Studies of the decay B+/- -->D(CP)K Abe, K; Abe, T; Akatsu, M ...
Physical review letters,
2003-Apr-04, 20030404, Letnik:
90, Številka:
13
Journal Article
Recenzirano
We report studies of the Cabibbo-suppressed decay B+/--->D(CP)K+/-, where D(CP) denotes CP eigenstates of the D0-D0; system. The analysis is based on a 29.1 fb(-1) sample collected at the Upsilon(4S) ...resonance with the Belle detector at the KEKB asymmetric e(+)e(-) storage ring. We measure ratios of branching fractions, relative to Cabibbo-favored B+/--->D(CP)pi(+/-), of B(B--->D1K-)/B(B--->D1pi(-))=0.125+/-0.036+/-0.010 and B(B--->D2K-)/B(B--->D2pi(-))=0.119+/-0.028+/-0.006; the index 1 (2) denotes the CP=+1 (-1) eigenstate. We also extract the partial rate asymmetries for B+/--->D(CP)K+/-, finding A(1)=0.29+/-0.26+/-0.05 and A(2)=-0.22+/-0.24+/-0.04.
We search for the \(B^0\to p\bar{\Sigma}^0\pi^-\) decay with \(\bar{\Sigma}^0 \to \bar{\Lambda}\gamma\), where the \(\gamma\) is not measured, using a data sample corresponding to an integrated ...luminosity of 711 \(\rm{fb^{-1}}\) which contains 772 \(\times\) \(10^{6}\) \(B\bar{B}\) pairs, collected around the \(\Upsilon\)(4S) resonance with the Belle detector at the KEKB asymmetric-energy \(e^{+}e^{-}\) collider. We measure for the first time the \(B^0\to p\bar{\Sigma}^0\pi^-\) branching fraction to be \(\mathcal{B}(B^0 \to p \bar\Sigma^0 \pi^-) = (1.17^{+0.43}_{-0.40}(\text{stat})\pm 0.07(\text{syst})) \times 10^{-6}\) with a significance of \(3.0\sigma\). We simultaneously measure the branching fraction for the related channel \(B^{0}\to p\bar{\Lambda}\pi^{-}\) with much improved precision.
The first simultaneous determination of the absolute value of the Cabibbo-Kobayashi-Maskawa matrix element \(V_{ub}\) using inclusive and exclusive decays is performed with the full Belle data set at ...the \(\Upsilon(4S)\) resonance, corresponding to an integrated luminosity of 711 fb\({}^{-1}\). We analyze collision events in which one \(B\) meson is fully reconstructed in hadronic modes. This allows for the reconstruction of the hadronic \(X_u\) system of the semileptonic \(b \to u \ell \bar \nu_\ell\) decay. We separate exclusive \(B \to \pi \, \ell\, \bar \nu_{\ell}\) decays from other inclusive \(B \to X_u \, \ell\, \bar \nu_{\ell}\) and backgrounds with a two-dimensional fit, that utilizes the number of charged pions in the \(X_u\) system and the four-momentum transfer \(q^2\) between the \(B\) and \(X_u\) system. Combining our measurement with information from lattice QCD and QCD calculations of the inclusive partial rate as well as external experimental information on the shape of the \(B \to \pi \, \ell\, \bar \nu_{\ell}\) form factor, we determine \(\left|V_{ub}^{\mathrm{excl.}} \right| = (3.78 \pm 0.23 \pm 0.16 \pm 0.14)\times 10^{-3}\) and \(\left|V_{ub}^{\mathrm{incl.}} \right| = (3.88 \pm 0.20 \pm 0.31 \pm 0.09)\times 10^{-3}\), respectively, with the uncertainties being the statistical error, systematic errors, and theory errors. The ratio of \(\left|V_{ub}^{\mathrm{excl.}} \right| / \left|V_{ub}^{\mathrm{incl.}} \right| = 0.97 \pm 0.12\) is compatible with unity.
Observation of the decay B0-->lambda+cp Gabyshev, N; Kichimi, H; Abe, T ...
Physical review letters,
2003-Mar-28, 20030328, Letnik:
90, Številka:
12
Journal Article
Recenzirano
We report the measurement of the charmed baryonic decay B(0)-->Lambda(+)(c)p with a branching fraction of (2.19(+0.56)(-0.49)+/-0.32+/-0.57)x10(-5) and a statistical significance of 5.8 sigma. The ...errors are statistical, systematic, and the error of the Lambda(+)(c)-->pK(-)pi(+) decay branching fraction. This is the first observation of a two-body baryonic B decay. The analysis is based on 78.2 fb(-1) of data accumulated at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric e(+)e(-) collider.
