作者机构：
[Wang, Xin-Nian; Cao, Shanshan; Luo, Tan] Lawrence Berkeley Natl Lab, Div Nucl Sci, Berkeley, CA 94720 USA.;[Qin, Guang-You; Wang, Xin-Nian; Luo, Tan] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.;[Qin, Guang-You; Wang, Xin-Nian; Luo, Tan] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.
通讯机构：
[Cao, Shanshan] L;Lawrence Berkeley Natl Lab, Div Nucl Sci, Berkeley, CA 94720 USA.
摘要：
A linearized Boltzmann transport (LBT) model coupled with hydrodynamical background is established to describe the evolution of jet shower partons and medium excitations in high energy heavy-ion collisions. We extend the LBT model to include both elastic and inelastic processes for light and heavy partons in the quark-gluon plasma. A hybrid model of fragmentation and coalescence is developed for the hadronization of heavy quarks. Within this framework, we investigate how heavy flavor observables depend on various ingredients, such as different energy loss and hadronization mechanisms, the momentum and temperature dependences of the transport coefficients, and the radial flow of the expanding fireball. Our model calculations show good descriptions of the D meson suppression and elliptic flow observed at the Larege Hadron Collider and the Relativistic Heavy-Ion Collider. The prediction for the Pb-Pb collisions at sNN=5.02 TeV is provided.
作者机构：
[Wang, Xin-Nian; Cao, Shanshan] Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Div Nucl Sci, 1 Cyclotron Rd, Berkeley, CA 94720 USA.;[Qin, Guang-You; Wang, Xin-Nian] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.;[Qin, Guang-You; Wang, Xin-Nian] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.
通讯机构：
[Cao, Shanshan] U;Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Div Nucl Sci, 1 Cyclotron Rd, Berkeley, CA 94720 USA.
摘要：
A sizable contribution to heavy-quark production in high-energy hadronic and nuclear collisions comes from heavy quark-antiquark pair production from gluon splitting during the parton shower evolution. We investigate the effect of gluon-medium interaction on open heavy flavor spectra in ultrarelativistic heavy-ion collisions. The interaction of hard gluons and heavy quarks with the hot QCD medium is simulated by utilizing a Langevin transport model that simultaneously incorporates contributions from collisional and radiative processes. It is found that, while the gluon splitting channel has quite an important contribution to the single D-meson production cross section, its influence on the final heavy-meson nuclear modification turns out to be quite modest because the average lifetime of hard gluons is short before splitting into heavy-quark-antiquark pairs during the evolution and propagation of the parton shower.
摘要：
Fermions become polarized in a vortical fluid due to spin-vorticity coupling. Such a polarization can be calculated from the Wigner function in a quantum kinetic approach. By extending previous results for chiral fermions, we derive the Wigner function for massive fermions up to next-to-leading order in spatial gradient expansion. The polarization density of fermions can be calculated from the axial vector component of the Wigner function and is found to be proportional to the local vorticity ω. The polarizations per particle for fermions and antifermions decrease with the chemical potential and increase with energy (mass). Both quantities approach the asymptotic value ℏω/4 in the large energy (mass) limit. The polarization per particle for fermions is always smaller than that for antifermions, whose ratio of fermions to antifermions also decreases with the chemical potential. The polarization per particle on the Cooper-Frye freeze-out hypersurface can also be formulated and is consistent with the previous result of Becattini et al. [11,27].
通讯机构：
[Wang, Xin-Nian] C;Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.
关键词：
quark-gluon plasma;heavy-ion collisions;QCD phase transition;properties of QGP
摘要：
Heavy-ion collisions at very high colliding energies are expected to produce a quark-gluon plasma (QGP) at the highest temperature obtainable in a laboratory setting. Experimental studies of these reactions can provide an unprecedented range of information on properties of the QGP at high temperatures. We report theoretical investigations of the physics perspectives of heavy-ion collisions at a future high-energy collider. These include initial parton production, collective expansion of the dense medium, jet quenching, heavy-quark transport, dissociation and regeneration of quarkonia, photon and dilepton production. We illustrate the potential of future experimental studies of the initial particle production and formation of QGP at the highest temperature to provide constraints on properties of strongly interaction matter.
作者机构：
[Zhang, Jia Jun; Wang, Xin-Nian] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.;[Gao, Jian-Hua; Zhang, Jia Jun; Wang, Xin-Nian] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.;[Gao, Jian-Hua] Shandong Univ, Inst Space Sci, Shandong Prov Key Lab Opt Astron & Solar Terr Env, Weihai 264209, Peoples R China.;[Wang, Xin-Nian] Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Nucl Sci Div, Berkeley, CA 94720 USA.
