evolution of quarkonium, one has to take into account plasma screening effects and recombination in a consistent way. Many previous studies calculate dissociation rates from QCD but use recombination models that are based on detailed balance or...
Charm quarks are an excellent probe of the quark-gluon plasma created in heavy-ion collisions as they are produced at very early stages of such collisions and subsequently experience the whole evolution of the system. At STAR experiment, charm quark production can be accessed by direct topological reconstruction of open-charm hadrons thanks to an excellent track pointing resolution provided by...
The evolution of QCD jets under the influence of a dense colored medium leads to the non trivial modification of the emission spectrum. In the multiple soft scattering regime, for sufficiently large mediums, soft and wide angle emissions can be resummed, at large number of colors, since the emissions become independent up to $\tau_{br}/L$ corrections. Similarly to DGLAP evolution, such...
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...
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...
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...
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...
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 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...
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...
In high energy heavy-ion collisions, the strong electromagnetic (EM) fields of the nuclei can produce energetic, high-density photon fluxes, leading to photon-induced interactions. Recently, significant enhancements of $e^{+}e^{-}$ pair and J/$\psi$ production at very low transverse momentum ($p_{T}$) were observed by the STAR [1, 2] and ALICE [3] collaborations in peripheral hadronic A+A...
We study the nuclear modification for the dijet cross section in eA deeply inelastic scattering (DIS) process. This nuclear modification comes from multiple scattering of final state parton in a large nucleus, including medium induced radiation. This extra modification to dijet cross section depends on transverse momentum dependent (TMD) quark-gluon correlation function, which can be...
Open heavy flavor and quarkonium are valuable probes to identify the underlying QCD dynamics behind high multiplicity events at RHIC and LHC. In previous studies [1,2], we explored $D$-meson and $J/\psi$ production vs. charged hadron multiplicity in $p+p$ and $p+A$ collisions in the CGC framework; we modeled an initial state effect in terms of the fluctuation of gluon saturation scale, $Q_s$....
At the LHC energies Multiple Parton Interactions (MPI) are expected to affect not only processes involving soft particle production, but also the hard momentum scales relevant for the production of heavy quarks, such as charm and beauty. Quarkonium measurements in high-multiplicity proton-proton (pp) collisions can shed light on the role of MPI at such hard momentum scales, as well as on the...
Jets recoiling from a direct photon are seen as a relatively clean probe, due to the more tightly constrained initial hard scattering kinematics compared to di-jet measurements. In this talk, we will present semi-inclusive measurements of jets recoiling from direct-photon and $\pi^0$ triggers in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV, both their yield and the transverse momentum...
Charmonium is considered a valuable probe to study the medium produced in
collisions involving nuclei and/or nucleons. With the recent observations of
collective behavior of produced particles in small system collisions,
measurements of the modification of charmonium in these systems have become
increasingly relevant. In this talk we will present the PHENIX results of
J/ measurements at...
The CMS Collaboration reports on new differential measurements of $\gamma\gamma \rightarrow \mu^{+}\mu^{-}$ production in PbPb collisions at $\sqrt{s_{\rm NN}}$ = 5.02~TeV, using data collected during the 2018 LHC run with an integrated luminosity of 1.6~nb$^{-1}$. Photon-photon interactions have been observed in hadronic heavy-ion collisions by STAR and ALTAS experiments at very low...
The dynamics of shower development for a jet traveling through the QGP involves a variety of scales, one of them being the mass for heavy flavors residing inside jets. Though the mass of the heavy quarks plays a subdominant role during the high virtuality portion of the jet, it does affect longitudinal drag and diffusion, stimulating additional radiation from heavy quarks [1]. These emissions...
Dielectron production is suggested as an excellent probe of the hot and dense medium created in relativistic heavy-ion collisions due to their minimal interactions with the partonic and hadronic medium. They can carry the information from the initial to the final stage of a collision. The study of the dielectron mass spectrum could help to disentangle various contributions. In the low mass...
The strong electromagnetic fields generated by ultra-relativistic heavy ions provide the possibility to study photon-induced processes at the LHC in new kinematic regions. ALICE has measured the exclusive and the coherent production of J/$\psi$ in p-Pb and Pb-Pb collisions at a center-of-mass energy of 5.02 TeV. These collisions correspond to photon-proton and photon-Pb interactions,...
Measurements of two-particle correlations in $pp$ collisions have demonstrated long-range azimuthal correlations between charged particle pairs, commonly interpreted as arising from a single particle azimuthal anisotropy. To better understand the origin and nature of these collective signatures, ATLAS presents studies in $pp$ collisions with a novel handle on the event geometry, and in...
The Glauber modeling plays a key role in centrality-dependent measurements of heavy-ion collisions.
A central input parameter in Glauber models is the inelastic nucleon-nucleon cross section $\sigma_{\rm nn}^{\rm inel}$ which is nearly always taken from proton-proton measurements. At the LHC energies $\sigma_{\rm nn}^{\rm inel}$ depends on the QCD dynamics at small $x$ and low interaction...
