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

Authors

STAR Collaboration

Abstract

The STAR Collaboration reports measurements of back-to-back azimuthal correlations of di-𝜋0s produced at forward pseudorapidities (2.6 < 𝜂 < 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 𝜋0 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 𝑄2/𝑠 on the mass number 𝐴. A linear scaling of the suppression with 𝐴1/3 is observed with a slope of −0.09 ±0.01.

Document Type

Article

Publication Date

2022

Notes/Citation Information

© 2022 American Physical Society

Digital Object Identifier (DOI)

https://doi.org/10.1103/PhysRevLett.129.092501

Funding Information

We thank the RHIC Operations Group and RCF at BNL, the NERSC Center at LBNL, and the Open Science Grid consortium for providing resources and support. This work was supported in part by the Office of Nuclear Physics within the U.S. DOE Office of Science, the U.S. National Science Foundation, National Natural Science Foundation of China, Chinese Academy of Science, the Ministry of Science and Technology of China and the Chinese Ministry of Education, the Higher Education Sprout Project by Ministry of Education at NCKU, the National Research Foundation of Korea, Czech Science Foundation and Ministry of Education, Youth and Sports of the Czech Republic, Hungarian National Research, Development and Innovation Office, New National Excellency Programme of the Hungarian Ministry of Human Capacities, Department of Atomic Energy and Department of Science and Technology of the Government of India, the National Science Centre of Poland, the Ministry of Science, Education and Sports of the Republic of Croatia, German Bundesministerium für Bildung, Wissenschaft, Forschung and Technologie (BMBF), Helmholtz Association, Ministry of Education, Culture, Sports, Science, and Technology (MEXT) and Japan Society for the Promotion of Science (JSPS).

Repository Citation

STAR Collaboration, "Evidence for Nonlinear Gluon Effects in QCD and Their Mass Number Dependence at STAR" (2022). Physics and Astronomy Faculty Publications. 755.
https://uknowledge.uky.edu/physastron_facpub/755