Arleo François, Chapon Émilien, Paukkunen Hannu
Laboratoire Leprince-Ringuet, École polytechnique, CNRS/IN2P3, Université Paris-Saclay, 91128 Palaiseau, France.
Department of Physics, University of Jyvaskyla, P.O. Box 35, 40014 University of Jyvaskyla, Finland.
Eur Phys J C Part Fields. 2016;76(4):214. doi: 10.1140/epjc/s10052-016-4049-1. Epub 2016 Apr 18.
We consider the hadroproduction of W gauge bosons in their leptonic decay mode. Starting from the leading-order expressions, we show that by defining a suitable scaling variable the centre-of-mass dependence of the cross sections at the LHC energies can be essentially described by a simple power law. The scaling exponent is directly linked to the small- behaviour of parton distribution functions (PDF) which, at the high virtualities involved in W production, is largely dictated by QCD evolution equations. This entails a particularly simple scaling law for the lepton charge asymmetry and also predicts that measurements in different collision systems (p-p, p-[Formula: see text], p-Pb Pb-Pb) are straightforwardly related. The expectations are compared with the existing data and a very good overall agreement is observed. It is shown that the PDF uncertainty in certain cross-section ratios between nearby centre-of-mass energies can be significantly reduced by taking the ratios at fixed value of the scaling variable instead of fixed rapidity.
我们考虑W规范玻色子在轻子衰变模式下的强子产生过程。从领头阶表达式出发，我们表明通过定义一个合适的标度变量，大型强子对撞机（LHC）能量下截面的质心依赖性基本上可以用一个简单的幂律来描述。标度指数直接与部分子分布函数（PDF）的小x行为相关，在W产生所涉及的高虚能情况下，这种行为在很大程度上由量子色动力学（QCD）演化方程决定。这导致了轻子电荷不对称性的一个特别简单的标度律，并且还预测了在不同碰撞系统（质子 - 质子、质子 - 反质子、质子 - 铅离子、铅离子 - 铅离子）中的测量结果是直接相关的。我们将这些预期与现有数据进行了比较，观察到了非常好的总体一致性。结果表明，通过在固定标度变量值而非固定快度下取比值，可以显著降低相邻质心能量之间某些截面比中的PDF不确定性。
