Study of the ψ 2(3823) and χ c1(3872) states in B+ → (J/ψπ + π )K+ decays

The LHCb Collaboration

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Abstract

The decays B+→ J/ψπ+πK+ are studied using a data set corresponding to an integrated luminosity of 9 fb−1 collected with the LHCb detector in proton-proton collisions between 2011 and 2018. Precise measurements of the ratios of branching fractions with the intermediate ψ2(3823), χc1(3872) and ψ(2S) states are reported. The values areBB+→ψ2(3823)K+×Bψ2(3823)→J/ψπ+π−BB+→χc1(3872)K+×Bχc1(3872)→J/ψπ+π−=(3.56±0.67±0.11)×10−2,BB+→ψ2(3823)K+×Bψ2(3823)→J/ψπ+π−BB+→ψ(2S)K+×Bψ(2S)→J/ψπ+π−=(1.31±0.25±0.04)×10−3,BB+→χc1(3872)K+×Bχc1(3872)→J/ψπ+π−BB+→ψ(2S)K+×Bψ(2S)→J/ψπ+π−=(3.69±0.07±0.06)×10−2, where the first uncertainty is statistical and the second is systematic. The decay of B+→ ψ2(3823)K+ with ψ2(3823) → J/ψπ+π is observed for the first time with a significance of 5.1 standard deviations. The mass differences between the ψ2(3823), χc1(3872) and ψ(2S) states are measured to be mχc1(3872)−mψ2(3823)=47.50±0.53±0.13MeV/c2,mψ2(3823)−mψ2(2S)=137.98±0.53±0.14MeV/c2,mχc1(3872)−mψ2(2S)=185.49±0.06±0.03MeV/c2, resulting in the most precise determination of the χc1(3872) mass. The width of the ψ2(3823) state is found to be below 5.2 MeV at 90% confidence level. The Breit-Wigner width of the χc1(3872) state is measured to be Γχc1(3872)BW=0.96−0.18+0.19±0.21MeV which is inconsistent with zero by 5.5 standard deviations. [Figure not available: see fulltext.]

Original languageEnglish
Article number123
JournalJournal of High Energy Physics
Volume2020
Issue number8
DOIs
Publication statusPublished - 1 Aug 2020

Keywords

  • B physics
  • Branching fraction
  • Hadron-Hadron scattering (experiments)
  • Quarkonium
  • Spectroscopy

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

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