TY - JOUR
T1 - Single transverse spin asymmetry of prompt photon production
AU - Gamberg, Leonard
AU - Kang, Zhong Bo
N1 - Funding Information:
We thank W. Vogelsang for providing us the NLO code used to calculate the ratio in Fig. 3 , and thank L. Eun, X. Jiang, M. Liu, R. Seto, A. Vossen, and I. Younus for useful discussions on the experimental measurements. This work was supported in part by the U.S. Department of Energy under Contract Nos. DE-FG02-07ER41460 (L.G.) and DE-AC02-05CH11231 (Z.K.).
PY - 2012/11/15
Y1 - 2012/11/15
N2 - We study the single transverse spin asymmetry of prompt photon production in high energy proton-proton scattering. We include the contributions from both the direct and fragmentation photons. While the asymmetry for direct photon production receives only the Sivers type of contribution, the asymmetry for fragmentation photons receives both the Sivers and Collins types of contributions. We make a model calculation for quark-to-photon Collins function, which is then used to estimate the Collins asymmetry for fragmentation photons. We find that the Collins asymmetry for fragmentation photons is very small, thus the single transverse spin asymmetry of prompt photon production is mainly coming from the Sivers asymmetry in direct and fragmentation photons. We make predictions for the prompt photon spin asymmetry at RHIC energy, and emphasize the importance of such a measurement. The asymmetry of prompt photon production can provide a good measurement for the important twist-three quark-gluon correlation function, which is urgently needed in order to resolve the "sign mismatch" puzzle.
AB - We study the single transverse spin asymmetry of prompt photon production in high energy proton-proton scattering. We include the contributions from both the direct and fragmentation photons. While the asymmetry for direct photon production receives only the Sivers type of contribution, the asymmetry for fragmentation photons receives both the Sivers and Collins types of contributions. We make a model calculation for quark-to-photon Collins function, which is then used to estimate the Collins asymmetry for fragmentation photons. We find that the Collins asymmetry for fragmentation photons is very small, thus the single transverse spin asymmetry of prompt photon production is mainly coming from the Sivers asymmetry in direct and fragmentation photons. We make predictions for the prompt photon spin asymmetry at RHIC energy, and emphasize the importance of such a measurement. The asymmetry of prompt photon production can provide a good measurement for the important twist-three quark-gluon correlation function, which is urgently needed in order to resolve the "sign mismatch" puzzle.
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U2 - 10.1016/j.physletb.2012.10.002
DO - 10.1016/j.physletb.2012.10.002
M3 - Article
AN - SCOPUS:84868204932
SN - 0370-2693
VL - 718
SP - 181
EP - 188
JO - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
JF - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
IS - 1
ER -