Charm quarks are excellent probes to study properties of the Quark-Gluon Plasma (QGP) created in ultra-relativistic heavy-ion collisions. In particular, measurements of the $D_{s}^{\pm}$ meson production can provide valuable information on the strangeness enhancement in the QGP as well as the charm quark hadronization mechanism in heavy-ion collisions. In this talk, we will present results...
The collective effects in high-multiplicity proton-proton, proton-nucleon and nucleon-nucleon collisions have not yet been attributed to a common mechanism. Within the Lund string model of partons, the interaction force between strings (aka. string shoving) could be responsible for such effects. So far, this aspect has only been present for pp in the existing PYTHIA8 framework, but after the...
Measurements of the jet spectra and nuclear modification factors for inclusive charged jets and inclusive full jets (containing both charged and neutral constituents) in Pb-Pb and pp collisions at $\sqrt{s_{NN}} = 5.02$ TeV recorded with the ALICE detector will be shown. These measurements use a novel machine learning based background correction [1] which reduces residual fluctuations. The...
The production of low-mass dielectrons is one of the most promising tools for the understanding of chiral symmetry restoration and the thermodynamical properties of the Quark-Gluon plasma (QGP) created in ultra-relativistic heavy-ion collisions. For low invariant masses ($m_{\rm ee} <$ 1.1 GeV/$c^{2}$), the dielectron invariant-mass spectrum is sensitive to the properties of short-lived vector...
W and Z bosons are created in the hard scattering processes occurring in the initial stage of heavy-ion collisions and they are insensitive to the presence of a strongly-interacting medium. This makes them clean probes of the initial-state effects of the collision, such as the nuclear modification of the parton distribution functions (nPDFs). The measurement of the electroweak-boson production...
Results of nuclear modification of Upsilon production in pPb collisions at 5.02 TeV and exclusive Upsilon photoproduction in Ultraperipheral collisions (UPC) of pPb at 8.16 TeV, are presented. The nuclear modification factors in pPb collisions are measured to quantify nuclear effects in such a small system and sequential suppression is observed among the three states following the ordering of...
The suppression of $J/\psi$ production caused by the color-screening effect in heavy-ion collisions is considered as an evidence of the creation of quark-gluon plasma. To interpret the observed suppression in heavy-ion collisions, a good understanding of its production mechanism in p+p collisions is needed. However, the production of $J/\psi$ in hadronic collisions remains not fully understood...
Observations of flow-like signals in small-system collisions, $pp$ and $p$/$d$+A, have led to a resurgence of interest and measurements, the results of which have perhaps permanently challenged the naive picture of initial geometry and subsequent early-time dynamics for these systems. In the wake of this renewed interest, jet and high-$p_\mathrm{T}$ particle measurements in small systems are...
Heavy quarks (charm and beauty) are produced in abundance during the early stage of ultra-relativistic heavy-ion collisions. They therefore experience the full evolution of the Quark-Gluon Plasma (QGP). This makes them unique probes of the collective behaviour of particles in the medium as it expands and cools. The anisotropy of the overlap region between the two colliding nuclei in 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...
Using novel lattice (non-relativistic) QCD techniques, we will present results pertaining to the fate of Υ(1S), Υ(2S) and Υ(3S) in QGP. We will present results on how the masses of these states change with temperature, as well as how their spatial sizes change. Finally, we will also show new lattice QCD results on the heavy quark potential from Wilson lines.
We investigate the medium induced fragmentation of jets in a high-temperature QCD plasma. Based on an effective kinetic theory of QCD, we study the non-equilibrium evolution of the jet shower and the chemical equilibration of jet fragments in the medium. By including radiative emissions as well as the elastic interactions evolution, our approach extends all the way from the jet energy scale...
Fully coherent energy loss (FCEL), predicted from first principle QCD calculations, affects the yields of hadrons in proton-nucleus collisions at all energies. The FCEL effects on quarkonia have been succesfully compared to existing measurements over the last few years. In this talk, our approach is generalized systematically to $2\to 2$ processes allowing for the first computation of FCEL...
The energy loss of heavy quarks propagating through the quark-gluon plasma (QGP) is expected to transit from an elastic regime at low and intermediate momenta to a radiative regime at high momenta. For the latter, a significant amount of energy dissipates by radiating rather soft gluons that can strongly interact with the surrounding medium through non-perturbative many-body effects. In order...
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...
Dijet processes can be used in several ways to probe the nuclear initial state. Exclusive dijet photoproduction in ultra-peripheral heavy-ion collisions has recently been suggested as a probe of the gluon Wigner distribution. In particular, the angular correlation of exclusive dijets can asses the azimuthal anisotropy of the gluon distribution in the nuclear target. In this talk we present,...
We present LHCb results on quarkonia production in proton-lead collisions, using the data collected in 2016 at sqrt(s_NN) = 8.16 TeV. Measurements are performed in the forward rapidity region (pseudorapidity between 2 and 5), covering both forward (pPb configuration) and backward (Pbp configuration) rapidities. Measurements for charmonium states include prompt and from-b-decay components...
