Manohar Aneesh, Nason Paolo, Salam Gavin P, Zanderighi Giulia
Department of Physics, University of California at San Diego, La Jolla, California 92093, USA.
CERN, Theoretical Physics Department, CH-1211 Geneva 23, Switzerland.
Phys Rev Lett. 2016 Dec 9;117(24):242002. doi: 10.1103/PhysRevLett.117.242002.
It has become apparent in recent years that it is important, notably for a range of physics studies at the Large Hadron Collider, to have accurate knowledge on the distribution of photons in the proton. We show how the photon parton distribution function (PDF) can be determined in a model-independent manner, using electron-proton (ep) scattering data, in effect viewing the ep→e+X process as an electron scattering off the photon field of the proton. To this end, we consider an imaginary, beyond the Standard Model process with a flavor changing photon-lepton vertex. We write its cross section in two ways: one in terms of proton structure functions, the other in terms of a photon distribution. Requiring their equivalence yields the photon distribution as an integral over proton structure functions. As a result of the good precision of ep data, we constrain the photon PDF at the level of 1%-2% over a wide range of momentum fractions.
近年来已经变得很明显的是，对于大型强子对撞机上的一系列物理研究而言，准确了解质子中光子的分布非常重要。我们展示了如何使用电子 - 质子（ep）散射数据以一种与模型无关的方式确定光子部分子分布函数（PDF），实际上是将ep→e + X过程视为电子从质子的光子场散射。为此，我们考虑一个超出标准模型的虚构过程，该过程具有味改变的光子 - 轻子顶点。我们用两种方式写出它的截面：一种用质子结构函数表示，另一种用光子分布表示。要求它们相等就得到了作为质子结构函数积分的光子分布。由于ep数据的高精度，我们在很宽的动量分数范围内将光子PDF限制在1% - 2%的水平。
