Study of e + e − → γ ω J / ψ and Observation of X ( 3872 ) → ω J / ψ

BESIII Collaboration, Evelina Gersabeck

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Abstract

We study the e+e−→γωJ/ψ process using 11.6  fb−1 e+e− annihilation data taken at center-of-mass energies from √s=4.008  GeV to 4.600 GeV with the BESIII detector at the BEPCII storage ring. The X(3872) resonance is observed for the first time in the ωJ/ψ system with a significance of more than 5σ. The relative decay ratio of X(3872)→ωJ/ψ and π+π−J/ψ is measured to be R=1.6+0.4−0.3±0.2, where the first uncertainty is statistical and the second systematic (the same hereafter). The √s-dependent cross section of e+e−→γX(3872) is also measured and investigated, and it can be described by a single Breit-Wigner resonance, referred to as the Y(4200), with a mass of 4200.6+7.9−13.3±3.0  MeV/c2 and a width of 115+38−26±12  MeV. In addition, to describe the ωJ/ψ mass distribution above 3.9  GeV/c2, we need at least one additional Breit-Wigner resonance, labeled as X(3915), in the fit. The mass and width of the X(3915) are determined. The resonant parameters of the X(3915) agree with those of the Y(3940) in B→KωJ/ψ and of the X(3915) in γγ→ωJ/ψ observed by the Belle and BABAR experiments within errors.
Original languageEnglish
JournalPhysical Review Letters
Early online date14 Jun 2019
DOIs
Publication statusPublished - 2019

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