Energy and centrality dependence of particle production at very low transverse momenta in Au+Au collisions

TL;DR

This paper reports measurements of particle yields at very low transverse momenta in gold-gold collisions at RHIC, revealing a flattening of spectra indicative of rapid transverse expansion, and compares these results with other collision systems.

Contribution

It provides new low-$p_{T}$ invariant yield data for various particles in Au+Au collisions, highlighting differences from d+Au collisions and evidence of system expansion.

Findings

No $m_{T}$ scaling in low $p_{T}$ region

Yields align with extrapolations from higher $p_{T}$

Spectral flattening suggests rapid transverse expansion

Abstract

The PHOBOS experiment at RHIC has the unique capability of measuring particle production at very low transverse momenta. New results on low-transverse momentum invariant yields of pions, kaons, protons and antiprotons in 200 GeV Au+Au collisions are presented as a function of the collision centrality for the 50% most central events. In contrast to the results from d+Au collisions, no $m_{T}$ scaling is observed in the very low $p_{T}$ region. The low transverse momentum yields agree with extrapolations from intermediate transverse momentum measurements. For all collision centralities a flattening of the transverse momentum spectra is observed, consistent with a rapid transverse expansion of the system.