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Register a new userFirst observation of the rare purely baryonic decay $B^0 to p bar{p}$
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The first observation of the decay of a $B^0$ meson to a purely baryonic final state, $B^0 to p bar{p}$, is reported. The proton-proton collision data sample used was collected with the LHCb experiment at center-of-mass energies of 7 and 8 TeV and corresponds to an integrated luminosity of 3.0 fb$^{-1}$. The branching fraction is determined to be $${cal B}(B^0 to p bar{p}) = ( 1.25 pm 0.27 pm 0.18 ) times 10^{-8} ,$$ where the first uncertainty is statistical and the second systematic. The decay mode $B^0 to p bar{p}$ is the rarest decay of the $B^0$ meson observed to date. The decay $B_s^0 to p bar{p}$ is also investigated. No signal is seen and the upper limit ${cal B}(B_s^0 to p bar{p}) < 1.5 times 10^{-8}$ at 90% confidence level is set on the branching fraction.
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The results of a search for the rare two-body charmless baryonic decays $B^0 to p bar{p}$ and $B_s^0 to p bar{p}$ are reported. The analysis uses a data sample, corresponding to an integrated luminosity of 0.9 fb$^{-1}$, of $pp$ collision data collected by the LHCb experiment at a centre-of-mass energy of 7 TeV. An excess of $B^0 to p bar{p}$ candidates with respect to background expectations is seen with a statistical significance of 3.3 standard deviations. This is the first evidence for a two-body charmless baryonic $B^0$ decay. No significant $B_s^0 to p bar{p}$ signal is observed, leading to an improvement of three orders of magnitude over previous bounds. If the excess events are interpreted as signal, the 68.3% confidence level intervals on the branching fractions are {eqnarray} cal{B}(B^0 to p bar{p}) & = & (1.47 ,^{+0.62}_{-0.51} ,^{+0.35}_{-0.14}) times 10^{-8} ,, *{0.3cm} cal{B}(B_s^0 to p bar{p}) & = & (2.84 ,^{+2.03}_{-1.68} ,^{+0.85}_{-0.18}) times 10^{-8} ,, {eqnarray} where the first uncertainty is statistical and the second is systematic.
Using E1 radiative transitions $psi(3686) to gammachi_{cJ}$ from a sample of $(448.1 pm 2.9)times10^{6}$ $psi(3686)$ events collected with the BESIII detector, the decays $chi_{cJ}to Sigma^{+}bar{p}K_{S}^{0}+c.c.~(J = 0, 1, 2)$ are studied. The decay branching fractions are measured to be $mathcal{B}(chi_{c0}to Sigma^{+}bar{p}K_{S}^{0}+c.c.) = (3.52 pm 0.19pm 0.21)times10^{-4}$, $mathcal{B}(chi_{c1}to Sigma^{+}bar{p}K_{S}^{0}+c.c.) = (1.53 pm 0.10pm 0.08)times10^{-4}$, and $mathcal{B}(chi_{c2}to Sigma^{+}bar{p}K_{S}^{0}+c.c.) = (8.25 pm 0.83 pm 0.49)times10^{-5}$, where the first and second uncertainties are the statistical and systematic ones, respectively. No evident intermediate resonances are observed in the studied processes.
The decay $Lambda_b^0 to eta_c(1S) p K^-$ is observed for the first time using a data sample of proton-proton collisions, corresponding to an integrated luminosity of 5.5 $fb^{-1}$, collected with the LHCb experiment at a center-of-mass energy of 13 TeV. The branching fraction of the decay is measured, using the $Lambda_b^0 to J/psi p K^-$ decay as a normalization mode, to be $mathcal{B}(Lambda_b^0 to eta_c(1S) p K^-)=(1.06pm0.16pm0.06^{+0.22}_{-0.19})times10^{-4}$, where the quoted uncertainties are statistical, systematic and due to external inputs, respectively. A study of the $eta_c(1S) p$ mass spectrum is performed to search for the $P_c(4312)^+$ pentaquark state. No evidence is observed and an upper limit of begin{equation*} frac{mathcal{B}(Lambda_b^0 to P_c(4312)^+ K^-)times mathcal{B}(P_c(4312)^+ to eta_c(1S) p)}{mathcal{B}(Lambda_b^0 to eta_c(1S) p K^-)} < 0.24 end{equation*} is obtained at the 95% confidence level.
The first observation of the decay $kstarkstar$ is reported using 35invpb of data collected by LHCb in proton-proton collisions at a centre-of-mass energy of 7 TeV. A total of $49.8 pm 7.5$ $B^0_s rightarrow (K^+pi^-)(K^-pi^+)$ events are {observed within $pm 50 mevcc$ of the Bs mass and $746 mevcc < m_{Kpi}< 1046 mevcc$, mostly coming from a resonant $kstarkstar$ signal.} The branching fraction and the CP-averaged Kstarz longitudinal polarization fraction are measured to be {$BR(kstarkstar) = (2.81 pm 0.46 ({rm stat.}) pm 0.45 ({rm syst.}) pm 0.34, (f_s/f_d))times10^{-5}$} and $f_L = 0.31 pm 0.12 ({rm stat.}) pm 0.04 ({rm syst.})$.
The decay $Lambda_b^0 to Lambda_c^+ p overline{p} pi^-$ is observed using $pp$ collision data collected with the LHCb detector at centre-of-mass energies of $sqrt{s}=$ 7 and 8 TeV, corresponding to an integrated luminosity of 3 $fb^{-1}$. The ratio of branching fractions between $Lambda_b^0 to Lambda_c^+ p overline{p} pi^-$ and $Lambda_b^0 to Lambda_c^+ pi^-$ decays is measured to be begin{equation*} frac{mathcal{B}(Lambda_b^0 to Lambda_c^+ p overline{p}pi^-)}{mathcal{B}(Lambda_b^0 to Lambda_c^+ pi^-)} = 0.0540 pm 0.0023 pm 0.0032. end{equation*} Two resonant structures are observed in the $ Lambda_c^+ pi^-$ mass spectrum of the ${Lambda_b^0 to Lambda_c^+ poverline{p} pi^-}$ decays, corresponding to the $Sigma_c(2455)^0$ and $Sigma_c^{*}(2520)^0$ states. The ratios of branching fractions with respect to the decay $Lambda_b^0 to Lambda_c^+ p overline{p} pi^-$ are begin{align*} frac{mathcal{B}(Lambda_b^0 to Sigma_c^0 poverline{p})timesmathcal{B}(Sigma_c^0to Lambda_c^+ pi^-)}{mathcal{B}(Lambda_b^0 to Lambda_c^+ p overline{p}pi^-)} = 0.089pm0.015pm0.006, frac{mathcal{B}(Lambda_b^0 to Sigma_c^{*0} poverline{p})timesmathcal{B}(Sigma_c^{*0}to Lambda_c^+ pi^-)}{mathcal{B}(Lambda_b^0 to Lambda_c^+ p overline{p}pi^-)} = 0.119pm0.020pm0.014. end{align*} In all of the above results, the first uncertainty is statistical and the second is systematic. The phase space is also examined for the presence of dibaryon resonances. No evidence for such resonances is found.
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