Automated parton-shower variations in pythia 8
Automated parton-shower variations in pythia 8
复制标题
Pythia 8 中的自动parton-shower变化
DOI：
10.1103/physrevd.94.074005
复制
发表时间：
2016
影响因子：
5
通讯作者：
Australia.
中科院分区：
文献类型：
--
作者：
S. Mrenna;P. Division;Fermilab;Batavia;IL Usa Department of Physics;Astronomy;M. University;Victoria;Australia.
在LHC精密物理测量的时代，对理论不确定性的有效和详尽的估计发挥着越来越重要的作用。在蒙特卡罗（MC）事件发生器的背景下，这种不确定性的估计传统上需要独立的MC运行每个变化，线性增加的总运行时间。在这项工作中，我们报告了一个占主导地位的（重正化尺度和非奇异）扰动的不确定性的自动评估的Pythia 8事件发生器，只有一个适度的计算开销。每个生成的事件都伴随着一个替代权重向量（每个不确定性变化一个），每个集合分别保留总截面。可以包括显式尺度补偿项，反映高阶分裂项的已知系数并减少变化的影响。这种形式主义也允许增强罕见的部分子分裂，例如$g\ensuremath{\rightarrow}B\overline{B}$和$q\ensuremath{\rightarrow}q\ensuremath{\gamma}$，以获得富含这些分裂的加权样本，同时保留正确的物理Sudakov因子。
In the era of precision physics measurements at the LHC, efficient and exhaustive estimations of theoretical uncertainties play an increasingly crucial role. In the context of Monte Carlo (MC) event generators, the estimation of such uncertainties traditionally requires independent MC runs for each variation, for a linear increase in total run time. In this work, we report on an automated evaluation of the dominant (renormalization-scale and nonsingular) perturbative uncertainties in the pythia 8 event generator, with only a modest computational overhead. Each generated event is accompanied by a vector of alternative weights (one for each uncertainty variation), with each set separately preserving the total cross section. Explicit scale-compensating terms can be included, reflecting known coefficients of higher-order splitting terms and reducing the effect of the variations. The formalism also allows for the enhancement of rare partonic splittings, such as $g\ensuremath{\rightarrow}b\overline{b}$ and $q\ensuremath{\rightarrow}q\ensuremath{\gamma}$, to obtain weighted samples enriched in these splittings while preserving the correct physical Sudakov factors.