Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Challenging the utility of third-order azimuth harmonics in the
  description of ultra-relativistic heavy-ion collisions   In recent years it has become conventional practice to include higher-order
cylindrical harmonics in the phenomenological description of two-particle
angular correlations from ultra-relativistic heavy-ion collisions. These model
elements, whose dependence on relative azimuth angle has the form
$\cos[m(\phi_1-\phi_2)]$ where $m > 2$, were introduced to support a
hydrodynamic flow interpretation of the same-side ($|\phi_1-\phi_2| < \pi/2$)
2D peak in the correlations. Previous studies have shown that the $m > 2$
harmonics are not required by the data, that they destabilize the fitting
models, and that their net effect is to decompose the same-side peak into two
components, one being dependent on and the other being independent of relative
pseudorapidity. Thus we are lead to question whether descriptions of angular
correlation data including higher-order harmonics inform our understanding of
the same-side peak or heavy-ion collisions in general. Results from analysis of
two-dimensional angular correlation data from the Relativistic Heavy-Ion
Collider (RHIC) and the Large Hadron Collider (LHC) show that the RHIC data do
not exclude a single-Gaussian hypothesis for the same-side peak. We find that
the net effect of including the $m = 3$ harmonic or azimuth sextupole in the
fitting model is the inclusion of small non-Gaussian dependence in the
mathematical description of the same-side peak. Those non-Gaussian effects are
systematically insignificant and can be accommodated by minor perturbations to
the same-side 2D Gaussian peak model, which act locally at small relative
azimuth. We also demonstrate that the 0-1% 2D angular correlation data for 2.76
TeV Pb+Pb collisions from ATLAS, which display an away-side double peak on
azimuth, do not require a sextupole and exclude a positive same-side sextupole.

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The categories of this paper are: solv-int
6
The categories of this paper are: astro-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: math
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The categories of this paper are: physics
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The categories of this paper are: nlin
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The categories of this paper are: math-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: comp-gas
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The categories of this paper are: q-bio
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The categories of this paper are: nucl-th
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The categories of this paper are: econ
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The categories of this paper are: atom-ph
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The categories of this paper are: q-fin
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The categories of this paper are: stat
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The categories of this paper are: hep-th