Exclusive dimuon production in ultraperipheral Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with ATLAS

Abstract

Exclusive dimuon production in ultraperipheral collisions (UPC), resulting from photon-photon interactions in the strong electromagnetic fields of colliding high-energy lead nuclei, $\mathrm{PbPb}(\gamma \gamma )\to {\mu }^{+}{\mu }^{-}({\mathrm{Pb}}^{(\star )}{\mathrm{Pb}}^{(\star )})$, 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 $p_{\mathrm{T}\mu }>4$ GeV, $|{\eta }_{\mu }|<2.4$, invariant mass $m_{\mu \mu }>10$ GeV, and $p_{\mathrm{T},\mu \mu }<2$ 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 $m_{\mu \mu }$, absolute pair rapidity ($|y_{\mu \mu }|$), scattering angle in the dimuon rest frame ($|\cos {\vartheta }_{\mu \mu }^{\star }|$) and the colliding photon energies. The total cross section of the UPC $\gamma \gamma \to {\mu }^{+}{\mu }^{-}$ process in the fiducial volume is measured to be ${\sigma }_{\mathrm{fid}}^{\mu \mu }=34.1\pm 0.3(stat.)\pm 0.7(syst.)$ $\mu \mathrm{b}$. 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 $|y_{\mu \mu }|$ 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.

50 pages in total, author list starting page 34, 12 figures, published by Phys. Rev. C. All figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2016-02/

References in corpus (18)

• PYTHIA 6.4 Physics and Manual
• An Introduction to PYTHIA 8.2
• Glauber Modeling in High Energy Nuclear Collisions
• The Physics of Ultraperipheral Collisions at the LHC
• Luminosity determination in pp collisions at $\sqrt{s}$ = 8 TeV using the ATLAS detector at the LHC
• Observation of exclusive charmonium production and gamma+gamma to mu+mu- in p+pbar collisions at sqrt{s} = 1.96 TeV
• Measurement of $e^{+}{e}^{-}$ Momentum and Angular Distributions from Linearly Polarized Photon Collisions
• Exclusive J/$\psi$ photoproduction off protons in ultra-peripheral p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV
• Photonuclear and Two-photon Interactions at High-Energy Nuclear Colliders
• Measurement of light-by-light scattering and search for axion-like particles with 2.2 nb${}^{-1}$ of Pb+Pb data with the ATLAS detector
• Lepton Pair Production Through Two Photon Process in Heavy Ion Collisions
• Measurement of the exclusive $\gamma \gamma \to {\mu }^{+}{\mu }^{-}$ process in proton--proton collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Exclusive muon-pair productions in ultrarelativistic heavy-ion collisions: Realistic nucleus charge form factor and differential distributions
• Observation of forward neutron multiplicity dependence of dimuon acoplanarity in ultraperipheral Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV
• Exclusive dilepton production in ultraperipheral $PbPb$ collisions at the LHC
• $Z$ boson production in Pb+Pb collisions at $\sqrt{s_{\text{NN}}}$= 5.02 TeV measured by the ATLAS experiment
• Acoplanarity of QED pairs accompanied by nuclear dissociation in ultra-peripheral heavy ion collisions
• Two-Photon Interactions with Nuclear Breakup in Relativistic Heavy Ion Collisions

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