Measurement of the prompt $D^0$ nuclear modification factor in $p$Pb collisions at $\sqrt{s_\mathrm{NN}} = 8.16$ TeV

TL;DR

This paper measures the nuclear modification factor of prompt D^0 mesons in proton-lead collisions at 8.16 TeV, revealing suppression effects that constrain nuclear parton distribution functions at very low Bjorken-x values.

Contribution

First measurement of prompt D^0 meson nuclear modification factor in pPb collisions at 8.16 TeV, providing new insights into nuclear PDFs at low Bjorken-x.

Findings

Significant suppression of D^0 production at forward rapidity.

Suppression observed at backward rapidity with 2.0-3.8 sigma significance.

Constraints on nuclear parton distributions at x~10^-5.

Abstract

The production of prompt $D^0$ mesons in proton-lead collisions in the forward and backward configurations at a center-of-mass energy per nucleon pair of $\sqrt{s_\mathrm{NN}} = 8.16~\mathrm{TeV}$ is measured by the LHCb experiment. The nuclear modification factor of prompt $D^0$ mesons is determined as a function of the transverse momentum $p_\mathrm{T}$, and rapidity in the nucleon-nucleon center-of-mass frame $y^*$. In the forward rapidity region, significantly suppressed production with respect to $pp$ collisions is measured, which provides significant constraints of nuclear parton distributions and hadron production down to the very low Bjorken-$x$ region of $\sim 10^{-5}$. In the backward rapidity region, a suppression with a significance of 2.0 - 3.8 standard deviations compared to nPDF expectations is found in the kinematic region of $p_\mathrm{T}>6~\mathrm{GeV}/c$ and $-3.25<y^*<-2.5$, corresponding to $x\sim 0.01$.