通讯机构：
[Zhang, Jia Jun] C;Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.
摘要：
Multiple scattering leads to transverse momentum broadening of the struck quark in semi-inclusive deeply inelastic scatterings. Nuclear broadening of the transverse momentum squared at the leading twist is determined by the twist-four collinear quark-gluon correlation function of the target nucleus that is in turn related to the jet transport parameter inside the nuclear medium. The twist-six contributions to the transverse momentum broadening are calculated as power corrections ∼1/Q2. Such power corrections are found to have no extra nuclear enhancement beyond the twist-four matrix elements and are determined by the nuclear modification of collinear parton distribution and correlation functions. They become important for an accurate extraction of the jet transport parameter inside large nuclei and its scale evolution at intermediate values of the hard scale Q2.
作者机构：
[Xiao, Bo-Wen; Wang, Xin-Nian; Pang, Long-Gang] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.;[Xiao, Bo-Wen; Wang, Xin-Nian; Pang, Long-Gang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.;[Hatta, Yoshitaka] Kyoto Univ, Yukawa Inst Theoret Phys, Kyoto 6068502, Japan.;[Wang, Xin-Nian] Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Div Nucl Sci, Berkeley, CA 94720 USA.
通讯机构：
[Pang, Long-Gang] C;Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.
摘要：
Evolution of quark-gluon plasma near equilibrium can be described by the second-order relativistic viscous hydrodynamic equations. Consistent and analytically verifiable numerical solutions are critical for phenomenological studies of the collective behavior of quark-gluon plasma in high-energy heavy-ion collisions. A novel analytical solution based on the conformal Gubser flow that is a boost-invariant solution with transverse fluid velocity is presented. Because of the nonlinear nature of the equation, the analytical solution is nonperturbative and exhibits features that are rather distinct from solutions to usual linear hydrodynamic equations. It is used to verify with high precision the numerical solution with a newly developed state-of-the-art (3+1)-dimensional second-order viscous hydro code (CLVisc). The perfect agreement between the analytical and numerical solutions demonstrates the reliability of the numerical simulations with the second-order viscous corrections. This lays the foundation for future phenomenological studies that allow one to gain access to the second-order transport coefficients.
摘要：
Jet quenching in high-energy heavy-ion collisions can be used to probe properties of hot and dense quark–gluon plasma. We provide a brief introduction to the concept and framework for the study of jet quenching. Different approaches and implementation of multiple scattering and parton energy loss are discussed. Recent progresses in the theoretical and phenomenological studies of jet quenching in heavy-ion collisions at RHIC and LHC are reviewed.
作者机构：
[Roy, Victor; Qin, Guang-You; Wang, Xin-Nian; Pang, Long-Gang] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.;[Roy, Victor; Qin, Guang-You; Wang, Xin-Nian; Pang, Long-Gang] Cent China Normal Univ, Key Lab Quarks & Lepton Phys MOE, Wuhan 430079, Peoples R China.;[Roy, Victor] Goethe Univ Frankfurt, Inst Theoret Phys, D-60438 Frankfurt, Germany.;[Wang, Xin-Nian] Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Div Nucl Sci, Berkeley, CA 94720 USA.;[Ma, Guo-Liang] Chinese Acad Sci, Shanghai Inst Appl Phys, Shanghai 201800, Peoples R China.
通讯机构：
[Pang, Long-Gang] C;Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.
摘要：
Fluctuations in the initial transverse energy-density distribution lead to anisotropic flows as observed in central high-energy heavy-ion collisions. Studies of longitudinal fluctuations of the anisotropic flows can shed further light on the initial conditions and dynamical evolution of the hot quark-gluon matter in these collisions. Correlations between anisotropic flows with varying pseudorapidity gaps in Pb+Pb collisions at the CERN Large Hadron Collider are investigated using both an event-by-event (3+1)-dimensional ideal hydrodynamical model with fluctuating initial conditions and a multiphase transport (AMPT) Monte Carlo model for high-energy heavy-ion collisions. Anisotropic flows at different pseudorapidities are found to become significantly decorrelated with increasing pseudorapidity gaps due to longitudinal fluctuations in the initial states of heavy-ion collisions. The longitudinal correlation of the elliptic flow shows a strong centrality dependence while the correlation of the triangular flow is independent of the centrality. Longitudinal fluctuations as a source of the decorrelation are further shown to consist of a twist or gradual rotation in flow angles between the forward and backward direction and additional fluctuations on top of the twist. Within the AMPT model, longitudinal correlations of anisotropic flows are also found to depend on the value of partonic cross sections. The implications of constraining the initial conditions and shear viscosity to entropy density ratio of the partonic matter in high-energy heavy-ion collisions are also discussed.
