Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 2108.11649

Search for $B^{0} \to \tau^\pm \ell^\mp$ ($\ell=e,\mu$) with a hadronic tagging method at Belle

Belle Collaboration·H. Atmacan·A. J. Schwartz·K. Kinoshita·I. Adachi·K. Adamczyk·H. Aihara·S. Al Said·D. M. Asner·V. Aulchenko·T. Aushev·R. Ayad·V. Babu·S. Bahinipati·M. Bauer·P. Behera·K. Belous·J. Bennett·F. Bernlochner·M. Bessner·V. Bhardwaj·B. Bhuyan·T. Bilka·J. Biswal·A. Bobrov·A. Bozek·M. Bračko·P. Branchini·T. E. Browder·A. Budano·M. Campajola·L. Cao·D. Červenkov·M. -C. Chang·P. Chang·V. Chekelian·A. Chen·B. G. Cheon·K. Chilikin·H. E. Cho·K. Cho·S. -K. Choi·Y. Choi·S. Choudhury·D. Cinabro·S. Cunliffe·S. Das·N. Dash·G. De Nardo·G. De Pietro·R. Dhamija·F. Di Capua·J. Dingfelder·Z. Doležal·T. V. Dong·S. Dubey·D. Epifanov·T. Ferber·D. Ferlewicz·A. Frey·B. G. Fulsom·R. Garg·V. Gaur·N. Gabyshev·A. Garmash·A. Giri·P. Goldenzweig·E. Graziani·D. Greenwald·T. Gu·Y. Guan·K. Gudkova·C. Hadjivasiliou·S. Halder·T. Hara·O. Hartbrich·K. Hayasaka·H. Hayashii·W. -S. Hou·C. -L. Hsu·K. Inami·G. Inguglia·A. Ishikawa·R. Itoh·M. Iwasaki·Y. Iwasaki·W. W. Jacobs·S. Jia·Y. Jin·K. K. Joo·A. B. Kaliyar·K. H. Kang·Y. Kato·T. Kawasaki·C. Kiesling·C. H. Kim·D. Y. Kim·K. -H. Kim·S. H. Kim·Y. -K. Kim
View original source ↗Read source document ↗Export metadata ↓

Abstract

We present a search for the lepton-flavor-violating decays $B^{0} \to \tau^\pm \ell^\mp$, where $\ell=(e,\,\mu)$, using the full data sample of $772 \times 10^6$ $B \overline{B}$ pairs recorded by the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. We use events in which one $B$ meson is fully reconstructed in a hadronic decay mode. The $\tau^\pm$ lepton is reconstructed indirectly using the momentum of the reconstructed $B$ and that of the $\ell^\mp$ from the signal decay. We find no evidence for $B^{0} \to \tau^\pm \ell^\mp$ decays and set upper limits on their branching fractions at 90% confidence level of $\cal B$($B^{0} \to \tau^\pm \mu^{\mp}$)$ < 1.5 \times 10^{-5}$ and $\cal B$($B^{0} \to \tau^\pm e^{\mp}$)$ < 1.6 \times 10^{-5}$.

Explore related subjects

hep-ex

Keep this discovery

BibTeXRIS

Belle Collaboration, H. Atmacan, A. J. Schwartz, K. Kinoshita, I. Adachi, K. Adamczyk, H. Aihara, S. Al Said, D. M. Asner, V. Aulchenko, T. Aushev, R. Ayad, V. Babu, S. Bahinipati, M. Bauer, P. Behera, K. Belous, J. Bennett, F. Bernlochner, M. Bessner, V. Bhardwaj, B. Bhuyan, T. Bilka, J. Biswal, A. Bobrov, A. Bozek, M. Bračko, P. Branchini, T. E. Browder, A. Budano, M. Campajola, L. Cao, D. Červenkov, M. -C. Chang, P. Chang, V. Chekelian, A. Chen, B. G. Cheon, K. Chilikin, H. E. Cho, K. Cho, S. -K. Choi, Y. Choi, S. Choudhury, D. Cinabro, S. Cunliffe, S. Das, N. Dash, G. De Nardo, G. De Pietro, R. Dhamija, F. Di Capua, J. Dingfelder, Z. Doležal, T. V. Dong, S. Dubey, D. Epifanov, T. Ferber, D. Ferlewicz, A. Frey, B. G. Fulsom, R. Garg, V. Gaur, N. Gabyshev, A. Garmash, A. Giri, P. Goldenzweig, E. Graziani, D. Greenwald, T. Gu, Y. Guan, K. Gudkova, C. Hadjivasiliou, S. Halder, T. Hara, O. Hartbrich, K. Hayasaka, H. Hayashii, W. -S. Hou, C. -L. Hsu, K. Inami, G. Inguglia, A. Ishikawa, R. Itoh, M. Iwasaki, Y. Iwasaki, W. W. Jacobs, S. Jia, Y. Jin, K. K. Joo, A. B. Kaliyar, K. H. Kang, Y. Kato, T. Kawasaki, C. Kiesling, C. H. Kim, D. Y. Kim, K. -H. Kim, S. H. Kim, Y. -K. Kim. 2021-08-26. Search for $B^{0} \to \tau^\pm \ell^\mp$ ($\ell=e,\mu$) with a hadronic tagging method at Belle. https://arxiv.org/abs/2108.11649

