• Open Access

Observation of an Excited Bc+ State

R. Aaij et al. (LHCb Collaboration)
Phys. Rev. Lett. 122, 232001 – Published 11 June 2019

Abstract

Using pp collision data corresponding to an integrated luminosity of 8.5fb1 recorded by the LHCb experiment at center-of-mass energies of s=7, 8, and 13 TeV, the observation of an excited Bc+ state in the Bc+π+π invariant-mass spectrum is reported. The observed peak has a mass of 6841.2±0.6(stat)±0.1(syst)±0.8(Bc+)MeV/c2, where the last uncertainty is due to the limited knowledge of the Bc+ mass. It is consistent with expectations of the Bc*(2S31)+ state reconstructed without the low-energy photon from the Bc*(1S31)+Bc+γ decay following Bc*(2S31)+Bc*(1S31)+π+π. A second state is seen with a global (local) statistical significance of 2.2σ (3.2σ) and a mass of 6872.1±1.3(stat)±0.1(syst)±0.8(Bc+)MeV/c2, and is consistent with the Bc(2S10)+ state. These mass measurements are the most precise to date.

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  • Received 29 March 2019
  • Revised 23 April 2019

DOI:https://doi.org/10.1103/PhysRevLett.122.232001

Published by the American Physical Society under the terms of the 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 SCOAP3.

© 2019 CERN, for the LHCb Collaboration

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Vol. 122, Iss. 23 — 14 June 2019

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