作者机构：
[Wang, Xin-Nian; He, Yayun; Luo, Tan] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.;[Wang, Xin-Nian; He, Yayun; Luo, Tan] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.;[Wang, Xin-Nian] Lawrence Berkeley Natl Lab, Div Nucl Sci, Berkeley, CA 94740 USA.;[Zhu, Yan] Univ Santiago de Compostela, Dept Fis Particulas, E-15706 Santiago De Compostela, Galicia, Spain.;[Zhu, Yan] Univ Santiago de Compostela, IGFAE, E-15706 Santiago De Compostela, Galicia, Spain.
通讯机构：
[He, Yayun] C;Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.
摘要：
A linear Boltzmann transport model within perturbative QCD is developed for the study of parton propagation inside the quark-gluon plasma. Both leading partons and thermal recoil partons are tracked so that one can also study jet-induced medium excitations. In this study, we implement the complete set of elastic parton scattering processes and investigate elastic parton energy loss, transverse momentum broadening, and their nontrivial energy and length dependence. We further investigate medium modifications of the jet shape and fragmentation functions of reconstructed jets. Contributions from thermal recoil partons are found to have significant influences on jet shape, fragmentation functions, and angular distribution of reconstructed jets.
期刊：
Journal of Physics: Conference Series,2015年612(1) ISSN：1742-6588
通讯作者：
Zhu, Yan
作者机构：
[Zhu, Yan] Univ Santiago de Compostela, Dept Fis Particulas, E-15706 Santiago De Compostela, Galicia, Spain.;[Zhu, Yan] Univ Santiago de Compostela, IGFAE, E-15706 Santiago De Compostela, Galicia, Spain.;[Wang, Xin-Nian] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.;[Wang, Xin-Nian] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.;[Wang, Xin-Nian] Lawrence Berkeley Natl Lab, Nucl Sci Div, Berkeley, CA 94740 USA.
通讯机构：
[Zhu, Yan] U;Univ Santiago de Compostela, Dept Fis Particulas, E-15706 Santiago De Compostela, Galicia, Spain.
会议名称：
6th Workshop on Young Scientists on the Physics of Ultrarelativistic Nucleus-Nucleus Collisions (Hot Quarks)
会议时间：
SEP 21-28, 2014
会议地点：
Las Negras, SPAIN
会议主办单位：
[Zhu, Yan] Univ Santiago de Compostela, Dept Fis Particulas, E-15706 Santiago De Compostela, Galicia, Spain.^[Zhu, Yan] Univ Santiago de Compostela, IGFAE, E-15706 Santiago De Compostela, Galicia, Spain.^[Wang, Xin-Nian] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.^[Wang, Xin-Nian] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.^[Wang, Xin-Nian] Lawrence Berkeley Natl Lab, Nucl Sci Div, Berkeley, CA 94740 USA.
作者机构：
[Wang, Xin-Nian; Chang, Ning-Bo] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.;[Wang, Xin-Nian; Chang, Ning-Bo] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.;[Deng, Wei-Tian] Huazhong Univ Sci & Technol, Sch Phys, Wuhan 430074, Peoples R China.;[Wang, Xin-Nian] Lawrence Berkeley Natl Lab, Div Nucl Sci, Berkeley, CA 94740 USA.
通讯机构：
[Chang, Ning-Bo] C;Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.
摘要：
Multiple scattering and induced parton splitting lead to a medium modification of the QCD evolution for jet fragmentation functions and final hadron spectra. Medium-induced parton splittings not only lead to energy loss of leading partons and suppression of leading hadron spectra, but also modify the flavor composition of a jet due to induced flavor conversion via gluon emission and quark pair production and annihilation. Through a numerical study of the medium-modified QCD evolution, leading K− strange meson spectra are found to be particularly sensitive to the medium-induced flavor conversion in semi-inclusive deeply inelastic scatterings (SIDIS) off a large nucleus. The induced flavor conversion can lead to an increased number of gluons and sea quarks in a jet shower and, as a consequence, enhance the leading K− spectrum to counter the effect of parton energy loss in SIDIS with large momentum fractions xB, where the struck quarks are mostly valence quarks of the nucleus.
