The PHENIX experiment has measured open heavy-flavor production via semileptonic decay over the transverse momentum range $1<p_T<6\mathrm{GeV}/c$ at forward and backward rapidity ($1.4<|y|<2.0$) in $d+\mathrm{Au}$ and $p+p$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$. In central $d+\mathrm{Au}$ collisions, relative to the yield in $p+p$ collisions scaled by the number of binary nucleon-nucleon collisions, a suppression is observed at forward rapidity (in the $d$-going direction) and an enhancement at backward rapidity (in the Au-going direction). Predictions using nuclear-modified-parton-distribution functions, even with additional nuclear-$p_T$ broadening, cannot simultaneously reproduce the data at both rapidity ranges, which implies that these models are incomplete and suggests the possible importance of final-state interactions in the asymmetric $d+\mathrm{Au}$ collision system. These results can be used to probe cold-nuclear-matter effects, which may significantly affect heavy-quark production, in addition to helping constrain the magnitude of charmonia-breakup effects in nuclear matter.

• Received 3 October 2013

DOI:https://doi.org/10.1103/PhysRevLett.112.252301