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.
Phys. Rev. D 103, 112001 (2021) We present an analysis of the exclusive
$B^{+}\to\pi^{+}\pi^{-}\ell^{+}\nu_{\ell}$ decay, where $\ell$ represents an
electron or a muon, with the assumption of ...charge-conjugation symmetry and
lepton universality. The analysis uses the full $\Upsilon(4S)$ data sample
collected by the Belle detector, corresponding to 711 fb$^{-1}$ of integrated
luminosity. We select the events by fully reconstructing one $B$ meson in
hadronic decay modes, subsequently determining the properties of the other $B$
meson. We extract the signal yields using a binned maximum-likelihood fit to
the missing-mass squared distribution in bins of the invariant mass of the two
pions or the momentum transfer squared. We measure a total branching fraction
of ${{\cal B}(B^{+}\to \pi^{+}\pi^{-}\ell^{+}\nu_{\ell})= 22.7 ^{+1.9}_{-1.6}
(\mathrm{stat}) \pm 3.5(\mathrm{syst}) \times 10^{-5}}$, where the
uncertainties are statistical and systematic, respectively. This result is the
first reported measurement of this decay.
Phys. Rev. D 102, 012003 (2020) We report searches for $B^0\to\rm{invisible}$ and
$B^0\to\rm{invisible}+\gamma$ decays, where the energy of the photon is
required to be larger than 0.5 GeV. These ...results are obtained from a
$711\,{\rm fb}^{-1}$ data sample that contains $772 \times 10^6 B\bar{B}$ pairs
and was collected near the $\Upsilon\,(4S)$ resonance with the Belle detector
at the KEKB $e^+ e^-$ collider. We observe no significant signal for either
decay and set upper limits on their branching fractions at $90\%$ confidence
level of $\mathcal{B}\,(B^0\to\rm{invisible}) < 7.8\times10^{-5}$ and
$\mathcal{B}\,(B^0\to\rm{invisible}+\gamma) < 1.6\times10^{-5}$.
A search for the decays \(B^+ \rightarrow h_c K^+\) and \(B^0 \rightarrow h_c K_S^0\) is performed. Evidence for the decay \(B^+ \rightarrow h_c K^+\) is found; its significance is \(4.8\sigma\). No ...evidence is found for \(B^0 \rightarrow h_c K_S^0\). The branching fraction for \(B^+ \rightarrow h_c K^+\) is measured to be \((3.7^{+1.0}_{-0.9}{}^{+0.8}_{-0.8}) \times 10^{-5}\); the upper limit for the \(B^0 \rightarrow h_c K_S^0\) branching fraction is \(1.4 \times 10^{-5}\) at \(90\%\) C.L. In addition, a study of the \(p \bar{p} \pi^+ \pi^-\) invariant mass distribution in the channel \(B^+ \to (p \bar{p} \pi^+ \pi^-) K^+\) results in the first observation of the decay \(\eta_c(2S) \to p \bar{p} \pi^+ \pi^-\) with \(12.1\sigma\) significance. The analysis is based on the 711 \(\mathrm{fb}^{-1}\) data sample collected by the Belle detector at the asymmetric-energy \(e^+ e^-\) collider KEKB at the \(\Upsilon(4S)\) resonance.
We report a search for \(X(3872)\) and \(X(3915)\) in \(B^+ \to \chi_{c1} \pi^0 K^+\) decays. We set an upper limit of \(\mathcal{B}(B^+ \to X(3872) K^+) \times \mathcal{B}(X(3872) \to \chi_{c1} ...\pi^0)\) \( < 8.1 \times 10^{-6}\) and \(\mathcal{B}(B^+ \to X(3915) K^+) \times \mathcal{B}(X(3915) \to \chi_{c1} \pi^0)\) \( < 3.8 \times 10^{-5}\) at 90\% confidence level. We also measure \(\mathcal{B}(X(3872) \to \chi_{c1} \pi^0)/\mathcal{B}(X(3872) \to J/\psi \pi^+ \pi^-) < 0.97\) at 90\% confidence level. The results reported here are obtained from \(772 \times 10^{6}\) \(B\overline{B}\) events collected at the \(\Upsilon(4S)\) resonance with the Belle detector at the KEKB asymmetric-energy \(e^+e^-\) collider.