作者机构：
[Wang, Xin-Nian; He, Yayun; Luo, Tan] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.;[Wang, Xin-Nian; He, Yayun; Luo, Tan] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.;[Wang, Xin-Nian] Lawrence Berkeley Natl Lab, Div Nucl Sci, Berkeley, CA 94740 USA.;[Zhu, Yan] Univ Santiago de Compostela, Dept Fis Particulas, E-15706 Santiago De Compostela, Galicia, Spain.;[Zhu, Yan] Univ Santiago de Compostela, IGFAE, E-15706 Santiago De Compostela, Galicia, Spain.
通讯机构：
[Luo, Tan] C;Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.
关键词：
Jet quenching;Jet transport;Parton energy loss;Quark-gluon plasma
摘要：
A Linearized Boltzmann Transport (LBT) model has been developed for the study of parton propagation inside quark-gluon plasma. Both leading and thermal recoiled partons are tracked in order to include the effect of jet-induced medium excitation. In this talk, we present a study within the LBT model in which we implement the complete set of elastic parton scattering processes. We investigate elastic parton energy loss and their energy and length dependence. We further investigate energy loss and transverse shape of reconstructed jets. Contributions from the recoiled thermal partons and jet-induced medium excitations are found to have significant influences on the jet energy loss and transverse profile. (C) 2014 Elsevier B.V. All rights reserved.
作者机构：
[Burke, Karen M.; Qin, Guang-You; Majumder, Abhijit] Wayne State Univ, Dept Phys & Astron, Detroit, MI 48201 USA.;[Buzzatti, Alessandro; Wang, Xin-Nian] Lawrence Berkeley Natl Lab, Div Nucl Sci, Berkeley, CA 94720 USA.;[Qin, Guang-You; Chang, Ningbo; Zhang, Hanzhong; Wang, Xin-Nian] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.;[Qin, Guang-You; Chang, Ningbo; Zhang, Hanzhong; Wang, Xin-Nian] Cent China Normal Univ, Key Lab Quarks & Lepton Phys MOE, Wuhan 430079, Peoples R China.;[Gale, Charles; Jeon, Sangyong] McGill Univ, Dept Phys, Montreal, PQ H3A 2T8, Canada.
通讯机构：
[Wang, Xin-Nian] L;Lawrence Berkeley Natl Lab, Div Nucl Sci, MS 70R0319, Berkeley, CA 94720 USA.
摘要：
Within five different approaches to parton propagation and energy loss in dense matter, a phenomenological study of experimental data on suppression of large- pT single inclusive hadrons in heavy-ion collisions at both the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC) was carried out. The evolution of bulk medium used in the study for parton propagation was given by 2 + 1 dimensional or 3 + 1 dimensional hydrodynamic models which are also constrained by experimental data on bulk hadron spectra. Values for the jet transport parameter q̂ at the center of the most central heavy-ion collisions are extracted or calculated within each model, with parameters for the medium properties that are constrained by experimental data on the hadron suppression factor RAA. For a quark with initial energy of 10 GeV we find that q̂≈1.2±0.3 GeV 2/fm at an initial time τ0=0.6 fm/ c in Au + Au collisions at s=200 GeV/n and q̂≈1.9±0.7 GeV 2/fm in Pb + Pb collisions at s=2.76 TeV/n. Compared to earlier studies, these represent significant convergence on values of the extracted jet transport parameter due to new constraints provided by recent experiment data from the LHC.
作者机构：
[Wang, Xin-Nian] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.;[Wang, Xin-Nian] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.;[Wang, Xin-Nian] Lawrence Berkeley Natl Lab, Div Nucl Sci, Berkeley, CA 94740 USA.;[Wang, Xin-Nian] Lawrence Berkeley Natl Lab, Div Nucl Sci, Mailstop 70R0319, Berkeley, CA 94740 USA.
通讯机构：
[Wang, Xin-Nian] L;Lawrence Berkeley Natl Lab, Div Nucl Sci, Mailstop 70R0319, Berkeley, CA 94740 USA.
