2017/07/31 by Yan-Qing Ma, Raju Venugopalan, K. Watanabe +2 · 2 citations
Physics and Astronomy · #Computer science #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #hep-ex #hep-ph #nucl-ex #nucl-th
paper · pdf · doi:10.1103/physrevc.97.014909
published as Phys. Rev. C 97, 014909 (2018) · 16 pages, 12 figures. v2: version accepted for publication in PRC
openalex publication_date 2018/01/31 · arxiv created 2018/02/01 · arxiv updated 2018/02/02 · openalex created_date 2018/04/13 · openalex updated_date 2026/08/05
We argue that the large suppression of the \ensuremathψ(2S) inclusive cross section relative to the J/\ensuremathψ inclusive cross section in proton-nucleus (p+A) collisions can be attributed to factorization breaking effects in the formation of quarkonium. These factorization breaking effects arise from soft color exchanges between charm-anticharm pairs undergoing hadronization and comoving partons that are long lived on time scales of quarkonium formation. We compute the short distance pair production of heavy quarks in the color glass condensate (CGC) effective field theory and employ an improved color evaporation model (ICEM) to describe their hadronization into quarkonium at large distances. The combined CGC+ICEM model provides a quantitative description of J/\ensuremathψ and \ensuremathψ(2S) data in proton-proton (p+p) collisions from both RHIC and the LHC. Factorization breaking effects in hadronization, due to additional parton comovers in the nucleus, are introduced heuristically by imposing a cutoff \mathrm\ensuremathΛ, representing the average momentum kick from soft color exchanges, in the ICEM. Such soft exchanges have no perceptible effect on J/\ensuremathψ suppression in p+A collisions. In contrast, the interplay of the physics of these soft exchanges at large distances, with the physics of semihard rescattering at short distances, causes a significant additional suppression of \ensuremathψ(2S) yields relative to that of the J/\ensuremathψ. A good fit of all RHIC and LHC J/\ensuremathψ and \ensuremathψ(2S) data, for transverse momenta P_\ensuremath⊥\ensuremath≤5 GeV in p+p and p+A collisions, is obtained for \mathrm\ensuremathΛ\ensuremath∼10 MeV.