The medium-temperature T dependence of the jet transport coefficient̂q was studied via the nuclear modification factor RAA(p_(T))and elliptical flow parameter v_(2)(p_(T))for large transverse momentum p_(T) hadrons in...The medium-temperature T dependence of the jet transport coefficient̂q was studied via the nuclear modification factor RAA(p_(T))and elliptical flow parameter v_(2)(p_(T))for large transverse momentum p_(T) hadrons in high-energy nucleus-nucleus collisions.Within a next-to-leading-order perturbative QCD parton model for hard scatterings with modified fragmentation functions due to jet quenching controlled by q,we check the suppression and azimuthal anisotropy for large p_(T) hadrons,and extract q by global fits to RAA(pT)and v_(2)(pT)data in A+A collisions at RHIC and LHC,respectively.The numerical results from the best fits show that q∕T^(3) goes down with local medium-temperature T in the parton jet trajectory.Compared with the case of a constant q∕T^(3),the going-down T dependence of q∕T^(3) makes a hard parton jet to lose more energy near T_(c) and therefore strengthens the azimuthal anisotropy for large pT hadrons.As a result,v_(2)(p_(T))for large pT hadrons was enhanced by approximately 10%to better fit the data at RHIC/LHC.Considering the first-order phase transition from QGP to the hadron phase and the additional energy loss in the hadron phase,v_(2)(p_(T))is again enhanced by 5-10%at RHIC/LHC.展开更多
Flow structure and heat transfer characteristics of an axisymmetric circularjet impinging on a hot 1Cr18Ni9Ti medium plate have been simulated numerically using computationalfluid dynamic (CFD) code. The relation betw...Flow structure and heat transfer characteristics of an axisymmetric circularjet impinging on a hot 1Cr18Ni9Ti medium plate have been simulated numerically using computationalfluid dynamic (CFD) code. The relation between flow field of jet impingement and its heat transfercapability is analyzed, and the phenomenon that heat transfer at stagnation point is smaller thanthat of points directly around is discussed. The simulation result provides boundary conditions forthermal analysis of medium plate quenching.展开更多
Heavy flavor particles provide important probes of the microscopic structure and thermodynamic properties of the quark-gluon plasma(QGP)produced in high-energy nucleus-nucleus collisions.We studied the energy loss and...Heavy flavor particles provide important probes of the microscopic structure and thermodynamic properties of the quark-gluon plasma(QGP)produced in high-energy nucleus-nucleus collisions.We studied the energy loss and flow of charm and bottom quarks inside the QGP via the nuclear modification factor(R_(AA))and elliptic flow coefficient(v_(2))of their decayed leptons in heavy-ion collisions at the LHC.The dynamical evolution of the QGP was performed using the CLVisc(3+1)-dimensional viscous hydrodynamics model;the evolution of heavy quarks inside the QGP was simulated with our improved Langevin model that considers both collisional and radiative energy loss of heavy quarks;the hadronization of heavy quarks was simulated via our hybrid coalescence-fragmentation model;and the semi-leptonic decay of D and B mesons was simulated via PYTHIA.Using the same spatial diffusion coefficient for charm and bottom quarks,we obtained smaller R_(AA) and larger v_(2) of charm decayed leptons than bottom decayed leptons,indicating stronger energy loss of charm quarks than bottom quarks inside the QGP within our current model setup.展开更多
We present a theoretical study of the medium modifications of the p_(T)balance (x_(J)) of dijets in Xe+Xe collisions at■.The initial production of dijets was carried out using the POWHEG+PYTHIA8 prescription,which ma...We present a theoretical study of the medium modifications of the p_(T)balance (x_(J)) of dijets in Xe+Xe collisions at■.The initial production of dijets was carried out using the POWHEG+PYTHIA8 prescription,which matches the next-toleading-order (NLO) QCD matrix elements with the parton shower (PS) effect.The SHELL model described the in-medium evolution of nucleus–nucleus collisions using a transport approach.The theoretical results of the dijet xJin the Xe+Xe collisions exhibit more imbalanced distributions than those in the p+p collisions,consistent with recently reported ATLAS data.By utilizing the Interleaved Flavor Neutralisation,an infrared-and-collinear-safe jet flavor algorithm,to identify the flavor of the reconstructed jets,we classify dijets processes into three categories:gluon–gluon (gg),quark–gluon (qg),and quark–quark (qq),and investigated the respective medium modification patterns and fraction changes of the gg,qg,and qq components of the dijet sample in Xe+Xe collisions.It is shown that the increased fraction of qg component at a small x_(J)contributes to the imbalance of the dijet;in particular,the q_(1)g_(2)(quark-jet-leading) dijets experience more significant asymmetric energy loss than the g_(1)q_(2)(gluon-jet-leading) dijets traversing the QGP.By comparing the■of inclusive,■ dijets in Xe+Xe collisions,we observe■.Moreover,ρ_(Xe),P_(b),the ratios of the nuclear modification factors of dijets in Xe+Xe to those in Pb+Pb,were calculated,which indicates that the yield suppression of dijets in Pb+Pb is more pronounced than that in Xe+Xe owing to the larger radius of the lead nucleus.展开更多
