摘要：
We calculate the differential cross section for the unpolarized semi-inclusive deeply inelastic scattering process e−+N→e−+q+X in leading order of perturbative QCD and up to twist-4 in power corrections and study, in particular, the azimuthal asymmetry ⟨cos2ϕ⟩. The final results are expressed in terms of transverse momentum dependent parton matrix elements of the target nucleon up to twist-4. We also apply it to e−+A→e−+q+X and illustrate numerically the nuclear dependence of the azimuthal asymmetry ⟨cos2ϕ⟩ by using a Gaussian ansatz for the transverse momentum dependent parton matrix elements.
期刊：
JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS,2011年38(12):124156 ISSN：0954-3899
通讯作者：
Ma, Guo-Liang
作者机构：
[Ma, Guo-Liang] Chinese Acad Sci, Shanghai Inst Appl Phys, Shanghai 201800, Peoples R China.;[Wang, Xin-Nian] Cent China Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.;[Wang, Xin-Nian] Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Nucl Sci Div MS 70R0319, Berkeley, CA 94720 USA.
摘要：
Quark splitting in non-trivial θ-vacuum with a given helicity is investigated in pQCD with a modified quark propagator. We found that the quark splitting functions were modified by the presence of a topologically non-trivial QCD background field, though there is no explicit helicity flip associated with the radiative processes. The interaction with the topological non-trivial field leads to the degeneracy of the quark splitting functions for left- and right-handed quarks. Such degeneracy can lead to imbalance of left- and right-handed quarks in quark jet showers. We also discuss phenomenological consequences of such imbalance if there exists non-trivial topological gluon field configuration in heavy-ion collisions.
期刊：
Progress of Theoretical Physics Supplement,2011年187(187):43-54 ISSN：0375-9687
通讯作者：
Wang, Xin-Nian
作者机构：
[Wang, Xin-Nian] Huazhong Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.;[Wang, Xin-Nian] Univ Calif Berkeley, Lawrence Berkeley Lab, Div Nucl Sci, Berkeley, CA 94720 USA.
通讯机构：
[Wang, Xin-Nian] H;Huazhong Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.
摘要：
Transverse momentum broadening and parton energy loss for a jet propagating inside a medium can be characterized by the jet transport parameter (q) over cap which is essentially the local gluon density as probed by an energetic jet. This is the underlying principle of jet tomography of dense matter in high-energy heavy-ion collisions. In this talk, I will discuss recent progress in the study of jet tomography in both semi-inclusive deeply inelastic scattering off large nuclei and high-energy heavy-ion collisions.
作者机构：
[Wang, Xin-Nian; Li, Hanlin; Liu, Fuming; Zhu, Yan] Hua Zhong Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.;[Ma, Guo-liang] Chinese Acad Sci, Shanghai Inst Appl Phys, Shanghai 201800, Peoples R China.;[Wang, Xin-Nian] Univ Calif Berkeley, Lawrence Berkeley Lab, Nucl Sci Div MS 70R0319, Berkeley, CA 94720 USA.
通讯机构：
[Li, Hanlin] H;Hua Zhong Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.
摘要：
Medium excitation by jet shower propagation inside a quark-gluon plasma is studied within a linear Boltzmann transport and a multiphase transport model. Contrary to the naive expectation, it is the deflection of both the jet shower and the Mach-cone-like excitation in an expanding medium that is found to give rise to a double-peak azimuthal particle distribution with respect to the initial jet direction. Such a deflection is the strongest for hadron-triggered jets which are often produced close to the surface of a dense medium due to trigger bias and travel against or tangential to the radial flow. Without such trigger bias, the effect of deflection on γ-jet showers and their medium excitation is weaker. Comparative study of hadron and γ-triggered particle correlations can therefore reveal the dynamics of jet-induced medium excitation in high-energy heavy-ion collisions.
作者机构：
[Wang, Enke; Zhang, Hanzhong; Wang, Xin-Nian; Chen, Xiao-Fang] Huazhong Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.;[Hirano, Tetsufumi] Univ Tokyo, Dept Phys, Tokyo 1130033, Japan.;[Wang, Xin-Nian; Hirano, Tetsufumi] Univ Calif Berkeley, Lawrence Berkeley Lab, Div Nucl Sci, MS 70R0319, Berkeley, CA 94720 USA.
通讯机构：
[Chen, Xiao-Fang] H;Huazhong Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.
