论文标题
纵向扩展培养基中的喷气辐射
Jet radiation in a longitudinally expanding medium
论文作者
论文摘要
在以前的一系列论文中，我们提出了一种基于扰动QCD的新方法，用于在浓密的夸克 - 胶状等离子体中演变。在原始配方中，假定血浆是均匀且静态的。在这项工作中，我们将描述及其蒙特卡洛实施扩展到了遵守Bjorken纵向扩张的等离子体。我们的关键观察是，在静态情况下得出的真空样和中诱导的排放之间的分解仍然适用于扩展的培养基，尽管中等诱导的排放速率和横向动量扩展的速率是修改的，并且对真空样排放的相位空间变化。我们强调了一个有效的缩放关系，适用于中等诱导的排放的能量，通过该关系，扩展培养基的情况被映射到有效的静态介质上。我们发现，由于真空样排放和横向动量扩展而导致的缩放违规在数值上很小。我们对Jets $ r_ {aa} $的核修饰因子的新预测，中等片段化功能和子结构分布与我们先前对静态介质的估计非常相似，并与现有的LHC测量值保持了整体良好的定性协议。在$ r_ {aa} $的情况下，我们发现与数据的协议在包括核部分分布功能的效果之后，在大型横向动量$ p_t \ gtrsim 500 $ GEV处得到显着改善。
In a series of previous papers, we have presented a new approach, based on perturbative QCD, for the evolution of a jet in a dense quark-gluon plasma. In the original formulation, the plasma was assumed to be homogeneous and static. In this work, we extend our description and its Monte Carlo implementation to a plasma obeying Bjorken longitudinal expansion. Our key observation is that the factorisation between vacuum-like and medium-induced emissions, derived in the static case, still holds for an expanding medium, albeit with modified rates for medium-induced emissions and transverse momentum broadening, and with a modified phase-space for vacuum-like emissions. We highlight a scaling relation valid for the energy spectrum of medium-induced emissions, through which the case of an expanding medium is mapped onto an effective static medium. We find that scaling violations due to vacuum-like emissions and transverse momentum broadening are numerically small. Our new predictions for the nuclear modification factor for jets $R_{AA}$, the in-medium fragmentation functions, and substructure distributions are very similar to our previous estimates for a static medium, maintaining the overall good qualitative agreement with existing LHC measurements. In the case of $R_{AA}$, we find that the agreement with the data is significantly improved at large transverse momenta $p_T\gtrsim 500$ GeV after including the effects of the nuclear parton distribution functions.