The production of vector boson tagged heavy quark jets potentially provides new tools to probe the jet quenching effect.In this paper,we present the first theoretical study on the angular correlations(ΔφbZ),transver...The production of vector boson tagged heavy quark jets potentially provides new tools to probe the jet quenching effect.In this paper,we present the first theoretical study on the angular correlations(ΔφbZ),transverse momentum imbalance(xbZ),and nuclear modification factor(IAA) of Z0boson tagged b-jets in heavy-ion collisions,which was performed using a Monte Carlo transport model.We find that the medium modification of theΔφbZfor Z0+b-jet has a weaker dependence on ΔφbZthan that for Z^(0)+jet,and the modification patterns are sensitive to the initial jet pTdistribution.Additionally,with the high purity of the quark jet in Z^(0)+(b-) jet production,we calculate the momentum imbalance xbZand the nuclear modification factor IAAof Z^(0)+b-jet in Pb+Pb collisions.We observe a smaller Δ<xjZ> and larger IAAof Z^(0)+b-jet in Pb+Pb collisions relative to those of Z^(0)+jet,which may be an indication of the mass effect of jet quenching and can be tested in future measurements.展开更多
We study the energy loss of a quark moving in a strongly coupled quark gluon plasma under the influence of anisotropy.The heavy quark drag force,diffusion coefficient,and jet quenching parameter are calculated using t...We study the energy loss of a quark moving in a strongly coupled quark gluon plasma under the influence of anisotropy.The heavy quark drag force,diffusion coefficient,and jet quenching parameter are calculated using the Einstein–Maxwell-dilaton model,where the anisotropic background is characterized by an arbitrary dynamical parameter A.Our findings indicate that as the anisotropic factor A increases,the drag force and jet quenching parameter both increase,while the diffusion coefficient decreases.Additionally,we observe that the energy loss becomes more significant when the quark moves perpendicular to the anisotropy direction in the transverse plane.The enhancement of the rescaled jet quenching parameters near critical temperature Tc,as well as drag forces for a fast-moving heavy quark is observed,which presents one of the typical features of quantum chromodynamics phase transition.展开更多
We report results of a comprehensive global х~2 analysis of nuclear collision data from RHIC(0.2 ATeV),LHC1(2.76 ATeV), and recent LHC2(5.02 ATeV) energies using the updated CUJET framework. The framework consistentl...We report results of a comprehensive global х~2 analysis of nuclear collision data from RHIC(0.2 ATeV),LHC1(2.76 ATeV), and recent LHC2(5.02 ATeV) energies using the updated CUJET framework. The framework consistently combines viscous hydrodynamic fields predicted by VISHNU2+1(validated with soft p_T﹤2 GeV bulk observables) and the DGLV theory of jet elastic and inelastic energy loss generalized to QGP fluids with an sQGMP color structure, including effective semi-QGP color electric quark and gluon as well as emergent color magnetic monopole degrees of freedom constrained by lattice QCD data. We vary the two control parameters of the model(the maximum value of the running QCD coupling, c, and the ratio cm of color magnetic to electric screening scales) and calculate the global х~2(α_c,c_m) compared with available jet fragment observables( R_(AA),v_2). A global х~2 minimum is found with α_c≈0.9±0.1 and c_m≈0.25±0.03. Using CIBJET, the event-by-event(ebe) generalization of the CUJET framework, we show that ebe fluctuations in the initial conditions do not significantly alter our conclusions(except for v_3). An important theoretical advantage of the CUJET and CIBJET frameworks is not only its global х~2 consistency with jet fragment observables at RHIC and LHC and with non-perturbative lattice QCD data, but also its internal consistency of the constrained jet transport coefficient, ■(E,T)/T^3, with the near-perfect fluid viscosity to entropy ratio(η/s～T^3/■～0.1-0.2) property of QCD fluids near Tc needed to account for the low p_T﹤2 GeV flow observables. Predictions for future tests at LHC with 5.44 ATeV Xe + Xe and 5.02 ATeV Pb + Pb are also presented.展开更多
Jet shape measurements are employed to explore the microscopic evolution mechanisms of parton-medium interaction in ultra-relativistic heavy-ion collisions. In this study, jet shape modifications are quantified in ter...Jet shape measurements are employed to explore the microscopic evolution mechanisms of parton-medium interaction in ultra-relativistic heavy-ion collisions. In this study, jet shape modifications are quantified in terms of the fragmentation function F(z), relative momentum p_T^(rel), density of charged particles p(r), jet angularity girth, jet momentum dispersion p_T^(disp),and LeS ub for proton-proton(pp) collisions at 0.9, 2.76. 5.02, 7,and 13 TeV, as well as for lead-lead collisions at 2.76 TeV and 5.02 TeV by JEWEL. A differential jet shape parameter Dgirth is proposed and studied at a smaller jet radius r < 0.3. The results indicate that the medium has the dominant effect on jet shape modification, which also has a weak dependence on the center-of-mass energy. Jet fragmentation is enhanced significantly at very low z < 0.02, and fragmented jet constituents are linearly spread to larger jet-radii for p_T^(rel) < 1. The waveform attenuation phenomena is observed in p_T^(rel),girth, and Dgirth distributions. The results obtained for D_(girth) from pp to Pb + Pb, where the wave-like distribution in pp collision is ahead of Pb + Pb collisions at small jetradii, indicates a strong medium effect.展开更多
