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Register a new userObservation of New Charmless Decays of Bottom Hadrons
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Michael J. Morello
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We search for new charmless decays of neutral $b$--hadrons to pairs of charged hadrons with the upgraded Collider Detector at the Fermilab Tevatron. Using a data sample corresponding to 1 fb$^{-1}$ of integrated luminosity, we report the first observation of the BsKpi decay, with a significance of $8.2sigma$, and measure $BR(BsKpi) = (5.0 pm 0.7stat pm 0.8syst)times 10^{-6}$. We also report the first observation of charmless $b$--baryon decays in the channels Lbppi and LbpK with significances of $6.0sigma$ and $11.5sigma$ respectively, and we measure $BR(Lbppi) = (3.5 pm 0.6stat pm 0.9syst)times 10^{-6}$ and $BR(LbpK) = (5.6 pm 0.8stat pm 1.5syst)times 10^{-6}$. No evidence is found for the decays BdKK and Bspipi, and we set an improved upper limit $BR(Bspipi) < 1.2times 10^{-6}$ at the 90% confidence level. All quoted branching fractions are measured using $BR(BdKpi)$ as a reference.
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We report final measurements of direct $mathit{CP}$--violating asymmetries in charmless decays of neutral bottom hadrons to pairs of charged hadrons with the upgraded Collider Detector at the Fermilab Tevatron. Using the complete $sqrt{s}=1.96$ TeV proton-antiproton collisions data set, corresponding to 9.3 fb$^{-1}$ of integrated luminosity, we measure $mathcal{A}(Lambda^0_b rightarrow ppi^{-}) = +0.06 pm 0.07mathrm{(stat)} pm 0.03mathrm{(syst)}$ and $mathcal{A}(Lambda^0_b rightarrow pK^{-}) = -0.10 pm 0.08mathrm{(stat)} pm 0.04mathrm{(syst)}$, compatible with no asymmetry. In addition we measure the $mathit{CP}$--violating asymmetries in $B^0_s rightarrow K^{-}pi^{+}$ and $B^0 rightarrow K^{+}pi^{-}$ decays to be $mathcal{A}(B^0_s rightarrow K^{-}pi^{+}) = +0.22 pm 0.07mathrm{stat)} pm 0.02mathrm{(syst)}$ and $mathcal{A}(B^0 rightarrow K^{+}pi^{-}) = -0.083pm 0.013 mathrm{(stat)} pm 0.004mathrm{(syst)}$, respectively, which are significantly different from zero and consistent with current world averages.
Based on data corresponding to an integrated luminosity of 0.37 fb^-1 collected by the LHCb experiment in 2011, the following ratios of branching fractions are measured: B(B0 -> pi+ pi-) / B(B0 -> K+pi-) = 0.262 +/- 0.009 +/- 0.017, (fs/fd) * B(Bs -> K+K-) / B(B^0 -> K+pi-) = 0.316 +/- 0.009 +/- 0.019, (fs/fd) * B(Bs ->pi+ K-) / B(B0 -> K+pi-) = 0.074 +/- 0.006 +/- 0.006, (fd/fs) * B(B0 -> K+K-) / B(Bs -> K+K-) = 0.018 {+ 0.008 - 0.007} +/- 0.009, (fs/fd) * B(Bs -> pi+pi-) / B(B0 -> pi+pi-) = 0.050 {+ 0.011 - 0.009} +/- 0.004, B(Lambda_b -> p pi-) / B(Lambda_b -> p K-) = 0.86 +/- 0.08 +/- 0.05, where the first uncertainties are statistical and the second systematic. Using the current world average of B(B0 -> K+pi-) and the ratio of the strange to light neutral B meson production fs/fd measured by LHCb, we obtain: B(B0 -> pi+pi-) = (5.08 +/- 0.17 +/- 0.37) x 10^-6, B(Bs -> K+K-) = (23.0 +/- 0.7 +/- 2.3) x 10^-6, B(Bs -> pi+K-) = (5.4 +/- 0.4 +/- 0.6) x 10^-6, B(B0 -> K+K-) = (0.11 {+ 0.05 - 0.04} +/- 0.06) x 10^-6, B(Bs -> pi+pi-) = (0.95 {+ 0.21 - 0.17} +/- 0.13) x 10^-6. The measurements of B(Bs -> K+K-), B(Bs -> pi+ K-) and B(B0 -> K+K-) are the most precise to date. The decay mode Bs -> pi+pi- is observed for the first time with a significance of more than 5 sigma.
Analyzing $Upsilon(nS)$ decays acquired with the CLEO detector operating at the CESR $e^+e^-$ collider, we measure for the first time the product branching fractions ${cal B}[Upsilon(nS)togammachi_{b}((n-1)P_J)] times {cal B}[chi_{b}(n-1)P_J)to X_i]$ for $n=2$ and 3, where $X_i$ denotes, for each $i$, one of the fourteen exclusive light-hadron final states for which we observe significant signals in both $chi_b(1P_J)$ and $chi_b(2P_J)$ decays. We also determine upper limits for the electric dipole (E1) transitions $Upsilon(3S) to gamma chi_b(1P_J)$.
Decays of $B^0$ and $B_{s}^0$ mesons to the charmless baryonic final states $p overline{p} h^+ h^{prime-}$, where $h$ and $h^prime$ each denote a kaon or a pion, are searched for using the LHCb detector. The analysis is based on a sample of proton-proton collision data collected at center-of-mass energies of $7$ and $8,$TeV, corresponding to an integrated luminosity of $3,$fb$^{-1}$. Four-body charmless baryonic $B_{s}^0$ decays are observed for the first time. The decays $B^0_{s}to p overline{p} K^+ K^-$, $B^0_{s}to p overline{p} K^pm pi^mp$, $B^0to p overline{p} K^pm pi^mp$ and $B^0to p overline{p} pi^+pi^-$ are observed with a significance greater than $5$ standard deviations; evidence at $4.1$ standard deviations is found for the $B^0to p overline{p} K^+ K^-$ decay and an upper limit is set on the branching fraction for $B^0_{s}to p overline{p} pi^+ pi^-$. Branching fractions in the kinematic region $m(p overline{p})<2850,$MeV$/c^2$ are measured relative to the $B^0 to J/psi (to p overline{p}) K^*(892)^0$ channel.
Rare decays of b-hadrons provide high sensitivity to New Physics effects. Several deviations with respect to the Standard Model predictions have been observed in recent years, leading to significant tensions in global fit analyses. It is thus crucial to update the existing measurements and study new decay modes to confirm the pattern. The latest results from LHCb and Belle on radiative, semileptonic penguin, lepton universality and lepton flavour violation decays are presented.
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