M. Watanabe

Test of lepton flavor universality with $B ˉ \to D^{()} τ^{-} ν ˉ_{τ}$ and $B ˉ \to D^{()} ℓ^{-} ν ˉ_{ℓ}$ decays at Belle II

Belle II Collaboration, M. Abumusabh, I. Adachi +494

We test lepton flavor universality with a measurement of the branching-fraction ratios $R(D^{(*)}) \equiv \mathcal{B}(\bar{B} \rightarrow D^{(*)} τ^{-} \barν_τ)/\mathcal{B}(\bar{B}…

Search for the lepton-flavor-violating decay $τ^{\pm} \to μ^{\pm} γ$ at Belle II

Belle II Collaboration, M. Abumusabh, I. Adachi +466

We present a search for the lepton-flavor-violating decay $τ^{\pm} \to μ^{\pm} γ$ using a data sample that corresponds to an integrated luminosity of 428 fb $^{- 1}$ recorded by the Bel…

Search for axion-like particles decaying to two photons at Belle II

Belle II Collaboration, M. Abumusabh, I. Adachi +450

Axion-like particles (ALPs) are predicted in many extensions of the Standard Model and provide a well-motivated portal between visible and hidden sectors through their coupling to…

Study of $e^{+} e^{-} \to h^{+} h^{-} J / ψ (h = π, K, p)$ via initial-state radiation at Belle~II

Belle II Collaboration, M. Abumusabh, I. Adachi +417

Using a data sample of 427.9 fb $^{- 1}$ collected by the Belle~II detector at or near the $Υ (4 S)$ and $Υ (10753)$ resonances, the cross sections for $e^{+} e^{-} \to h^{+} h^{-} J / ψ$ $(h = π / K / p)$ …

Measurements of the mass difference $m (B^{0}) - m (B^{+})$ and the energy dependence of the cross-section ratio $σ (e^{+} e^{-} \to B^{0} B ˉ^{0}) / σ (e^{+} e^{-} \to B^{+} B^{-})$ at Belle and Belle II

Belle, Belle II Collaborations, : +396

Using data samples collected by the Belle and Belle II experiments at the $Υ (4 S)$ resonance with integrated luminosities of 571 fb $^{- 1}$ and 365 fb $^{- 1}$ , respectively, we measur…

hep-ex2025★ 1 cited

Search for the lepton-flavor-violating $τ^{-} \to e^{\mp} ℓ^{\pm} ℓ^{\mp}$ decays at Belle II

Belle II Collaboration, I. Adachi, L. Aggarwal +447

We present the result of a search for the charged-lepton-flavor violating decays $τ^{-} \to e^{\mp} ℓ^{\pm} ℓ^{-}$ , where $ℓ$ is a muon or an electron, using a data sample…

hep-ex2025★ 1 cited

Measurement of the $D^{0} \to K^{-} π^{+} e^{+} e^{-}$ branching fraction and search for $D^{0} \to π^{+} π^{-} e^{+} e^{-}$ and $D^{0} \to K^{+} K^{-} e^{+} e^{-}$ decays at Belle

Belle, Belle II Collaborations, : +481

We present a study of the rare charm meson decays $D^{0} \to K^{+} K^{-} e^{+} e^{-}$ , $π^{+} π^{-} e^{+} e^{-}$ , and $K^{-} π^{+} e^{+} e^{-}$ using a 942 fb $^{- 1}$ data set c…

Charged-hadron identification at Belle II

Belle II Collaboration, I. Adachi, H. Ahmed +408

The Belle II experiment's ability to identify particles critically affects the sensitivity of its measurements. We describe Belle II's algorithms for identifying charged particles…

hep-ex2025★ 4 cited

Search for a Dark Higgs Boson Produced in Association with Inelastic Dark Matter at the Belle II Experiment

Belle II Collaboration, I. Adachi, L. Aggarwal +437

Inelastic dark matter models that have two dark matter particles and a massive dark photon can reproduce the observed relic dark matter density without violating cosmological limit…

Search for lepton flavor-violating decay modes $B^{0} \to K^{* 0} τ^{\pm} ℓ^{\mp}$ ( $ℓ = e, μ$ ) with hadronic B-tagging at Belle and Belle II

Belle, Belle II Collaborations, : +375

We present the results of a search for the charged-lepton-flavor violating decays $B^{0} \to K^{* 0} τ^{\pm} ℓ^{\mp}$ , where $ℓ^{\mp}$ is either an electron or a muon. The…

hep-ex2025★ 1 cited

Search for lepton-flavor-violating $τ^{-} \to ℓ^{-} K_{s}^{0}$ decays at Belle and Belle II

Belle, Belle II Collaborations, : +419

We present the results of a search for charged-lepton-flavor violating decays $τ^{-} \to ℓ^{-} K_{S}^{0}$ , where $ℓ^{-}$ is either an electron or a muon. We combine $e…

hep-ex2025★ 3 cited

Search for $B^{0} \to K^{* 0} τ^{+} τ^{-}$ decays at the Belle II experiment

Belle II Collaboration, I. Adachi, K. Adamczyk +446

We present a search for the rare flavor-changing neutral-current decay $B^{0} \to K^{* 0} τ^{+} τ^{-}$ with data collected by the Belle II experiment at the SuperKEKB electron-positro…

hep-ex2025★ 5 cited

Test of lepton flavor universality with measurements of $R (D^{+})$ and $R (D^{*+})$ using semileptonic $B$ tagging at the Belle II experiment

