Azimuth Quadrupole Spectra derived from 2.76 TeV Pb-Pb PID Differential $v_2(p_t)$ Data

TL;DR

This paper analyzes 2.76 TeV Pb-Pb collision data to extract a unique azimuth quadrupole spectrum, revealing insights into elliptic flow and radial boost effects using Cooper-Frye formalism.

Contribution

It introduces a method to isolate the quadrupole $p_t$ spectrum from $v_2(p_t)$ data and compares it directly with single-particle spectra and hydrodynamic models.

Findings

Isolation of a unique quadrupole $p_t$ spectrum from $v_2(p_t)$ data.

Estimation of monopole (radial) flow boost from $v_2(p_t)$.

Insights into the influence of boost factors on elliptic flow interpretation.

Abstract

$v_2(p_t)$ data are intended to estimate the amplitude of an azimuth component of particle spectra interpreted as representing elliptic flow of a dense QCD medium. As defined, $ v_2(p_t)$ is a ratio with a single-particle spectrum appearing in its denominator. Its numerator represents a spectrum Fourier component arising from a boosted particle source. The Cooper-Frye (CF) formalism may be used to describe emission from a boosted source. CF analysis reveals that the $v_2(p_t)$ numerator includes a factor $ p_t$ in the boost frame with major consequences for data interpretation. A unique quadrupole $p_t$ spectrum may be isolated from $v_2(p_t)$ data and compared directly with the single-particle spectrum in the $v_2$ denominator and with hydro theory. A monopole boost (aka radial flow) value may be estimated from $v_2(p_t)$ data. Several novel results emerge via the Cooper-Frye analysis.