ALICE,A Large Ion Collider Experiment,is dedicated to study the QCD matter at extreme high temperature and density to understand the Quark Gluon Plasma （QGP） and phase transition.High-transversemomentum photons and ...ALICE,A Large Ion Collider Experiment,is dedicated to study the QCD matter at extreme high temperature and density to understand the Quark Gluon Plasma （QGP） and phase transition.High-transversemomentum photons and neutral mesons from the initial hard scattering of partons can be measured with ALICE calorimeters,PHOS （PHOton Spectrometer） and EMCAL （ElectroMagnetic CALorimeter）.Combing the additional central tracking detectors,the γ-jet and π 0-jet measurements thus can be accessed.These measurements offer us a sensitive tomography probe of the hot-dense medium generated in the heavy ion collisions.In this paper,high p T and photon physics is discussed and the ALICE calorimeters capabilities of high-transverse-momentum neutral mesons and γ-jet measurements are presented.展开更多
Jet measurement is an ideal probe to explore the properties of the hot dense matter created in ultra- relativistic heavy-ion collisions. Recent results at the LHC show that large angle radiation is non-negligible, but...Jet measurement is an ideal probe to explore the properties of the hot dense matter created in ultra- relativistic heavy-ion collisions. Recent results at the LHC show that large angle radiation is non-negligible, but the mechanisms and phenomenology of large angle radiation are still unclear and hotly debated. Considering the coexistence and competition of different physics mechanisms qualitatively, it is assumed that the radiation angle is enhanced randomly over a wide range based on the collinear approximation. Its effects on di-jet momentum imbalance, jet fragmentation function and jet shape are studied in pp collisions at 7 TeV. The results show that di-jet asymmetry is insensitive to large angle radiation, while jet shape and jet fragmentation functions are more sensitive and could explain experimental data well. We conclude that de-collimated radiation cannot be ignored for soft jets, and there is a contribution from large angle radiation （Ф 〉 0.7） of about 8%, which is significant for jet intrinsic structure measurement at PT,jeT 〈80 GeV/c.展开更多
Angular correlations between a heavy quark(HQ)and its tagged jet are potentially new tools to gain insight into the in-medium partonic interactions in relativistic heavy-ion collisions.In this work,we present the firs...Angular correlations between a heavy quark(HQ)and its tagged jet are potentially new tools to gain insight into the in-medium partonic interactions in relativistic heavy-ion collisions.In this work,we present the first theoretical study on the radial profiles of B mesons in jets in Pb+Pb collisions at the Large Hadron Collider(LHC).The initial production of a bottom quark tagged jet in p+p is computed by SHERPA,which matches the next-to-leading order matrix elements with contributions of parton showers,whereas the massive quark traversing the quark-gluon plasma is described by a Monte Carlo model,SHELL,which can simultaneously simulate light and heavy flavor in-medium energy loss within the framework of Langevin evolution.In p+p collisions,we find that at lower PQ/T the radial profiles of heavy flavors in jets are sensitive to the heavy quark mass.In 0-10%Pb+Pb collisions at√SNN=5.02 TeV,we observe an inverse modification pattern of the B meson radial profiles in jets at4PQ/T<20 GeV compared to those of D mesons:the jet quenching effects narrow the jet radial profiles of B mesons in jets while broadening those of D mesons in jets.We find that in A+A collisions,the contribution dissipated from the higher PQ/T>20 GeV region naturally has a narrower initial distribution and consequently leads to a narrower modification pattern of the radial profile;however the diffusion nature of the heavy flavor in-medium interactions will give rise to a broader modification pattern of the radial profile.These two effects consequently compete and offset with each other,and the b quarks in jets benefit more from the former and suffer less diffusion effect compared to that of c quarks in jets.These findings can be tested in the future experimental measurements at the LHC to gain better understanding of the mass effect of jet quenching.展开更多
