Transverse Single-Spin Asymmetry for Very Forward Neutral Pion Production in Polarized p+p Collisions at s =510 GeV

M. H. Kim, O. Adriani, E. Berti, L. Bonechi, R. D'Alessandro, Y. Goto, B. Hong, Y. Itow, K. Kasahara, J. H. Lee, T. Ljubicic, Y. Makino, H. Menjo, I. Nakagawa, A. Ogawa, J. S. Park, T. Sako, N. Sakurai, K. Sato, R. SeidlK. Tanida, S. Torii, A. Tricomi, M. Ueno, Q. D. Zhou

Research output: Contribution to journalArticle

Abstract

Transverse single-spin asymmetries of very forward neutral pions generated in polarized p+p collisions allow us to understand the production mechanism in terms of perturbative and nonperturbative strong interactions. During 2017, the RHICf Collaboration installed an electromagnetic calorimeter in the zero-degree region of the STAR detector at the Relativistic Heavy Ion Collider (RHIC) and measured neutral pions produced at pseudorapidity larger than 6 in polarized p+p collisions at s=510 GeV. The large nonzero asymmetries increasing both in longitudinal momentum fraction xF and transverse momentum pT have been observed at low transverse momentum pT<1 GeV/c for the first time, at this collision energy. The asymmetries show an approximate xF scaling in the pT region where nonperturbative processes are expected to dominate. A non-negligible contribution from soft processes may be necessary to explain the nonzero neutral pion asymmetries.

Original languageEnglish
Article number252501
JournalPhysical review letters
Volume124
Issue number25
DOIs
Publication statusPublished - 2020 Jun 26

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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    Kim, M. H., Adriani, O., Berti, E., Bonechi, L., D'Alessandro, R., Goto, Y., Hong, B., Itow, Y., Kasahara, K., Lee, J. H., Ljubicic, T., Makino, Y., Menjo, H., Nakagawa, I., Ogawa, A., Park, J. S., Sako, T., Sakurai, N., Sato, K., ... Zhou, Q. D. (2020). Transverse Single-Spin Asymmetry for Very Forward Neutral Pion Production in Polarized p+p Collisions at s =510 GeV. Physical review letters, 124(25), [252501]. https://doi.org/10.1103/PhysRevLett.124.252501