Nucleon-gold collisions at 200A GeV using tagged d + Au interactions in the PHOBOS detector

Le résumé fourni par la source

Forward calorimetry in the PHOBOS detector has been used to study charged hadron production in $d+\text{Au}, p+\text{Au}$, and $n+\text{Au}$ collisions at $\sqrt{{s}_{NN}}=200\phantom{\rule{4pt}{0ex}}\mathrm{GeV}$. The forward proton calorimeter detectors are described and a procedure for determining collision centrality with these detectors is detailed. The deposition of energy by deuteron spectator nucleons in the forward calorimeters is used to identify $p+\text{Au}$ and $n+\text{Au}$ collisions in the data. A weighted combination of the yield of $p+\text{Au}$ and $n+\text{Au}$ is constructed to build a reference for $\mathrm{Au}+\mathrm{Au}$ collisions that better matches the isospin composition of the gold nucleus. The ${p}_{\mathrm{T}}$ and centrality dependence of the yield of this improved reference system is found to match that of $d+\text{Au}$. The shape of the charged-particle transverse momentum distribution is observed to extrapolate smoothly from $p+\overline{p}$ to central $d+\text{Au}$ as a function of the charged-particle pseudorapidity density. The asymmetry of positively and negatively charged hadron production in $p+\text{Au}$ is compared to that of $n+\text{Au}$. No significant asymmetry is observed at midrapidity. These studies augment recent results from experiments at the CERN Large Hadron Collider and BNL Relativistic Heavy Ion Collider facilities to give a more complete description of particle production in $p+A$ and $d+A$ collisions, essential for the understanding the medium produced in high-energy nucleus-nucleus collisions.

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