Inclusive pi^0, eta, and direct photon production at high transverse momentum in p+p and d+Au collisions at sqrt(s_NN) = 200 GeV

TL;DR

This paper presents measurements of high transverse momentum inclusive pi^0, eta, and direct photon production in proton-proton and deuteron-gold collisions at 200 GeV, confirming theoretical predictions and providing new eta and direct photon data.

Contribution

First STAR measurement of eta and direct photon production at high p_T in p+p and d+Au collisions, with results consistent with perturbative QCD calculations.

Findings

Measured inclusive pi^0, eta, and direct photon cross sections.

First eta measurement by STAR at high p_T.

Good agreement with NLO pQCD calculations.

Abstract

We report a measurement of high-p_T inclusive pi^0, eta, and direct photon production in p+p and d+Au collisions at sqrt(s_NN) = 200 GeV at midrapidity (0 < eta < 1). Photons from the decay pi^0 -> gamma gamma were detected in the Barrel Electromagnetic Calorimeter of the STAR experiment at the Relativistic Heavy Ion Collider. The eta -> gamma gamma decay was also observed and constituted the first eta measurement by STAR. The first direct photon cross section measurement by STAR is also presented, the signal was extracted statistically by subtracting the pi^0, eta, and omega(782) decay background from the inclusive photon distribution observed in the calorimeter. The analysis is described in detail, and the results are found to be in good agreement with earlier measurements and with next-to-leading order perturbative QCD calculations.