Abstract
Hard-scattered parton probes produced in collisions of large nuclei indicate large partonic energy loss, possibly with collective produced-medium response to the lost energy. We present measurements of trigger particles at transverse momenta and associated charged hadrons () vs relative azimuthal angle in and collisions at . The distribution at low , whose shape has been interpreted as a medium effect, is modified for . At higher , the data are consistent with unmodified or very weakly modified shapes, even for the lowest measured , which quantitatively challenges some medium response models. The associated yield of hadrons opposing the trigger particle in relative to () is suppressed at high (), but less than for inclusive suppression ().
- Received 5 February 2010
DOI:https://doi.org/10.1103/PhysRevLett.104.252301
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