In this study,we investigate the impact of jet quenching on the p_(T) dispersion(p_(T)D)of inclusive jets(R=0.2)in central Pb+Pb(0%-10%)collisions at √s=2.76 TeV.The partonic spectrum in the initial hard scattering o...In this study,we investigate the impact of jet quenching on the p_(T) dispersion(p_(T)D)of inclusive jets(R=0.2)in central Pb+Pb(0%-10%)collisions at √s=2.76 TeV.The partonic spectrum in the initial hard scattering of elementary collisions is obtained by an event generator POWHEG+PYTHIA,which matches the next-to-leading order(NLO)matrix elements with parton showering,and the energy loss of a fast parton traversing through hot/dense QCD medium is calculated using Monte Carlo simulation within the Higher-Twist formalism of jet quenching in heavy-ion collisions.We present model calculations of the normalized p_(T)D distributions of inclusive jets in p+p and central Pb+Pb collisions at √s=2.76 TeV,which offer good descriptions of ALICE measurements.It is shown that the p_(T)D distributions of inclusive jets in central Pb+Pb collisions shift significantly to a higher p_(T)D region relative to those in p+p collisions.Thus,the nuclear modification ratio of the p_(T)D distributions of inclusive jets is smaller than unity in the small p_(T)D region and larger than one in the large p_(T)D region.This behavior is caused by a more uneven p_(T) distribution for jet constituents as well as the fraction alteration of quark/gluon initiated jets in heavy-ion collisions.The difference in p_(T)D distribution between groomed and ungroomed jets in Pb+Pb collisions is also discussed.展开更多
We carry out a detailed study of medium modifications on Z^(0)/γ+hadron correlations as well as jet substructures in association with Z^(0)/γ in Pb+Pb collisions with √S_(NN)=5.02TeV at the LHC.We utilize the linea...We carry out a detailed study of medium modifications on Z^(0)/γ+hadron correlations as well as jet substructures in association with Z^(0)/γ in Pb+Pb collisions with √S_(NN)=5.02TeV at the LHC.We utilize the linear Boltzmann transport(LBT)model to simulate the jet-medium interactions and medium response,and an extended cluster hadronization model to investigate the nonperturbative transition of quarks and gluons into final hadrons in heavy-ion collisions.Including hadronization effect,we can well describe Z^(0)/γ+hadrons correlations and Z^(0)/γ-tagged jet substructures in both p+p and Pb+Pb collisions simultaneously.Medium modification on jet profile and jet fragmentation functions indicate that particles carrying a large fraction of the jet momentum are generally closely aligned with the jet axis,whereas low-momentum particles are observed to have a much broader angular distribution relative to jet axis in Pb+Pb collisions due to jet-medium interactions.In particular,we find that Z^(0)/γ-tagged hadron correlations are sensitive to the soft particles from the dense medium and medium response,while jet-substructures show weak dependence on those soft hadrons with only a fraction of them falling inside the jet area.展开更多
The energy loss during jet quenching due to the existence of Quark Gluon Plasma (QGP) is calculated by Optical Glaube Monte Carlo model with data collected by ATLAS Collaboration using the LHC detector. An energy loss...The energy loss during jet quenching due to the existence of Quark Gluon Plasma (QGP) is calculated by Optical Glaube Monte Carlo model with data collected by ATLAS Collaboration using the LHC detector. An energy loss formula for this situation was modeled and took the form . The nuclear modification factor, RAA, for jets in a 208Pb + 208Pb nucleus collision with rapidity interval of ∣у∣=2.8 and the initial transverse momentum of 50 GeV ≤ pT ≤ 1000 GeV, are compared with various data plots produced by ATLAS Collaboration. RAA results are plotted in different centrality bins, which are defined by the distribution of number of participating nucleons Npart. The RAA value was found to slowly increase at lower transverse momenta and flatten out at higher transverse momenta. The model’s theoretical calculation results turned out to be similar to the plots produced by the ATLAS Collaboration using data from the LHC with small differences for higher systematic uncertainty events.展开更多
In this article, a model based on Glauber Monte Carlo is built to simulate the procedure of jet quenching in Quark-Gluon Plasma (QGP). In this model, energy loss of jets in QGP is parametrized by two quantities: path ...In this article, a model based on Glauber Monte Carlo is built to simulate the procedure of jet quenching in Quark-Gluon Plasma (QGP). In this model, energy loss of jets in QGP is parametrized by two quantities: path length of jets in QGP, L, and the initial transverse momentum of the jet PT. The path length of each branch of the jet are labeled L1 and L2. As input data, original jet energy data of p + p collisions were obtained from CMS measurement. After being processed by our model, simulated Pb + Pb jet energy data could be given and were compared to the data of ATLAS’s measurement in Ref. [1]. Distributions of (1/N)dN/dxJ? where?xJ=PT2/PT1, also noted as “frequency”, are presented as a function of PT1 and collision centrality. As the final result, two different forms of energy loss formula were found, both of which have good adaptation to certain centrality and PT ranges.展开更多
基金Guangdong Major Project of Basic and Applied Basic Research(No.2020B0301030008)Science and Technology Program of Guangzhou(No.2019050001)National Science Foundation of China(Nos.12347130 and 11935007).
