Bounds on the width, mass difference and other properties of X(3872) → π+π-J/ψ decays

The Belle Collaboration

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We present results from a study of X(3872) → ππJ/ψ decays produced via exclusive B → KX(3872) decays. We determine the mass to be MX(3872)= (3871.85 ± 0.27(stat) ± 0.19(syst)) MeV, a 90% confidence level upper limit on the natural width of ΓX(3872)< 1.2 MeV, the product branching fraction B(B+→ K+X(3872)) X B(X(3872) → π+π-J/ψ) = (8.63±0.82(stat)±0.52(syst)) × 10-6, and a ratio of branching fractions B(B0→ K0X(3872))/B(B+→ K+X(3872)) = 0.50±0.14(stat) ±0.04(syst). The difference in mass between the X(3872) → π+π-J/ψ signals in B+and B0decays is ΔMX(3872)= (-0.71 ± 0.96(stat) ± 0.19(syst)) MeV. A search for a charged partner of the X(3872) in the decays B¯0→ K-X+or B+→ K0X+, X+→ π+π0J/ψ resulted in upper limits on the product branching fractions for these processes that are well below expectations for the case that the X(3872) is the neutral member of an isospin triplet. In addition, we examine possible JPCquantum number assignments for the X(3872) based on comparisons of angular correlations between final state particles in X(3872) → π+π-J/ψ decays with simulated data for JPCvalues of 1++and 2-+. We examine the influence of ρ-ω interference in the M(π+π-) spectrum. The analysis is based on a 711 fb-1data sample that contains 772 × 106BB¯ meson pairs collected at the Γ(4S) resonance in the Belle detector at the KEKB e+e-collider.

Original languageEnglish
Article number052004
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Issue number5
Publication statusPublished - 2011 Sept 7

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Physics and Astronomy (miscellaneous)


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