Speaker
Dr
Andrew Adare
(Yale University)
Description
Angular correlations between unidentified hadron trigger and
associated particles are measured by the ALICE experiment for $0.5 <
p_{t}^{(t),(a)} < 15$ GeV/c, where $p_t^{(t)} > p_t^{(a)}$. The
modification of conditional yields in central Pb--Pb collisions is
measured with respect to p--p ($I_{AA}$) and with respect to peripheral
events ($I_{CP}$). Significant suppression is observed on the side
opposing the trigger, while an enhancement is measured on the near
side. The latter result is a notable departure from RHIC measurements.
In addition, the shape of the pair azimuthal distribution is examined
in a variety of centrality categories for pairs in $|\eta| < 0.8$
where $|\eta^{(t)} - \eta^{(a)}| > 0.8$. A set of two-particle Fourier
components $V_{n\Delta} \equiv \langle \cos(n\Delta\phi)\rangle$ are
computed directly from the long-range azimuthal correlation
functions. A series including $V_{1\Delta}$ to $V_{5\Delta}$ describes
the data. For each $n$, a fit is applied over all $p_{T}$ bins
simultaneously to test the collectivity hypothesis $V_{n\Delta} \simeq
v_n^{(t)} \, v_n^{(a)}$. This factorization hypothesis is satisfied at
low $p_{T}$ but not at higher $p_{T}$. The divergence between the data
and the global fit provides a new measure of the onset of nonflow
dominance in long-range correlations due to the away side jet. The
first five single-particle $v_n$ coefficients are presented as new
results from the global fit, and are compared to $v_n$ values
measured by more established methods.
Primary author
Dr
Andrew Adare
(Yale University)
