Exclusive four pion photoproduction in ultraperipheral Pb-Pb collisions at s ₍₍ = 5. 02 TeV

The intense photon fluxes from relativistic nuclei provide an opportunity to study photonuclear interactions in ultraperipheral collisions. The measurement of coherently photoproduced ^+^-^+^- final states in ultraperipheral Pb-Pb collisions at s₍₍=5. 02 TeV is presented for the first time. The cross section, d/dy, times the branching ratio (^+ ^+ ^- ^-) is found to be 47. 82. 3~ (stat. ) 7. 7~ (syst. ) mb in the rapidity interval |y| < 0. 5. The invariant mass distribution is not well described with a single Breit-Wigner resonance. The production of two interfering resonances, (1450) and (1700), provides a good description of the data. The values of the masses (m) and widths () of the resonances extracted from the fit are m₁=138514~ (stat. ) 3~ (syst. ) MeV/c², ₁=43136~ (stat. ) 82~ (syst. ) MeV/c², m₂=166313~ (stat. ) 22~ (syst. ) MeV/c² and ₂=357 31~ (stat. ) 49~ (syst. ) MeV/c², respectively. The measured cross sections times the branching ratios are compared to recent theoretical predictions.