arXiv 1809.017442018-09hep-exhep-phnucl-ex

用LHC能量下的事件观测量探测色重联

Probing color reconnection with underlying event observables at the LHC energies

Antonio Ortiz, Lizardo Valencia Palomo

备注：: Accepted for publication in Physical Review D
发表信息：: Phys. Rev. D 99, 034027 (2019)
DOI：: 10.1103/PhysRevD.99.034027

摘要：

在这项工作中，我们研究了潜在的事件（UE）的活动作为最高的喷流横向动量（$p_{\rm T}^{\rm jet}$）的数量和合计$p_{\rm T}^{\rm jet}$密度的方位角区域横向的$p_{\rm T}^{\rm jet}$方向的函数。归一化到INEL多重性的UE观测值服从近似的Koba-Nielsen-Olesen（KNO）标度。基于PYTHIA~8.2在LHC能量下对$pp$碰撞的模拟，我们表明KNO标度的剩余缺陷是由于在较高的$\sqrt{s}$下多个部分子相互作用（MPI）的重要性日益增加。受此启发，我们研究了在$\sqrt{s}=7$ \，TeV的$pp$碰撞中考虑不同$p_{\rm T}$间隔内的带电粒子的UE活动。我们证明，饱和的数量和总和$p_{\rm T}$密度，这是通常声称，只观察到低\pt带电粒子（$0.5<p_{\rm T}<2$ \，GeV/ $c$）。此外，对于$p_{\rm T}$整合的情况（$p_{\rm T}>0.5$ \，GeV/ $c$），合计的$p_{\rm T}$密度对颜色重连（CR）的变化不敏感，然而在低p_{\rm T}时，其随着CR的增加而降低，而在中等$p_{\rm T}$（$2<p_{\rm T}<10$ \，GeV/ $c$）时发现相反的行为.最后，我们表明，CR产生流样的行为，只有在UE区域和效果减少增加$p_{\rm T}^{\rm jet}$由于hardering UE。这些结果鼓励测量与UE相关的包容性和确定的带电粒子$p_{\rm T}$光谱（在广泛的$p_{\rm T}$范围内），旨在更好地理解$pp$和LHC发现的重离子数据之间的相似性。

英文摘要：

In this work we study the underlying event (UE) activity as a function of the highest jet transverse momentum ($p_{\rm T}^{\rm jet}$) in terms of the number and summed $p_{\rm T}$ densities of charged particles in the azimuthal region transverse to the $p_{\rm T}^{\rm jet}$ direction. The UE observables normalised to the INEL multiplicity obey an approximate Koba-Nielsen-Olesen (KNO) scaling. Based on PYTHIA~8.2 simulations of $pp$ collisions at LHC energies, we show that the remaining imperfection of the KNO scaling is due to the increasing importance of multiple partonic interactions (MPI) at higher $\sqrt{s}$. Motivated by this, we studied the UE activity considering charged particles within different $p_{\rm T}$ intervals in $pp$ collisions at $\sqrt{s}=7$\,TeV. We demonstrate that the saturations of both number and summed $p_{\rm T}$ densities, which are commonly claimed, are only observed for low-\pt charged particles ($0.5<p_{\rm T}<2$\,GeV/$c$). Moreover, for the $p_{\rm T}$-integrated case ($p_{\rm T}>0.5$\,GeV/$c$) the summed $p_{\rm T}$ density is not sensitive to the variation of color reconnection (CR), however at low-p_{\rm T} it is reduced with increasing CR, whereas an opposite behaviour is found at intermediate-$p_{\rm T}$ ($2<p_{\rm T}<10$\,GeV/$c$). Finally, we show that CR produces flow-like behaviour only in the UE region and the effects are reduced with increasing $p_{\rm T}^{\rm jet}$ due to the hardering of UE. The outcomes encourage the measurement of inclusive and identified charged particle $p_{\rm T}$ spectra (over a wide range of $p_{\rm T}$) associated to UE aimed at better understanding the similarities between $pp$ and heavy-ion data discovered at the LHC.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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