SPS上的双轻子和直接光子

Probing the photonic content of the proton using photon-induced dilepton production in $p+\textrm{Pb}$ collisions at the LHC

We propose a new experimental method to probe the photon parton distribution function inside the proton (photon PDF) at LHC energies. The method is based on the measurement of dilepton production from the $γp\rightarrow\ell^+\ell^-+X$ reaction in proton--lead collisions. These experimental conditions guarantee a clean environment, both in terms of reconstruction of the final state and in terms of possible background. We firstly calculate the cross sections for this process with collinear photon PDFs, where we identify optimal choice of the scale, in analogy to deep inelastic scattering kinemat…

PHENIX光子和双轻子

PHENIX photons and dileptons

电磁探针如双轻子和光子是研究碰撞早期阶段的物理状态的强有力的探针，因为它们使系统毫发无损。PHENIX实验测量了p+p，d+Au和Au+Au碰撞中的光子和双轻子。在0.2- 0.8GeV/ $c^2$的Au+Au碰撞中，双轻子产额超过预期的强子贡献，这在较低的$p_T$和最中心的区域是突出的.直接光子通过其内部转换为电子对来测量。我们看到Au+Au碰撞比p+p产率有很大的提高，其比例取决于二元碰撞的数量。根据d+Au碰撞的最新结果，这种增强不能用核效应来解释。

Photon-induced Background for Dilepton Searches and Measurements in pp Collisions at 13 TeV

The production of high invariant mass opposite sign lepton pairs in proton-proton collisions at the LHC is dominated by the Drell-Yan process. In addition to this photon or Z exchange mediated mechanism, gamma-gamma collisions, where photons radiated by the incoming protons collide, can produce lepton pairs. This is an important additional source of background for high mass resonant (like Z') or non-resonant (like contact interactions) searches. In this paper detailed calculations of the Drell-Yan and photon-induced cross sections in the typical acceptance of a multi-purpose LHC detector at ce…

光子多重性测量：从SPS到RHIC和LHC

Photon Multiplicity Measurements : From SPS to RHIC and LHC

讨论了在CERN SPS上使用细粒度预散射光子多重性探测器（PMD）测量光子多重性的结果。这些研究包括光子的伪快度分布、光子多重性与参与核子数的比例关系、光子平均横动量的中心依赖性、光子多重性的逐事件波动和局部带电中性波动。文中还讨论了用于RHIC STAR实验和LHC ALICE实验的PMD的基本特性。

Constraints on the kinetic mixing parameter $ε^2$ for the light dark photons from dilepton production in heavy-ion collisions in the few-GeV energy range

The vector $U$-bosons, or so called 'dark photons', are one of the possible candidates for the dark matter mediators. They are supposed to interact with the standard matter via a 'vector portal' due to the $U(1)-U(1)^\prime$ symmetry group mixing which might make them visible in particle and heavy-ion experiments. While there is no confirmed observation of dark photons, the detailed analysis of different experimental data allows to estimate the upper limit for the kinetic mixing parameter $ε^2$ depending on the mass $M_U$ of $U$-bosons which is also unknown. In this study we present theoretica…

通过双轻子产生照亮光子维格纳分布

Lighting up the Photon Wigner Distribution via Dilepton Productions

本研究系统探究重离子碰撞中光子-光子聚变产生轻子对的过程，提出基于重核光子维格纳分布的统一公式，能全面描述RHIC至LHC的相关数据，揭示准实光子的相干与非相干辐射机制，并预测动量关联各向异性以约束光子维格纳分布。

从 dilepton 光谱对暗光子的动能混合进行限制

Constraints on Kinetic Mixing of Dark Photons from Dilepton Spectra

通过分析重离子碰撞中的 dilepton 光谱，研究暗光子的动能混合参数限制及其实验精度要求。