Phys. Rev. D 101, 032007 (2020) We report the result for a search for the leptonic decay of $B^+ \to \mu^+ \,
\nu_{\mu}$ using the full Belle data set of 711 fb^{-1}$ of integrated
luminosity at the ...$\Upsilon(4S)$ resonance. In the Standard Model leptonic
$B$-meson decays are helicity and CKM suppressed. To maximize sensitivity an
inclusive tagging approach is used to reconstruct the second $B$ meson produced
in the collision. The directional information from this second $B$ meson is
used to boost the observed $\mu$ into the signal $B$ meson rest-frame, in which
the $\mu$ has a monochromatic momentum spectrum. Though its momentum is smeared
by the experimental resolution, this technique improves the analysis
sensitivity considerably. Analyzing the $\mu$ momentum spectrum in this frame
we find $\mathcal{B}(B^+ \to \mu^+ \, \nu_\mu) = \left( 5.3 \pm 2.0 \pm 0.9
\right) \times 10^{-7}$ with a one-sided significance of 2.8 standard
deviations over the background-only hypothesis. This translates to a
frequentist upper limit of $\mathcal{B}(B^+ \to \mu^+ \, \nu_{\mu}) < 8.6
\times 10^{-7}$ at 90% CL. The experimental spectrum is then used to search for
a massive sterile neutrino, $B^+ \to \mu^+ \, N$, but no evidence is observed
for a sterile neutrino with a mass in a range of 0 - 1.5 GeV. The determined
$B^+ \to \mu^+ \, \nu_{\mu}$ branching fraction limit is further used to
constrain the mass and coupling space of the type II and type III
two-Higgs-doublet models.
We present the first measurement of the Michel parameter \(\xi^\prime\) in the \(\tau^-\to\mu^-\bar{\nu}_\mu\nu_\tau\) decay using the full data sample of \(988\,\text{fb}^{-1}\) collected by the ...Belle detector operating at the KEKB asymmetric energy \(e^+ e^-\) collider. The method is based on the reconstruction of the \(\mu^- \to e^- \bar{\nu}_e\nu_\mu\) decay-in-flight in the Belle central drift chamber and relies on the correlation between muon spin and its daughter electron momentum. We study the main sources of the background that can imitate the signal decay, such as kaon and pion decays-in-flight and charged particle scattering on the detector material. Highly efficient methods of their suppression are developed and applied to select 165 signal-candidate events. We obtain \(\xi^\prime=0.22\pm0.94\pm0.42\) where the first uncertainty is statistical, and the second one is systematic. The result is in agreement with the Standard Model prediction of \(\xi^\prime=1\).
We report a measurement of the ratios of branching fractions $\mathcal{R}(D)
= {\cal B}(\bar{B} \to D \tau^- \bar{\nu}_{\tau})/{\cal B}(\bar{B} \to D \ell^-
\bar{\nu}_{\ell})$ and ...$\mathcal{R}(D^{\ast}) = {\cal B}(\bar{B} \to D^* \tau^-
\bar{\nu}_{\tau})/{\cal B}(\bar{B} \to D^* \ell^- \bar{\nu}_{\ell})$, where
$\ell$ denotes an electron or a muon. The results are based on a data sample
containing $772\times10^6$ $B\bar{B}$ events recorded at the $\Upsilon(4S)$
resonance with the Belle detector at the KEKB $e^+ e^-$ collider. The analysis
utilizes a method where 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 $\mathcal{R}(D^{\ast})= 0.283 \pm 0.018 \pm 0.014$, where the
first uncertainties are statistical and the second are systematic. These
results are in agreement with the Standard Model predictions within $0.2$ and
$1.1$ standard deviations, respectively, while their combination agrees with
the Standard Model predictions within $1.2$ standard deviations.
We present a search for the direct production of a light pseudoscalar a decaying into two photons with the Belle II detector at the SuperKEKB collider. We search for the process e(+)e(-) -> gamma a, ...a -> gamma gamma in the mass range 0.2 < m(a) < 9.7 GeV/c(2) using data corresponding to an integrated luminosity of (445 +/- 3) pb(-1). Light pseudoscalars interacting predominantly with standard model gauge bosons (so-called axionlike particles or ALPs) are frequently postulated in extensions of the standard model. We find no evidence for ALPs and set 95% confidence level upper limits on the coupling strength g(a gamma gamma) of ALPs to photons at the level of 10(-3) GeV-1. The limits are the most restrictive to date for 0.2 < m(a) < 1 GeV/c(2).
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