Study of nuclear effects on charm production in light-ion collisions

The onset of nuclear effects in light-ion collisions is studied by measuring the ratio of $D^0$ meson production between NeNe and OO collisions at a center-of-mass energy per nucleon pair of $5.36\mathrm{T}\mathrm{e}\mathrm{V}$ recorded by the LHCb detector. The $D^0$ meson yields are measured differentially in transverse momentum ($p_{\mathrm{T}}$) for $0.5<p_{\mathrm{T}}<20\mathrm{G}\mathrm{e}\mathrm{V}$ in the rapidity ($y$) region $2.0<y<4.5$, and are normalized to the total number of recorded inelastic nucleus-nucleus collisions in each data sample. The resulting production ratio shows evidence of variation as a function of $p_{\mathrm{T}}$, which is inconsistent with predictions based on nuclear modification of nucleon structure alone. This measurement is consistent with the onset of quark-gluon plasma production with increasing nucleus size in high-energy nuclear collisions.