Using a data sample of 921.9 fb\(^{-1}\) collected with the Belle detector, we study the process of \(e^+e^-\to D^+_sD_{s1}(2536)^-+c.c.\) via initial-state radiation. We report the first observation ...of a vector charmoniumlike state decaying to \(D^+_sD_{s1}(2536)^-+c.c.\) with a significance of 5.9\(\sigma\), including the systematic uncertainties. The measured mass and width are \((4625.9^{+6.2}_{-6.0}({\rm stat.})\pm0.4({\rm syst.}))~{\rm MeV}/c^{2}\) and \((49.8^{+13.9}_{-11.5}({\rm stat.})\pm4.0({\rm syst.}))~{\rm MeV}\), respectively. The product of the \(e^+e^-\to D^+_sD_{s1}(2536)^-+c.c.\) cross section and the branching fraction of \(D_{s1}(2536)^-\to{\bar D}^{*0}K^-\) is measured from the \(D_s \bar{D}_{s1}(2536)\) threshold to 5.59~GeV.
We present the results of an amplitude analysis of anti-B0 -> J/psi K- pi+ decays. A new charged charmoniumlike state Zc(4200)+ decaying to J/psi pi+ is observed with a significance of 6.2 sigma. The ...mass and width of the Zc(4200)+ are 4196 +31-29 +17-13 MeV/c^2 and 370 +70-70 +70-132 MeV, respectively; the preferred assignment of the quantum numbers is J^P = 1^+. In addition, we find evidence for Zc(4430)+ -> J/psi pi+. The analysis is based on a 711 fb^-1 data sample collected by the Belle detector at the asymmetric-energy e+ e- collider KEKB.
We present a new measurement of the CKM matrix element \(|V_{cb}|\) from \(B^{0} \to D^{*-} \ell^+ \nu_\ell\) decays, reconstructed with the full Belle data set of \(711 \, \rm fb^{-1}\) integrated ...luminosity. Two form factor parameterizations, originally conceived by the Caprini-Lellouch-Neubert (CLN) and the Boyd, Grinstein and Lebed (BGL) groups, are used to extract the product \(\mathcal{F}(1)\eta_{\rm EW}|V_{cb}|\) and the decay form factors, where \(\mathcal{F}(1)\) is the normalization factor and \(\eta_{\rm EW}\) is a small electroweak correction. In the CLN parameterization we find \(\mathcal{F}(1)\eta_{\rm EW}|V_{cb}| = (35.06 \pm 0.15 \pm 0.56) \times 10^{-3}\), \(\rho^{2}=1.106 \pm 0.031 \pm 0.007\), \(R_{1}(1)=1.229 \pm 0.028 \pm 0.009\), \(R_{2}(1)=0.852 \pm 0.021 \pm 0.006\). For the BGL parameterization we obtain \(\mathcal{F}(1)\eta_{\rm EW}|V_{cb}|= (34.93 \pm 0.23 \pm 0.59)\times 10^{-3}\), which is consistent with the World Average when correcting for \(\mathcal{F}(1)\eta_{\rm EW}\). The branching fraction of \(B^{0} \to D^{*-} \ell^+ \nu_\ell\) is measured to be \(\mathcal{B}(B^{0}\rightarrow D^{*-}\ell^{+}\nu_{\ell}) = (4.90 \pm 0.02 \pm 0.16)\%\). We also present a new test of lepton flavor universality violation in semileptonic \(B\) decays, \(\frac{{\cal B }(B^0 \to D^{*-} e^+ \nu)}{{\cal B }(B^0 \to D^{*-} \mu^+ \nu)} = 1.01 \pm 0.01 \pm 0.03~\). The errors correspond to the statistical and systematic uncertainties respectively. This is the most precise measurement of \(\mathcal{F}(1)\eta_{\rm EW}|V_{cb}|\) and form factors to date and the first experimental study of the BGL form factor parameterization in an experimental measurement.
We report a search for the charmless baryonic decay \(B^0\to p\bar{p}\pi^0\) with a data sample corresponding to an integrated luminosity of 711~\(\rm fb^{-1}\) containing \((772\pm 10)\times 10^6\) ...\(B^0\bar{B}^0\) pairs. The data was collected by the Belle experiment running on the \(\Upsilon(4S)\) resonance at the KEKB \(e^+e^-\) collider. We measure a branching fraction \(\mathcal{B}(B^0\to p\bar{p}\pi^0)= (5.0\pm1.8\pm0.6 )\times 10^{-7}\), where the first uncertainty is statistical and the second is systematic. The signal has a significance of 3.1 standard deviations and constitutes the first evidence for this decay mode. We also search for the intermediate two-body decays \(B^{0}\to\Delta^+\bar{p}\) and \(B^0\to\bar{\Delta}^-p\), and set an upper limit on the branching fraction: \(\mathcal{B}(B^0\to \Delta^+\bar{p})+\mathcal{B}(B^0\to\bar{\Delta}^-p)<1.6\times10^{-6}\) at 90% confidence level.
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