Recent Belle II results on BSM physics

TL;DR

This paper presents recent Belle II experiment results on BSM physics, including tests of lepton-flavor universality violations in B-meson decays and searches for new particles in dark sector models, based on 189 fb$^{-1}$ of data.

Contribution

It reports novel measurements of lepton-flavor universality and searches for long-lived particles, advancing the experimental exploration of physics beyond the standard model.

Findings

Evidence of lepton-flavor universality violation in B decays

Constraints on long-lived spin-0 particles in b→s transitions

Implications for dark sector models

Abstract

We report on recent results obtained by the Belle II experiment related to searches for beyond-the-standard-model physics. The $B$ meson decay data sample used corresponds to an integrated luminosity of $L = 189$ fb$^{-1}$. In recent years, discrepancies from standard-model predictions, which suggest violation of lepton-flavor universality, have emerged in multiple measurements of $B$-meson decays. In this document two analyses aimed to search for violation of the light-lepton universality are reported: the inclusive $R(X_{e/\mu})$ measurement and an angular analysis of the $B^0 \to D^{*-} l^+ \nu_l$, with $l=e,\mu$, decays. In addition, beyond-the-standard-model physics can manifests itself with the production of new particles. The search for a long-lived spin-0 particle in $b\to s$ transitions, and its interpretation in two dark sector models, is reported.