Observation of B+ --> Lambda c+ Lambda c- K+ and B0 --> Lambda c+ Lambda c- K0 decays

We report the first measurements of the doubly charmed baryonic B decays B --> Lambda c+ Lambda c- K. The B+ --> Lambda c+ Lambda c- K+ decay is observed with a branching fraction of (6.5(-0.9)(+1.0)+/-1.1+/-3.4)x10(-4) and a statistical significance of 15.4sigma. The B0 --> Lambda c+ Lambda c- K0 decay is observed with a branching fraction of (7.9(-2.3)(+2.9)+/-1.2+/-4.1)x10(-4) and a statistical significance of 6.6sigma. The branching fraction errors are statistical, systematic, and the error resulting from the uncertainty of the Lambda c+ --> pK- pi+ decay branching fraction. The analysis is based on 357 fb(-1) of data accumulated at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+ e- collider.     

Measurement of the Lambda b lifetime in the exclusive decay Lambda b --> J/psi Lambda

We have measured the Lambda b lifetime using the exclusive decay Lambda b --> J/psi Lambda, based on 1.2 fb(-1) of data collected with the D0 detector during 2002-2006. From 171 reconstructed Lambda b decays, where the J/psi and Lambda are identified via the decays J/psi --> mu+ mu- and Lambda --> ppi, we measured the Lambda b lifetime to be tau(Lambda b)=1.218 (+0.130)/(-0.115) (stat) +/- 0.042(syst) ps. We also measured the B0 lifetime in the decay B0 --> J/psi(mu+ mu-)K(0)/(S)(pi+ pi-) to be tau(B0)=1.501 (+0.078)/(-0.074) (stat) +/- 0.050(syst) ps, yielding a lifetime ratio of tau(Lambda b)/tau(B0)=0.811 (+0.096)/(-0.087) (stat) +/- 0.034(syst).     

Weak decays of pseudoscalar mesons with the formation of leptons in the final state

Leptonic and semileptonic decays of pseudoscalar mesons are considered. The functional dependence of the weak form factors on the wave functions of the (q₁¯q₂) system is found. Numerical values of the coefficients and (for , K, D, and F mesons) determining the interquark potential are obtained. Within the framework of the Coulomb and oscillator models, the probability of semileptonic decays of D and F mesons is found. For D mesons, comparison with experiment is undertaken. Agreement with experiment is observed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 19–23, March, 1982.     

Measurement of bottom-quark hadron masses in exclusive J/psi decays with the CDF detector

We measure the masses of b hadrons in exclusively reconstructed final states containing a J/psi --> mu-mu+ decay using 220 pb(-1) of data collected by the CDF II experiment. We find: m(B+) = 5279.10 +/- 0.41(stat.) +/- 0.36(sys.) MeV/c2, m(B0) = 5279.63 +/- 0.53(stat.) +/- 0.33(sys.) MeV/c2, m(B(s)0) = 5366.01 +/- 0.73(stat.) +/- 0.33(sys.) MeV/c2, m(lambda(b)0) = 5619.7 +/- 1.2(stat.) +/- 1.2(sys.) MeV/c2. m(B+) - m(B0) = -0.53 +/- 0.67(stat.) +/- 0.14(sys.) MeV/c2, m(B(s)0) - m(B0) = 86.38 +/- 0.90(stat.) +/- 0.06(sys.) MeV/c2, m(lambda(b)0) - m(B0) = 339.2 +/- 1.4(stat.) +/- 0.1(sys.) MeV/c2. The measurements of the B(s)0, lambda(b)0 mass, m(B(s)0) - m(B0) and m(lambda(b)0) - m(B0) mass difference are of better precision than the current world averages.