文摘The medium-temperature T dependence of the jet transport coefficient̂q was studied via the nuclear modification factor RAA(p_(T))and elliptical flow parameter v_(2)(p_(T))for large transverse momentum p_(T) hadrons in high-energy nucleus-nucleus collisions.Within a next-to-leading-order perturbative QCD parton model for hard scatterings with modified fragmentation functions due to jet quenching controlled by q,we check the suppression and azimuthal anisotropy for large p_(T) hadrons,and extract q by global fits to RAA(pT)and v_(2)(pT)data in A+A collisions at RHIC and LHC,respectively.The numerical results from the best fits show that q∕T^(3) goes down with local medium-temperature T in the parton jet trajectory.Compared with the case of a constant q∕T^(3),the going-down T dependence of q∕T^(3) makes a hard parton jet to lose more energy near T_(c) and therefore strengthens the azimuthal anisotropy for large pT hadrons.As a result,v_(2)(p_(T))for large pT hadrons was enhanced by approximately 10%to better fit the data at RHIC/LHC.Considering the first-order phase transition from QGP to the hadron phase and the additional energy loss in the hadron phase,v_(2)(p_(T))is again enhanced by 5-10%at RHIC/LHC.
文摘Flow structure and heat transfer characteristics of an axisymmetric circularjet impinging on a hot 1Cr18Ni9Ti medium plate have been simulated numerically using computationalfluid dynamic (CFD) code. The relation between flow field of jet impingement and its heat transfercapability is analyzed, and the phenomenon that heat transfer at stagnation point is smaller thanthat of points directly around is discussed. The simulation result provides boundary conditions forthermal analysis of medium plate quenching.
基金Supported in part by the National Natural Science Foundation of China(12225503,11935007,11890710,11890711,12175122,2021-867)China Postdoctoral Science Foundation(2023M742099)。
文摘Heavy flavor particles provide important probes of the microscopic structure and thermodynamic properties of the quark-gluon plasma(QGP)produced in high-energy nucleus-nucleus collisions.We studied the energy loss and flow of charm and bottom quarks inside the QGP via the nuclear modification factor(R_(AA))and elliptic flow coefficient(v_(2))of their decayed leptons in heavy-ion collisions at the LHC.The dynamical evolution of the QGP was performed using the CLVisc(3+1)-dimensional viscous hydrodynamics model;the evolution of heavy quarks inside the QGP was simulated with our improved Langevin model that considers both collisional and radiative energy loss of heavy quarks;the hadronization of heavy quarks was simulated via our hybrid coalescence-fragmentation model;and the semi-leptonic decay of D and B mesons was simulated via PYTHIA.Using the same spatial diffusion coefficient for charm and bottom quarks,we obtained smaller R_(AA) and larger v_(2) of charm decayed leptons than bottom decayed leptons,indicating stronger energy loss of charm quarks than bottom quarks inside the QGP within our current model setup.
基金Guangdong Major Project of Basic and Applied Basic Research(No.2020B0301030008)National Natural Science Foundation of China with Project(Nos.11935007,12035007,12247127,and 12247132)China Postdoctoral Science Foundation supports S.Wang under project No.2021M701279.
文摘We present a theoretical study of the medium modifications of the p_(T)balance (x_(J)) of dijets in Xe+Xe collisions at■.The initial production of dijets was carried out using the POWHEG+PYTHIA8 prescription,which matches the next-toleading-order (NLO) QCD matrix elements with the parton shower (PS) effect.The SHELL model described the in-medium evolution of nucleus–nucleus collisions using a transport approach.The theoretical results of the dijet xJin the Xe+Xe collisions exhibit more imbalanced distributions than those in the p+p collisions,consistent with recently reported ATLAS data.By utilizing the Interleaved Flavor Neutralisation,an infrared-and-collinear-safe jet flavor algorithm,to identify the flavor of the reconstructed jets,we classify dijets processes into three categories:gluon–gluon (gg),quark–gluon (qg),and quark–quark (qq),and investigated the respective medium modification patterns and fraction changes of the gg,qg,and qq components of the dijet sample in Xe+Xe collisions.It is shown that the increased fraction of qg component at a small x_(J)contributes to the imbalance of the dijet;in particular,the q_(1)g_(2)(quark-jet-leading) dijets experience more significant asymmetric energy loss than the g_(1)q_(2)(gluon-jet-leading) dijets traversing the QGP.By comparing the■of inclusive,■ dijets in Xe+Xe collisions,we observe■.Moreover,ρ_(Xe),P_(b),the ratios of the nuclear modification factors of dijets in Xe+Xe to those in Pb+Pb,were calculated,which indicates that the yield suppression of dijets in Pb+Pb is more pronounced than that in Xe+Xe owing to the larger radius of the lead nucleus.
