F. Meier

Search for the $B^{0} \to K_{S}^{0} τ^{+} τ^{-}$ decay

Belle, Belle II Collaborations, : +432

We present the first search for $B^{0} \to K_{S}^{0} τ^{+} τ^{-}$ decays. We look for signal decays in $B^{0} B ˉ^{0}$ events produced in asymmetric-energy electron-positron collisions. T…

Observation of the decays $B^{+} \to Σ_{c} (2455)^{++} Ξ ˉ_{c}^{' -}$ and $B^{0} \to Σ_{c} (2455)^{0} Ξ ˉ_{c}^{'0}$

Belle, Belle II Collaborations, : +403

We report the first observation of the decays $B^{+} \to Σ_{c} (2455)^{++} Ξ ˉ_{c}^{' -}$ and $B^{0} \to Σ_{c} (2455)^{0} Ξ ˉ_{c}^{'0}$ , with significances of $6.4 σ$ a…

Measurement of time-dependent $C P$ violation parameters in $B^{0} \to K_{S}^{0} π^{0} γ$ decays at Belle and Belle II

Belle, Belle II Collaborations, : +417

We perform a measurement of time-dependent $C P$ violation parameters in $B^{0} \to K_{S}^{0} π^{0} γ$ decays using a dataset of approximately $772 \times 1 0^{6}$ and $521 \times 10^6…

Search for $Ξ^{0} p$ , $Ω^{-} p$ , and $Ω^{-} n$ dibaryons in $Υ (1 S)$ and $Υ (2 S)$ decays at Belle

Belle, Belle II Collaborations, : +367

We search for $Ξ^{0} p$ , $Ω^{-} p$ , and $Ω^{-} n$ dibaryon states in $Υ (1 S)$ and $Υ (2 S)$ decays, probing mass regions near the corresponding baryon-pair thresholds. Multistrange baryon-bary…

Search for the decay $B^{+} \to K^{+} τ^{+} τ^{-}$ using data from the Belle and Belle II experiments

Belle, Belle II Collaborations, : +435

We report a search for the rare decay $B^{+} \to K^{+} τ^{+} τ^{-}$ using $1.2 \times 1 0^{9}$ $Υ (4 S)$ mesons produced near threshold in electron-positron collisions and colle…

Study of $e^{+} e^{-} \to π^{+} π^{-} Υ (1 D)$ at Belle II

Belle II Collaboration, M. Abumusabh, I. Adachi +404

The bottomonium spectrum, consisting of bound states of a $b$ quark and an anti- $b$ quark, provides an excellent laboratory for probing quantum chromodynamics in the non-pertur…

Study of $B^{+} \to μ^{+} ν_{μ}$ decays at Belle and Belle II

Belle, Belle II Collaborations, : +412

We report a measurement of the branching fraction for the leptonic decay $B^{+} \to μ^{+} ν_{μ}$ . This work presents the first $B^{+} \to μ^{+} ν_{μ}$ result using Belle~II data, an updated Belle me…

A search for feebly-interacting particles in $B$ decays with missing energy at Belle

Belle, Belle II Collaborations, : +406

We present a search for an invisible hidden-sector particle $X_{inv}$ , produced in $B^{0} \to D ˉ^{0} X_{inv}$ and $B^{\pm} \to h X_{inv}$ decays, where $h = π^{\pm}$ , $…

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…

Improved measurement of Born cross sections for $χ_{b J} ω$ and $χ_{b J} (π^{+} π^{-} π^{0})_{non - ω}$ ( $J$ = 0, 1, 2) at Belle and Belle II

Belle, Belle II Collaborations, : +424

We study the processes $χ_{b J} ω$ and $χ_{b J} (π^{+} π^{-} π^{0})_{non - ω}$ ( $J$ = 0, 1, 2) at center-of-mass energies $s$ from 10.73 to 11.02 GeV using a $142.5\,\mathrm{fb}^{…

Observation of $e^{+} e^{-} \to η Υ (2 S)$ and search for $e^{+} e^{-} \to η Υ (1 S), γ X_{b}$ at $s$ near 10.75 GeV

Belle II Collaboration, I. Adachi, L. Aggarwal +435

We present an analysis of the processes $e^{+} e^{-} \to η Υ (1 S)$ , $η Υ (2 S)$ , and $γ X_{b}$ with $X_{b} \to π^{+} π^{-} χ_{b J}, χ_{b J} \to γ Υ (1 S)$ $(J = 1, 2)$ reconstructed from $γγπ^+π^-\ell^+\ell^-~(…

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★ 3 cited

Observation of the decays $B^{+} \to Σ_{c} (2455)^{++} Ξ_{c}^{-}$ and $B^{0} \to Σ_{c} (2455)^{0} Ξ_{c}^{0}$

Belle, Belle II Collaborations, : +386

We report the first observation of the two-body baryonic decays $B^{+} \to Σ_{c} (2455)^{++} Ξ_{c}^{-}$ and $B^{0} \to Σ_{c} (2455)^{0} Ξ_{c}^{0}$ with significance…

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…

Search for an Axion-Like Particle in $B \to K^{(*)} a (\to γ γ)$ Decays at Belle

Belle, Belle II Collaborations, : +422

We report a search for an axion-like particle $a$ in $B \to K^{(*)} a (\to γ γ)$ decays using data collected with the Belle detector at the KEKB asymmetric energy elec…

hep-ex2025★ 2 cited

Measurement of the CP asymmetry in $D^{+} \to π^{+} π^{0}$ decays at Belle II

Belle II Collaboration, I. Adachi, L. Aggarwal +402

We measure the CP asymmetry in $D^{+} \to π^{+} π^{0}$ decays reconstructed in $e^{+} e^{-}$ collisions at the Belle II experiment using a data set corresponding to an integrated luminosity…

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…

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★ 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 lepton-flavor-violating tau decays to $ℓ α$ at Belle

Belle Collaboration, K. Uno, K. Hayasaka +123

We report a search for the lepton-flavor-violating decays $τ^{\pm} \to ℓ^{\pm} α$ ~( $ℓ = e, μ$ ), where $α$ is an undetected spin-0 particle, such as an axion-like particle using $73…