Observation of an Excited Bc+ State

(LHCb Collaboration)

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

Using pp collision data corresponding to an integrated luminosity of 8.5 fb-1 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.

Original languageEnglish
Article number232001
JournalPhysical Review Letters
Volume122
Issue number23
DOIs
Publication statusPublished - 11 Jun 2019

Funding

We thank Chao-Hsi Chang and Xing-Gang Wu for frequent and interesting discussions on the production of the mesons. We express our gratitude to our colleagues in the CERN accelerator departments for the excellent performance of the LHC. We thank the technical and administrative staff at the LHCb institutes. We acknowledge support from CERN and from the national agencies: CAPES, CNPq, FAPERJ and FINEP (Brazil); MOST and NSFC (China); CNRS/IN2P3 (France); BMBF, DFG and MPG (Germany); INFN (Italy); NWO (Netherlands); MNiSW and NCN (Poland); MEN/IFA (Romania); MSHE (Russia); MinECo (Spain); SNSF and SER (Switzerland); NASU (Ukraine); STFC (United Kingdom); NSF (USA). We acknowledge the computing resources that are provided by CERN, IN2P3 (France), KIT and DESY (Germany), INFN (Italy), SURF (Netherlands), PIC (Spain), GridPP (United Kingdom), RRCKI and Yandex LLC (Russia), CSCS (Switzerland), IFIN-HH (Romania), CBPF (Brazil), PL-GRID (Poland) and OSC (USA). We are indebted to the communities behind the multiple open-source software packages on which we depend. Individual groups or members have received support from AvH Foundation (Germany); EPLANET, Marie Skłodowska-Curie Actions and ERC (European Union); ANR, Labex P2IO and OCEVU, and Région Auvergne-Rhóne-Alpes (France); Key Research Program of Frontier Sciences of CAS, CAS PIFI, and the Thousand Talents Program (China); RFBR, RSF and Yandex LLC (Russia); GVA, XuntaGal and GENCAT (Spain); the Royal Society and the Leverhulme Trust (United Kingdom); Laboratory Directed Research and Development program of LANL (USA).

FundersFunder number
Not addedST/J004332/1, ST/N000250/1, ST/K003410/1, 1796908, ST/N000331/1, ST/L003163/1, ST/N000242/1
EPLANET
Key Research Program of Frontier Sciences of CAS
MSHE
OCEVU
XuntaGal
Yandex LLC
National Science Foundation
Alexander von Humboldt-Stiftung
Laboratory Directed Research and Development
Los Alamos National Laboratory
Horizon 2020 Framework Programme792684
H2020 Marie Skłodowska-Curie Actions
CERN
Science and Technology Facilities CouncilST/N000234/1, GRIDPP
Leverhulme Trust
Royal Society
European Research Council
Deutsche Forschungsgemeinschaft
Agence Nationale de la Recherche
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
National Natural Science Foundation of China
Russian Foundation for Basic Research
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Bundesministerium für Bildung und Forschung
Chinese Academy of Sciences
Nederlandse Organisatie voor Wetenschappelijk Onderzoek
Generalitat Valenciana
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Instituto Nazionale di Fisica Nucleare
Narodowe Centrum Nauki
Ministerstwo Nauki i Szkolnictwa Wyższego
Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro
Ministry of Science and Technology, Taiwan
National Academy of Sciences of Ukraine
Centre National de la Recherche Scientifique
Financiadora de Estudos e Projetos
Russian Science Foundation
Région Auvergne-Rhône-Alpes
Recruitment Program of Global Experts
Institut national de physique nucléaire et de physique des particules
Sociedad Española de Reumatología

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