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

(BESIII Collaboration)

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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

Bibliographical note

Funding Information:
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 - Ξ ¯ + by means of a single baryon-tag method. After performing a fit to the dressed cross section of e + e - → Ξ - Ξ ¯ + , no significant ψ ( 4230 ) or ψ ( 4260 ) resonance is observed in the Ξ - Ξ ¯ + final states, and upper limits at the 90% confidence level on Γ e e B for the processes ψ ( 4230 ) / ψ ( 4260 ) → Ξ - Ξ ¯ + are determined. In addition, an excited Ξ baryon at 1820     MeV / c 2 is observed with a statistical significance of 6.2 – 6.5 σ by including the systematic uncertainty, and the mass and width are measured to be M = ( 1825.5 ± 4.7 ± 4.7 )     MeV / c 2 and Γ = ( 17.0 ± 15.0 ± 7.9 )     MeV , which confirms the existence of the J P = 3 2 - state Ξ ( 1820 ) . National Key Basic Research Program of China 10.13039/501100012166 2015CB856700 China Postdoctoral Science Foundation 10.13039/501100002858 2018M630206 National Natural Science Foundation of China 10.13039/501100001809 11521505 11625523 11635010 11675184 11705209 11735014 11822506 11835012 11875115 11905236 Chinese Academy of Sciences 10.13039/501100002367 U1532257 U1532258 U1732263 U1832207 National 1000 Talents Program of China CAS Key Research Program of Frontier Sciences QYZDJ-SSW-SLH003 QYZDJ-SSW-SLH040 100 Talents Program of CAS Institute of Nuclear and Particle Physics, Astronomy and Cosmology Shanghai Key Laboratory for Particle Physics and Cosmology H2020 European Research Council 10.13039/100010663 758462 Deutsche Forschungsgemeinschaft 10.13039/501100001659 CRC 1044 FOR 2359 Istituto Nazionale di Fisica Nucleare 10.13039/501100004007 Koninklijke Nederlandse Akademie van Wetenschappen 10.13039/501100001722 530-4CDP03 Ministry of Development of Turkey DPT2006K-120470 National Science and Technology fund Science and Technology Facilities Council 10.13039/501100000271 Knut och Alice Wallenbergs Stiftelse 10.13039/501100004063 2016.0157 Royal Society 10.13039/501100000288 DH140054 DH160214 Vetenskapsrådet 10.13039/501100004359 U.S. Department of Energy 10.13039/100000015 DE-FG02-05ER41374 DE-SC-0010118 DE-SC-0012069 University of Groningen (RuG) Helmholtzzentrum fuer Schwerionenforschung GmbH (GSI) 10.13039/501100010958

Funding Information:
The BESIII Collaboration thanks the staff of BEPCII and the IHEP computing center for their strong support. This work is supported in part by National Key Basic Research Program of China under Contract No. 2015CB856700; China Postdoctoral Science Foundation under Contract No. 2018M630206; National Natural Science Foundation of China (NSFC) under Contracts No. 11521505, No. 11625523, No. 11635010, No. 11675184, No. 11705209, No. 11735014, No. 11822506, No. 11835012, No. 11875115, No. 11905236; Chinese Academy of Science Focused Science Grant; National 1000 Talents Program of China; the Chinese Academy of Sciences (CAS) Large-Scale Scientific Facility Program; Joint Large-Scale Scientific Facility Funds of the NSFC and CAS under Contracts No. U1532257, No. U1532258, No. U1732263, No. U1832207; CAS Key Research Program of Frontier Sciences under Contracts No. QYZDJ-SSW-SLH003, No. QYZDJ-SSW-SLH040; 100 Talents Program of CAS; Institute of Nuclear and Particle Physics, Astronomy and Cosmology (INPAC) and Shanghai Key Laboratory for Particle Physics and Cosmology; ERC under Contract No. 758462; German Research Foundation DFG under Contracts Nos. Collaborative Research Center CRC 1044, FOR 2359; Istituto Nazionale di Fisica Nucleare, Italy; Koninklijke Nederlandse Akademie van Wetenschappen (KNAW) under Contract No. 530-4CDP03; Ministry of Development of Turkey under Contract No. DPT2006K-120470; National Science and Technology fund; STFC (United Kingdom); The Knut and Alice Wallenberg Foundation (Sweden) under Contract No. 2016.0157; The Royal Society, UK under Contracts No. DH140054, No. DH160214; The Swedish Research Council; U.S. Department of Energy under Contracts No. DE-FG02-05ER41374, No. DE-SC-0010118, No. DE-SC-0012069; University of Groningen (RuG) and the Helmholtzzentrum fuer Schwerionenforschung GmbH (GSI), Darmstadt.

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© 2020 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP.

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