Résumé : The first measurement of the dependence of γγ→μ+μ- production on the multiplicity of neutrons emitted very close to the beam direction in ultraperipheral heavy ion collisions is reported. Data for lead-lead interactions at sNN=5.02 TeV, with an integrated luminosity of approximately 1.5 nb-1, are collected using the CMS detector at the LHC. The azimuthal correlations between the two muons in the invariant mass region 8