Search for $\mathrm{GeV}$-scale axion-like particles in PbPb collisions

Abstract

A search is performed for the production of axion-like particles with masses in the range 3-10 GeV using PbPb collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of $0.228{\mathrm{nb}}^{-1}$ and a nucleon-nucleon centre-of-mass energy of $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV. This is the first search for axion-like particles produced exclusively by two photons ($\gamma \gamma \to a\to \gamma \gamma$) in the forward direction. It extends sensitivity to previously unexplored regions of the parameter space, probing axion-like particle masses and couplings down to 3.0 GeV and $3.2\times 10^{-4}{\mathrm{GeV}}^{-1}$, respectively. This result provides the most stringent limits to date on the production of axion-like particles from exclusive photon-photon fusion processes with masses between 3 and 5 GeV.

arXiv commentAll figures and tables, along with any supplementary material and additional information, are available at https://lhcb-glance.cern.ch/alcm/public/analysis/full-details/6090 (LHCb public pages)