γ-hadron azimuthal correlations in STAR
نویسنده
چکیده
One of the most exciting results at RHIC is the suppression of hadrons in central Au+Au collisions, compared to p+p collisions [1] and to cold nuclear matter [2] at high pT . This suppression is well described by very different pQCD-based energy loss models in the light flavor sector [3] . However, the observation of a similar level of suppression for the heavy flavor [4], and the unexpected smaller suppression of baryons compared to mesons at intermediate to high pT [5], cannot be easily reconciled in these pQCD-based energy loss models that incorporate gluon radiation as the main source of in-medium energy loss. In fact the applicability of pQCD in describing the parton–matter interaction has been increasingly challenged by the strongly coupled nature of the produced matter at RHIC. As a result there is no single commonly accepted calculation of the underlying physics to describe in-medium energy loss for different quark generations as well as for the gluon. On the other hand, experimental observables based on single-particle spectra are not sensitive enough to discriminate between the different energy loss mechanisms, indicating the need for additional experimental observables in order to better constrain the energy loss mechanism. Azimuthal correlation measurements of di-hadron and γ -hadron provide a complementary way to quantify the energy loss, and its dependence on path length, and the initial parton energy. In particular, γ -hadron is an ideal probe [6] for the dependence on the initial parton energy and possibly the color-factor.
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