High energy partons has been a useful tool to study the hot and dense matter produced in heavy-ion collisions. To this end, it has been shown that is important to incorporate the most realistic description of the Quark Gluon Plasma using relativistic hydrodynamics in order to study many properties at high pT. Therefore, in this work we couple a modified JEWEL code to event-by-event...
Extraction of the multi-TeV proton and lead LHC beams with a bent crystal or by using an internal gas target allows one to perform the most energetic fixed-target experiment ever. $pp$, $pd$ and $pA$ collisions at $\sqrt{s_{NN}}=115$ GeV and Pb$p$ and PbA collisions at $\sqrt{s_{NN}}=72$ GeV can be studied with high precision and modern detection techniques over a broad rapidity range.
Using...
LHCb measurements of the electroweak boson production in forward and backward configuration of proton-lead collisions are sensitive to the nPDFs in a unique kinematic domain, allowing to study in a complementary fashion the structure of the nucleus.
In this talk, we present the latest results obtained on the Z production in pPb and Pbp collisions by LHCb, being the most precise measurements...
ATLAS measurements of flow harmonics ($v_n$) and their fluctuations in Pb+Pb and Xe+Xe collisions covering a wide range of transverse momenta, pseudorapidity and collision centrality are presented. The measurements are performed using data from Xe+Xe collisions at 5.44 TeV, Pb+Pb collisions at 5.02 TeV, and $p$+Pb collisions at 5.02 and 8.16 TeV. The $v_{n}$ are measured up to $n=6$ using the...
The measurements of the charmed baryons are fundamental to investigate charm-quark production and hadronization mechanisms in different collision systems.
Recent measurements of charm-baryon production in small systems at LHC energies show a baryon-over-meson ratio significantly higher than that in e$^{+}$e$^{-}$ and e$^{\pm}$p collisions, and higher than expectations from Monte Carlo...
Measurement of jet structure in heavy-ion collisions allows studying properties of the hot and dense QCD medium created in these collisions and the mechanism of the jet quenching. This talk presents the latest ATLAS measurements of the internal structure of jets to better constrain the modifications of the parton showering process. A new measurement of how the suppression of large-radius jets...
Muon pairs produced via two-photon scattering processes in hadronic Pb+Pb collisions provide a potentially sensitive electromagnetic probe of the quark gluon plasma.
First measurements by ATLAS and STAR of dileptons produced via two-photon scattering in non-ultra-peripheral (non-UPC) nucleus-nucleus collisions showed an unexpected centrality-dependent broadening of the angular correlation...
We study chemical equilibration in out-of-equilibrium Quark-Gluon Plasma using the QCD effective kinetic theory in longitudinally expanding systems. We find that chemical equilibration takes place after hydrodynamization, but well before local thermalization. By relating the transport properties of QGP and the system size we estimate that hadronic collisions with final state multiplicities...
We report new jet substructure measurements in Pb-Pb and pp collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with the ALICE detector. For the first time, fully corrected measurements of the groomed jet momentum fraction, $z_g$, the groomed jet radius, $\theta_g \equiv R_g/R$, and the number of Soft Drop splittings, $n_{\mathrm{SD}}$, will be shown in Pb-Pb collisions, along with their ratio to...
Beauty quarks are considered as one of the best probes of the strongly interacting medium created in relativistic heavy-ion collisions because they are predominantly produced via initial hard scatterings. Measurements of B meson production provide information about the diffusion of beauty quarks and the flavor dependence of in-medium energy loss. In these studies, clarifying the hadronization...
Gauge boson associated with jet production is a perfect channel for jet quenching. Z+jet and $\gamma+$jet correlations have already been investigated by several theory models and experimental groups in both p+p and Pb-Pb collisions at $\sqrt s=5.02$ TeV. However, W+jets are dominated by quark jet and H+jet are mainly gluon jet, the comparison of W+jet and H+jet would provide complementary...
Jet substructure represents a cornerstone in the on-going endeavor to pinpoint the effect of a hot, thermal medium, namely the QGP, on QCD dynamics. In this talk, based on [1], I will present a new set of jet substructure observables and an associated grooming technique, dubbed "dynamical grooming". This procedure is rooted on identifying the hardest splitting in an angular ordered shower and...
We establish a non-equilibrium QCD evolution model with light quark and gluon degrees of freedom. By including both elastic and inelastic scattering for quarks and gluon, the model is proficient to describe kinetic and chemical equilibration of quark-gluon plasma, and thus connect the initial (semi-) hard production of partons at early times with the hydrodynamic description of a...
The region of the QCD phase diagram at high $\mu_{\rm B}$ can be accessed by fixed-target experiments working at future or existing facilities providing nuclear beams in the multi-GeV energy range. In particular, the CERN SPS is able to provide high-intensity beams over a wide energy interval ($\sqrt{s_{\rm NN}}$ = 5-17 GeV) that are ideal for the study of rare signals. Recently, an expression...
