Evidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV

Bakhshiansohi, Hamed;Bondu, Olivier;Brochet, Sébastien;Bruno, Giacomo;CMS Collaboration;et.al.
(2019) Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics — Vol. B797, p. 134826 (2019)

Files

181004602.pdf
  • Open Access
  • Adobe PDF
  • 1.08 MB
Download

Details

Authors
  • Bakhshiansohi, HamedUCLouvain
    Author
  • Bondu, OlivierUCLouvain
    Author
  • Brochet, SébastienUCLouvain
    Author
  • Bruno, GiacomoUCLouvain
    Author
  • Caputo, ClaudioUCLouvain
    Author
  • David, PieterUCLouvain
    Author
  • Delaere, Christopheorcid-logoUCLouvain
    Author
  • Delcourt, MartinUCLouvain
    Author
  • François, BrieucUCLouvain
    Author
  • Giammanco, Andreaorcid-logoUCLouvain
    Author
  • Krintiras, GeorgiosUCLouvain
    Author
  • Lemaitre, VincentUCLouvain
    Author
  • Magitteri, AlessioUCLouvain
    Author
  • Mertens, AlexandreUCLouvain
    Author
  • Musich, MarcoUCLouvain
    Author
  • Piotrzkowski, KrzysztofUCLouvain
    Author
  • Saggio, AlessiaUCLouvain
    Author
  • Vidal Marono, MiguelUCLouvain
    Author
  • Wertz, SébastienUCLouvain
    Author
  • Zobec, JozeUCLouvain
    Author
  • CMS Collaboration
    Author
  • et. al.
Show more
Abstract
Evidence for the light-by-light scattering process, $\gamma\gamma$ $\to$ $\gamma\gamma$, in ultraperipheral PbPb collisions at a centre-of-mass energy per nucleon pair of 5.02 TeV is reported. The analysis is conducted using a data sample corresponding to an integrated luminosity of 390 $\mu$b$^{-1}$ marc:recorded by the CMS experiment at the LHC. Light-by-light scattering processes are selected in events with two photons exclusively produced, each with transverse energy E$_\mathrm{T}^{\gamma}$ $>$ 2 GeV, pseudorapidity $|\eta^{\gamma}|$ $\lt$ 2.4, diphoton invariant mass $m^{\gamma\gamma}$ $\gt$ 5 GeV, diphoton transverse momentum $p_\mathrm{T}^{\gamma\gamma}$ $\lt$ 1 GeV, and diphoton acoplanarity below 0.01. After all selection criteria are applied, 14 events are observed, compared to expectations of 9.0 $\pm$ 0.9 (theo) events for the signal and 4.0 $\pm$ 1.2 (stat) for the background processes. The excess observed in data relative to the background-only expectation corresponds to a significance of 3.7 standard deviations, and has properties consistent with those expected for the light-by-light scattering signal. The measured fiducial light-by-light scattering cross section, $\sigma_\mathrm{fid} (\gamma\gamma$ $\to$ $\gamma\gamma) =$ 120 $\pm$ 46 (stat) $\pm$ 28 (syst) $\pm$ 12 (theo) nb, is consistent with the standard model prediction. The $m^{\gamma\gamma}$ distribution is used to set new exclusion limits on the production of pseudoscalar axion-like particles, via the $\gamma\gamma$ $\to$ a $\to$ $\gamma\gamma$ process, in the mass range $m_{\mathrm{a}} =$ 5-90 GeV.
Affiliations

Citations

  • APA
  • Chicago
  • FWB

Bakhshiansohi, H., Bondu, O., Brochet, S., Bruno, G., Caputo, C., David, P., Delaere, C., Delcourt, M., François, B., Giammanco, A., Krintiras, G., Lemaitre, V., Magitteri, A., Mertens, A., Musich, M., Piotrzkowski, K., Saggio, A., Vidal Marono, M., Wertz, S., et al. (2019). Evidence for light-by-light scattering and searches for axion-like particles in ultraperipheral PbPb collisions at $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV. Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics, B797, 134826. https://doi.org/10.1016/j.physletb.2019.134826 (Original work published 2019)