Abstract
Back-to-back hadron pair yields in and collisions at were measured with the PHENIX detector at the Relativistic Heavy Ion Collider. Rapidity separated hadron pairs were detected with the trigger hadron at pseudorapidity and the associated hadron at forward rapidity (deuteron direction, ). Pairs were also detected with both hadrons measured at forward rapidity; in this case, the yield of back-to-back hadron pairs in collisions with small impact parameters is observed to be suppressed by a factor of 10 relative to collisions. The kinematics of these pairs is expected to probe partons in the Au nucleus with a low fraction of the nucleon momenta, where the gluon densities rise sharply. The observed suppression as a function of nuclear thickness, , and points to cold nuclear matter effects arising at high parton densities.
- Received 2 June 2011
DOI:https://doi.org/10.1103/PhysRevLett.107.172301
© 2011 American Physical Society