Determination of Vub from a simultaneous study of untagged Btopilnu and Btorholnu decays at Belle II

Abstract We present a measurement of Vub from a simultaneous study of the charmless semileptonic decays Btopilnu and Btorholnu, where ell = e, \mu, using 387 million pairs of BB mesons recorded by the Belle II detector at the SuperKEKB electron-positron collider between 2019 and 2022. The decays are reconstructed without identifying the partner B mesons. We simultaneously measure the differential branching fractions as functions of q^2 (momentum transfer squared) of Btopilnu and Btorholnu using x and x decays, respectively. We find total branching fractions B(Btopilnu) = x and B(Btorholnu) = x. By fitting the measured Btopilnu partial branching fractions as functions of q^2, together with constraints on the nonperturbative hadronic contribution from lattice QCD calculations, we measure Vub = x. Here, the first uncertainty is statistical, the second is systematic, and the third is theoretical. Upon including constraints from light-cone sum rule calculations, we obtain Vub = x. From a simultaneous fit to the Btorholnu partial branching fractions as functions of q^2 and constraints from light-cone sum rule calculations, we determine Vub = x.
Tags
Working group Semileptonic and Missing Energy Decay
Principal authors @  Florian Bernlochner, Jochen Dingfelder, Svenja Granderath, Peter Lewis
Reference Phys.Rev.D 111, 112009 (2025), DOI: 10.1103/jnwn-ts6q
Document BELLE2-PUB-DRAFT-2023-010
Links arXiv:2407.17403, Inspire,
Bibtex 
@article{Belle-II:2024xwh,
    author = "Adachi, I. and others",
    collaboration = "Belle-II",
    title = "{Determination of |Vub| from simultaneous measurements of untagged B0{\textrightarrow}{\ensuremath{\pi}}-{\ensuremath{\ell}}+{\ensuremath{\nu}}{\ensuremath{\ell}} and B+{\textrightarrow}{\ensuremath{\rho}}0{\ensuremath{\ell}}+{\ensuremath{\nu}}{\ensuremath{\ell}} decays}",
    eprint = "2407.17403",
    archivePrefix = "arXiv",
    primaryClass = "hep-ex",
    reportNumber = "Belle II Preprint 2024-023, KEK Preprint 2024-21",
    doi = "10.1103/jnwn-ts6q",
    journal = "Phys. Rev. D",
    volume = "111",
    number = "11",
    pages = "112009",
    year = "2025"
}