### Abstract

The decays B^{+}→ J/ψπ^{+}π^{−}K^{+} 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 ψ_{2}(3823), χ_{c1}(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^{+}→ ψ_{2}(3823)K^{+} with ψ_{2}(3823) → J/ψπ^{+}π^{−} is observed for the first time with a significance of 5.1 standard deviations. The mass differences between the ψ_{2}(3823), χ_{c1}(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 χ_{c1}(3872) mass. The width of the ψ_{2}(3823) state is found to be below 5.2 MeV at 90% confidence level. The Breit-Wigner width of the χ_{c1}(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 language | English |
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Article number | 123 |

Journal | Journal of High Energy Physics |

Volume | 2020 |

Issue number | 8 |

DOIs | |

Publication status | Published - 1 Aug 2020 |

### Keywords

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

### ASJC Scopus subject areas

- Nuclear and High Energy Physics

## Fingerprint Dive into the research topics of 'Study of the ψ <sub>2</sub>(3823) and χ <sub>c1</sub>(3872) states in B<sup>+</sup> → (J/ψπ <sup>+</sup> π <sup> −</sup>)K<sup>+</sup> decays'. Together they form a unique fingerprint.

## Cite this

_{2}(3823) and χ

_{c1}(3872) states in B

^{+}→ (J/ψπ

^{+}π

^{ −})K

^{+}decays.

*Journal of High Energy Physics*,

*2020*(8), [123]. https://doi.org/10.1007/JHEP08(2020)123