摘要：
The nuclear modification factor RAA(pT) for large transverse momentum pion spectra in Pb+Pb collisions at s=2.76 TeV is predicted within the next-to-leading order perturbative QCD parton model. The effect of jet quenching is incorporated through medium-modified fragmentation functions within the higher-twist approach. The jet transport parameter that controls medium modification is proportional to the initial parton density, and the coefficient is fixed by data on the suppression of large- pT hadron spectra obtained at the BNL Relativistic Heavy Ion Collider. Data on charged hadron multiplicity dNch/dη=1584±80 in central Pb+Pb collisions from the ALICE experiment at the CERN Large Hadron Collider are used to constrain the initial parton density both for determining the jet transport parameter and the 3 + 1 dimensional (3 + 1D) ideal hydrodynamic evolution of the bulk matter that is employed for the calculation of RPbPb(pT) for neutral pions.
摘要：
Transverse momentum correlations in the azimuthal angle of hadrons produced owing to minijets are first studied within the HIJING Monte Carlo model in high-energy heavy-ion collisions. Quenching of minijets during thermalization is shown to lead to significant diffusion (broadening) of the correlation. Evolution of the transverse momentum density fluctuation that gives rise to this correlation in azimuthal angle in the later stage of heavy-ion collisions is further investigated within a linearized diffusion-like equation and is shown to be determined by the shear viscosity of the evolving dense matter. This diffusion equation for the transverse momentum fluctuation is solved with initial values given by HIJING and together with the hydrodynamic equation for the bulk medium. The final transverse momentum correlation in azimuthal angle is calculated along the freeze-out hypersurface and is found to be further diffused for higher values of the shear viscosity to entropy density ratio, η/s~0.2–0.4. Therefore the final transverse momentum correlation in azimuthal angle can be used to study the thermalization of minijets in the early stage of heavy-ion collisions and the viscous effect in the hydrodynamic evolution of strongly coupled quark-gluon plasma.
作者机构：
[Long-gang Pang; Qun Wang] Interdisciplinary Center for Theoretical Study and Department of Modem Physics,University of Science and Technology of China,Anhui 230026,People's Republic of China;[Xin-nian Wang] Nuclear Science Division,Lawrence Berkeley National Laboratory,Cyclotron road,Berkeley,CA 94720,USA;[Rong Xu] Institute of Particle Physics,Huazhong Normal University,Wuhan 430079,People's Republic of China
会议名称：
The 10th International Conference on Nucleus-Nucleus Collisions(第十届国际核—核碰撞会议
会议时间：
2009-8-16
会议地点：
北京
会议主办单位：
中国物理学会;中国核学会
会议论文集名称：
The 10th International Conference on Nucleus-Nucleus Collisions(第十届国际核—核碰撞会议论文集
关键词：
Jet quenching;Modified fragmentation;Parton energy loss
摘要：
Modifications to quark and antiquark fragmentation functions due to quark-quark (antiquark) double scattering in nuclear medium are studied systematically up to order O(alpha(2)(s)) in deeply inelastic scattering (DIS) off nuclear targets. At the order O(alpha(2)(s)), twist-four contributions from quark-quark (antiquark) rescattering also exhibit the Landau-Pomeranchuk-Migdal (LPM) interference feature similar to gluon bremsstrahlung induced by multiple parton scattering. Compared to quark-gluon scattering, the modification, which is dominated by t-channel quark-quark (antiquark) scattering, is only smaller by a factor of C-F/C-A = 4/9 times the ratio of quark and gluon distributions in the medium. Such a modification is not negligible for realistic kinematics and finite medium size. The modifications to quark (antiquark) fragmentation functions from quark-antiquark annihilation processes are shown to be determined by the antiquark (quark) distribution density in the medium. The asymmetry in quark and antiquark distributions in nuclei will lead to different modifications of quark and antiquark fragmentation functions inside a nucleus, which qualitatively explains the experimentally observed flavor dependence of the leading hadron suppression in semi-inclusive DIS off nuclear targets. The quark-antiquark annihilation processes also mix quark and gluon fragmentation functions in the large fractional momentum region, leading to a flavor dependence of jet quenching in heavy-ion collisions. (C) 2007 Elsevier B.V. All rights reserved.
作者机构：
[Zhang, Ben-Wei] Huazhong Normal Univ, Inst Particle Phys, Wuhan 430070, Peoples R China.;Univ Regensburg, Inst Theoret Phys, D-8400 Regensburg, Germany.;Texas A&M Univ, Cyclotron Inst, College Stn, TX 77843 USA.;Lawrence Berkeley Lab, Nucl Sci Div, Berkeley, CA 94720 USA.
通讯机构：
[Zhang, Ben-Wei] H;Huazhong Normal Univ, Inst Particle Phys, Wuhan 430070, Peoples R China.
