Midrapidity Neutral-Pion Production in Proton-Proton Collisions at $\sqrt{s}=200\mathrm{G}\mathrm{e}\mathrm{V}$

The invariant differential cross section for inclusive neutral-pion production in $p+p$ collisions at $\sqrt{s}=200\mathrm{G}\mathrm{e}\mathrm{V}$ has been measured at midrapidity ($|\eta |<0.35$) over the range $1<p_T\lesssim 14\mathrm{G}\mathrm{e}\mathrm{V}/c$ by the PHENIX experiment at the Relativistic Heavy Ion Collider. Predictions of next-to-leading order perturbative QCD calculations are consistent with these measurements. The precision of our result is sufficient to differentiate between prevailing gluon-to-pion fragmentation functions.

Figure 1

(a) The efficiency of the $2\times 2$ high-$p_T$ trigger for ${\pi }^0$ as a function of the $p_T$ of the ${\pi }^0$. The dashed and solid lines show the results of a Monte Carlo simulation based on the $2\times 2$ trigger tile efficiencies and the limit derived from the fraction of active trigger tiles, respectively. (b) The fraction of the inclusive ${\pi }^0$ yield which satisfied the MB trigger condition. The solid line shows a fit of these data to a constant.

Figure 2

(a) The invariant differential cross section for inclusive ${\pi }^0$ production (points) and the results from NLO pQCD calculations with equal renormalization and factorization scales of $p_T$ using the “Kniehl-Kramer-Pötter” (solid line) and “Kretzer” (dashed line) sets of fragmentation functions. (b) The relative statistical (points) and point-to-point systematic (band) errors. (c),(d) The relative difference between the data and the theory using KKP (c) and Kretzer (d) fragmentation functions with scales of $p_T/2$ (lower curve), $p_T$, and $2p_T$ (upper curve). In all figures, the normalization error of 9.6% is not shown.