DREENA framework is based on our dynamical energy loss formalism, which takes into account finite size, finite temperature QCD medium consisting of dynamical (moving) partons. Both radiative and collisional energy losses are calculated under the same theoretical framework in the dynamical energy loss formalism, which is applicable to both light and heavy flavor observables. We generalized the...
One of the greatest uncertainties in heavy-ion collisions is the description of the initial state. Different models predict a wide range of initial energy density distributions based on their underlying assumptions. Final flow harmonics are sensitive to these differences in the initial state due to the nearly linear mapping between eccentricities and anisotropic flow harmonics. The Trento...
With our coupled jet-fluid model [1, 2, 3], we study the nuclear modifications of full jets and jet structures for single inclusive jets and $\gamma$-jets in Pb+Pb collisions at $5.02$ ATeV and $2.76$ ATeV. The in-medium evolution of full jet shower is described by a set of coupled transport equations including the effects of collisional energy loss, transverse momentum broadening and...
It is now well established that jet modification is a multistage effect; hence a single model alone cannot describe all facets of jet modification. The JETSCAPE framework is a multistage framework that uses several modules to simulate different stages of jet propagation through the QGP medium. These simulations require a set of parameters to ensure a smooth transition between stages. We fine...
The differential yields of Z bosons decaying to lepton pairs are measured in PbPb collisions collected in 2018 by the CMS experiment at the LHC. The measurement uses 1.8 nb$^{-1}$ of 5.02~TeV data. The yields in various centrality bins are compared to the HG-PYTHIA model, which indicates that geometric and selection biases could be present for peripheral events. In some cases, the...
Experimental measurements indicate no suppression (e.g. RpPb ∼ 1) but a surprisingly large D meson v2 was measured in pPb collisions. In order to understand these results we use Trento+v-USPhydro+DAB-MOD to make predictions and propose a system size scan at the LHC involving $^{208}PbPb$, $^{129}XeXe$, $^{40}ArAr$, and $^{16}OO$ collisions. We find that the nuclear modification factor...
Whether, how, and to what extent solutions of Bjorken-expanding systems become insensitive to aspects of their initial conditions is of importance for heavy-ion collisions. In this talk I will present attractor solutions in hydrodynamics, kinetic theory and holography, whereby we show that in hydrodynamics and kinetic theory the attractor extends to arbitrarily early times, whereas in...
We consider the following conundrum: On one hand the proton as a quantum object is in a pure state and is described by a completely coherent wave function with zero entropy. On the other hand in high energy experiments (DIS) when probed by a small external probe, it behaves like an incoherent ensemble of (quasi-free)
partons.
In this talk, we define the "entropy of ignorance" which...
Due to recent advances in jet finding techniques and larger data samples, measurements of inclusive or recoil jets with large resolution parameters are now experimentally accessible via semi-inclusive hadron-jet or machine learning techniques, the latter of which enables the measurement of charged jet spectra down to low jet transverse momentum for jet resolution parameters up to $R=0.6$. By...
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. Heavy ion collisions, as well as high...
The structure of the exotic meson $\chi_{c1}(3872)$, also known as $X(3872)$, is still under debate. The similarity of the $\chi_{c1}(3872)$ mass and the $D-\bar{D}^{*}$ mass threshold inspired the interpretation that $\chi_{c1}(3872)$ is a $D-\bar{D}^{*}$ “molecule” with small binding energy. Another explanation is that this meson is a tetra-quark, consisting of a di-quark and di-antiquark....
The angular dependence of jet suppression encodes key information about the process of energy and momentum hydrodynamization, and for this reason can be used to greatly improve our understanding of fundamental aspects of the jet/QGP interaction. In this work we study jet suppression from small to very large radius, for low and very high energy jets at the LHC and RHIC. We use the hybrid...
Jets in the vacuum correspond to multi-parton configurations that form predominantly via a branching process sensitive to the soft and collinear divergences of QCD. In heavy-ion collisions, energy loss processes, stimulated via interactions with the medium, affect jet observables in a profound way. On the level of Feynman diagrams this can be traced back to the difference of medium...
The splitting processes of bremsstrahlung and pair-production in a medium are coherent over large distances in the high energy limit leading to a suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. Avoiding soft-emission approximations and working in the large-Nc limit, we consider corrections to the LPM effect from cases where the coherence lengths of two consecutive splittings...
A unified description of jet evolution through deconfined QCD matter remains one of the challenging problems in the area of heavy-ion physics. To gain a comprehensive understanding of the properties of the QGP, we need an energy-loss model that effectively captures the physics of multi-scale jet quenching and provides a simultaneous description of a wide variety of integrated and differential...
The interplay between the small x limit of QCD amplitudes and QCD factorization at moderate x has been studied extensively in recent years. It was finally shown that semiclassical formulations of small x physics can have the form of an infinite twist framework involving Transverse Momentum Dependent (TMD) distributions in the eikonal limit. In this work, we demonstrate that small x...
Recently, LHCb collaboration has presented the relative production rates of promptly produced X(3872) over ψ(2S) as a function of particle multiplicity, given by the total number of charged particle tracks reconstructed in the VELO detector for the forward pseudorapidity region, 2 < η < 5. This ratio is found to decrease with increasing multiplicity.
