K. Kojima

activity

20222026

B^{+} \to K^{+} ν ν ˉ

decays

90 citations · 320 across the 28 of their papers we have counts for

collaborators

33 papers

hep-ex2026

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}…

hep-ex2026

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 $h = π^{\pm}$ , $…

hep-ex2024★ 8 cited

The Belle II Detector Upgrades Framework Conceptual Design Report

H. Aihara, A. Aloisio, D. P. Auguste +207

We describe the planned near-term and potential longer-term upgrades of the Belle II detector at the SuperKEKB electron-positron collider operating at the KEK laboratory in Tsukuba…

hep-ex2024

Measurement of $C P$ asymmetries in $B^{0} \to K_{S}^{0} K_{S}^{0} K_{S}^{0}$ decays at Belle II

Belle II Collaboration, I. Adachi, L. Aggarwal +450

We report a measurement of decay-time dependent charge-parity ( $C P$ ) asymmetries in $B^{0} \to K_{S}^{0} K_{S}^{0} K_{S}^{0}$ decays. We use $387 \times 1 0^{6} B B ˉ$ pairs collected at…

hep-ex2024★ 10 cited

Search for a $μ^{+} μ^{-}$ resonance in four-muon final states at Belle II

Belle II Collaboration, I. Adachi, K. Adamczyk +401

We report on a search for a resonance $X$ decaying to a pair of muons in $e^{+} e^{-} \to μ^{+} μ^{-} X$ events in the 0.212-9.000 GeV/ $c^{2}$ mass range, using 178 fb $^{- 1}$ of…

hep-ex2024★ 13 cited

New graph-neural-network flavor tagger for Belle II and measurement of $sin 2 ϕ_{1}$ in $B^{0} \to J / ψ K_{S}^{0}$ decays

Belle II Collaboration, I. Adachi, L. Aggarwal +413

We present GFlaT, a new algorithm that uses a graph-neural-network to determine the flavor of neutral $B$ mesons produced in $Υ (4 S)$ decays. It improves previous algorithms by usin…

hep-ex2024

A test of lepton flavor universality with a measurement of $R (D^{*})$ using hadronic $B$ tagging at the Belle II experiment

Belle II Collaboration, I. Adachi, K. Adamczyk +434

The ratio of branching fractions $R (D^{*}) = B (B \to D^{*} τ^{-} ν_{τ})$ /$\mathcal{B} (\overline{B} \rightarrow D^{*} \ell^{-} \overlineν_{\ell}…

hep-ex2023

Search for the $e^{+} e^{-} \to η_{b} (1 S) ω$ and $e^{+} e^{-} \to χ_{b 0} (1 P) ω$ processes at $s = 10.745 GeV$

Belle II Collaboration, I. Adachi, L. Aggarwal +419

We search for the $e^{+} e^{-} \to η_{b} (1 S) ω$ and $e^{+} e^{-} \to χ_{b 0} (1 P) ω$ processes at a center-of-mass energy of 10.745 GeV, which is close to the peak of the $Υ (10753)$ state. We use data…

hep-ex2023★ 90 cited

Evidence for $B^{+} \to K^{+} ν ν ˉ$ decays

Belle II Collaboration, I. Adachi, K. Adamczyk +452

We search for the rare decay $B^{+} \to K^{+} ν ν ˉ$ in a $362 fb^{- 1}$ sample of electron-positron collisions at the $Υ (4 S)$ resonance collected with the Belle II det…

hep-ex2023★ 8 cited

Measurement of branching fractions and direct $C P$ asymmetries for $B \to K π$ and $B \to π π$ decays at Belle II

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

We report measurements of the branching fractions and direct $CP$ asymmetries of the decays $B^{0} \to K^{+} π^{-}$ , $B^{+} \to K^{+} π^{0}$ , $B^{+} \to K^{0} π^{+}$ , and $B^{0} \to K^{0} π^{0}$ , and…

hep-ex2023

Measurement of branching-fraction ratios and $C P$ asymmetries in $B^{\pm} \to D_{C P \pm} K^{\pm}$ decays at Belle and Belle II

The Belle, Belle II Collaborations, : +427

We report results from a study of $B^{\pm} \to D K^{\pm}$ decays followed by $D$ decaying to $C P$ ~eigenstates, where $D$ indicates a $D^{0}$ or $D ˉ^{0}$ meson. These decays a…

hep-ex2023★ 7 cited

Tests of light-lepton universality in angular asymmetries of $B^{0} \to D^{*-} ℓ ν$ decays

Belle II Collaboration, I. Adachi, K. Adamczyk +416

We present the first comprehensive tests of light-lepton universality in the angular distributions of semileptonic $B^{0}$ -meson decays to charged spin-1 charmed mesons. We measure f…

hep-ex2023★ 10 cited

Search for a $τ^{+} τ^{-}$ resonance in $e^{+} e^{-} \to μ^{+} μ^{-} τ^{+} τ^{-}$ events with the Belle II experiment

