Abstract
Two-particle correlation measurements projected onto two-dimensional,
transverse rapidity coordinates ($y_{T1},y_{T2}$), allow access to dynamical
properties of the QCD medium produced in relativistic heavy-ion collisions that
angular correlation measurements are not sensitive to. We report non-identified
charged-particle correlations for Au + Au minimum-bias collisions at
$\sqrt{s_{\rm NN}}$ = 200 GeV taken by the STAR experiment at the Relativistic
Heavy-Ion Collider (RHIC). Correlations are presented as 2D functions of
transverse rapidity for like-sign, unlike-sign and all charged-particle pairs,
as well as for particle pairs whose relative azimuthal angles lie on the
near-side, the away-side, or at all relative azimuth. The correlations are
constructed using charged particles with transverse momentum $p_T \geq 0.15$
GeV/$c$, pseudorapidity from $-$1 to 1, and azimuthal angles from $-\pi$ to
$\pi$. The significant correlation structures that are observed evolve smoothly
with collision centrality. The major correlation features include a saddle
shape plus a broad peak with maximum near $y_T \approx 3$, corresponding to
$p_T \approx$ 1.5 GeV/$c$. The broad peak is observed in both like- and
unlike-sign charge combinations and in near- and away-side relative azimuthal
angles. The all-charge, all-azimuth correlation measurements are compared with
the theoretical predictions of {\sc hijing} and {\sc epos}. The results
indicate that the correlations for peripheral to mid-central collisions can be
approximately described as a superposition of nucleon + nucleon collisions with
minimal effects from the QCD medium. Strong medium effects are indicated in
mid- to most-central collisions.