基金Supported by the Guangdong Major Project of Basic and Applied Basic Research (2020B0301030008)the Science and Technology Program of Guangzhou(2019050001)+1 种基金the NSFC of China (11935007,12035007,12247127)supported by China Postdoctoral Science Foundation (2021M701279)
文摘The production of vector boson tagged heavy quark jets potentially provides new tools to probe the jet quenching effect.In this paper,we present the first theoretical study on the angular correlations(ΔφbZ),transverse momentum imbalance(xbZ),and nuclear modification factor(IAA) of Z0boson tagged b-jets in heavy-ion collisions,which was performed using a Monte Carlo transport model.We find that the medium modification of theΔφbZfor Z0+b-jet has a weaker dependence on ΔφbZthan that for Z^(0)+jet,and the modification patterns are sensitive to the initial jet pTdistribution.Additionally,with the high purity of the quark jet in Z^(0)+(b-) jet production,we calculate the momentum imbalance xbZand the nuclear modification factor IAAof Z^(0)+b-jet in Pb+Pb collisions.We observe a smaller Δ<xjZ> and larger IAAof Z^(0)+b-jet in Pb+Pb collisions relative to those of Z^(0)+jet,which may be an indication of the mass effect of jet quenching and can be tested in future measurements.
基金the Guangdong Major Project of Basic and Applied Basic Research No.2020B0301030008the Natural Science Foundation of China with Project Nos.11935007。
文摘We study the energy loss of a quark moving in a strongly coupled quark gluon plasma under the influence of anisotropy.The heavy quark drag force,diffusion coefficient,and jet quenching parameter are calculated using the Einstein–Maxwell-dilaton model,where the anisotropic background is characterized by an arbitrary dynamical parameter A.Our findings indicate that as the anisotropic factor A increases,the drag force and jet quenching parameter both increase,while the diffusion coefficient decreases.Additionally,we observe that the energy loss becomes more significant when the quark moves perpendicular to the anisotropy direction in the transverse plane.The enhancement of the rescaled jet quenching parameters near critical temperature Tc,as well as drag forces for a fast-moving heavy quark is observed,which presents one of the typical features of quantum chromodynamics phase transition.
基金Supported by the National Science Foundation(PHY-1352368)IOPP of CCNU Wuhan China,the computations in this study were performed on IU's Big Red Ⅱ clusters,supported in part by the Lilly Endowment,Inc.+1 种基金support for the Indiana University Pervasive Technology Institute,and in part by the Indiana METACyt InitiativeThe Indiana METACyt Initiative at IU was also supported in part by the Lilly Endowment,Inc.
文摘We report results of a comprehensive global х~2 analysis of nuclear collision data from RHIC(0.2 ATeV),LHC1(2.76 ATeV), and recent LHC2(5.02 ATeV) energies using the updated CUJET framework. The framework consistently combines viscous hydrodynamic fields predicted by VISHNU2+1(validated with soft p_T﹤2 GeV bulk observables) and the DGLV theory of jet elastic and inelastic energy loss generalized to QGP fluids with an sQGMP color structure, including effective semi-QGP color electric quark and gluon as well as emergent color magnetic monopole degrees of freedom constrained by lattice QCD data. We vary the two control parameters of the model(the maximum value of the running QCD coupling, c, and the ratio cm of color magnetic to electric screening scales) and calculate the global х~2(α_c,c_m) compared with available jet fragment observables( R_(AA),v_2). A global х~2 minimum is found with α_c≈0.9±0.1 and c_m≈0.25±0.03. Using CIBJET, the event-by-event(ebe) generalization of the CUJET framework, we show that ebe fluctuations in the initial conditions do not significantly alter our conclusions(except for v_3). An important theoretical advantage of the CUJET and CIBJET frameworks is not only its global х~2 consistency with jet fragment observables at RHIC and LHC and with non-perturbative lattice QCD data, but also its internal consistency of the constrained jet transport coefficient, ■(E,T)/T^3, with the near-perfect fluid viscosity to entropy ratio(η/s～T^3/■～0.1-0.2) property of QCD fluids near Tc needed to account for the low p_T﹤2 GeV flow observables. Predictions for future tests at LHC with 5.44 ATeV Xe + Xe and 5.02 ATeV Pb + Pb are also presented.