Belle II Collaboration, I. Adachi, K. Adamczyk +464

We report the first search for a non-standard-model resonance decaying into $τ$ pairs in $e^{+} e^{-} \to μ^{+} μ^{-} τ^{+} τ^{-}$ events in the 3.6-10 GeV/ $c^{2}$ mass range. We u…

hep-ex2023★ 16 cited

Search for a long-lived spin-0 mediator in $b \to s$ transitions at the Belle II experiment

Belle II Collaboration, I. Adachi, K. Adamczyk +411

Additional spin-0 particles appear in many extensions of the standard model. We search for long-lived spin-0 particles $S$ in $B$ -meson decays mediated by a $b \to s$ quark transiti…

hep-ex2023★ 5 cited

Precise measurement of the $D_{s}^{+}$ lifetime at Belle II

Belle II Collaboration, I. Adachi, L. Aggarwal +359

We measure the lifetime of the $D_{s}^{+}$ meson using a data sample of 207 fb $^{- 1}$ collected by the Belle II experiment running at the SuperKEKB asymmetric-energy $e^{+} e^{-}$ collider…

hep-ex2023

Search for lepton-flavor-violating $τ^{-} \to ℓ^{-} ϕ$ decays in 2019-2021 Belle II data

Belle II Collaboration, F. Abudinén, I. Adachi +575

We report a search for lepton-flavor-violating decays $τ^{-} \to ℓ^{-} ϕ$ ( $ℓ^{-} = e^{-}, μ^{-}$ ) at the Belle II experiment, using a sample of electron-positron data produced at the Su…

hep-ex2023★ 2 cited

Observation of $B \to D^{(*)} K^{-} K_{S}^{0}$ decays using the 2019-2022 Belle II data sample

Belle II Collaboration, F. Abudinén, I. Adachi +575

We present a measurement of the branching fractions of four $B^{0, -} \to D^{(*) +, 0} K^{-} K_{S}^{0}$ decay modes. The measurement is based on data from SuperKEKB electron-positron colli…

hep-ex2023★ 10 cited

Measurement of the $B^{0}$ lifetime and flavor-oscillation frequency using hadronic decays reconstructed in 2019-2021 Belle II data

Belle II Collaboration, F. Abudinén, I. Adachi +393

We measure the $B^{0}$ lifetime and flavor-oscillation frequency using $B^{0} \to D^{(*) -} π^{+}$ decays collected by the Belle II experiment in asymmetric-energy $e^{+} e^{-}$ collisions produ…

hep-ex2023★ 10 cited

Measurement of decay-time-dependent $CP$ violation in $B^{0} \to J / ψ K_{S}^{0}$ decays using 2019-2021 Belle II data

Belle II Collaboration, I. Adachi, L. Aggarwal +392

We report a measurement of the mixing-induced and direct $CP$ violation parameters $S_{CP}$ and $A_{CP}$ from $B^{0} \to J / ψ K_{S}^{0}$ decays reconstructed by the…

hep-ex2023★ 24 cited

Measured and projected beam backgrounds in the Belle II experiment at the SuperKEKB collider

A. Natochii, T. E. Browder, L. Cao +43

The Belle II experiment at the SuperKEKB electron-positron collider aims to collect an unprecedented data set of $50 ab^{- 1}$ to study $C P$ -violation in the $B$ -meson system…

hep-ex2023★ 3 cited

Measurement of the $B^{0} \to D^{*-} ℓ^{+} ν_{ℓ}$ branching ratio and $∣ V_{c b} ∣$ with a fully reconstructed accompanying $B$ meson in 2019-2021 Belle II data

F. Abudinén, I. Adachi, K. Adamczyk +581

We present a measurement of the $B^{0} \to D^{*-} ℓ^{+} ν_{ℓ}$ ( $ℓ = e, μ$ ) branching ratio and of the CKM parameter $∣ V_{c b} ∣$ using signal decays accompanied by a f…

hep-ex2023★ 19 cited

A test of light-lepton universality in the rates of inclusive semileptonic $B$ -meson decays at Belle II

Belle II Collaboration, L. Aggarwal, H. Ahmed +349

We present the first measurement of the ratio of branching fractions of inclusive semileptonic $B$ -meson decays, $R(X_{e/μ}) = \mathcal{B}(B\to X \, e \, ν) / \mathcal{B}(B\to X \,…

hep-ex2022★ 21 cited

Search for an invisible $Z^{'}$ in a final state with two muons and missing energy at Belle II

Belle II Collaboration, I. Adachi, K. Adamczyk +385

The $L_{μ} - L_{τ}$ extension of the standard model predicts the existence of a lepton-flavor-universality-violating $Z^{'}$ boson that couples only to the heavier lepton families.…

hep-ex2022★ 3 cited

Determination of $∣ V_{u b} ∣$ from untagged $B^{0} \to π^{-} ℓ^{+} ν_{ℓ}$ decays using 2019-2021 Belle II data

Belle II Collaboration, K. Adamczyk, L. Aggarwal +588

We present an analysis of the charmless semileptonic decay $B^{0} \to π^{-} ℓ^{+} ν_{ℓ}$ , where $ℓ = e, μ$ , from 198.0 million pairs of $B B ˉ$ mesons recorded by the Belle II…

