000001731 001__ 1731
000001731 005__ 20191010130714.0
000001731 037__ $$aBELLE2-TALK-CONF-2019-138
000001731 041__ $$aeng
000001731 088__ $$aBELLE2-TALK-DRAFT-2019-133
000001731 100__ $$aEiichi Nakano
000001731 245__ $$aB Leptonic Decay
000001731 260__ $$a2019 Lattice X Workshop$$c2019-09-23
000001731 300__ $$amult. p
000001731 500__ $$a30 min
000001731 520__ $$aThe search for the leptonic decay of B+ → μ+ νμ using the full Belle data set of 711 fb−1 of integrated luminosity near the Υ(4S) resonance is described. In the Standard Model leptonic B meson decays are helicity and CKM suppressed and to maximize sensitivity an inclusive tagging approach is used in this measurement to reconstruct the second B meson produced in the collision. The directional information is used after a dedicated calibration to boost the signal-side μ into the frame, where the signal B meson is at rest. This improves the sensitivity of the analysis considerably as in this frame the signal μ possesses a monochromatic momentum, which is smeared by the experimental resolution. Analyzing the μ momentum spectrum in this frame we find B(B+ → μ+ νμ) = (5.3 ± 2.0 ± 0.9) × 10−7 with a one-sided significance of 2.8 standard deviations over the background only hypothesis. This translates to a frequentist upper limit of B(B+ → μ+ νμ) < 8.6 × 10−7 at 90% CL. The experimental spectrum is then used to search for a massive sterile neutrino, B+ → μ+ N, finding no evidence for such a process for the range of 0 - 1.5 GeV of the sterile neutrino mass. The determined B+ → μ+ νμ branching fraction limit is further used to constrain the mass and coupling space of the type II and type III two Higgs doublet model.
000001731 8560_ $$fdoris.yangsoo.kim@desy.de
000001731 8564_ $$uhttps://docs.belle2.org/record/1731/files/BELLE2-TALK-CONF-2019-138.pdf