会议名称：
2nd International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions
会议时间：
JUN 09-16, 2006
会议地点：
Pacific Grove q, CA
会议主办单位：
Huazhong Normal Univ, Inst Particle Phys, Wuhan 430070, Peoples R China.^Univ Regensburg, Inst Theoret Phys, D-8400 Regensburg, Germany.^Texas A&M Univ, Cyclotron Inst, College Stn, TX 77843 USA.^Lawrence Berkeley Lab, Nucl Sci Div, Berkeley, CA 94720 USA.
摘要：
Quark-quark double scattering in eA DIS and its contribution to quark and anti-quark fragmentation functions are investigated with the generalized factorization of the relevant twist-four processes in pQCD. It is shown that the resulting modifications to quark and anti-quark fragmentation functions are different. While the numerical size of these effects cannot be determined from pQCD, the structure of our result leads to a number of qualitative predictions for the relative size of the effect for different hadrons. These qualitative predictions agree with the multiplicity ratios for positive and negative hadrons as observed by HERMES.
作者机构：
Lawrence Berkeley Lab, Div Nucl Sci, Berkeley, CA 94720 USA.;Huazhong Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.;[Wang, XN] Lawrence Berkeley Lab, Div Nucl Sci, MS 70R0319, Berkeley, CA 94720 USA.
通讯机构：
[Wang, XN] L;Lawrence Berkeley Lab, Div Nucl Sci, MS 70R0319, Berkeley, CA 94720 USA.
摘要：
Multiple scattering, induced radiative energy loss and modified fragmentation functions of a heavy quark in nuclear matter are studied within the framework of generalized factorization in perturbative QCD. Modified heavy quark fragmentation functions and energy loss are derived in detail with illustration of the mass dependencies of the Landau-Pomeranchuk-Migdal interference effects and heavy quark energy loss. Due to the quark mass dependence of the gluon formation time, the nuclear size dependencies of nuclear modification of the heavy quark fragmentation function and heavy quark energy loss are found to change from a linear to a quadratic form when the initial energy and momentum scale are increased relative to the quark mass. The radiative energy loss of the heavy quark is also significantly suppressed due to limited cone of gluon radiation imposed by the mass. Medium modification of the heavy quark fragmentation functions is found to be limited to the large z region due to the form of heavy quark fragmentation functions in vacuum. (c) 2005 Elsevier B.V. All rights reserved.
作者机构：
Lawrence Berkeley Natl Lab, Div Nucl Sci, Berkeley, CA 94720 USA.;Huazhong Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.;Shandong Univ, Dept Phys, Jinan 250100, Peoples R China.;[Wang, XN] Lawrence Berkeley Natl Lab, Div Nucl Sci, MS 70R0319, Berkeley, CA 94720 USA.
通讯机构：
[Wang, XN] L;Lawrence Berkeley Natl Lab, Div Nucl Sci, MS 70R0319, Berkeley, CA 94720 USA.
摘要：
Multiple parton scattering and induced parton energy loss in deeply inelastic scattering (DlS) off heavy nuclei is studied within the framework of generalized factorization in perturbative QCD with a complete calculation beyond the helicity amplitude (or soft bremsstrahlung) approximation. Such a calculation gives rise to new corrections to the modified quark fragmentation functions. The effective parton energy loss is found to be reduced by a factor of 5/6 from the result of helicity amplitude approximation. (C) 2003 Published by Elsevier Science B.V.
作者机构：
Univ Calif Berkeley, Lawrence Berkeley Lab, Div Nucl Sci, Berkeley, CA 94720 USA.;Huazhong Normal Univ, Inst Particle Phys, Wuhan 430079, Peoples R China.;Shandong Univ, Dept Phys, Jinan 250100, Peoples R China.;[Osborne, JA] Univ Calif Berkeley, Lawrence Berkeley Lab, Div Nucl Sci, 1 Cyclotron Rd, Berkeley, CA 94720 USA.
通讯机构：
[Osborne, JA] U;Univ Calif Berkeley, Lawrence Berkeley Lab, Div Nucl Sci, 1 Cyclotron Rd, Berkeley, CA 94720 USA.
摘要：
The first order correction to the parton fragmentation functions in a thermal medium is derived in the leading logarithmic approximation in the framework of thermal field theory. The medium-modified evolution equations of the parton fragmentation functions are also derived. It is shown that all infrared divergences, both linear and logarithmic, in the real processes are canceled among themselves and by corresponding virtual corrections. The evolution of the quark number and the energy loss (or gain) induced by the thermal medium are investigated.