Test of lepton flavor universality with Bˉ→D(∗)τ−νˉτ​ and Bˉ→D(∗)ℓ−νˉℓ​ decays at Belle II

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

The Belle II Detector Upgrades Framework Conceptual Design Report

Measurement of CP asymmetries in B0→KS0​KS0​KS0​ decays at Belle II

Search for a μ+μ− resonance in four-muon final states at Belle II

New graph-neural-network flavor tagger for Belle II and measurement of sin2ϕ1​ in B0→J/ψKS0​ decays

A test of lepton flavor universality with a measurement of R(D∗) using hadronic B tagging at the Belle II experiment

Search for the e+e−→ηb​(1S)ω and e+e−→χb0​(1P)ω processes at s​=10.745GeV

Evidence for B+→K+ννˉ decays

Measurement of branching fractions and direct CP asymmetries for B→Kπ and B→ππ decays at Belle II

Measurement of branching-fraction ratios and CP asymmetries in B±→DCP±​K± decays at Belle and Belle II

Tests of light-lepton universality in angular asymmetries of B0→D∗−ℓν decays

Search for a τ+τ− resonance in e+e−→μ+μ−τ+τ− events with the Belle II experiment

Search for a long-lived spin-0 mediator in b→s transitions at the Belle II experiment

Precise measurement of the Ds+​ lifetime at Belle II

Search for lepton-flavor-violating τ−→ℓ−ϕ decays in 2019-2021 Belle II data

Observation of B→D(∗)K−KS0​ decays using the 2019-2022 Belle II data sample

Measurement of the B0 lifetime and flavor-oscillation frequency using hadronic decays reconstructed in 2019-2021 Belle II data

Measurement of decay-time-dependent CP violation in B0→J/ψKS0​ decays using 2019-2021 Belle II data

Measured and projected beam backgrounds in the Belle II experiment at the SuperKEKB collider

Measurement of the B0→D∗−ℓ+νℓ​ branching ratio and ∣Vcb​∣ with a fully reconstructed accompanying B meson in 2019-2021 Belle II data

A test of light-lepton universality in the rates of inclusive semileptonic B-meson decays at Belle II

Search for an invisible Z′ in a final state with two muons and missing energy at Belle II

Determination of ∣Vub​∣ from untagged B0→π−ℓ+νℓ​ decays using 2019-2021 Belle II data

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

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

Measurement of $C P$ asymmetries in $B^{0} \to K_{S}^{0} K_{S}^{0} K_{S}^{0}$ decays at Belle II

Search for a $μ^{+} μ^{-}$ resonance in four-muon final states at Belle II

New graph-neural-network flavor tagger for Belle II and measurement of $sin 2 ϕ_{1}$ in $B^{0} \to J / ψ K_{S}^{0}$ decays

A test of lepton flavor universality with a measurement of $R (D^{*})$ using hadronic $B$ tagging at the Belle II experiment

Search for the $e^{+} e^{-} \to η_{b} (1 S) ω$ and $e^{+} e^{-} \to χ_{b 0} (1 P) ω$ processes at $s = 10.745 GeV$

Evidence for $B^{+} \to K^{+} ν ν ˉ$ decays

Measurement of branching fractions and direct $C P$ asymmetries for $B \to K π$ and $B \to π π$ decays at Belle II

Measurement of branching-fraction ratios and $C P$ asymmetries in $B^{\pm} \to D_{C P \pm} K^{\pm}$ decays at Belle and Belle II

Tests of light-lepton universality in angular asymmetries of $B^{0} \to D^{*-} ℓ ν$ decays

Search for a $τ^{+} τ^{-}$ resonance in $e^{+} e^{-} \to μ^{+} μ^{-} τ^{+} τ^{-}$ events with the Belle II experiment

Search for a long-lived spin-0 mediator in $b \to s$ transitions at the Belle II experiment

Precise measurement of the $D_{s}^{+}$ lifetime at Belle II

Search for lepton-flavor-violating $τ^{-} \to ℓ^{-} ϕ$ decays in 2019-2021 Belle II data

Observation of $B \to D^{(*)} K^{-} K_{S}^{0}$ decays using the 2019-2022 Belle II data sample

Measurement of the $B^{0}$ lifetime and flavor-oscillation frequency using hadronic decays reconstructed in 2019-2021 Belle II data

Measurement of decay-time-dependent $CP$ violation in $B^{0} \to J / ψ K_{S}^{0}$ decays using 2019-2021 Belle II data

Measurement of the $B^{0} \to D^{*-} ℓ^{+} ν_{ℓ}$ branching ratio and $∣ V_{c b} ∣$ with a fully reconstructed accompanying $B$ meson in 2019-2021 Belle II data

A test of light-lepton universality in the rates of inclusive semileptonic $B$ -meson decays at Belle II

Search for an invisible $Z^{'}$ in a final state with two muons and missing energy at Belle II

Determination of $∣ V_{u b} ∣$ from untagged $B^{0} \to π^{-} ℓ^{+} ν_{ℓ}$ decays using 2019-2021 Belle II data