Elastic and proton dissociative J/ψ photoproduction at low Wγp with the H1 detector at HERA

Elastic and proton dissociative photoproduction of J/ψ mesons is measured with the H1 detector at the HERA electron proton collider in the photon virtuality phase space of Q2<or similar 2.5 GeV2. Two data sets are analysed, one measured with a nominal proton beam energy of 920 GeV, corresponding to an ep centre of mass energy of 318 GeV and one recorded with a reduced beam energy of 460 GeV, corresponding to an ep centre of mass energy of 225 GeV. The combination of the two data sets allow to perform the J/ψ measurement with central tracks in an extended kinematic phase space in a photon proton centre of mass energy range of 20 GeV<Wγp<110 GeV. The integrated luminosity for both data sets are 130 pb-1 and 10.8 pb-1, respectively, corresponding to more than two times the statistics used in previous H1 analyses. Due to an online selection purely based on tracks both leptonic decay channels J/ψ→ee and J/ψ→μμ are available for the analysis. Elastic (γp→ J/ψp) and proton dissociative (γp→ J/ψY) differential γp cross sections are determined in a simultaneous measurement as function of the squared momentum transfer at the proton vertex t and as function of Wγp by means of an unfolding procedure, taking not only all bin correlations into account, but also the correlation between the elastic and proton dissociative process. The obtained elastic and proton dissociative differential cross sections are analysed in a simultaneous fit, taking the full statistical covariance matrices and systematic uncertainty sources into account.