基金Supported by National Natural Science Foundation of China(11505130,11847014,11775097 and CCNU18ZDPY04)
文摘Jet shape measurements are employed to explore the microscopic evolution mechanisms of parton-medium interaction in ultra-relativistic heavy-ion collisions. In this study, jet shape modifications are quantified in terms of the fragmentation function F(z), relative momentum p_T^(rel), density of charged particles p(r), jet angularity girth, jet momentum dispersion p_T^(disp),and LeS ub for proton-proton(pp) collisions at 0.9, 2.76. 5.02, 7,and 13 TeV, as well as for lead-lead collisions at 2.76 TeV and 5.02 TeV by JEWEL. A differential jet shape parameter Dgirth is proposed and studied at a smaller jet radius r < 0.3. The results indicate that the medium has the dominant effect on jet shape modification, which also has a weak dependence on the center-of-mass energy. Jet fragmentation is enhanced significantly at very low z < 0.02, and fragmented jet constituents are linearly spread to larger jet-radii for p_T^(rel) < 1. The waveform attenuation phenomena is observed in p_T^(rel),girth, and Dgirth distributions. The results obtained for D_(girth) from pp to Pb + Pb, where the wave-like distribution in pp collision is ahead of Pb + Pb collisions at small jetradii, indicates a strong medium effect.
基金Supported partly by the NSFC (10875051,10635020 and 10975061)State Key Development Program of Basic Research of China (2008CB317106)+1 种基金the Key Project of Chinese Ministry of Education (306022 and IRT0624)Program of Introducing Talents of Discipline to Universities of China: B08033
文摘ALICE,A Large Ion Collider Experiment,is dedicated to study the QCD matter at extreme high temperature and density to understand the Quark Gluon Plasma （QGP） and phase transition.High-transversemomentum photons and neutral mesons from the initial hard scattering of partons can be measured with ALICE calorimeters,PHOS （PHOton Spectrometer） and EMCAL （ElectroMagnetic CALorimeter）.Combing the additional central tracking detectors,the γ-jet and π 0-jet measurements thus can be accessed.These measurements offer us a sensitive tomography probe of the hot-dense medium generated in the heavy ion collisions.In this paper,high p T and photon physics is discussed and the ALICE calorimeters capabilities of high-transverse-momentum neutral mesons and γ-jet measurements are presented.
基金Supported by National Natural Science Foundation of China(11505130,11775097,IRG1152106,11475068)CTGU(1910103,B2018023)
文摘Jet measurement is an ideal probe to explore the properties of the hot dense matter created in ultra- relativistic heavy-ion collisions. Recent results at the LHC show that large angle radiation is non-negligible, but the mechanisms and phenomenology of large angle radiation are still unclear and hotly debated. Considering the coexistence and competition of different physics mechanisms qualitatively, it is assumed that the radiation angle is enhanced randomly over a wide range based on the collinear approximation. Its effects on di-jet momentum imbalance, jet fragmentation function and jet shape are studied in pp collisions at 7 TeV. The results show that di-jet asymmetry is insensitive to large angle radiation, while jet shape and jet fragmentation functions are more sensitive and could explain experimental data well. We conclude that de-collimated radiation cannot be ignored for soft jets, and there is a contribution from large angle radiation （Ф 〉 0.7） of about 8%, which is significant for jet intrinsic structure measurement at PT,jeT 〈80 GeV/c.
基金Trond Mohn基金(编号:BFS2018REK01)卑尔根大学(University of Bergen)基金+2 种基金挪威研究委员会(Norwegian Research Council)基金(编号:255253/F50-CERN Heavy Ion Theory)Marie Sk?odowska-Curie基金(编号:754496)的欧盟远景2020研究和创新项目挪威电子基础设施UNINETT Sigma2数据存储和高性能计算资源(编号:NS9753K,NN9753K)资助。
基金Supported by the Guangdong Major Project of Basic and Applied Basic Research(2020B0301030008)the Science and Technology Program of Guangzhou(2019050001)the NSFC of China with Project(11935007,11805167)。
文摘Angular correlations between a heavy quark(HQ)and its tagged jet are potentially new tools to gain insight into the in-medium partonic interactions in relativistic heavy-ion collisions.In this work,we present the first theoretical study on the radial profiles of B mesons in jets in Pb+Pb collisions at the Large Hadron Collider(LHC).The initial production of a bottom quark tagged jet in p+p is computed by SHERPA,which matches the next-to-leading order matrix elements with contributions of parton showers,whereas the massive quark traversing the quark-gluon plasma is described by a Monte Carlo model,SHELL,which can simultaneously simulate light and heavy flavor in-medium energy loss within the framework of Langevin evolution.In p+p collisions,we find that at lower PQ/T the radial profiles of heavy flavors in jets are sensitive to the heavy quark mass.In 0-10%Pb+Pb collisions at√SNN=5.02 TeV,we observe an inverse modification pattern of the B meson radial profiles in jets at4PQ/T<20 GeV compared to those of D mesons:the jet quenching effects narrow the jet radial profiles of B mesons in jets while broadening those of D mesons in jets.We find that in A+A collisions,the contribution dissipated from the higher PQ/T>20 GeV region naturally has a narrower initial distribution and consequently leads to a narrower modification pattern of the radial profile;however the diffusion nature of the heavy flavor in-medium interactions will give rise to a broader modification pattern of the radial profile.These two effects consequently compete and offset with each other,and the b quarks in jets benefit more from the former and suffer less diffusion effect compared to that of c quarks in jets.These findings can be tested in the future experimental measurements at the LHC to gain better understanding of the mass effect of jet quenching.