In fact, suppression of weakly-bound...
Quantifying the nuclear modification due to multiple scatterings between jet and nuclear medium can provide a solid baseline for the identification of the medium fundamental property, which can be partly encoded in the nonperturbative jet transport coefficient ($\hat q$). In this work, we perform the first global extraction of the $\hat q$ for cold nuclear matter within the framework of the...
We compute for the first time the spectrum for emitting 1, 2, and 3 soft and collinear gluons from a hard scattering process in full QCD. This result is important because 1) all current energy loss calculations assume QED-like independent emissions of multiple gluons, which obviously misses all correlations from the non-Abelian nature of QCD, and 2) the average high-p$_{\mathrm{T}}$ parton...
It is believed that the properties of quark-gluon plasma (QGP) can be studied through measurements of the jet quenching phenomenon. More specifically, detailed studies of the jet substructure may reveal the microscopic properties of the QGP.
Recently the modification of groomed jet observables was studied in heavy-ion collisions [1][2]. In addition, the Lund radiation plane was introduced...
We revisit the [calculation of multiple parton scattering of a heavy quark in nuclei][1] within [the framework of recently improved high-twist factorization formalism][2], in which gauge invariance is ensured by a delicate setup of the initial partons’ transverse momenta. We derive [a new result for the heavy quark radiative energy loss in deeply inelastic scattering][3]. By taking the...
Because of their large mass, the interactions of heavy quarks with the quark-gluon plasma (QGP) may be different from those of light quarks and hence can provide essential inputs in understanding the QGP. With strange quark yields being enhanced in the presence of a QGP, the production of $D_{s}^{+}$ is expected to be enhanced if recombination plays an important role in the hadronization...
Jet quenching is used to explore the detailed dynamics of QCD at high densities and temperature. In order to study the parton energy loss dependence on the flavor, we measure the b-jet nuclear modification factor with the latest recorded data-sets of pp and PbPb collisions at 5.02 TeV with CMS detector in 2017 and 2018. The higher center-of-mass energy, compared to the previous study at 2.76...
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,...
Heavy flavor production and collectivity in A+A collisions provide insight into the energy loss mechanism and transport properties of heavy quarks in the QGP medium. In this talk, ATLAS measurements on nuclear modification factor and $v_{2}$ and $v_{3}$ flow coefficients of muons from heavy flavor decays in Pb+Pb collisions are presented as a function of muon $p_{T}$ and centralities. Muons...
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. In this talk, the ALICE Collaboration reports results of a novel approach to jet-quenching measurements in high-multiplicity pp collisions at √𝑠=13 TeV, searching for the broadening of the acoplanarity...
“Hybrid Hadronization” is a new Monte Carlo package to hadronize systems of partons. It smoothly combines quark recombination applicable when distances between partons in phase space are small, and string fragmentation appropriate for dilute parton systems, following the picture outlined by Han et al. [PRC 93, 045207 (2016)]. Hybrid Hadronization integrates with PYTHIA 8 and can be applied to...
We present the results for PbPb collisions at 2.76 TeV LHC energy from a parton shower integrated with a hydrodynamic evolution. The initial hard (jet) partons are produced along with soft partons in the initial state EPOS approach (EPOS3 model). The EPOS3 initial state typically contains multiple hard scatterings in each event. The soft partons, represented by strings, melt into a thermalized...
The largely unknown parton distribution functions of nuclei and the similarities observed between high-multiplicity pp and pPb events compared to PbPb, often described by means of hydrodynamics, are the main motivations for an extended pPb data taking program during LHC Run 3 and Run 4.
The future increase in luminosity combined with the LHCb unique and improved detector capabilities in the...
Dileptons are considered as one of the cleanest signals of the quark-gluon plasma (QGP),however, the QGP radiation is masked by many 'background' sources from either hadronic decays or semileptonic decays from correlated charm pairs. In this study we investigate the relative contribution of these channels in heavy-ion collisions from $\sqrt{s_{\rm NN}}=$ 8 GeV to 5 TeV with a focus on the...
Measurements of heavy-flavor hadron production and elliptic flow ($v_{2}$) provide unique and indispensable information for understanding the properties of the quark-gluon plasma. Recent STAR measurements indicate that in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=$ 200 GeV $D^{0}$ mesons develop large $v_{2}$ similarly as light-favor hadrons, implying that charm quarks interact strongly with...
In ultra-relativistic heavy-ion collisions, partons with intermediate energy (5-10) GeV excite ripples as they travel through the Quark-Gluon Plasma (QGP).
These ripples' effect on particle production phenomenology is not very well studied.
In this work, we extend our previous work \cite{Ryu:2018ckh} and present study using a state-of-the-art hybrid framework that consists of the IP-Glasma...
A Large Ion Collider Experiment plans intensive use of silicon technologies for extensions of the experiment, beyond the currently ongoing upgrade during the Long Shutdown 2 of the LHC. For Run 4, we will discuss the plans for the installation of three new layers of the Inner Tracking system, based on wafer-sized sensors sufficiently thinned to be rolled to a cylinder. This will lead to an...
