Measurements of the mass difference m(B0) − m(B+) and the energy dependence of the cross-section ratio $$\sigma ({e}^{+}{e}^{-}\to {B}^{0}{\overline{B} }^{0})/\sigma ({e}^{+}{e}^{-}\to {B}^{+}{B}^{-})$$ at Belle and Belle II

Le résumé fourni par la source

A bstract Using data samples collected by the Belle and Belle II experiments at the Υ(4 S ) resonance with integrated luminosities of 571 fb − 1 and 365 fb − 1 , respectively, we measure the pseudoscalar B -meson mass difference to be m ( B 0 ) − m ( B + ) = (0 . 495 ± 0 . 024 ± 0 . 005) MeV/ c 2 . The results are based on a simultaneous fit to the variable $${\overline{M} }_{bc}$$ , which is related to the B momentum, for B 0 and B + candidates; and to the energy dependence of $$\mathcal{R}=\sigma ({e}^{+}{e}^{-}\to {B}^{0}{\overline{B} }^{0}) / \sigma ({e}^{+}{e}^{-}\to {B}^{+}{B}^{-})$$ , which is measured using changes in the average center-of-mass energy over the data taking periods. The phase-space hypothesis $$\mathcal{R}={({p}_{{B}^{0}} /{p}_{{B}^{+}})}^{3}$$ , upon which previous measurements rely, is strongly disfavored by our fit; the measured mass-difference value for the phase-space hypothesis also differs significantly from our measurement. We constrain $$\mathcal{R}$$ in a broader energy range than covered by the direct measurement and extract the energy dependence of $$\mathcal{R}$$ in the range from the $$B\overline{B }$$ threshold up to 10.59 GeV. We interpret the results using a phenomenological model and constrain the parameters of the $$B\overline{B }$$ potential in the isovector channel.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.