基金Supported in part by Guangdong Major Project of Basic and Applied Basic Research(2020B0301030008)the National Natural Science Foundation of China(NSFC)(11935007,12035007)the MOE Key Laboratory of Quark and Lepton Physics(CCNU)(QLPL2020P01)。
文摘In this study,we investigate the impact of jet quenching on the p_(T) dispersion(p_(T)D)of inclusive jets(R=0.2)in central Pb+Pb(0%-10%)collisions at √s=2.76 TeV.The partonic spectrum in the initial hard scattering of elementary collisions is obtained by an event generator POWHEG+PYTHIA,which matches the next-to-leading order(NLO)matrix elements with parton showering,and the energy loss of a fast parton traversing through hot/dense QCD medium is calculated using Monte Carlo simulation within the Higher-Twist formalism of jet quenching in heavy-ion collisions.We present model calculations of the normalized p_(T)D distributions of inclusive jets in p+p and central Pb+Pb collisions at √s=2.76 TeV,which offer good descriptions of ALICE measurements.It is shown that the p_(T)D distributions of inclusive jets in central Pb+Pb collisions shift significantly to a higher p_(T)D region relative to those in p+p collisions.Thus,the nuclear modification ratio of the p_(T)D distributions of inclusive jets is smaller than unity in the small p_(T)D region and larger than one in the large p_(T)D region.This behavior is caused by a more uneven p_(T) distribution for jet constituents as well as the fraction alteration of quark/gluon initiated jets in heavy-ion collisions.The difference in p_(T)D distribution between groomed and ungroomed jets in Pb+Pb collisions is also discussed.
基金supported by the Guangdong Major Project of Basic and Applied Basic Research(Grant No.2020B0301030008)the National Natural Science Foundation of China(Grant Nos.12147131,11935007,12035007,and 12022512)supported by the MOE Key Laboratory of Quark and Lepton Physics(CCNU)(Grant No.QLPL2021P01)。
文摘We carry out a detailed study of medium modifications on Z^(0)/γ+hadron correlations as well as jet substructures in association with Z^(0)/γ in Pb+Pb collisions with √S_(NN)=5.02TeV at the LHC.We utilize the linear Boltzmann transport(LBT)model to simulate the jet-medium interactions and medium response,and an extended cluster hadronization model to investigate the nonperturbative transition of quarks and gluons into final hadrons in heavy-ion collisions.Including hadronization effect,we can well describe Z^(0)/γ+hadrons correlations and Z^(0)/γ-tagged jet substructures in both p+p and Pb+Pb collisions simultaneously.Medium modification on jet profile and jet fragmentation functions indicate that particles carrying a large fraction of the jet momentum are generally closely aligned with the jet axis,whereas low-momentum particles are observed to have a much broader angular distribution relative to jet axis in Pb+Pb collisions due to jet-medium interactions.In particular,we find that Z^(0)/γ-tagged hadron correlations are sensitive to the soft particles from the dense medium and medium response,while jet-substructures show weak dependence on those soft hadrons with only a fraction of them falling inside the jet area.
文摘The energy loss during jet quenching due to the existence of Quark Gluon Plasma (QGP) is calculated by Optical Glaube Monte Carlo model with data collected by ATLAS Collaboration using the LHC detector. An energy loss formula for this situation was modeled and took the form . The nuclear modification factor, RAA, for jets in a 208Pb + 208Pb nucleus collision with rapidity interval of ∣у∣=2.8 and the initial transverse momentum of 50 GeV ≤ pT ≤ 1000 GeV, are compared with various data plots produced by ATLAS Collaboration. RAA results are plotted in different centrality bins, which are defined by the distribution of number of participating nucleons Npart. The RAA value was found to slowly increase at lower transverse momenta and flatten out at higher transverse momenta. The model’s theoretical calculation results turned out to be similar to the plots produced by the ATLAS Collaboration using data from the LHC with small differences for higher systematic uncertainty events.
文摘In this article, a model based on Glauber Monte Carlo is built to simulate the procedure of jet quenching in Quark-Gluon Plasma (QGP). In this model, energy loss of jets in QGP is parametrized by two quantities: path length of jets in QGP, L, and the initial transverse momentum of the jet PT. The path length of each branch of the jet are labeled L1 and L2. As input data, original jet energy data of p + p collisions were obtained from CMS measurement. After being processed by our model, simulated Pb + Pb jet energy data could be given and were compared to the data of ATLAS’s measurement in Ref. [1]. Distributions of (1/N)dN/dxJ? where?xJ=PT2/PT1, also noted as “frequency”, are presented as a function of PT1 and collision centrality. As the final result, two different forms of energy loss formula were found, both of which have good adaptation to certain centrality and PT ranges.
