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Register a new userEvidence for Semileptonic B- to p pbar l nubar Decays
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We find evidence for the semileptonic baryonic decay $B^-to pbar pell^-bar u_ell$ ($ell=e,mu$), based on a data sample of 772 million $Bbar B$ pairs collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy electron-positron collider. A neural-network based hadronic $B$-meson tagging method is used in this study. The branching fraction of $B^-to pbar pell^-bar u_ell$ is measured to be $(5.8^{+2.4}_{-2.1}textrm{(stat.)}pm 0.9textrm{(syst.)})times 10^{-6}$ with a significance of 3.2$sigma$, where lepton universality is assumed. We also estimate the corresponding upper limit: $mathcal{B}(B^-to pbar pell^-bar u_ell) < 9.6times 10^{-6}$ at the 90% confidence level. This measurement helps constrain the baryonic transition form factor in B decays.
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We present measurements of the semileptonic decays B- --> D0 tau- nubar, B- --> D*0 tau- nubar, B0bar --> D+ tau- nubar, and B0bar --> D*+ tau- nubar, which are potentially sensitive to non--Standard Model amplitudes. The data sample comprises 232x10^6 Upsilon(4S) --> BBbar decays collected with the BaBar detector. From a combined fit to B- and B0bar channels, we obtain the branching fractions B(B --> D tau- nubar) = (0.86 +/- 0.24 +/- 0.11 +/- 0.06)% and B(B --> D* tau- nubar) = (1.62 +/- 0.31 +/- 0.10 +/- 0.05)% (normalized for the B0bar), where the uncertainties are statistical, systematic, and normalization-mode-related.
We report measurements of the decays B- -> Ds(*)+ K- l- nubar in a data sample containing 657x10^6 BBbar pairs collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. We observe a signal with a significance of 6 sigma for the combined Ds and Ds* modes and find the first evidence of the B- -> Ds+ K- l- nubar decay with a significance of 3.4 sigma. We measure the following branching fractions: BF(B- -> Ds+ K- l nubar) = (0.30 +/- 0.09(stat) +0.11 -0.08(syst)) x 10^-3 and BF(B- -> Ds*+ K- l- nubar) = (0.59 +/- 0.12(stat) +/- 0.15(syst)) x 10^-3 and set an upper limit BF(B- -> Ds*+ K- l- nubar) < 0.56 x 10^-3 at the 90% confidence level. We also present the first measurement of the Ds+K- invariant mass distribution in these decays, which is dominated by a prominent peak around 2.6 GeV/c^2.
We report a search for the charmless baryonic decay $B^0to pbar{p}pi^0$ with a data sample corresponding to an integrated luminosity of 711~$rm fb^{-1}$ containing $(772pm 10)times 10^6$ $B^0bar{B}^0$ 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 $mathcal{B}(B^0to pbar{p}pi^0)= (5.0pm1.8pm0.6 )times 10^{-7}$, 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 $B^{0}toDelta^+bar{p}$ and $B^0tobar{Delta}^-p$, and set an upper limit on the branching fraction: $mathcal{B}(B^0to Delta^+bar{p})+mathcal{B}(B^0tobar{Delta}^-p)<1.6times10^{-6}$ at 90% confidence level.
Three-body $B^+to p overline p K^+$ and $B^+to p overline p pi^+$ decays are studied using a data sample corresponding to an integrated luminosity of 3.0 $fb^{-1}$ collected by the LHCb experiment in proton-proton collisions at center-of-mass energies of $7$ and $8$ TeV. Evidence of CP violation in the $B^+to p overline p K^+$ decay is found in regions of the phase space, representing the first measurement of this kind for a final state containing baryons. Measurements of the forward-backward asymmetry of the light meson in the $poverline p$ rest frame yield $A_{mathrm{FB}}(p overline p K^+,~m_{poverline p}<2.85mathrm{,Gekern -0.1em V!/}c^2)=0.495pm0.012~(mathrm{stat})pm0.007~(mathrm{syst})$ and $A_{mathrm{FB}}(poverline p pi^+,~m_{poverline p}<2.85mathrm{,Gekern -0.1em V!/}c^2)=-0.409pm0.033~(mathrm{stat})pm0.006~(mathrm{syst})$. In addition, the branching fraction of the decay $B^+tokern 0.1emoverline{kern -0.1emLambda}(1520)p$ is measured to be $mathcal{B}(B^+ to kern 0.1emoverline{kern -0.1emLambda}(1520)p)=(3.15pm0.48~(mathrm{stat})pm0.07~(mathrm{syst})pm0.26~(mathrm{BF}))times 10^{-7}$, where BF denotes the uncertainty on secondary branching fractions.
We present our study on $B to pi l u$ semileptonic decay form factors with NRQCD action for heavy quark from a quenched lattice QCD simulation at $beta$=5.9 on a $16^3times 48$ lattice. We obtain form factors defined in the context of heavy quark effective theory by Burdman et al. and find that their $1/m_B$ correction is small. The limit of physical heavy and light quark masses can be performed without introducing any model function, and we obtain a prediction for the differential decay rate $dGamma/dq^2$. We also discuss the soft pion limit of the form factors.
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