Exclusive dimuon production in ultraperipheral collisions (UPC), resulting from photon-photon interactions in the strong electromagnetic fields of colliding high-energy lead nuclei, $\mathrm{PbPb}(γγ) \rightarrow μ^+μ^- (\mathrm{Pb}^{(\star)}\mathrm{Pb}^{(\star)} )$, is studied using $\mathcal{L}_{\mathrm{int}} = 0.48$ nb$^{-1}$ of $\sqrt{s_\mathrm{NN}}=5.02$ TeV lead-lead collision data at the LHC with the ATLAS detector. Dimuon pairs are measured in the fiducial region $p_{\mathrm{T}μ} > 4$ GeV, $|η_μ| < 2.4$, invariant mass $m_{μμ} > 10$ GeV, and $p_{\mathrm{T,μμ}} < 2$ GeV. The primary background from single-dissociative processes is extracted from the data using a template fitting technique. Differential cross sections are presented as a function of $m_{μμ}$, absolute pair rapidity ($|y_{μμ}|$), scattering angle in the dimuon rest frame ($|\cos \vartheta^{\star}_{μμ}|$) and the colliding photon energies. The total cross section of the UPC $γγ\rightarrow μ^{+}μ^{-}$ process in the fiducial volume is measured to be $σ_{\mathrm{fid}}^{μμ} = 34.1 \! \pm \! 0.3 \mathrm{(stat.)} \! \pm \! 0.7 \mathrm{(syst.)}$ $μ\mathrm{b}$. Generally good agreement is found with calculations from STARlight, which incorporate the leading-order Breit-Wheeler process with no final-state effects, albeit differences between the measurements and theoretical expectations are observed. In particular, the measured cross sections at larger $|y_{μμ}|$ are found to be about 10-20% larger in data than in the calculations, suggesting the presence of larger fluxes of photons in the initial state. Modification of the dimuon cross sections in the presence of forward and/or backward neutron production is also studied and is found to be associated with a harder incoming photon spectrum, consistent with expectations.
Measurement of muon pairs produced via $γγ$ scattering in non-ultraperipheral Pb+Pb collisions at $\sqrt{s_{_\mathrm{NN}}} = 5.02$ TeV with the ATLAS detector
gamma-UPC: Automated generation of exclusive photon-photon processes in ultraperipheral proton and nuclear collisions with varying form factors
在MadGraph5_aMC@NLO和HelacOnia Monte Carlo代码中实现了在质子和/或核的超外围高能碰撞中通过光子聚变产生的任意排他性最终状态的自动生成。在等效光子近似下，利用由电偶极子和电荷形状因子导出的$γ$通量，并结合强子的存活几率，计算了散射截面。多个例子的$γγ$截面计算与此设置，命名为γ-UPC，质子-质子，质子-核，核-核超周边碰撞（UPC）在大型强子对撞机和未来的圆形对撞机。给出了自旋为0，2的共振态（夸克偶素、重子和希格斯玻色子，以及轴子和引力子）和粒子对（$J/ψJ/ψ$、WW、ZZ、Z、$γ$、$t\bar{t}$、HH）的全部光子聚变截面。微分截面独家双轻子和光的光散射进行比较，大型强子对撞机的数据。这一发展为即将到来的任何UPC最终状态的自动事件生成铺平了道路，并具有次领先阶精度和更高的电弱校正。
Exclusive dimuon production and coherent charmonium photoproduction at forward rapidity in ultra-peripheral Pb$-$Pb collisions at $\mathbf{\sqrt{s_{\rm NN}}=5.36}$ TeV
European Organization for Nuclear Research（欧洲核子研究中心）
Measurement of coherent exclusive $J/ψ\toμ^+μ^-$ production in ultraperipheral Pb+Pb collisions at $\sqrt{s_{\textrm{NN}}}=5.36$ TeV with the ATLAS detector
EUROPEAN ORGANISATION FOR NUCLEAR RESEARCH (CERN)（欧洲核子研究中心）
Evidence of Spin-Interference Effects in Exclusive $J/ψ\to e^+e^-$ Photoproduction in Ultraperipheral Heavy-Ion Collisions
Texas A&M University（德克萨斯农工大学）；Czech Technical University in Prague（布拉格捷克理工大学）；AGH University of Krakow（克拉科夫AGH科技大学）；Panjab University（潘杰布大学）；Variable Energy Cyclotron Centre（变能回旋加速器中心）；Kent State University（肯特州立大学）；Brookhaven National Laboratory（布鲁克海文国家实验室）；Fudan University（复旦大学）；Abilene Christian University（阿比林基督教大学）；Instituto de Alta Investigación, Universidad de Tarapacá（塔拉帕卡大学高等研究所）；Shandong University（山东大学）；Indian Institute of Science Education and Research (IISER)（印度科学教育与研究机构）；University of California, Riverside（加州大学河滨分校）；Indian Institute of Science Education and Research (IISER) Tirupati（提鲁帕蒂印度科学教育与研究机构）；University of Houston（休斯顿大学）；University of Jammu（詹穆大学）；State University of New York, Stony Brook（纽约州立大学石溪分校）
Nuclear effects in photoproduction of heavy quarks and vector mesons in ultraperipheral PbPb and pPb collisions at the LHC
通过比较$c\bar{c}$和b-b（bar）在PbPb和pPb碰撞中的光生截面，可以得到对核遮蔽效应的敏感性.光生矢量介子对底层胶子的分布更为敏感。本文研究了在sqrt（s_NN）=5 TeV和sqrt（s_NN）=2.76 $ TeV, respectively. The potentials of using these processes for constraining nuclear gluon shadowing are explored. It is found that photoproduction of $ J/J条件下，在大型强子对撞机上进行的超周边pPb和PbPb碰撞中，重夸克光生和矢量介子光生的截面及其与快度的关系。特别是PbPb碰撞中的$ and $对胶子遮蔽表现出很好的敏感性。
Measurement of light-by-light scattering and the Breit-Wheeler process, and search for axion-like particles in ultraperipheral PbPb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV
