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New LHCb pentaquarks as hadrocharmonium states

High Energy Physics - Phenomenology 2020-06-16 v2

Abstract

New LHCb Collaboration results on pentaquarks with hidden charm [1] are discussed. These results fit nicely in the hadrocharmonium pentaquark scenario [2,3]. In the new data the old LHCb pentaquark Pc(4450)P_c(4450) splits into two states Pc(4440)P_c(4440) and Pc(4457)P_c(4457). We interpret these two almost degenerate hadrocharmonium states with JP=1/2J^P=1/2^- and JP=3/2J^P=3/2^- as a result of hyperfine splitting between hadrocharmonium states predicted in [2]. It arises due to QCD multipole interaction between color-singlet hadrocharmonium constituents. We improve the theoretical estimate of hyperfine splitting [2,3] that is compatible with the experimental data. The new Pc(4312)P_c(4312) state finds a natural explanation as a bound state of χc0\chi_{c0} and a nucleon, with I=1/2I=1/2, JP=1/2+J^P=1/2^+ and binding energy 42 MeV. As a bound state of a spin-zero meson and a nucleon, hadrocharmonium pentaquark Pc(4312)P_c(4312) does not experience hyperfine splitting. We find a series of hadrocharmonium states in the vicinity of the wide Pc(4380)P_c(4380) pentaquark that can explain its apparently large decay width. We compare the hadrocharmonium and molecular pentaquark scenarios and discuss their relative advantages and drawbacks.

Keywords

Cite

@article{arxiv.1904.11616,
  title  = {New LHCb pentaquarks as hadrocharmonium states},
  author = {Michael I. Eides and Victor Yu. Petrov and Maxim V. Polyakov},
  journal= {arXiv preprint arXiv:1904.11616},
  year   = {2020}
}

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10 pages