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Register a new userObservation of $B^{0} rightarrow pbar{Lambda} D^{(*)-}$
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We report the first observation of the decays $B^0 rightarrow pbar{Lambda} D^{(*)-}$. The data sample of $711$ fb$^{-1}$ used in this analysis corresponds to $772$ million $Bbar{B}$ pairs, collected at the $Upsilon(4S)$ resonance by the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. We observe $19.8sigma$ and $10.8sigma$ excesses of events for the two decay modes and measure the branching fractions of $B^0 rightarrow pbar{Lambda} D^{-}$ and $B^0 rightarrow pbar{Lambda} D^{*-}$ to be $(25.1pm2.6pm3.5)times10^{-6}$ and $(33.6pm6.3pm4.4)times10^{-6}$, respectively, where the first uncertainties are statistical and the second are systematic. These results are not compatible with the predictions based on the generalized factorization approach. In addition, a threshold enhancement in the di-baryon ($pbar{Lambda}$) system is observed, consistent with that observed in similar $B$ decays.
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We report the study of OK and SK using a $772 times 10^6$ $Bbar{B}$ pair data sample recorded on the $Upsilon({rm 4S})$ resonance with the Belle detector at KEKB. The following branching fractions are measured: $mathcal{B}$(OKPHSP) $=$ $(4.22^{+0.45}_{-0.44}pm 0.51)times10^{-6}$, $mathcal{B}$(SKPHSP) $=$ $(3.81^{+0.39}_{-0.37} pm 0.45)times 10^{-6}$, $mathcal{B}$(ETACD+c.c.) $=$ $(2.91^{+0.37}_{-0.35}pm 0.36)times 10^{-3}$ and $mathcal{B}$(PLPHI) $=$ $(8.18 pm 2.15 pm 0.79)times10^{-7}$, where c.c. denotes the corresponding charge-conjugation process. The intermediate resonance decays are excluded in the four-body decay measurements. We also found evidences for $mathcal{B}$(ETACS+c.c.) $=$ $(3.59 pm 1.52 pm 0.47) times 10^{-3}$ and $mathcal{B}$(LLKO) $=$ $(2.30 pm 0.65 pm 0.25) times 10^{-6}$. No significant signals are found for JPSIS+c.c. and LLKS ; we set the 90% confidence level upper limits on their decay branching fractions as $< 1.85times10^{-3}$ and $< 2.14times10^{-6}$, respectively.
The first observation of the decay $B^0 rightarrow D^0 overline{D}{}^0 K^+ pi^-$ is reported using proton-proton collision data corresponding to an integrated luminosity of 4.7 $mathrm{fb}^{-1}$ collected by the LHCb experiment in 2011, 2012 and 2016. The measurement is performed in the full kinematically allowed range of the decay outside of the $D^{*-}$ region. The ratio of the branching fraction relative to that of the control channel $B^0 rightarrow D^{*-} D^0 K^+$ is measured to be $mathcal{R} = (14.2 pm 1.1 pm 1.0)%$, where the first uncertainty is statistical and the second is systematic. The absolute branching fraction of $B^0 rightarrow D^0 overline{D}{}^0 K^+ pi^-$ decays is thus determined to be $mathcal{B}(B^0 rightarrow D^0 overline{D}{}^0 K^+ pi^-) = (3.50 pm 0.27 pm 0.26 pm 0.30) times 10^{-4}$, where the third uncertainty is due to the branching fraction of the control channel. This decay mode is expected to provide insights to spectroscopy and the charm-loop contributions in rare semileptonic decays.
The suppressed decay $Lambda^{0}_{b}rightarrow ppi^{-}mu^{+}mu^{-}$, excluding the $J/psi$ and $psi(2S)rightarrow mu^{+}mu^{-}$ resonances, is observed for the first time with a significance of 5.5 standard deviations. The analysis is performed with proton-proton collision data corresponding to an integrated luminosity of $3mathrm{fb}^{-1}$ collected with the LHCb experiment. The $Lambda^{0}_{b}rightarrow ppi^{-}mu^{+}mu^{-}$ branching fraction is measured relative to the $Lambda^{0}_{b}rightarrow J/psi(rightarrow mu^{+}mu^{-})ppi^{-}$ branching fraction giving begin{align} onumber frac{mathcal{B}(Lambda^{0}_{b}rightarrow ppi^{-}mu^{+}mu^{-})}{mathcal{B}({Lambda^{0}_{b}rightarrow J/psi(rightarrow mu^{+}mu^{-})ppi^{-}})} &= 0.044pm0.012pm0.007, end{align} where the first uncertainty is statistical and the second is systematic. This is the first observation of a $brightarrow d$ transition in a baryonic decay.
Using $2.25times10^{8}$ $J/psi$ events collected with the BESIII detector at the BEPCII storage rings, we observe for the first time the process $J/psirightarrow pbar{p}a_{0}(980)$, $a_{0}(980)rightarrow pi^{0}eta$ with a significance of $6.5sigma$ ($3.2sigma$ including systematic uncertainties). The product branching fraction of $J/psirightarrow pbar{p}a_{0}(980)rightarrow pbar{p}pi^{0}eta$ is measured to be $(6.8pm1.2pm1.3)times 10^{-5}$, where the first error is statistical and the second is systematic. This measurement provides information on the $a_{0}$ production near threshold coupling to $pbar{p}$ and improves the understanding of the dynamics of $J/psi$ decays to four body processes.
The $CP$ violation observables $S$ and $C$ in the decay channel $B^0 !rightarrow D^+ D^-$ are determined from a sample of proton-proton collisions at center-of-mass energies of 7 and 8 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 3 fb$^{-1}$. The observable $S$ describes $CP$ violation in the interference between mixing and the decay amplitude, and $C$ parametrizes direct $CP$ violation in the decay. The following values are obtained from a flavor-tagged, decay-time-dependent analysis: begin{align*} S &= -0.54 , ^{+0.17}_{-0.16} , text{(stat)} pm 0.05 , text{(syst)},, ewline C &= phantom{-}0.26 , ^{+0.18}_{-0.17} , text{(stat)} pm 0.02 , text{(syst)},. end{align*} These values provide evidence for $CP$ violation at a significance level of 4.0 standard deviations. The phase shift due to higher-order Standard Model corrections is constrained to a small value of begin{align*} Deltaphi = -0.16,^{+0.19}_{-0.21},text{rad},. end{align*}
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