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Angular analysis of $B \to K^{*} e^{+} e^{-}$ in the low- $q^{2}$ region with new electron identification at Belle

https://doi.org/10.1103/PhysRevD.110.072005

Ferlewicz, D; Urquijo, P; Adachi, I; Adamczyk, K; Aihara, H; Asner, D M; Atmacan, H; Ayad, R; Babu, V; Banerjee, Sw; et al (October 2024, Physical Review D)

We perform an angular analysis of the $B \to K^{*} e^{+} e^{-}$ decay for the dielectron mass squared, $q^{2}$ , range of $0.0008 - 1.1200 {GeV}^{2} / c^{4}$ using the full Belle dataset in the $K^{* 0} \to K^{+} π^{-}$ and $K^{* +} \to K_{S}^{0} π^{+}$ channels, incorporating new methods of electron identification to improve the statistical power of the dataset. This analysis is sensitive to contributions from right-handed currents from physics beyond the Standard Model by constraining the Wilson coefficients $C_{7}^{(')}$ . We perform a fit to the $B \to K^{*} e^{+} e^{-}$ differential decay rate and measure the imaginary component of the transversality amplitude to be $A_{T}^{Im} = - 1.27 \pm 0.52 \pm 0.12$ , and the $K^{*}$ transverse asymmetry to be $A_{T}^{(2)} = 0.52 \pm 0.53 \pm 0.11$ , with $F_{L}$ and $A_{T}^{Re}$ fixed to the Standard Model values. The resulting constraints on the value of $C_{7}^{'}$ are consistent with the Standard Model within a $2 σ$ confidence interval. Published by the American Physical Society2024
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Measurement of Angular Coefficients of $\bar{B} \to D^{*} ℓ {\bar{ν}}_{ℓ}$ : Implications for $| V_{c b} |$ and Tests of Lepton Flavor Universality

https://doi.org/10.1103/PhysRevLett.133.131801

Prim, M T; Bernlochner, F; Metzner, F; Aihara, H; Asner, D M; Aushev, T; Ayad, R; Babu, V; Banerjee, Sw; Behera, P; et al (September 2024, Physical Review Letters)

We measure the complete set of angular coefficients $J_{i}$ for exclusive $\bar{B} \to D^{*} ℓ {\bar{ν}}_{ℓ}$ decays ( $ℓ = e$ , $μ$ ). Our analysis uses the full $711 {fb}^{- 1}$ Belle dataset with hadronic tag-side reconstruction. The results allow us to extract the form factors describing the $\bar{B} \to D^{*}$ transition and the Cabibbo-Kobayashi-Maskawa matrix element $| V_{cb} |$ . Using recent lattice QCD calculations for the hadronic form factors, we find $| V_{cb} | = (40.7 \pm 0.7) \times 10^{- 3}$ using the Boyd-Grinstein-Lebed parametrization, compatible with determinations from inclusive semileptonic decays. We search for lepton flavor universality violation as a function of the hadronic recoil parameter $w$ and investigate the differences of the electron and muon angular distributions. We find no deviation from standard model expectations. Published by the American Physical Society2024
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Search for charged-lepton flavor violation in Υ(2S) → ℓ∓τ± (ℓ = e, μ) decays at Belle

https://doi.org/10.1007/JHEP02(2024)187

Dhamija, R; Nishida, S; Giri, A; Adachi, I; Aihara, H; Asner, D M; Aushev, T; Ayad, R; Babu, V; Bahinipati, S; et al (February 2024, Journal of High Energy Physics)

A<sc>bstract</sc> We report a search for the charged-lepton flavor violation in Υ(2S) →ℓ^∓τ^±(ℓ=e, μ) decays using a 25 fb⁻¹Υ(2S) sample collected by the Belle detector at the KEKBe⁺e⁻asymmetric-energy collider. We find no evidence for a signal and set upper limits on the branching fractions ($$ \mathcal{B} $$ $B$ ) at 90% confidence level. We obtain the most stringent upper limits:$$ \mathcal{B} $$ $B$ (Υ(2S)→ μ^∓τ^±)<0.23×10⁻⁶and$$ \mathcal{B} $$ $B$ (Υ(2S)→ e^∓τ^±)<1.12×10⁻⁶.
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Search for a dark leptophilic scalar produced in association with $τ^{+} τ^{-}$ pair in $e^{+} e^{-}$ annihilation at center-of-mass energies near 10.58 GeV

https://doi.org/10.1103/PhysRevD.109.032002

Biswas, D; Banerjee, Sw; Adachi, I; Aihara, H; Asner, D M; Aushev, T; Ayad, R; Babu, V; Behera, P; Bennett, J; et al (February 2024, Physical Review D)

