Zurich Open Repository and Archive University of Zurich Main Library Strickhofstrasse 39 CH-8057 Zurich www.zora.uzh.ch Year: 2014 Observation of a peaking structure in the J/psi phi mass spectrum from B+/- to J/psi phi K+/- decays CMS Collaboration ; Chatrchyan, S ; Khachatryan, V ; Sirunyan, A M ; et al ; Chiochia, V ; Kilminster, B ; Robmann, P Abstract: A peaking structure in the J/psi phi mass spectrum near threshold is observed in B(+/-) to J/psi phi K(+/-) decays, produced in pp collisions at sqrt(s) = 7 TeV collected with the CMS detector at the LHC. The data sample, selected on the basis of the dimuon decay mode of the J/psi, corresponds to an integrated luminosity of 5.2 inverse femtobarns. Fitting the structure to an S-wave relativistic Breit-Wigner lineshape above a three-body phase-space nonresonant component gives a signal statistical signifcance exceeding fve standard deviations. The ftted mass and width values are m=4148.0 +/- 2.4 (stat.) +/- 6.3 (syst.) MeV and Gamma=28 -11+15 (stat.) +/- 19 (syst.) MeV, respectively. Evidence for an additional peaking structure at higher J/psi phi mass is also reported. DOI: https://doi.org/10.1016/j.physletb.2014.05.055 Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-92232 Journal Article Accepted Version Originally published at: CMS Collaboration; Chatrchyan, S; Khachatryan, V; Sirunyan, A M; et al; Chiochia, V; Kilminster, B; Robmann, P (2014). Observation of a peaking structure in the J/psi phi mass spectrum from B+/- to J/psi phi K+/- decays. Physics Letters B, 734:261-281. DOI: https://doi.org/10.1016/j.physletb.2014.05.055