Paper detail

Measurement of differential $J/ψ$ production cross-sections and forward-backward ratio in p+Pb collisions with the ATLAS detector

Measurements of differential cross-sections for $J/ψ$ production in p+Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV at the LHC with the ATLAS detector are presented. The data set used corresponds to an integrated luminosity of 28.1 nb$^{-1}$. The $J/ψ$ mesons are reconstructed in the dimuon decay channel over the transverse momentum range $8<p_{\mathrm{T}}<30$ GeV and over the center-of-mass rapidity range $-2.87<y^{*}<1.94$. Prompt $J/ψ$ are separated from $J/ψ$ resulting from $b$-hadron decays through an analysis of the distance between the $J/ψ$ decay vertex and the event primary vertex. The differential cross-section for production of nonprompt $J/ψ$ is compared to a FONLL calculation that does not include nuclear effects. Forward-backward production ratios are presented and compared to theoretical predictions. These results constrain the kinematic dependence of nuclear modifications of charmonium and $b$-quark production in p+Pb collisions.