Charged particle multiplicity near mid-rapidity in central Au+Au collisions at $\sqrt{s} = $ 56 and 130 AGeV

TL;DR

This paper reports the first measurements of charged particle densities near mid-rapidity in central gold-gold collisions at two energies, revealing significant increases over previous nuclear collision data and proton-antiproton interactions.

Contribution

It provides the first pseudorapidity density measurements at these energies, showing higher particle production than previously observed in nuclear collisions.

Findings

Charged particle density at 56 AGeV: 408 ± 12 (stat) ± 30 (syst)

Charged particle density at 130 AGeV: 555 ± 12 (stat) ± 35 (syst)

Density increase per participant exceeds 40% at higher energy

Abstract

We present the first measurement of pseudorapidity densities of primary charged particles near mid-rapidity in Au+Au collisions at $\sqrt{s} =$ 56 and 130 AGeV. For the most central collisions, we find the charged particle pseudorapidity density to be $dN/d\eta |_{|\eta|<1} = 408 \pm 12 {(stat)} \pm 30 {(syst)}$ at 56 AGeV and $555 \pm 12 {(stat)} \pm 35 {(syst)}$ at 130 AGeV, values that are higher than any previously observed in nuclear collisions. Compared to proton-antiproton collisions, our data show an increase in the pseudorapidity density per participant by more than 40% at the higher energy.