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

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 M_X(3872)= (3871.85 ± 0.27(stat) ± 0.19(syst)) MeV, a 90% confidence level upper limit on the natural width of Γ_X(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 ΔM_X(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 J^PCquantum 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 J^PCvalues 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.