Belle II Collaboration, I. Adachi, K. Adamczyk +450

We report measurements of the ratios of branching fractions ${\cal R}(D^{(*)+}) = \frac{{\cal B}(\overline{B}{}^0 \to D^{(*)+} \,τ^- \, \overlineν_τ)}{{\cal B}(\overline{B}{}^0 \to…

Measurement of the Branching Fraction of $Λ_{c}^{+} \to p K_{S}^{0} π^{0}$ at Belle

The Belle, Belle II Collaborations, : +426

We report a precise measurement of the ratio of branching fractions $B (Λ_{c}^{+} \to p K_{S}^{0} π^{0}) / B (Λ_{c}^{+} \to p K^{-} π^{+})$ using 980 fb $^{- 1}$ of $e^{+} e^{-}$ data from th…

Search for Pcs(4459) and Pcs(4338) in Upsilon(1S,2S) inclusive decays at Belle

I. Adachi, L. Aggarwal, H. Ahmed +402

Using data samples of 102 million Upsilon(1S) events and 158 million Upsilon(2S) events collected by the Belle detector at the KEKB asymmetric-energy $e^{+} e^{-}$ collider, we search f…

Search for lepton flavor-violating decay modes $B^{0} \to K_{S}^{0} τ^{\pm} ℓ^{\mp} (ℓ = μ, e)$ with hadronic $B$ -tagging at Belle and Belle II

Belle, Belle II Collaborations, : +425

We present the first search for the lepton flavor-violating decay modes $B^{0} \to K_{S}^{0} τ^{\pm} ℓ^{\mp} (ℓ = μ, e)$ using the 711 fb $^{- 1}$ and 365 fb $^{- 1}$ data samples re…

Measurement of the branching fraction and $CP$ -violating asymmetry of the decay $B^{0} \to π^{0} π^{0}$ using $387$ million bottom-antibottom meson pairs in Belle II data

Belle II Collaboration, I. Adachi, L. Aggarwal +437

We measure the branching fraction and $CP$ -violating flavor-dependent rate asymmetry of $B^{0} \to π^{0} π^{0}$ decays reconstructed using the Belle II detector in an electron-…

Measurement of the branching fraction, polarization, and time-dependent $C P$ asymmetry in $B^{0} \to ρ^{+} ρ^{-}$ decays and constraint on the CKM angle $ϕ_{2}$

Belle II Collaboration, I. Adachi, L. Aggarwal +377

We present a measurement of the branching fraction and fraction of longitudinal polarization of $B^{0} \to ρ^{+} ρ^{-}$ decays, which have two $π^{0}$ 's in the final state. We also measure…

Measurement of the inclusive branching fractions for $B_{s}^{0}$ decays into $D$ mesons via hadronic tagging

Belle, Belle II Collaborations, : +452

We report measurements of the absolute branching fractions $B (B_{s}^{0} \to D_{s}^{\pm} X)$ , $B (B_{s}^{0} \to D^{0} / D ˉ^{0} X)$ , and $B (B_{s}^{0} \to D^{\pm} X)$ , w…

hep-ex2024★ 1 cited

Measurement of $B \to K^{*} (892) γ$ decays at Belle II

Belle II Collaboration, I. Adachi, L. Aggarwal +451

We present measurements of $B \to K^{*} (892) γ$ decays using $365 fb^{- 1}$ of data collected from 2019 to 2022 by the Belle~II experiment at the SuperKEKB asymmetric-energy…

hep-ex2024★ 3 cited

Measurement of the time-integrated CP asymmetry in $D^{0} \to K_{S}^{0} K_{S}^{0}$ decays using Belle and Belle II data

Belle, Belle II Collaborations, : +360

We measure the time-integrated CP asymmetry in $D^{0} \to K_{S}^{0} K_{S}^{0}$ decays reconstructed in $e^{+} e^{-} \to c c$ events collected by the Belle a…

hep-ex2024★ 1 cited

Model-independent measurement of $D^{0}$ - $D^{0}$ mixing parameters in $D^{0} \to K_{S}^{0} π^{+} π^{-}$ decays at Belle and Belle II

Belle, Belle II Collaborations, : +339

We perform a model-independent measurement of the $D^{0}$ - $D^{0}$ mixing parameters using samples of $e^{+} e^{-}$ -collision data collected by the Belle and Belle II experiment…

Determination of $∣ V_{u b} ∣$ from simultaneous measurements of untagged $B^{0} \to π^{-} ℓ^{+} ν_{ℓ}$ and $B^{+} \to ρ^{0} ℓ^{+} ν_{ℓ}$ decays

Belle II Collaboration, I. Adachi, L. Aggarwal +417

We present a measurement of $∣ V_{u b} ∣$ from a simultaneous study of the charmless semileptonic decays $B^{0} \to π^{-} ℓ^{+} ν_{ℓ}$ and $B^{+} \to ρ^{0} ℓ^{+} ν_{ℓ}$ , where $\ell = e, μ…