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-x 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–, 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.
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机译：我们考虑了W规格玻色子在轻子衰变模式下的强生。从前导表达式开始，我们表明，通过定义合适的比例变量，LHC能量处的截面的质心相关性基本上可以通过简单的幂定律来描述。比例指数直接与parton分布函数（PDF）的small-x行为相关联，该函数在参与W生产的高度虚拟化条件下很大程度上由QCD演化方程决定。这为轻子电荷不对称带来了特别简单的缩放定律，并且还预测了在不同碰撞系统中的测量结果（p–p，p– <数学xmlns：mml =“ http://www.w3.org/1998/Math/MathML “ id =” M4“ overflow =” scroll“> <移动器> p ¯ ，p–Pb Pb– Pb）直接相关。将期望与现有数据进行比较，并观察到非常好的总体一致性。结果表明，通过将比例取为比例变量的固定值而不是固定的速度，可以显着降低附近质心能量之间的特定横截面比率的PDF不确定性。
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