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Observation of a threshold enhancement in the p \bar{Lambda} invariant mass spectrum

BES Collaboration·M. Ablikim
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Abstract

An enhancement near the m_p + M_Λ mass threshold is observed in the combined p \barΛ and \bar{p}Λinvariant mass spectrum from J/ψ--> p K^- \bar{Lambda} + c.c. decays. It can be fit with an S-wave Breit-Wigner resonance with a mass m = 2075 +- 12 (stat) +- 5 (syst) MeV and a width of Γ= 90 +- 35 (stat) +- 9 (syst) MeV; it can also be fit with a P-wave Breit-Wigner resonance. Evidence for a similar enhancement is also observed in ψ' --> p K^- \barΛ + c.c. decays. The analysis is based on samples of 5.8 X 10^7 J/ψand 1.4 X 10^7 ψ' decays accumulated in the BES II detector at the Beijing Electron-Positron Collider.

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BES Collaboration, M. Ablikim. 2004-05-18. Observation of a threshold enhancement in the p \bar{Lambda} invariant mass spectrum. https://doi.org/10.1103/physrevlett.93.112002

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