Conservation Laws and the Multiplicity Evolution of Spectra at the Relativistic Heavy Ion Collider

TL;DR

This paper discusses how conservation laws significantly influence the spectra in heavy ion collisions, suggesting that energy and momentum conservation effects may explain many observed features, making $p+p$ and heavy ion collisions more similar than previously believed.

Contribution

It highlights the importance of conservation laws in interpreting collision spectra and challenges the assumption that heavy ion and $p+p$ collisions are fundamentally different.

Findings

Conservation laws dominate the systematics of spectra.

Energy and momentum conservation effects are crucial.

$p+p$ collisions may resemble heavy ion collisions more than thought.

Abstract

Transverse momentum distributions in ultra-relativistic heavy ion collisions carry considerable information about the dynamics of the hot system produced. Direct comparison with the same spectra from $p+p$ collisions has proven invaluable to identify novel features associated with the larger system, in particular, the "jet quenching" at high momentum and apparently much stronger collective flow dominating the spectral shape at low momentum. We point out possible hazards of ignoring conservation laws in the comparison of high- and low-multiplicity final states. We argue that the effects of energy and momentum conservation actually dominate many of the observed systematics, and that $p+p$ collisions may be much more similar to heavy ion collisions than generally thought.