Figure. The minimumbias values of v_{2}, v_{4}, and v_{6}
with respect to the second harmonic event plane as a function of transverse
momentum. The v_{2} values have been divided by a factor of two to
fit on scale. Also shown are the threeparticle cumulant values (triangles)
for v_{4} (v_{4}{3}). The dashed curves are
1.2 v_{2}^{2} and 1.2 v_{2}^{3}

Higher Harmonics of the Azimuthal Anisotropy
This is the first measurement of higher harmonics of the momentum
anisotropy at RHIC, and it is expected that these higher harmonics
will be a sensitive test of the initial configuration of the system,
since they provide a Fourier analysis of the shape in momentum space
which can be related back to the initial shape in position space.
The results as a function of transverse momentum are shown in the
figure for minimum bias collisions (0  80% centrality). Shown for
v_{4} are both the analysis relative to the second harmonic
event plane, v_{4}{EP_{2}}, and the threeparticle
cumulant, v_{4}{3}. Both methods determine the sign of
v_{4} to be positive. As a function of p_{t},
v_{4} rises more slowly from the origin than v_{2},
but does flatten out at high p_{t} like v_{2}. The
v_{6}(p_{t}) values are consistent with zero.
It has proposed that for the higher harmonics, v_{n} might
be proportional to v_{2}^{n/2}. In order to test
the applicability of this scaling, we have also plotted
v_{2}^{2} and v_{2}^{3} in the
figure as dashed lines. The proportionality constant has been taken
to be 1.2 in order to fit the v_{4} data. The fit is good,
and v_{6}, although essentially zero, is not inconsistent
with scaling as v_{2}^{3}.
Related STAR papers
Azimuthal anisotropy at the Relativistic Heavy Ion Collider: the first and fourth harmonics
Phys. Rev. Lett. 92 (2004) 062301
ePrint Archives (nuclex/0310029):
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Journal article:
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