Studying Parton Energy Loss in Heavy-Ion Collisions via Direct-Photon and Charged-Particle Azimuthal Correlations

The STAR Collaboration; B. I. Abelev

doi:10.1103/PhysRevC.82.034909

paper

Studying Parton Energy Loss in Heavy-Ion Collisions via Direct-Photon and Charged-Particle Azimuthal Correlations

arXiv:0912.1871 · doi:10.1103/PhysRevC.82.034909

Abstract

Charged-particle spectra associated with direct photon ( $γ_{d i r}$ ) and $π^{0}$ are measured in $p$ + $p$ and Au+Au collisions at center-of-mass energy $s_{_{N N}} = 200$ GeV with the STAR detector at RHIC. A hower-shape analysis is used to partially discriminate between $γ_{d i r}$ and $π^{0}$ . Assuming no associated charged particles in the $γ_{d i r}$ direction (near side) and small contribution from fragmentation photons ( $γ_{f r a g}$ ), the associated charged-particle yields opposite to $γ_{d i r}$ (away side) are extracted. At mid-rapidity ( $∣ η ∣ < 0.9$ ) in central Au+Au collisions, charged-particle yields associated with $γ_{d i r}$ and $π^{0}$ at high transverse momentum ( $8 < p_{T}^{t r i g} < 16$ GeV/ $c$ ) are suppressed by a factor of 3-5 compared with $p$ + $p$ collisions. The observed suppression of the associated charged particles, in the kinematic range $∣ η ∣ < 1$ and $3 < p_{T}^{a ssoc} < 16$ GeV/ $c$ , is similar for $γ_{d i r}$ and $π^{0}$ , and independent of the $γ_{d i r}$ energy within uncertainties. These measurements indicate that the parton energy loss, in the covered kinematic range, is insensitive to the parton path length.

submitted to Phys. Rev. Lett, 6 pages, 4 figures

Studying Parton Energy Loss in Heavy-Ion Collisions via Direct-Photon and Charged-Particle Azimuthal Correlations

Abstract

References in corpus (5)

Cited by in corpus (43)