Azimuthal di-hadron correlations in d_s16Au and Au_s16Au collisions at $sqrts_NN=200$ GeV from STAR

Abstract

Yields, correlation shapes, and mean transverse momenta pt{} of charged particles associated with intermediate to high-pt{} trigger particles ($2.5 < pt < 10$ GeVc) in d_s16Au and Au_s16Au collisions at $snn=200$ GeV are presented. For associated particles at higher $pt gtrsim 2.5$ GeVc, narrow correlation peaks are seen in d_s16Au and Au_s16Au, indicating that the main production mechanism is jet fragmentation. At lower associated particle $pt < 2$ GeVc, a large enhancement of the near- ($dphi sim 0$) and away-side ($dphi sim pi$) associated yields is found, together with a strong broadening of the away-side azimuthal distributions in Au_s16Au collisions compared to d_s16Au measurements, suggesting that other particle production mechanisms play a role. This is further supported by the observed significant softening of the away-side associated particle yield distribution at $dphi sim pi$ in central Au_s16Au collisions.