Observation of Two Excited B⁺_c States and Measurement of the B⁺_c (2S) Mass in pp Collisions at √s = 13 TeV

Authors

A. M. Sirunyan, CMS Collaboration

Date of this Version

4-2-2019

Citation

PHYSICAL REVIEW LETTERS 122, 132001 (2019). DOI: 10.1103/PhysRevLett.122.132001

Comments

Used by permission.

Abstract

Signals consistent with the B⁺_c (2S) and B*_c⁺(2S) states are observed in proton-proton collisions at √s = 13 TeV, in an event sample corresponding to an integrated luminosity of 143 fb⁻¹, collected by the CMS experiment during the 2015–2018 LHC running periods. These excited []c states are observed in the B⁺_c π⁺π⁻ invariant mass spectrum, with the ground state B⁺_c reconstructed through its decay to J/ψπ⁺. The two states are reconstructed as two well-resolved peaks, separated in mass by 29.1 ± 1.5(stat) ± 0.7(syst) MeV. The observation of two peaks, rather than one, is established with a significance exceeding five standard deviations. The mass of the B⁺_c (2S) meson is measured to be 6871.0 ± 1.2(stat) ± 0.8(syst) ± 0.8(B⁺_c) MeV, where the last term corresponds to the uncertainty in the world-average B⁺_c mass.