Heavy quarks are predominantly produced at the early stages of relativistic heavy-ion collisions before the formation of the quark-gluon plasma (QGP) medium. Heavy quarks subsequently traverse the QGP throughout its whole evolution, and thus are suggested as excellent probes to study the properties of the QGP. Theory predicts heavy quarks lose less energy than light quarks through gluon...
The Compact Muon Solenoid (CMS) detector at the CERN Large Hadron Collider (LHC) is undergoing an extensive Phase II upgrade program to prepare for the challenging conditions of the High-Luminosity LHC (HL-LHC). A new timing layer is designed to measure minimum ionizing particles (MIPs) with a time resolution of ~30 ps and hermetic coverage up to a pseudo-rapidity of $|\eta|$=3. The precision...
Away from the strictly soft and collinear limit of QCD radiation the choice of evolution scale in a parton shower algorithm is ambiguous and several options have been implemented in existing Monte Carlo event generators for proton-proton collisions [1]. However, the resulting space-time evolution could result in subtle differences depending on the particular choice. In this work we quantify...
We present recent developments of the POWLANG transport model for the study of heavy-flavour (HF) production in heavy-ion collisions. In particular we focus on the results of recent/ongoing work concerning:
- Event-shape engineering studies of D-meson distributions;
- Full 3+1 transport simulations validated against soft-particle production data. The realistic 3+1 hydrodynamic...
Interactions between hard partons and the quark-gluon plasma range from frequent soft interactions to rare hard interactions. While it is reasonable that hard interactions can be described perturbatively, soft interactions likely suffer from significant non-perturbative effects. Since the effect of the soft interactions can be encoded into parton transport coefficients, these non-perturbative...
Electroweak bosons can be used to constrain the kinematics, as well as the flavor, of the recoiling parton, before its interaction with the quark-gluon plasma. While photons are more abundant, they suffer from larger systematic uncertainties, particularly at low transverse momentum ($p_\mathrm{T}$), from the background photons from neutral meson decays. Tagging with Z bosons is a complementary...
The STAR Collaboration designs, constructs, and installs a suite of new detectors in the forward rapidity region (2.5<$\eta$<4) over the next two years, enabling a program of novel measurements in pp, pA, and AA collisions. This extension of STAR’s kinematic reach will allow detailed studies of cold QCD physics at both very high and very low partonic momentum fraction, i.e., when the...
In hadronic collisions, beauty quarks are produced in hard scattering processes with large momentum transfer. Their production provides a very important test of perturbative QCD calculations in pp collisions.
In heavy-ion collisions, the measurement of beauty hadron production is a unique tool to investigate the properties of the Quark-Gluon Plasma. In particular, beauty quarks, being four...
Transverse momentum broadening and energy loss of a propagating parton are dictated by the space-time profile of the jet transport coefficient $\hat q$ in dense QCD medium. Spatial gradient of $\hat q$ perpendicular to the propagation direction can lead to a drift and asymmetry in parton transverse momentum distribution. Such an asymmetry depends on both the spatial position along the...
A solid hadronization model is essential for understanding hadronic observables in high-energy nuclear collisions, while still remains a challenge due to its non-perturbative nature. We have developed an advanced hadronization model for heavy quarks [1] and studied their suppression, flow and hadron chemistry in heavy-ion collisions. A complete set of both $s$ and $p$-wave hadronic states are...
Complementary to jet reconstruction, two-particle correlations in $\Delta\eta$ and $\Delta\varphi$ are used to study jets, and in particular their particle composition. While in Pb-Pb collisions this is done to characterize the quark-gluon plasma, pp and p-Pb collisions serve as a reference and are of interest on their own for their input into the understanding of particle production...
In proton-proton collisions the underlying event is rather well
reproduced by general purpose event generators such as Herwig, Pythia
and Sherpa. The key to this success has been the modelling of
multi-parton interactions (MPI). Since long it has been recognised
that the (semi-) soft partonic sub-scatterings in such a scenario
cannot be treated completely independent and the concept of...
The jet transport coefficient $\hat{q}$ is the leading property of a strongly interacting medium that effects jet propagation. It introduces momentum transverse to a jet parton’s direction, changing its virtuality and thus controls the modification of hard jets in a dense extended medium. In this talk, we present the first unquenched lattice QCD calculation of $\hat{q}$. The calculation is...
Polarization measurements represent an important tool for understanding the particle production mechanisms occurring in proton–proton collisions. In particular, for quarkonium states, the very small polarization measured at the LHC represents a serious and a long-lasting challenge for theoretical models. When considering heavy-ion collisions, particle polarization could also be used to...
We study the response of a Bjorken-expanding quark-gluon plasma (QGP) to the passage of an energetic parton through it. We compute the non-equilibrium stress-energy tensor induced by such moving energetic parton using linearized Boltzmann equation under the relaxation time approximation. At large distances and large Bjorken time, the QGP exhibits hydrodynamic response, meaning the disturbance...
