期刊
PHYSICAL REVIEW LETTERS
卷 123, 期 7, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevLett.123.072001
关键词
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资金
- U.S. Department of Energy
- U.S. National Science Foundation
- German Research Foundation
- GSI Helmholtzzentrum fur Schwerionenforschung GmbH
- Natural Sciences and Engineering Research Council of Canada
- Russian Foundation for Basic Research
- United Kingdom Science and Technology Facilities Council
- Chilean Comision Nacional de Investigacion Cientifica y Tecnologica
- National Natural Science Foundation of China
- China Scholarship Council
- U.S. Department of Energy, Office of Science, Office of Nuclear Physics [DE-AC05-06OR23177]
- Jefferson Science Associates, LLC
- STFC [ST/P004458/1] Funding Source: UKRI
We report on the measurement of the gamma p -> J/psi p cross section from E-gamma = 11.8 GeV down to the threshold at 8.2 GeV using a tagged photon beam with the GlueX experiment. We find that the total cross section falls toward the threshold less steeply than expected from two-gluon exchange models. The differential cross section d sigma/dt has an exponential slope of 1.67 +/- 0.39 GeV-2 at 10.7 GeV average energy. The LHCb pentaquark candidates P-c(+) can be produced in the s channel of this reaction. We see no evidence for them and set model-dependent upper limits on their branching fractions B(P-c(+) -> J/psi p) and cross sections sigma(gamma p -> P-c(+)) x B(P-c(+) -> J/psi p).
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