More Like this

1. Study of the muon decay-in-flight in the ${\tau }^{-}\to {\mu }^{-}{\overline{\nu }}_{\mu }{\nu }_{\tau }$ decay to measure the Michel parameter ${\xi }^{\prime }$

   https://doi.org/10.1103/PhysRevD.108.012003  

   Bodrov, D; Pakhlov, P; Adachi, I; Aihara, H; Al_Said, S; Asner, D M; Atmacan, H; Aushev, T; Ayad, R; Babu, V; et al (July 2023, Physical Review D)
2. Search for $B^{-}\to {\mu }^{-}{\overline{\nu }}_{\mu }$ Decays at the Belle Experiment

   https://doi.org/10.1103/PhysRevLett.121.031801  

   Sibidanov, A.; Varvell, K. E.; Adachi, I.; Aihara, H.; Al Said, S.; Asner, D. M.; Aushev, T.; Ayad, R.; Babu, V.; Badhrees, I.; et al (July 2018, Physical Review Letters)
3. Measurement of the $\tau$ lepton polarization and $R\left(D^{*}\right)$ in the decay $\overline{B}\to D^{*}{\tau }^{-}{\overline{\nu }}_{\tau }$ with one-prong hadronic $\tau$ decays at Belle

   https://doi.org/10.1103/PhysRevD.97.012004  

   Hirose, S.; Iijima, T.; Adachi, I.; Adamczyk, K.; Aihara, H.; Al Said, S.; Asner, D. M.; Atmacan, H.; Aushev, T.; Ayad, R.; et al (January 2018, Physical Review D)

   null (Ed.)
4. Study of $B^{+}\to {\mu }^{+}{\nu }_{\mu }$ decays at Belle and Belle II

   https://doi.org/10.1103/zxyy-3znn  

   Abumusabh, M; Adachi, I; Adamczyk, K; Aggarwal, A; Aggarwal, L; Ahmed, H; Ahn, Y; Aihara, H; Akopov, N; Alghamdi, S; et al (June 2026, Physical Review D)

   We report a measurement of the branching fraction for the leptonic decay $B^{+}\to {\mu }^{+}{\nu }_{\mu }$. This work presents the first $B^{+}\to {\mu }^{+}{\nu }_{\mu }$result using Belle II data, an updated Belle measurement that supersedes the previous result, and their combination, which yields the most precise search to date. The analysis is based on $1076{\mathrm{fb}}^{-1}$of $e^{+}{e}^{-}$collision data collected at a center-of-mass energy of 10.58 GeV with the Belle and Belle II detectors at the KEKB and SuperKEKB colliders, respectively. We measure $\mathcal{B}(B^{+}\to {\mu }^{+}{\nu }_{\mu })=(4.4\pm 1.9\pm 1.0)\times {10}^{-7}$, where the first uncertainty is statistical and the second systematic. The observed significance relative to the background-only hypothesis is 2.4 standard deviations. We set a 90% confidence level upper limit of $\mathcal{B}(B^{+}\to {\mu }^{+}{\nu }_{\mu })<6.7\times {10}^{-7}$using a frequentist approach and a 90% credibility level upper limit of $\mathcal{B}(B^{+}\to {\mu }^{+}{\nu }_{\mu })<7.2\times {10}^{-7}$using a Bayesian approach. These are the most stringent limits to date. The result is interpreted as an exclusion region in the parameter space of type II and type III two-Higgs-doublet models. We search for stable sterile neutrinos with masses $m_N\in [0,1.5]\mathrm{GeV}$. No signal is observed, and the resulting exclusion on the squared mixing parameter $|U_{\mu N}{|}^2$provides improvement over previous limits. We report a measurement of the partial branching fraction of semileptonic $B\to X_u\ell {\nu }_{\ell }$decays with $p_{\mu }^B>2.2\mathrm{GeV}$, obtaining $\mathrm{\Delta }\mathcal{B}(B\to X_u\ell {\nu }_{\ell })=(2.72\pm 0.05\pm 0.29)\times {10}^{-4}$. We present a model-dependent study of weak annihilation decays using the muon momentum spectrum. We observe a signal of 2.4 standard deviations above the background-only hypothesis in regions where the distribution resembles that of $B\to X_u\ell {\nu }_{\ell }$decays. 

   more » « less
5. Effective-field theory analysis of the ${\tau }^{-}\to K^{-}({\eta }^{(\prime )},K^0){\nu }_{\tau }$ decays

   https://doi.org/10.1103/PhysRevD.101.034010  

   Gonzàlez-Solís, Sergi; Miranda, Alejandro; Rendón, Javier; Roig, Pablo (February 2020, Physical Review D)