Heavy flavor puzzle from data measured at the BNL Relativistic Heavy Ion Collider: Analysis of the underlying effects

Abstract

© 2014 American Physical Society. Suppressions of light- and heavy-flavor observables are considered to be excellent probes of QCD matter created in ultrarelativistic heavy ion collisions. Suppression predictions of quark and gluon jets appear to suggest a clear hierarchy according to which neutral pions should be more suppressed than D mesons, which in turn should be more suppressed than single electrons. However, joint comparison of neutral pion (light probe) and nonphotonic single-electron (heavy probe) suppression data at the BNL Relativistic Heavy Ion Collider (RHIC) unexpectedly showed similar jet suppression for these two probes, which presents the well-known heavy-flavor puzzle at RHIC. We here analyze which effects are responsible for this unexpected result by using the dynamical energy-loss formalism. We find that the main effect is a surprising reversal in the suppression hierarchy between neutral pions and D mesons, which is due to the deformation of the suppression patterns of light partons by fragmentation functions. Furthermore, we find that, due to the decay functions, the single-electron suppression approaches the D-meson suppression. Consequently, we propose that these two effects, taken together, provide a clear intuitive explanation of this longstanding puzzle.