Inclusiveπ0,η, and direct photon production at high transverse momentum inp+p

Abstract

We report a measurement of high-p T inclusive π 0 , η, and direct photon production in p + p and d + Au collisions at √ s NN = 200 GeV at midrapidity (0 < η < 1). Photons from the decay π 0 → γ γ were detected in the barrel electromagnetic calorimeter of the STAR experiment at the Relativistic Heavy Ion Collider. The η → γ γ decay was also observed and constituted the first η measurement by STAR. The first direct photon cross-section measurement by STAR is also presented; the signal was extracted statistically by subtracting the π 0 , η, and ω(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.

A QCD analysis of LHCb D-meson data in p+Pb collisions

“…energy √ s, these data provide constraints only for momentum fractions x 0.01, and the gluons are constrained only indirectly via scale-evolution effects and momentum sum rule [12]. To obtain better gluon constraints, the potential of inclusive pion production in d+Au collisions at RHIC [13][14][15][16] was first discussed in ref. [17] and eventually the data were incorporated into the global fits [18][19][20][21].…”

Illuminating Light

“…Both the observations at lower and higher M inv are now shown to be related to the jet fragmentation, where the effects at lower and higher M inv are then related to the near-and away-side jet structures, respectively. A qualitatively similar effect at low M inv was already seen in studies at RHIC [169], but the jet correlations observed were significantly weaker than what is found at LHC energy. The ratios of the energy asymmetry α and opening angle ψ are also individually much closer to unity.…”

Nuclear gluons at RHIC in a multiobservable approach

“…Along with the precise data from the Large Hadron Collider (LHC), the list of data types that are included in state-of-the-art PDF analyses has grown, now ranging from traditional inclusive deeply-inelastic scattering to jet, top-quark and heavy gauge-boson production [2,3]. At this moment, global fits of proton PDFs do not use any data from the Relativistic Heavy-Ion Collider (RHIC), and nuclear-PDF fits [4,5] use only inclusive pion data from RHIC [6,7]. The advantage of the lower center-of-mass (c.m.)…”