Cabouat Baptiste, Sjöstrand Torbjörn
1Theoretical Particle Physics, Department of Astronomy and Theoretical Physics, Lund University, 223 62, Lund, Sweden.
2School of Physics and Astronomy, University of Manchester, Schuster Building, Oxford Road, Manchester, M13 9PL UK.
Eur Phys J C Part Fields. 2018;78(3):226. doi: 10.1140/epjc/s10052-018-5645-z. Epub 2018 Mar 16.
Parton showers have become a standard component in the description of high-energy collisions. Nowadays most final-state ones are of the dipole character, wherein a pair of partons branches into three, with energy and momentum preserved inside this subsystem. For initial-state showers a dipole picture is also possible and commonly used, but the older global-recoil strategy remains a valid alternative, wherein larger groups of partons share the energy-momentum preservation task. In this article we introduce and implement a dipole picture also for initial-state radiation in Pythia, and compare with the existing global-recoil one, and with data. For the case of Deeply Inelastic Scattering we can directly compare with matrix element expressions and show that the dipole picture gives a very good description over the whole phase space, at least for the first branching.
部分子簇射已成为高能碰撞描述中的标准组成部分。如今，大多数末态部分子簇射具有偶极子特征，即一对部分子分支为三个，在该子系统内能量和动量守恒。对于初态簇射，偶极子图像也是可行且常用的，但较老的全局反冲策略仍是一种有效的替代方法，其中更大的部分子群分担能量 - 动量守恒任务。在本文中，我们还在Pythia中为初态辐射引入并实现了偶极子图像，并与现有的全局反冲方法以及数据进行比较。对于深度非弹性散射的情况，我们可以直接与矩阵元表达式进行比较，并表明偶极子图像在整个相空间中都给出了非常好的描述，至少对于第一次分支是这样。