Heavy flavor observables provide valuable information on the properties of the hot and dense quark gluon plasma (QGP) created in ultrarelativistic nucleus-nucleus collisions. Various microscopic models have successfully described many of the observables associated with its formation. Their transport coefficients differ, however, due to different assumptions about the underlying interaction of...
Jets can be used to study in-medium modifications of the parton shower and the energy loss mechanisms in heavy-ion collisions. Several recent works have alluded to a modification in the fractions of quark and gluon jets in QGP due to color-charge dependent quenching. The jet charge is defined as the momentum-weighted sum of charges of particles inside a jet. The sensitivity of jet charge to...
In heavy-ion collisions the Quark Gluon Plasma (QGP) is recreated which is believed to have filled our universe shortly after the Big Bang. The quenching of highly energetic jets which are also produced in these collisions are powerful probes of the QGP. We propose the measurement of leading and subleading jets as a new probe of the underlying dynamics of the QGP. The dynamics of leading jets...
Jet modification is a multi-stage (multi-scale) process: an initial high virtuality stage gives way to a lower virtuality transport stage for high energy partons, and a strongly coupled phase for lower energy parts of the shower. The transition from the high virtuality medium-modified DGLAP stage takes place when the virtuality reaches the medium induced scale $\hat{q} \tau$, where $\tau$ is...
Measurements of hard-scattered partons produced in conjunction with a high-pT photon or Z boson offer a discerning way to study the quark gluon plasma (QGP) created in ultrarelativistic nucleus-nucleus collisions. The high-pT boson tags the initial energy, direction, and flavor of the opposing parton or partons before they begin to shower and propagate through the QGP, offering a valuable...
We calculate the double differential cross section for production of a quark parton and a photon in proton-nucleus collisions using a newly proposed formalism which generalizes the Color Glass Condensate approach by including large x gluons of the target. We investigate transverse momentum, rapidity and A dependence of azimuthal angular correlations between the produced parton and the photon...
Heavy flavor physics in high-energy heavy-ion collisions is a promising and active area to study the `` jet quenching " effects both at the RHIC and the LHC. The recent reported $D^0$ meson radial profiles in jets measured by CMS collaboration provide new experimental constraints on the mechanisms of heavy flavor production in proton-proton collisions and give new insights into the in-medium...
The modification of jet substructure in heavy-ion collisions compared to that in the vacuum reference is one of the main features of jet quenching. Such modification has been observed at LHC kinematics with various observables, such as jet fragmentation and jet shapes. In this talk, we report measurements of the differential jet shape and semi-inclusive jet fragmentation functions in Au+Au...
J/$\psi$ mesons have been found to be produced with more jet activity than predicted by models in pp collisions at the LHC. J/$\psi$ production has long been known to be modified in nuclear collisions, via Debye screening, as well as by other effects. Indirect evidence, in particular, the non-vanishing $v_{2}$ of J/$\psi$ at large transverse momentum, however, suggests that jet quenching may...
Under the assumption that a quark-gluon plasma droplet is produced in $p$ + A collisions, $\gamma$-triggered hadron spectra [1,2] are studied within a next-to-leading-order perturbative QCD parton model with the medium-modified parton fragmentation functions in $p$ + Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV. The initial conditions and space-time evolution of the small system of hot and...
A new mechanism of photon emission in the quark-gluon plasma is proposed. Photon dispersion relation in the presence of the CP-odd topological regions generated by the chiral anomaly acquires an imaginary mass. It allows photon radiation through the decay $q→q\gamma$ and annihilation $q \bar q→\gamma$ processes closely related to the chiral Cherenkov radiation. Unlike previous proposals this...
Measurement of the azimuthal anisotropy ($v_{2}$) of the hadrons in heavy-ion collisions has provided significant information on the collective behavior of the Quark-Gluon Plasma. In the case of bottomonia states, the contribution from late-stage recombination effects is smaller since the bottom quark is much heavier than the temperature scale of the QGP. In this presentation, we will review...
The measurement of modification of jet yields in heavy-ion collisions provides a powerful method to probe the dynamics of the hot, dense medium formed in these collisions at the LHC. Jet quenching in heavy-ion collisions is expected
to depend on the flavor of the fragmenting parton. For light partons, energy loss via gluon bremsstrahlung is expected to dominate, while in the case of...
The LHC-ALICE experiment is considering to install a Forward Calorimeter (FoCal) during LS3 in 2025-2026 at the LHC. The FoCal is a sampling calorimeter composed of an electromagnetic calorimeter (FoCal-E) and a hadronic calorimeter (FoCal-H) covering forward pseudo-rapidity of $3.2\le \eta \le 5.8$.
The FoCal-E consists of 20 alternating layers of tungsten absorber plates and two types of...
Dielectrons are excellent probes of the Quark-Gluon Plasma (QGP) created in high-energy heavy-ion collisions. Because they can be produced at all stages of the collision system evolution and do not interact with the medium strongly, dielectrons carry the information from the initial stage to the final stage. In the low mass region (LMR, $\rm M_{ee} < M_{\phi}$), the mass spectra of vector...