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Observation of charmed strange meson pair production in $ϒ (2 S)$ decays and in $e^{+} e^{-}$ annihilation at $\sqrt{s} = 10.52 GeV$

https://doi.org/10.1103/PhysRevD.108.112015

Gao, B S; Zhu, W J; Wang, X L; Adachi, I; Aihara, H; Asner, D M; Aulchenko, V; Aushev, T; Ayad, R; Babu, V; et al (December 2023, Physical Review D)

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Search for $C P$ violation in $D_{(s)}^{+} \to K^{+} K_{S}^{0} h^{+} h^{-}$ ( $h = K$ , $π$ ) decays and observation of the Cabibbo-suppressed decay $D_{s}^{+} \to K^{+} K^{-} K_{S}^{0} π^{+}$

https://doi.org/10.1103/PhysRevD.108.L111102

Moon, H K; Won, E; Adachi, I; Aihara, H; Asner, D M; Atmacan, H; Aulchenko, V; Aushev, T; Ayad, R; Babu, V; et al (December 2023, Physical Review D)

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Study of $B^{+} \to p \bar{n} π^{0}$

https://doi.org/10.1103/PhysRevD.108.112007

Chu, K-N; Lin, Y-R; Wang, M-Z; Adachi, I; Adamczyk, K; Aihara, H; Al_Said, S; Asner, D M; Atmacan, H; Aulchenko, V; et al (December 2023, Physical Review D)

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

https://doi.org/10.1103/PhysRevD.110.072020

Adachi, I; Adamczyk, K; Aggarwal, L; Ahmed, H; Aihara, H; Akopov, N; Aloisio, A; Anh_Ky, N; Asner, D M; Atmacan, H; et al (October 2024, Physical Review D)

The ratio of branching fractions $R (D^{*}) = B (\bar{B} \to D^{*} τ^{-} {\bar{ν}}_{τ}) / B (\bar{B} \to D^{*} ℓ^{-} {\bar{ν}}_{ℓ})$ , where $ℓ$ is an electron or muon, is measured using a Belle II data sample with an integrated luminosity of $189 {fb}^{- 1}$ at the SuperKEKB asymmetric-energy $e^{+} e^{-}$ collider. Data is collected at the $ϒ (4 S)$ resonance, and one $B$ meson in the $ϒ (4 S) \to B \bar{B}$ decay is fully reconstructed in hadronic decay modes. The accompanying signal $B$ meson is reconstructed as $\bar{B} \to D^{*} τ^{-} {\bar{ν}}_{τ}$ using leptonic $τ$ decays. The normalization decay, $\bar{B} \to D^{*} ℓ^{-} {\bar{ν}}_{ℓ}$ , produces the same observable final-state particles. The ratio of branching fractions is extracted in a simultaneous fit to two signal-discriminating variables in both channels and yields $R (D^{*}) = {0.262}_{- 0.039}^{+ 0.041} (stat)_{- 0.032}^{+ 0.035} (syst)$ . This result is consistent with the current world average and with Standard Model predictions. Published by the American Physical Society2024
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First Simultaneous Determination of Inclusive and Exclusive $| V_{u b} |$

https://doi.org/10.1103/PhysRevLett.131.211801

Cao, L; Bernlochner, F; Tackmann, K; Adachi, I; Aihara, H; Al_Said, S; Asner, D M; Atmacan, H; Aushev, T; Ayad, R; et al (November 2023, Physical Review Letters)

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Measurement of the energy dependence of the e+e− → $$ B\overline{B} $$, $$ B{\overline{B}}^{\ast } $$, and $$ {B}^{\ast }{\overline{B}}^{\ast } $$ cross sections at Belle II

https://doi.org/10.1007/JHEP10(2024)114

Adachi, I; Aggarwal, L; Ahmed, H; Aihara, H; Akopov, N; Aloisio, A; Althubiti, N; Anh_Ky, N; Asner, D M; Atmacan, H; et al (October 2024, Journal of High Energy Physics)

A<sc>bstract</sc> We report measurements of thee⁺e⁻→$$ B\overline{B} $$ $B \bar{B}$ ,$$ B{\overline{B}}^{\ast } $$ $B {\bar{B}}^{*}$ , and$$ {B}^{\ast }{\overline{B}}^{\ast } $$ $B^{*} {\bar{B}}^{*}$ cross sections at four energies, 10653, 10701, 10746 and 10805 MeV, using data collected by the Belle II experiment. We reconstruct oneBmeson in a large number of hadronic final states and use its momentum to identify the production process. In the first 2 – 5 MeV above$$ {B}^{\ast }{\overline{B}}^{\ast } $$ $B^{*} {\bar{B}}^{*}$ threshold, thee⁺e⁻→$$ {B}^{\ast }{\overline{B}}^{\ast } $$ $B^{*} {\bar{B}}^{*}$ cross section increases rapidly. This may indicate the presence of a pole close to the threshold.
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