articlePhysical Review LettersSep 28, 2005LVBRONZE OA

Observation of a Broad Structure in the π + π − J / ψ Mass Spectrum around 4.26     GeV / c 2

Laboratoire d’Annecy de Physique des Particules · Universitat Autònoma de Barcelona · +85 more institutions

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Abstract

We study initial-state radiation events, e+ e- --> gammaISR pi+ pi- J/psi, with data collected with the BABAR detector. We observe an accumulation of events near 4.26 GeV/c2 in the invariant-mass spectrum of pi+ pi- J/psi. Fits to the mass spectrum indicate that a broad resonance with a mass of about 4.26 GeV/c2 is required to describe the observed structure. The presence of additional narrow resonances cannot be excluded. The fitted width of the broad resonance is 50 to 90 MeV/c2, depending on the fit hypothesis.

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