• Accepted Paper

First measurement of the masses of the Υ1(1D) and Υ3(1D) states and the energy dependence of the cross sections for e+e−→ΥJ(1D)η and e+e−→ΥJ(1D)π+π−

M. Abumusabh et al.

Phys. Rev. Lett. - Accepted 20 October, 2026

DOI: https://doi.org/10.1103/9wrm-99hg

Abstract

We study the processes e+e−→ΥJ(1D)η and e+e−→ΥJ(1D)π+π− at center-of-mass energies s=(10.73 – 11.02) GeV using a 142.5fb−1 data sample, including 122~fb−1 near the Υ(10860) peak (s = 10.866 GeV), collected with the Belle detector at the KEKB asymmetric-energy e+e− collider. From the peak sample, the products of Born cross section times branching fraction are obtained for $\sigma_{\rm Born}(e^+e^-\to\Upsilon_J(1D)\eta)$ or $\sigma_{\rm Born}(e^+e^-\to\Upsilon_J(1D)\pi^+\pi^-)$ and ${\cal B}(\Upsilon_J(1D)\to\chi_{b1}\gamma)$ or ${\cal B}(\Upsilon_J(1D)\to\chi_{b2}\gamma)$ for each ΥJ(1D) state. The corresponding branching fractions for Υ(10860) decays are also obtained. The significances of the Υ1(1D), Υ2(1D), and Υ3(1D) signals are 4.8σ, >10σ, and 3.0σ, respectively, including systematic uncertainties. The mass for Υ2(1D) is measured to be (10167.0±1.0±0.2) MeV/c2, where the first and second uncertainties are statistical and systematic. The mass splittings Δm12=m(Υ2(1D))−m(Υ1(1D)) and Δm23=m(Υ3(1D))−m(Υ2(1D)) are (11.8±1.5±0.4) MeV/c2 and (7.6±2.4±0.6) MeV/c2, respectively. We determine the energy dependence of the cross sections for e+e−→ΥJ(1D)η and e+e−→ΥJ(1D)π+π− for the Υ1(1D), Υ2(1D), and Υ3(1D) states, combined.

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