Probing $R$-parity violation in $B$-meson decays to a baryon and a light neutralino

Abstract

We propose a search for B meson decays to a proton or a hyperon plus missing energy at the Belle II experiment to probe supersymmetry with a GeV-scale lightest neutralino χ01 and R-parity violation (RPV). We perform analytic computations of the signal branching fractions in the framework of effective field theory, with a single nonzero RPV operator λ 1j3 Ū c 1 Dc j Dc 3 , where j = 1, 2. The hadronic form factors are calculated using an SU(3) phenomenological Lagrangian approach. Since the decay of the neutralino is kinematically and CKM suppressed in this theoretical scenario, it decays outside the detector and appears experimentally only as missing energy. We detail the analysis techniques at the experimental level and estimate the background in the B + → p χ01 search using published results for B + → K + ν ν. Our final sensitivity plots are shown for both λ 113 versus the squark mass m q and λ 113 /m 2 q versus the neutralino mass m χ0 1 . We find that the search at Belle II could probe λ 113 /m 2 q down to the order of 10 −8 GeV −2 in the kinematically allowed m χ0 1 range. We also obtain current limits on B 0 → Λ 0 χ0 1 by recasting an existing search, and comment about searches for B + → Σ + χ01 and B 0 → Σ 0 χ0 1 . In closing, we briefly discuss potential searches at the LHCb and BESIII experiments.

Searching for light neutralinos with a displaced vertex at the LHC

“…If either the lightest neutralino is light or the RPV couplings are small enough, the lightest neutralino becomes long-lived and may be searched for at collider, beam-dump experiments and even atmospheric neutrino detectors [37]. Phenomenological studies on the exclusion limits in the same scenario already exist from the planned SHiP experiment [38,39], proposed LHC far detectors [40][41][42][43][44][45], Belle II [46,47], and future lepton colliders [48,49]. These works mainly focus on the lightest neutralino produced from either B-or D-mesons decays, or Z-boson decays, constraining masses below ∼ 45 GeV.…”