Measurement of the Cross Section for e+e- → Ξ- Ξ ̄ + and Observation of an Excited Ξ Baryon

(BESIII Collaboration)

Research output: Contribution to journalArticle

Abstract

Using a total of 11.0 fb-1 of e+e- collision data with center-of-mass energies between 4.009 and 4.6 GeV and collected with the BESIII detector at BEPCII, we measure fifteen exclusive cross sections and effective form factors for the process e+e-→Ξ-Ξ̄+ by means of a single baryon-tag method. After performing a fit to the dressed cross section of e+e-→Ξ-Ξ̄+, no significant ψ(4230) or ψ(4260) resonance is observed in the Ξ-Ξ̄+ final states, and upper limits at the 90% confidence level on ΓeeB for the processes ψ(4230)/ψ(4260)→Ξ-Ξ̄+ are determined. In addition, an excited Ξ baryon at 1820 MeV/c2 is observed with a statistical significance of 6.2-6.5σ by including the systematic uncertainty, and the mass and width are measured to be M=(1825.5±4.7±4.7) MeV/c2 and Γ=(17.0±15.0±7.9) MeV, which confirms the existence of the JP=32- state Ξ(1820).

Original languageEnglish (US)
Article number032002
JournalPhysical review letters
Volume124
Issue number3
DOIs
StatePublished - Jan 24 2020

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