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Production of Light Nuclei and Hypernuclei in Heavy-Ion Collisions

We review recent STAR and ALICE measurements of light-nucleus and hypernucleus yields, femtoscopic correlations, and collective flow presented at SQM 2026. Statistical-hadronization calculations provide a useful baseline for integrated yields but do not simultaneously describe all measured light-nucleus ratios across collision energies and system sizes. For bound states with mass number $A<4$, current coalescence calculations provide a broadly consistent description of yields, femtoscopic correlations, and collective flow, although the quantitative hypertriton comparison depends on the assumed few-body wave function. The suppressed production of resonant $^{4}$Li relative to compact $^{4}$He indicates an effect of nuclear structure and late-stage dynamics. However, the quantitative model comparison also depends on the treatment of feed-down from unstable states. In high-multiplicity $p$+$p$ collisions, pion-deuteron femtoscopy further indicates that most observed (anti)deuterons are formed through nucleon fusion after strong decays of short-lived resonances. Taken together, these measurements show that production chronology and internal nuclear structure leave measurable imprints on the physics observables.

hep-ex↗
arXiv2026

Search for the process $e^+e^-\to f_1(1285)$ at the SND detector

In the experiment with the SND detector at the VEPP-2000 $e^+e^-$ collider, a search is performed for the direct production of the $C$-even $f_1(1285)$ resonance in $e^+e^-$ collisions. The analysis is based on data with an integrated luminosity of about 200 pb$^{-1}$, accumulated in the center-of-mass energy range of 1.14--1.46 GeV, of which about 72 pb$^{-1}$ were recorded near the maximum of the $f_1(1285)$ resonance. The $f_1(1285)$ production cross section at the resonance maximum $\sigma(e^+e^-\to f_1)=(31\pm 13\pm 2)$ pb and the branching fraction $B(f_1(1285)\to e^+e^-)=(3.5\pm 1.4\pm 0.3)\times 10^{-9}$ have been measured. The significance of the observation of the $e^+e^-\to f_1(1285)$ process is $2.5\sigma$. Since the significance is low, we also present the upper limits at the 90% confidence level: $\sigma(e^+e^-\to f_1)<48\mbox{ pb}$ and $B(f_1(1285)\to e^+e^-)<5.4\times 10^{-9}$.

hep-ex↗
arXiv2026

Projected Sensitivity to Slow Muonphilic Dark Matter with Accelerator Muon Beams

The nature of dark matter (DM) remains one of the most enduring open questions in modern physics, and muonphilic DM has emerged as a promising scenario that complements traditional DM candidates. Following the recently established cosmic-ray muon scattering approach, we investigate the sensitivity for probing slow muonphilic DM with accelerator muon beams. A Geant4-based simulation framework is developed, incorporating the detector geometry from the PKMu muon tomography system and a dedicated elastic $\mu$-DM scattering process. The projected sensitivity is found to be largely insensitive to both the beam energy and the transverse beam size when the beam is fully contained within the detector acceptance. For a benchmark beam intensity of $10^5/\rm{s}$, the simulated pure-muon beam surpasses the existing cosmic-ray limit of $1.61\times10^{-17}$ cm$^2$ at $m_{\rm DM}=1$ GeV within approximately 11 seconds. A realistic muon beam phase-space distribution based on simulations for the High Intensity heavy-ion Accelerator Facility (HIAF) is also implemented, yielding projected limits that improve upon the cosmic-ray results by nearly two orders of magnitude in a one-day exposure. These results demonstrate that a beam-muon scattering experiment offers a robust and promising route toward significantly improved sensitivity to slow muonphilic DM.

hep-ex↗