We report a search for the charmless hadronic decay \(B^0\to\eta \pi^0\) with a data sample corresponding to an integrated luminosity of 694 \(\rm fb^{-1}\) containing \(753\times10^6\) \(B\bar{B}\) ...pairs. The data were collected by the Belle experiment running on the \(\Upsilon(4S)\) resonance at the KEKB \(e^+e^-\) collider. We measure a branching fraction \(\mathcal{B}(B^0\to\eta\pi^0)=(4.1^{+1.7+0.5}_{-1.5-0.7})\times 10^{-7}\), where the first uncertainty is statistical and the second is systematic. Our measurement gives an upper limit of \(\mathcal{B}(B^0\to\eta\pi^0)<6.5\times 10^{-7}\) at 90\% confidence level. The signal has a significance of \(3.0\) standard deviations and constitutes the first evidence for this decay mode.
Phys. Rev. D 92, 072014 (2015) We report a measurement of the branching fraction ratios R(D(*)) of Bbar ->
D(*) tau- nubar_tau relative to Bbar -> D()* l- nubar_l (where l = e or mu)
using the full ...Belle data sample of 772 x 10^6 BBbar pairs collected at the
Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e-
collider. The measured values are R(D)= 0.375 +- 0.064(stat.) +- 0.026(syst.)
and R(D*) = 0.293 +- 0.038(stat.) +- 0.015(syst.). The analysis uses hadronic
reconstruction of the tag-side B meson and purely leptonic tau decays. The
results are consistent with earlier measurements and do not show a significant
deviation from the standard model prediction.
Evidence for the decay B 0 → η π 0 Schwartz, A. J.; Adachi, I.; Aihara, H. ...
Physical review. D, Particles, fields, gravitation, and cosmology,
07/2015, Letnik:
92, Številka:
1
Journal Article
Phys. Rev. Lett. 115, 142001 (2015) Using a sample of $771.6 \times 10^{6}$ $\Upsilon(4S)$ decays collected by
the Belle experiment at the KEKB $e^+e^-$ collider, we observe for the first
time the ...transition $\Upsilon(4S) \to \eta h_b(1P)$ with the branching fraction
${\cal B}\Upsilon(4S) \to \eta h_b(1P)= (2.18 \pm 0.11 \pm 0.18) \times
10^{-3}$ and we measure the $h_b(1P)$ mass $M_{h_{b}(1P)} = (9899.3 \pm 0.4 \pm
1.0)$ MeV/$c^{2}$, corresponding to the hyperfine splitting $\Delta M_{\mathrm
HF}(1P) = (0.6 \pm 0.4 \pm 1.0)$ MeV/$c^{2}$. Using the transition $h_b(1P) \to
\gamma \eta_b(1S)$, we measure the $\eta_b(1S)$ mass $M_{\eta_{b}(1S)} =
(9400.7 \pm 1.7 \pm 1.6)$ MeV/$c^{2}$, corresponding to $\Delta M_{\mathrm
HF}(1S) = (59.6 \pm 1.7 \pm 1.6)$ MeV/$c^{2}$, the $\eta_b(1S)$ width
$\Gamma_{\eta_{b}(1S)} = (8 ^{+6}_{-5} \pm 5)$ MeV/$c^{2}$ and the branching
fraction ${\cal B}h_b(1P) \to \gamma \eta_b(1S)= (56 \pm 8 \pm 4) \%$.
Phys. Rev. D 92, 012013 (2015) We report on the first observations of $\bar{B}^0 \to D_1(2430)^0 \omega$,
$\bar{B}^0 \to D_1(2420)^0 \omega$ and $\bar{B}^0 \to D^*_2(2460)^0 \omega$
decays. The ...$\bar{B}^0 \to D^{*+} \rho(1450)^-$ decay is also observed. The
branching fraction measurements are based on $(771.6 \pm 10.6)\times 10^6$
$B\bar{B}$ events collected at the $\Upsilon(4S)$ resonance with the Belle
detector at the KEKB asymmetric-energy $e^+e^-$ collider. The fractions of
longitudinal polarization of the $D^{**}$ states as well as partial wave
fractions of the $D_1(2430)^0$ are obtained. We also set a $90\%$ confidence
level upper limit for the product of branching fractions of
$\mathcal{B}(\bar{B}^0 \to D^{*+} b_1(1235)^-) \times \mathcal{B}(b_1(1235)^-
\to \omega \pi^-)$. The measurements show evidence of nontrivial final-state
interaction phases for the $\rho$-like amplitudes.
We report searches for the processes \(e^+e^-\to\pi^+\pi^-\pi^0\chi_{bJ}\) and \(e^+e^-\to\phi\chi_{bJ}\) (J=1,2) based on data samples collected by the Belle experiment at the KEKB collider. We ...report the first observation of the process \(e^+e^-\to (\pi^+\pi^-\pi^0)_{\rm non-\omega}\chi_{b1}\) and first evidence for \(e^+e^-\to\omega\chi_{bJ}\) in the vicinity of the \(\Upsilon(11020)\) resonance, with center-of-mass energies from 10.96 to 11.05~GeV. The significances for \((\pi^+\pi^-\pi^0)_{\rm non-\omega}\chi_{b1}\) and \(\omega\chi_{bJ}\) are greater than \(5.3\sigma\) and \(4.0\sigma\), respectively. We also investigate the energy dependence of the \(e^+e^-\to\pi^+\pi^-\pi^0\chi_{bJ}\) cross section, but we cannot determine whether the contributions are from the \(\Upsilon(10860)\) and \(\Upsilon(11020)\) resonances or non-resonant continuum processes. The signals for \(e^+e^-\to \phi\chi_{bJ}\) are not significant, and the upper limits of the Born cross sections at the 90\% confidence level are \(0.7\) and \(1.0\)~pb for \(e^+e^-\to \phi\chi_{b1}\) and \(\phi\chi_{b2}\), respectively, for center-of-mass energies from 10.96 to 11.05~GeV.
We search for the decay B+ -> l+ nu gamma with l+ = e+ or mu+ using the full Belle data set of 772 x 10^6 BBbar pairs, collected at the Y(4S) resonance with the Belle detector at the KEKB ...asymmetric-energy e+e- collider. We reconstruct one B meson in a hadronic decay mode and search for the B+ -> l+ nu gamma decay in the remainder of the event. We observe no significant signal within the phase space of E_gamma^sig > 1 GeV and obtain upper limits of BR(B+ -> e+ nu gamma) < 6.1 x 10^-6, BR(B+ -> mu+ nu gamma) < 3.4 x 10^-6, and BR(B+ -> l+ nu gamma) < 3.5 x 10^-6 at 90 % credibility level.
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