关键词：
Jet quenching;Jet transport;Parton energy loss;Quark-gluon plasma
摘要：
Using theoretical tools developed by the JET Collaboration in which one employs (2 + 1)D or (3 + 1)D hydrodynamic models for the bulk medium evolution and jet quenching models, the combined data on suppression of single inclusive hadron spectra at both RHIC and LHC are systematically analyzed with five different approaches to the parton energy loss. The jet transport parameter is extracted from the best fits to the data with values of (q) over cap approximate to 1.2 +/- 0.3 and 1.9 +/- 0.7 GeV2/fm in the center of the most central Au + Au collisions at root s = 200 GeV and Pb + Pb collisions at root s = 2.67 TeV, respectively, at an initial time tau(0) = 0.6 fm/c for a quark jet with an initial energy of 10 GeV/c. (C) 2014 Elsevier B.V. All rights reserved.
摘要：
Initial conditions are required to solve medium modified Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (mDGLAP) evolution equations for modified fragmentation functions due to multiple scatterings and parton energy loss. Such initial conditions should in principle include energy loss for partons at scale Q0 above which mDGLAP evolution equations can be applied. Several models for the initial condition motivated by induced gluon bremsstrahlung in perturbative QCD are used to calculate the modified fragmentation functions in nuclear medium and to extract the jet transport parameter q̂ from fits to experimental data in deeply inelastic scattering (DIS) off nuclei. The model with a Poisson convolution of multiple gluon emissions is found to provide the overall best χ2/d.o.f. fit to the HERMES data and gives a value of q̂0≈0.020±0.005 GeV 2/fm at the center of a large nucleus.
摘要：
We study how the shear viscosity, η, entropy density, s, and η/s depend on growing hadron chemical potentials resulting from the loss of chemical equilibrium during the evolution of a relativistic heavy-ion collision. Our calculations here are for an interacting pion gas in a system of net baryon number zero. Time evolution of the temperature and pion chemical potential are taken from ideal fluid hydrodynamic calculations of RHIC and LHC collisions. We find that the shear viscosity decreases whereas the entropy density increases with increasing pion chemical potential resulting in values of η/s that are slightly reduced from the case of chemical potentials being zero when chemical equilibrium prevails. Our results indicate that the inclusion of additional mesons and baryons will likely lead to further reduction in the value of η/s.
作者机构：
[Song, Yu-kun] Univ Sci & Technol China, Dept Modern Phys, Hefei 230026, Anhui, Peoples R China.;[Liang, Zuo-tang] Shandong Univ, Key Lab Particle Phys & Particle Irradiat MOE, Jinan 250100, Peoples R China.;[Liang, Zuo-tang] Shandong Univ, Sch Phys, Jinan 250100, Peoples R China.;[Wang, Xin-Nian] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.;[Wang, Xin-Nian] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.
通讯机构：
[Song, Yu-kun] U;Univ Sci & Technol China, Dept Modern Phys, Hefei 230026, Anhui, Peoples R China.
摘要：
We extend the study of nuclear dependence of the transverse momentum dependent parton distribution functions and azimuthal asymmetries to semi-inclusive deep inelastic scattering (SIDIS) off polarized nuclear targets. We show that azimuthal asymmetries are suppressed for SIDIS off a polarized nuclear target relative to that off a polarized nucleon due to multiple scattering inside the nucleus. Using the value of transport parameter inside large nuclei extracted from jet quenching analyses in SIDIS off nuclear targets, we also present a numerical estimate of the nuclear suppression of the azimuthal asymmetry that might be useful to guide the future experimental studies of SIDIS off polarized nuclear targets.
作者机构：
[Wang, Xin-Nian] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.;[Wang, Xin-Nian] Cent China Normal Univ, Key Lab Quark & Lepton Phys MOE, Wuhan 430079, Peoples R China.;[Wang, Xin-Nian] Lawrence Berkeley Natl Lab, Div Nucl Sci, Berkeley, CA 94740 USA.;[Wang, Xin-Nian] Lawrence Berkeley Natl Lab, Div Nucl Sci, Mailstop 70R0319, Berkeley, CA 94740 USA.
通讯机构：
[Wang, Xin-Nian] L;Lawrence Berkeley Natl Lab, Div Nucl Sci, Mailstop 70R0319, Berkeley, CA 94740 USA.
关键词：
EM emission;Hard probes;Heavy-ion collisions;Jet quenching;QGP
摘要：
In the study of the quark-gluon plasma in high-energy heavy-ion collisions, hard and electromagnetic (EM) processes play an essential role as probes of the properties of the dense medium. They can be used to study a wide range of properties of the dense medium in high-energy heavy-ion collisions, from space-time profiles of the dense matter, bulk transport coefficients to EM responses and the jet transport parameter. I review in this talk these medium properties, how they can be studied through hard and EM probes and the status of recent theoretical and phenomenological investigations.
