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論文

Measurements of $$q^2$$ moments of inclusive $$B rightarrow X_c ell^+ nu_{ell}$$ decays with hadronic tagging

van Tonder, R.*; 谷田 聖; Belle Collaboration*; 他202名*

Physical Review D, 104(11), p.112011_1 - 112011_32, 2021/12

 被引用回数:10 パーセンタイル:65.5(Astronomy & Astrophysics)

We present the measurement of the first to fourth order moments of the four-momentum transfer squared, $$q^2$$, of inclusive $$B rightarrow X_c ell^+ nu_{ell}$$ decays using the full Belle data set of 711 $$mathrm{fb}^{-1}$$ of integrated luminosity at the $$Upsilon(4S)$$ resonance where $$ell = e, mu$$. The determination of these moments and their systematic uncertainties open new pathways to determine the absolute value of the CKM matrix element $$V_{cb}$$ using a reduced set of matrix elements of the heavy quark expansion. In order to identify and reconstruct the $$X_c$$ system, we reconstruct one of the two $$B$$-mesons using machine learning techniques in fully hadronic decay modes. The moments are measured with progressively increasing threshold selections on $$q^2$$ starting with a lower value of 3.0 $$mathrm{GeV}^2$$ in steps of 0.5 $$mathrm{GeV}^2$$ up to a value of 10.0 $$mathrm{GeV}^2$$. The measured moments are further unfolded, correcting for reconstruction and selection effects as well as QED final state radiation. We report the moments separately for electron and muon final states and observe no lepton flavor universality violating effects.

論文

Measurement of branching fractions and $$CP$$ asymmetries for $$D_s^{+} rightarrow K^+ (eta, pi^0) $$ and $$D_s^{+} rightarrow pi^+ (eta, pi^0)$$ decays at Belle

Guan, Y.*; 谷田 聖; Belle Collaboration*; 他202名*

Physical Review D, 103(11), p.112005_1 - 112005_11, 2021/06

 被引用回数:5 パーセンタイル:45.23(Astronomy & Astrophysics)

We report measurements of the branching fractions and $$CP$$ asymmetries for $$D_s^{+} rightarrow K^{+} eta $$, $$D_s^{+} rightarrow K^{+} pi^0 $$, and $$D_s^{+} rightarrow pi^{+} eta $$ decays, and the branching fraction for $$D_s^{+} rightarrow pi^{+} pi^0$$. Our results are based on a data sample corresponding to an integrated luminosity of 921 fb$$^{-1}$$ collected by the Belle detector at the KEKB $$e^+e^-$$ asymmetric-energy collider. Our measurements of $$CP$$ asymmetries in these decays are the most precise to-date; no evidence for $$CP$$ violation is found.

論文

Measurement of $$mathcal{R}(D)$$ and $$mathcal{R}(D^*)$$ with a semileptonic tagging method

Caria, G.*; 谷田 聖; Belle Collaboration*; 他202名*

Physical Review Letters, 124(16), p.161803_1 - 161803_8, 2020/04

 被引用回数:76 パーセンタイル:97.68(Physics, Multidisciplinary)

The experimental results on the ratios of branching fractions $$mathcal{R}(D) = {cal B}(bar{B} to D tau^- bar{nu_{tau}})/{cal B}(bar{B} to D ell^- barnu_{ell})$$ and $$mathcal{R}(D^*) = {cal B}(bar{B} to D^* tau^- bar{nu_{tau}})/{cal B}(bar{B} to D^* ell^- bar{nu_{ell}})$$, where $$ell$$ denotes an electron or a muon, show a long-standing discrepancy with the Standard Model predictions, and might hint to a violation of lepton flavor universality. We report a new simultaneous measurement of $$mathcal{R}(D)$$ and $$mathcal{R}(D^*)$$, based on a data sample containing $$772 times 10^6$$ $$Bbar{B}$$ events recorded at the $$Upsilon(4S)$$ resonance with the Belle detector at the KEKB $$e^+ e^-$$ collider. In this analysis the tag-side $$B$$ meson is reconstructed in a semileptonic decay mode and the signal-side $$tau$$ is reconstructed in a purely leptonic decay. The measured values are $$mathcal{R}(D)= 0.307 pm 0.037 pm 0.016$$ and $$mathcal{R}(D^*) = 0.283 pm 0.018 pm 0.014$$, where the first uncertainties are statistical and the second are systematic. These results are in agreement with the Standard Model predictions within $$0.2$$, $$1.1$$ and $$0.8$$ standard deviations for $$mathcal{R}(D)$$, $$mathcal{R}(D^*)$$ and their combination, respectively. This work constitutes the most precise measurements of $$mathcal{R}(D)$$ and $$mathcal{R}(D^*)$$ performed to date as well as the first result for $$mathcal{R}(D)$$ based on a semileptonic tagging method.

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