Zhao Wenbin, Ko Che Ming, Liu Yu-Xin, Qin Guang-You, Song Huichao
Department of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China.
Collaborative Innovation Center of Quantum Matter, Beijing 100871, China.
Phys Rev Lett. 2020 Aug 14;125(7):072301. doi: 10.1103/PhysRevLett.125.072301.
We investigate the role of partonic degrees of freedom in high-multiplicity p-Pb collisions at sqrt[s_{NN}]=5.02 TeV carried out at the Large Hadron Collider (LHC) by studying the production and collective flow of identified hadrons at intermediate p_{T} via the coalescence of soft partons from the viscous hydrodynamics (VISH2+1) and hard partons from the energy loss model, linear Boltzmann transport (LBT). We find that combining these intermediate p_{T} hadrons with the low p_{T} hadrons from the hydrodynamically expanding fluid and high p_{T} hadrons from the fragmentation of quenched jets, the resulting hydro-dynamics-coalescence-fragmentation model provides a nice description of measured p_{T} spectra and differential elliptic flow v_{2}(p_{T}) of pions, kaons, and protons over the p_{T} range from 0 to 6 GeV. We further demonstrate the necessity of including the quark coalescence contribution to reproduce the experimentally observed approximate number of constituent quark scaling of hadron v_{2} at intermediate p_{T}. Our results thus indicate the importance of partonic degrees of freedom and also hint at the possible formation of quark-gluon plasma in high-multiplicity p-Pb collisions at the LHC.
我们通过研究中间横动量($p_T$)处鉴别强子的产生和集体流,来探究在大型强子对撞机(LHC)上进行的$\sqrt[s_{NN}]=5.02$ TeV的高多重数质子-铅离子碰撞中部分子自由度的作用,这些强子是通过粘性流体动力学(VISH2+1)中的软部分子与能量损失模型(线性玻尔兹曼输运,LBT)中的硬部分子的聚结产生的。我们发现,将这些中间横动量强子与来自流体动力学膨胀流体的低横动量强子以及淬火喷注碎裂产生的高横动量强子相结合,由此产生的流体动力学-聚结-碎裂模型能够很好地描述在0到6 GeV的横动量范围内测量得到的π介子、K介子和质子的横动量谱以及微分椭圆流$v_2(p_T)$。我们进一步证明,为了重现实验观测到的中间横动量处强子$v_2$的近似组成夸克数标度,必须包含夸克聚结贡献。因此,我们的结果表明了部分子自由度的重要性,也暗示了在LHC上高多重数质子-铅离子碰撞中可能形成夸克-胶子等离子体。