Evidence for Nonlinear Gluon Effects in QCD and Their Mass Number Dependence at STAR

作者：Abdallah, M. S.; Aboona, B. E.; Adam, J.; Adamczyk, L.; Adams, J. R.; Adkins, J. K.; Agakishiev, G.; Aggarwal, I; Aggarwal, M. M.; Ahammed, Z.; Alekseev, I; Anderson, D. M.; Aparin, A.; Aschenauer, E. C.; Ashraf, M. U.; Atetalla, F. G.; Attri, A.; Averichev, G. S.; Bairathi, V; Baker, W.; Cap, J. G. Ball; Barish, K.; Behera, A.; Bellwied, R.; Bhagat, P.; Bhasin, A.; Bielcik, J.; Bielcikova, J.; Bordyuzhin, I. G.; Brandenburg, J. D.; Brandin, A., V; Bunzarov, I; Cai, X. Z.; Caines, H.

来源：Physical Review Letters, 2022, 129(9): 092501.

DOI：10.1103/PhysRevLett.129.092501

• DEUTERON-GOLD COLLISIONS
• AZIMUTHAL CORRELATIONS
• SATURATION

The STAR Collaboration reports measurements of back-to-back azimuthal correlations of di-pi(0)s produced at forward pseudorapidities (2.6 < eta < 4.0) in p + p, p + Al, and p + Au collisions at a center-of-mass energy of 200 GeV. We observe a clear suppression of the correlated yields of back-to-back pi(0) pairs in p + Al and p + Au collisions compared to the p + p data. The observed suppression of back-to-back pairs as a function of transverse momentum suggests nonlinear gluon dynamics arising at high parton densities. The larger suppression found in p + Au relative to p + Al collisions exhibits a dependence of the saturation scale Q(s)(2) on the mass number A. A linear scaling of the suppression with A(1/3) is observed with a slope of -0.09 +/- 0.01.