Direct photons are a unique probe to investigate properties of a thermalized matter created in relativistic heavy-ion collisions, the quark-gluon plasma (QGP). In particular, direct photons at low transverse momentum are very important since thermal photons are supposed to contribute. In recent years, collective behavior has been observed in high particle multiplicity pp and p-Pb collisions at...
Azimuthal anisotropy scaling functions can provide crucial constraints for the properties of the medium produced in ion-ion collisions, because they leverage the characteristic scaling patterns for viscous-flow and jet quenching, to simultaneously delineate the respective role of initial-state eccentricity $\varepsilon_n$, dimensionless size $RT \propto \left< N_{\rm chg}\right>^{1/3}$, the...
Heavy quarkonium is one of the probes of the formation of a quark-gluon
plasma in heavy-ion collisions. Recently, it has been found that its
interaction with the medium can be described, in the intermediate
temperature regime, by a rate equation for the singlet to octet
transition combined with a Langevin equation for the octet to octet
transition. Such a description can be justified...
With the observation of flow-like correlations in small system collisions (p+Pb, p+Au and d+Au) at the LHC and RHIC, the existence of quark-gluon plasma (QGP) in small systems, which was initially assumed to be absent, became an open question and has been actively investigated over recent years. High momentum partons produced at early stages of heavy ion collisions generate collimated sprays...
In non-central heavy-ion collisions, the fast-moving charged ions can produce a strong magnetic field with the magnitude about $eB ∼m^2_π∼10^{18}$ to $10^{19}$ Gauss from the energy available at the BNL Relativistic Heavy Ion Collider (RHIC) to the energy available at the CERN Large Hadron Collider (LHC). Meanwhile, it is believed that relativistic heavy-ion collisions at RHIC and LHC produce...
The very strong electromagnetic fields found in PbPb collisions at the LHC make it effectively a photon-photon collider. Observation of the light-by-light scattering process, $\gamma\gamma \to \gamma\gamma$, in ultraperipheral PbPb collisions at a centre-of-mass energy per nucleon pair of 5.02 TeV recorded in 2018 by the CMS experiment is reported. The exclusive production of dielectrons is...
PHENIX has observed in A+A collision systems a large yield of low p$_\mathrm{T}$ direct photon, as an indication of a hot strongly-coupled system being formed.
In recent years, data from small systems have revealed evidence for collective behavior in small systems. In such a scenario, we expect that the matter formed in small system also radiates thermal photons.
PHENIX is in an ideal...
Heavy quarks, charm and beauty, due to their large masses, are produced in hard partonic scattering processes in the initial stages of the collision. In pp collisions, cross section measurements of open-charmed mesons are an essential test for the predictions of models based on perturbative QCD calculations. In Pb-Pb collisions open-charmed mesons allow us to study the properties of the...
Beauty quarks, due to their large masses are produced in the initial hard scattering processes of hadronic collisions. They witness the whole evolution of the produced medium and serve as an excellent probes for the QGP. In proton--proton collisions, the measurement of beauty-hadron production cross sections are very important to test the perturbative QCD (pQCD) calculations. In addition, it...
It has been shown that high energy partons lose energy when traversing the hot, dense medium produced in heavy-ion collisions. However, the mechanism of the energy loss, including its dependence on the path-length of the shower in the medium, is not fully understood. This poster presents a measurement of single jet yields as a function of the azimuthal angle with respect to the event plane in...
The suppression and enhancement of jets in heavy-ion collisions provides a powerful method to probe the dynamics of the hot, dense plasma formed in these collisions at the LHC. Jet quenching in heavy-ion collisions is expected to depend on the flavor of the fragmenting parton. For light partons, energy loss via gluon bremsstrahlung is expected to dominate, while in the case of...
Jets are excellent probes of the properties of the quark-gluon-plasma. Understanding the evolution of jets inside the hot and dense medium requires a good understanding of the interaction between the medium and the leading parton within the jet. We use a newly developed transport model called LIDO to study this phenomenon. The model includes both large-angle scattering and diffusion processes,...
When partons traverse the Quark-Gluon Plasma (QGP), they lose energy via collisional and radiative processes. This manifests in a suppression of the measured jet yield and a modification of the jet fragmentation pattern in heavy-ion collisions relative to minimum-bias proton-proton collisions, for which no QGP is expected to form. The amount of energy that is lost is expected to depend on the...
I will present a new class of jet substructure observable called collinear drop and its use in the search for novel signatures of jet modifications and medium responses. I will demonstrate using Monte Carlo simulations generated with Jewel how underlying jet-medium interactions can be systematically examined using collinear-drop observables. I will also give analytic insights on the...
The sPHENIX detector at BNL’s Relativistic Heavy Ion Collider (RHIC) will enable a comprehensive measurement of jets in relativistic heavy ion collisions. The detector will cover the full azimuth and a pseudorapidity range of |η| < 1.1. The tracking system will consist of a silicon detector (MVTX) based on MAPS (Monolithic Active Pixel Sensors), followed by an Intermediate Tracker (INTT),...
