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Title: Evidence for x-dependent proton color fluctuations in pA collisions at the CERN Large Hadron Collider

The centrality dependence of forward jet production in pA collisions at the Large Hadron Collider (LHC) has been found to grossly violate the Glauber model prediction in a way that depends on the x in the proton. In this paper, we argue that this modification pattern provides the first experimental evidence for x-dependent proton color fluctuation effects. On average, parton configurations in the projectile proton containing a parton with large x interact with a nuclear target with a significantly smaller than average cross section and have smaller than average size. We implement the effects of fluctuations of the interaction strength and, using the ATLAS analysis of how hadron production at backward rapidities depends on the number of wounded nucleons, make quantitative predictions for the centrality dependence of the jet production rate as a function of the x-dependent interaction strength σ(x). We find that σ(x) ~ 0.6(σ) gives a good description of the data at x = 0.6. Finally, these findings support an explanation of the European Muon Collaboration effect as arising from the suppression of small-size nucleon configurations in the nucleus.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Research Inst. for Geo-Hydrological Protection (IRPI), Perugia (Italy). National Research Council (CNR)
  2. Columbia Univ., New York, NY (United States). Physics Dept.
  3. Tel Aviv Univ. (Israel). Dept. of Particle Physics
  4. Brookhaven National Lab. (BNL), Upton, NY (United States)
  5. Pennsylvania State Univ., University Park, PA (United States)
Publication Date:
OSTI Identifier:
1341651
Report Number(s):
BNL-113375-2016-JA
Journal ID: ISSN 2469-9985
Grant/Contract Number:
AC02-98CH10886; FG02-86ER40281; FG02-93ER40771; POR-FESR Umbria 20072013; 0603216203
Type:
Accepted Manuscript
Journal Name:
Physical Review C
Additional Journal Information:
Journal Volume: 93; Journal Issue: 1; Journal ID: ISSN 2469-9985
Publisher:
APS
Research Org:
Brookhaven National Lab. (BNL), Upton, NY (United States); Research Inst. for Geo-Hydrological Protection (IRPI), Perugia (Italy)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26); Region of Umbria (Italy); Dept. of Civil Protection (Italy); United States-Israel Binational Science Foundation (BSF) (Israel)
Contributing Orgs:
Columbia Univ., New York, NY (United States); Tel Aviv Univ. (Israel); Pennsylvania State Univ., University Park, PA (United States)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; Relativistic Heavy Ion Collider