Abstrakt
Exclusive production of dielectron pairs,
! e+e-, is studied using Lint = 1.72 nb-1 of data from ultraperipheral collisions of lead nuclei at p sNN = 5.02TeV recorded by the ATLAS detector at the LHC. The process of interest proceeds via photon-photon interactions in the strong electromagnetic fields of relativistic lead nuclei. Dielectron production is measured in the fiducial region defined by following requirements: electron transverse momentum pe
T > 2.5 GeV, absolute electron pseudorapidity |e| < 2.5, dielectron invariant mass mee > 5 GeV, and dielectron transverse momentum pee
T < 2 GeV. Differential cross-sections are measured as a function of mee, average pe
T, absolute dielectron rapidity
|yee|, and scattering angle in the dielectron rest frame, | cos |, in the inclusive sample, and also with a requirement of no activity in the forward direction. The total integrated fiducial cross-section is measured to be 215 +- 1(stat.) +23
-20(syst.) +- 4(lumi.) μb. Within experimental uncertainties the measured integrated cross-section is in good agreement with the QED predictions from the Monte Carlo programs Starlight and SuperChic, confirming the broad features of the initial photon fluxes. The differential cross-sections show systematic differences from these predictions which are more pronounced at high |yee| and
| cos | values.