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Title: The small-x gluon distribution in centrality biased pA and pp collisions

Here, the nuclear modification factor R pA(p T) provides information on the small- x gluon distribution of a nucleus at hadron colliders. Several experiments have recently measured the nuclear modification factor not only in minimum bias but also for central pA collisions. In this paper we analyze the bias on the configurations of soft gluon fields introduced by a centrality selection via the number of hard particles. Such bias can be viewed as reweighting of configurations of small- x gluons. We find that the biased nuclear modification factor Q pA(p T) for central collisions is above R pA(p T) for minimum bias events, and that it may redevelop a “Cronin peak” even at small x . The magnitude of the peak is predicted to increase approximately like 1/A ν, ν~0.6±0.1 , if one is able to select more compact configurations of the projectile proton where its gluons occupy a smaller transverse area A . We predict an enhanced Q pp(p T)–1~1/(p T 2) ν and a Cronin peak even for central pp collisions.
 [1] ;  [2] ;  [3]
  1. Baruch College, New York, NY (United States); The City Univ. of New York, New York, NY (United States); Brookhaven National Lab. (BNL), Upton, NY (United States)
  2. The City Univ. of New York, New York, NY (United States)
  3. Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 0375-9474
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Nuclear Physics. A
Additional Journal Information:
Journal Volume: 974; Journal Issue: C; Journal ID: ISSN 0375-9474
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26); RIKEN
Country of Publication:
United States
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; Cronin peak; Saturation; CGC; Small x; pA collisions
OSTI Identifier: