We present measurements of the first to fourth moments of the lepton mass squared $q$2 of $B$ → $X_cℓ\overline{ν}_ℓ$ decays for $ℓ = e, μ$ and with $X_c$ a hadronic system containing a charm quark. ...These results use a sample of electron-positron collisions at the $Υ$($4S$) resonance corresponding to 62.8 fb-1 of integrated luminosity and collected by the Belle II 2 experiment in 2019 and 2020. To identify the $X_c$ system and reconstruct $q$2, one of the $B$ mesons from an $Υ$($4S$) → $B\overline{B}$ decay is fully reconstructed in a hadronic decay mode using a multivariate $B$ tagging algorithm. We report raw and central moments for $q$2 > 1.5 $GeV$2=$c$4 up to $q$2 > 8.5 $GeV$2=$c$4, probing up to 77% of the accessible $B$ → $X_cℓ\overline{ν}_ℓ$ phase space. This is the first measurement of moments in the experimentally challenging range of 1.5; 2.5 $GeV$2=$c$4. The results can be used for a new determination of |$V_{cb}$| using inclusive $B$ → $X_cℓ\overline{ν}_ℓ$ decays.
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. The lifetime is determined ...by fitting the decay-time distribution of a sample of 116 × 103 $D^+_s$ → φπ+ decays. Our result is τ$D^+_s$ = (499.5 ± 1.7 ± 0.9) fs, where the first uncertainty is statistical and the second is systematic. This result is significantly more precise than previous measurements.
We present the results of the first Dalitz plot analysis of the decay D0 → K−π+η. The analysis is performed on a data set corresponding to an integrated luminosity of 953 fb−1 collected by the ...Belle detector at the asymmetric-energy e+e− KEKB collider. The Dalitz plot is well described by a combination of the six resonant decay channels K* ( 892 )0η, K−a0 ( 980 )+, K−a2 ( 1320 )+, K* ( 1410 )0η, K* ( 1680 )−π+ and K2* ( 1980 )−π+, together with Kπ and Kη S-wave components. The decays K* ( 1680 )− → K−η and K2* ( 1980 )− → K−η are observed for the first time. We measure ratio of the branching fractions, ... (B PDG). Using the Dalitz fit result, the ratio ... is measured to be ...; this is much lower than the theoretical expectations ( ≈ 1 ) made under the assumption that K*( 1680 ) is a pure 13D1 state. The product branching fraction ... is determined. In addition, the π η ′ contribution to the a0( 980 )± resonance shape is confirmed with 10.1 σ statistical significance using the three-channel Flatté model. We also measure ... . This is consistent with, and more precise than, the current world average ( 1.02 ± 0.30 ) % , deviates with a significance of more than 3 σ from the theoretical predictions of (0.51–0.92)%. (ProQuest: ... denotes formulae omited.).
We present the study of Bover ¯^{0}→Σ_{c}(2455)^{0,++}π^{±}pover ¯ decays based on 772×10^{6} BBover ¯ events collected with the Belle detector at the KEKB asymmetric-energy e^{+}e^{-} collider. The ...Σ_{c}(2455)^{0,++} candidates are reconstructed via their decay to Λ_{c}^{+}π^{∓} and Λ_{c}^{+} decays to pK^{-}π^{+}, pK_{S}^{0}, and Λπ^{+} final states. The corresponding branching fractions are measured to be B(Bover ¯^{0}→Σ_{c}(2455)^{0}π^{+}pover ¯)=(1.09±0.06±0.07)×10^{-4} and B(Bover ¯^{0}→Σ_{c}(2455)^{++}π^{-}pover ¯)=(1.84±0.11±0.12)×10^{-4}, which are consistent with the world average values with improved precision. A new structure is found in the M_{Σ_{c}(2455)^{0,++}π^{±}} spectrum with a significance of 4.2σ including systematic uncertainty. The structure is possibly an excited Λ_{c}^{+} and is tentatively named Λ_{c}(2910)^{+}. Its mass and width are measured to be (2913.8±5.6±3.8) MeV/c^{2} and (51.8±20.0±18.8) MeV, respectively. The products of branching fractions for the Λ_{c}(2910)^{+} are measured to be B(Bover ¯^{0}→Λ_{c}(2910)^{+}pover ¯)×B(Λ_{c}(2910)^{+}→Σ_{c}(2455)^{0}π^{+})=(9.5±3.6±1.6)×10^{-6} and B(Bover ¯^{0}→Λ_{c}(2910)^{+}pover ¯)×B(Λ_{c}(2910)^{+}→Σ_{c}(2455)^{++}π^{-})=(1.24±0.35±0.10)×10^{-5}. Here, the first and second uncertainties are statistical and systematic, respectively.
Using 980 fb−1 of data collected with the Belle detector operating at the KEKB asymmetric-energy e+e− collider, we report a study of the electromagnetic decays of excited charmed baryons Ξc(2790) and ...Ξc(2815). A clear signal (8.6 standard deviations) is observed for ... and we measure: ... We also present evidence (3.8 standard deviations) for the similar decay of the Ξc(2790)0 and measure: ... The first quoted uncertainties are statistical and the second systematic. We find no hint of the analogous decays of the Ξc(2815)+ and Ξc(2790)+ baryons and set upper limits at the 90% confidence level of: ..., and ... Approximate values of the partial widths of the decays are extracted, which can be used to discriminate between models of the underlying quark structure of these excited states. (ProQuest: ... denotes formula omitted.)
We report a measurement of the $C\!P$-violating parameters $A$ and $S$ in $B^{0}\to K_{S}^{0} \pi^{0}$ decays at Belle II using a sample of $387\times 10^{6}$ $B\bar{B}$ events recorded in ...$e^{+}e^{-}$ collisions at a center-of-mass energy corresponding to the $\Upsilon(4S)$ resonance. These parameters are determined by fitting the proper decay-time distribution of a sample of 415 signal events. We obtain $A = 0.04^{+0.15}_{-0.14}\pm 0.05$ and $S = 0.75^{+0.20}_{-0.23}\pm 0.04$, where the first uncertainties are statistical and the second are systematic.
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