Measurement of the Prompt D0 Nuclear Modification Factor in p-Pb Collisions at sNN=8.16 TeV

The production of prompt 𝐷0 mesons in proton-lead collisions in both the forward and backward rapidity regions at a center-of-mass energy per nucleon pair of √𝑠𝑁⁢𝑁=8.16  TeV is measured by the LHCb experiment. The nuclear modification factor of prompt 𝐷0 mesons is determined as a function of the transverse momentum 𝑝𝑇, and the rapidity in the nucleon-nucleon center-of-mass frame 𝑦*. In the forward rapidity region, significantly suppressed production with respect to 𝑝⁢𝑝 collisions is measured, which provides significant constraints on models of nuclear parton distributions and hadron production down to the very low Bjorken-𝑥 region of ∼10−5. In the backward rapidity region, a suppression with a significance of 2.0–3.8 standard deviations compared to parton distribution functions in a nuclear environment expectations is found in the kinematic region of 𝑝𝑇>6  GeV/𝑐 and −3.25<𝑦*<−2.5, corresponding to 𝑥∼0.01.