Measurement of charged pion double spin asymmetries at midrapidity in longitudinally polarized p+p collisions at s =510 GeV
© 2020 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3. The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the longitudinal double spin asymmetries, ALL, for charged pions at midrapidity (|η|<0.35) in longitudinally polarized p+p collisions at s=510 GeV. These measurements are sensitive to the gluon spin contribution to the total spin of the proton in the parton momentum fraction x range between 0.04 and 0.09. One can infer the sign of the gluon polarization from the ordering of pion asymmetries with charge alone. The asymmetries are found to be consistent with global quantum-chromodynamics fits of deep-inelastic scattering and data at s=200 GeV, which show a nonzero positive contribution of gluon spin to the proton spin.
Acharya, U.; Adare, A.; Aidala, C.; Ajitanand, N. N.; Akiba, Y.; Akimoto, R.; Alfred, M.; Apadula, N.; Aramaki, Y.; Asano, H.; Atomssa, E. T.; Awes, T. C.; Azmoun, B.; Babintsev, V.; Bai, M.; Bandara, N. S.; Bannier, B.; Barish, K. N.; Bathe, S.; Bazilevsky, A.; Beaumier, M.; Beckman, S.; Belmont, R.; Berdnikov, A.; Berdnikov, Y.; Black, D.; Bok, J. S.; Danley, T. W.; Frantz, J. E.; Pun, A.; Riveli, N.; and Xia, B., "Measurement of charged pion double spin asymmetries at midrapidity in longitudinally polarized p+p collisions at s =510 GeV" (2020). Physics & Astronomy Open Access Publications. 4.