We re-examine the current state of the art for the calculation of photon- initiated processes at the LHC, as formulated in terms of a photon PDF in the proton that may be determined rather precisely from the known proton structure functions. We in particular demonstrate that a by construction more precise calculation is provided by a direct application of the structure function approach, best known from the case of Higgs Boson production via vector boson fusion. This avoids any artificial scale variation uncertainties, which can otherwise be rather significant for processes calculated within the standard approach thus far. To understand the source of these, we present a detailed comparison of the structure function approach and its relation to the photon PDF. We then provide precise predictions for the photon-initiated contribution to lepton pair production at the LHC, including the lepton pair transverse momentum distribution. Thus, by a direct application of the structure function formalism we show how the contribution from initial-state photons at the LHC may for the first time be included with high precision in a universal and straightforward way, providing a high definition picture of the photon content of the proton.

中文翻译：

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高清质子：重温高能碰撞中光子引发的产生

我们重新审视了 LHC 光子引发过程计算的当前技术水平，如根据质子中的光子 PDF 制定的，该 PDF 可以从已知的质子结构函数中相当精确地确定。我们特别证明了结构函数方法的直接应用提供了更精确的计算，这在通过矢量玻色子融合产生希格斯玻色子的情况下最为人所知。这避免了任何人为的尺度变化不确定性，否则这对于迄今为止在标准方法内计算的过程来说可能相当重要。为了理解这些来源，我们详细比较了结构函数方法及其与光子 PDF 的关系。然后，我们对光子引发对 LHC 轻子对产生的贡献提供精确预测，包括轻子对横向动量分布。因此，通过直接应用结构函数形式，我们展示了如何首次以通用和直接的方式高精度地包含 LHC 中初始状态光子的贡献，提供光子内容的高清图片的质子。