从RHIC到LHC能量下质子-质子碰撞中 underlying event（ underlying事件）与非广延热力学的演化
Evolution of the underlying event and non-extensive thermodynamics in pp collisions from RHIC to LHC energies
AI总结：
该研究用PYTHIA8分析RHIC到LHC能量下质子-质子碰撞，发现underlying事件主导区域可扩展至40°≲|Δφ|≲140°，明确了Tsallis参数的能量依赖特性，为相关热力学研究提供了新依据。
AI中文摘要：
我们使用PYTHIA8研究了质心系能量范围从√s=62.4 GeV到13 TeV的质子-质子碰撞中粒子产生的几何与热力学方面，分析了相对于领头粒子的带电粒子产生的方位角依赖关系，包括在相对于领头带电粒子的固定Δφ区间内，从带电粒子横动量谱中提取Tsallis-Pareto参数的研究。通过对带电粒子多重数和事件拓扑的同步分析，发现underlying event（ underlying事件）主导区域可在RHIC和LHC能量下扩展至传统横向侧区域之外。为进一步区分软、硬粒子产生机制的影响，研究在不同横向 spherocity（ spherocity， sphericity的一种变体，用于描述事件形状）和带电粒子 flattenicity（ 扁度）类别中进行。结果表明，underlying事件区域确实扩展至传统横向区域之外，验证了从RHIC到LHC能量下，40°≲|Δφ|≲140°的扩大角区间；事件形状筛选显示，喷注型事件的q值始终大于各向同性事件，Tsallis温度Ts则更低；尽管整体事件活跃度大幅提升，带电粒子多重数和横向 spherocity的Δφ分布形状在各碰撞能量下仍保持普适性，而Tsallis参数在近侧和远侧区域仍保留由领头粒子驱动的残余能量依赖关系。
英文摘要：
We investigate the geometrical and thermodynamical aspects of particle production in pp collisions over a broad center-of-mass energy, ranging from $\sqrt{s}=62.4$ GeV to 13 TeV using PYTHIA8. We study the azimuthal dependence of charged-particle production relative to the leading particle. This includes the study of the Tsallis--Pareto parameters extracted from the charged-particle transverse-momentum spectra in fixed $Δϕ$ intervals relative to the leading charged particle. The simultaneous analysis of charged-particle multiplicity and event topology demonstrates that the underlying event (UE) dominated region can be extended beyond the conventional transverse side region across RHIC and LHC energies. To further disentangle effects from soft and hard particle production mechanisms, the study is performed in different transverse spherocity and charged-particle flattenicity classes. We demonstrate that the UE region extends beyond the conventional transverse region, validating an enlarged angular interval of $40^\circ\lesssim|Δϕ|\lesssim140^\circ$ from RHIC to LHC energies. Event-shape selections reveal that jetty events consistently exhibit larger $q$ and lower $T_{\rm s}$ than isotropic events. The $Δϕ$ profiles of charged-particle multiplicity and transverse spherocity remain universal in shape across collision energies despite the strong increase in overall event activity, whereas the Tsallis parameters retain a residual, leading-particle-driven energy dependence in the near- and away-side regions.
