论文标题
在LHC处搜索质子 - 普罗顿碰撞中的流体动力液的小液滴
Searching for small droplets of hydrodynamic fluid in proton--proton collisions at the LHC
论文作者
论文摘要
在本文中,我们使用Iebe-vishnu混合模型具有三种不同初始条件的IEBE-VISHNU混合模型,研究了Proton-Proton碰撞的高多物质事件中的流体动力集体性,即$ \ sqrt {s} = $ 13 TEV。使用正确调整的参数,每个初始模型的流体动力模拟都可以合理地描述测得的两粒子相关性,包括所有带电和识别的Hadron的集成和$ p _ {\ rm t} $ - 差分流。但是,流体动力模拟未能描述四粒子累积$ C_2^V \ {4 \} $的负值,如实验中所测量的。进一步的调查表明,椭圆流$ v_2 $与初始偏心$ \ varepsilon_2 $之间的非线性响应在小型P-P系统中变得很重要。这导致了与线性偏心缩放的巨大偏差,并产生了其他流动波动,即使从初始状态产生了$ C_2^V \ {4 \} $的正$ C_2^v \ {4 \} $,即使来自初始状态的负$ C_2^\ VAREPSILON \ {4 \} $。 We also presented the first hydrodynamic calculations of multi-particle mixed harmonic azimuthal correlations in p-p collisions, such as normalized asymmetric cumulant $nac_n\{3\}$, normalized Symmetric-Cumulant, $nsc_{2,3}\{4\}$ and $nsc_{2,4}\{4\}$.尽管许多定性特征是通过选定参数的流体动力模拟复制的,但测得的负$ nsc_ {2,3} \ {4 \} $无法再现。 The failure of the description of negative $c_2\{4\}$ and $nsc_{2,3}\{4\}$ triggers the question on whether hydrodynamics with a fundamentally new initial state model could solve this puzzle, or hydrodynamics itself might not be the appreciated mechanism of the observed collectivity in p-p collisions at the LHC.
In this paper, we investigate the hydrodynamic collectivity in high-multiplicity events of proton-proton collisions at $\sqrt{s}=$ 13 TeV, using iEBE-VISHNU hybrid model with three different initial conditions, namely, HIJING, super-MC and TRENTo. With properly tuned parameters, hydrodynamic simulations with each initial model give reasonable descriptions of the measured two-particle correlations, including the integrated and $p_{\rm T}$-differential flow for all charged and identified hadrons. However, the hydrodynamic simulations fail to describe the negative value of the four-particle cumulant $c_2^v\{4\}$ as measured in experiments. Further investigations show that the non-linear response between the elliptic flow $v_2$ and the initial eccentricity $\varepsilon_2$ becomes significant in the small p-p systems. This leads to a large deviation from linear eccentricity scaling and generates additional flow fluctuations, which results in a positive $c_2^v\{4\}$ even with a negative $c_2^\varepsilon\{4\}$ from the initial state. We also presented the first hydrodynamic calculations of multi-particle mixed harmonic azimuthal correlations in p-p collisions, such as normalized asymmetric cumulant $nac_n\{3\}$, normalized Symmetric-Cumulant, $nsc_{2,3}\{4\}$ and $nsc_{2,4}\{4\}$. Although many qualitative features are reproduced by the hydrodynamic simulations with chosen parameters, the measured negative $nsc_{2,3}\{4\}$ cannot be reproduced. The failure of the description of negative $c_2\{4\}$ and $nsc_{2,3}\{4\}$ triggers the question on whether hydrodynamics with a fundamentally new initial state model could solve this puzzle, or hydrodynamics itself might not be the appreciated mechanism of the observed collectivity in p-p collisions at the LHC.