Evidence of Final-State Suppression of High-p_T Hadrons in Au + Au Collisions Using d + Au Measurements at RHIC
Abstract
Transverse momentum spectra of charged hadrons with
p
T
<
6 GeV/c have been measured near mid-rapidity (0.2
<η<
1.4) by the PHOBOS experiment at RHIC in Au + Au and d + Au collisions at
s
NN
−
−
−
√
=200GeV
. The spectra for different collision centralities are compared to
p+
p
¯
collisions at the same energy. The resulting nuclear modification factor for central Au + Au collisions shows evidence of strong suppression of charged hadrons in the high-
p
T
region (
>2
GeV/c). In contrast, the d + Au nuclear modification factor exhibits no suppression of the high-
p
T
yields. These measurements suggest a large energy loss of the high-
p
T
particles in the highly interacting medium created in the central Au + Au collisions. The lack of suppression in d + Au collisions suggests that it is unlikely that initial state effects can explain the suppression in the central Au + Au collisions.