Measurement of the branching fraction and polarization for the decay B--->D*0K*-

We present a study of the decay B--->D(*0)K(*-) based on a sample of 86 x 10(6) Upsilon(4S)-->BBmacr; decays collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We measure the branching fraction B(B--->D(*0)K(*-))=(8.3+/-1.1(stat)+/-1.0(syst)) x 10(-4), and the fraction of longitudinal polarization in this decay to be Gamma(L)/Gamma=0.86+/-0.06(stat)+/-0.03(syst).     

Search for lepton-flavor violation in the decay tau- --> l- l+ l-

A search for the lepton-flavor-violating decay of the tau into three charged leptons has been performed using 91.5 fb(-1) of data collected at an e(+)e(-)center-of-mass energy around 10.58 GeV with the BABAR detector at the SLAC storage ring PEP-II. In all six decay modes considered, the numbers of events found in data are compatible with the background expectations. Upper limits on the branching fractions are set in the range (1-3)x10(-7) at 90% confidence level.     

Measurements of branching fractions and CP-violating asymmetries in B0-->rho(+/-)h(-/+) decays

We present measurements of branching fractions and CP-violating asymmetries in B0-->rho(+/-)pi(-/+) and B0-->rho-K+ decays. The results are obtained from a data sample of 88.9 x 10(6) Upsilon(4S)-->BB decays collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B Factory. From a time-dependent maximum likelihood fit we measure the branching fractions B(B0-->rho(+/-)pi(-/+))=[22.6+/-1.8 (stat)+/-2.2 (syst)]x10(-6) and B(B0-->rho-K+)=(7.3 -1.2( +1.3)+/-1.3)x10(-6), and the CP-violating charge asymmetries A(rhopi)(CP)=-0.18+/-0.08+/-0.03 and A(rhoK)(CP)=0.28+/-0.17+/-0.08, the direct CP violation parameter C(rhopi)=0.36+/-0.18+/-0.04 and the mixing-induced CP violation parameter S(rhopi)=0.19+/-0.24+/-0.03, and the dilution parameters DeltaC(rhopi)=0.28 -0.19( +0.18)+/-0.04 and DeltaS(rhopi)=0.15+/-0.25+/-0.03.     

Observation of a narrow meson state decaying to D(+)(s)pi(0) at a mass of 2.32 GeV/c(2)

We have observed a narrow state near 2.32 GeV/c(2) in the inclusive D(+)(s)pi(0) invariant mass distribution from e(+)e(-) annihilation data at energies near 10.6 GeV. The observed width is consistent with the experimental resolution. The small intrinsic width and the quantum numbers of the final state indicate that the decay violates isospin conservation. The state has natural spin-parity and the low mass suggests a J(P)=0(+) assignment. The data sample corresponds to an integrated luminosity of 91 fb(-1) recorded by the BABAR detector at the SLAC PEP-II asymmetric-energy e(+)e(-) storage ring.     

Evidence for B+-->J/psip(-)Lambda; and search for B0-->J/psip(-)p

We have performed a search for the decays B+-->J/psip(-)Lambda; and search for B0-->J/psip(-)p. in a data set of (88.9+/-1.0) x 10(6) Upsilon(4S) decays collected by the BABAR experiment at the PEP-II e(+)e(-) storage ring at the Stanford Linear Accelerator Center. Four charged B candidates have been observed with an expected background of 0.21+/-0.14 events. The corresponding branching fraction is (12(+9)(-6)) x 10(-6), where statistical and systematic uncertainties have been combined. The result can be interpreted as a 90% confidence level (C.L.) upper limit of 26 x 10(-6). We also find one B0 candidate, with an expected background of 0.64+/-0.17 events, implying a 90% C.L. upper limit of 1.9 x 10(-6).     

Measurement of the Cabibbo-Kobayashi-Maskawa matrix element V(ub) with B-->rhoenu decays

We present a measurement of the branching fraction for the rare decays B-->rhoenu and extract a value for the magnitude of V(ub), one of the smallest elements of the Cabibbo-Kobayashi-Maskawa quark-mixing matrix. The results are given for five different calculations of form factors used to para-metrize the hadronic current in semileptonic decays. Using a sample of 55 x 10(6) BB meson pairs recorded with the BABAR detector at the PEP-II e(+)e(-) storage ring, we obtain B(B0-->rho(-)e(+)nu)=(3.29+/-0.42+/-0.47+/-0.55) x 10(-4) and |V(ub)|=(3.64+/-0.22+/-0.25(+0.39)(-0.56)) x 10(-3), where the uncertainties are statistical, systematic, and theoretical, respectively.     

Search for decays of B0-->e+ e-, B0-->mu+ mu-, B0-->e +/- mu-/+

We present a search for the decays B0-->e+ e-, B0-->mu+ mu-, and B0-->e (+/-) mu (-/+) in data collected at the Upsilon(4S) resonance with the BABAR detector at the SLAC B Factory. Using a data set of 111 fb(-1), we find no evidence for a signal in any of the three channels investigated and set the following branching fraction upper limits at the 90% confidence level: B(B0-->e+ e-) < 6.1 x 10(-8), B(B0-->mu+ mu-) < 8.3 x 10(-8), and B(B0-->e (+/-) mu (-/+) )<18 x 10(-8).     

Search for the decay B+ --> K+nunu

We search for the rare flavor-changing neutral-current decay B(+)--> K(+)nunu in a data sample of 82 fb(-1) collected with the BABAR detector at the PEP-II B-factory. Signal events are selected by examining the properties of the system recoiling against either a reconstructed hadronic or semileptonic charged-B decay. Using these two independent samples we obtain a combined limit of B(B(+)-->K(+)nunu ) < 5.2 x 10(-5) at the 90% confidence level. In addition, by selecting for pions rather than kaons, we obtain a limit of B(B+-->pi(+)nunu) < 1.0 x 10(-4) using only the hadronic B reconstruction method.     

Inclusive π0 production at the CERN p-p̄ collider

Inclusive π⁰ production has been measured at the CERN pp? collider, $\text{s}\text{=540}\text{GeV}$, for 90° production angle and in a range of transverse momenta between 1.5 and 4.5 GeV/c. The invariant production cross section is larger than that measured at $\text{s}\text{= 53}\text{GeV}$ for p-p collisions. The production of μ mesons aand of direct photons is also investigated.     

The price of natural flavour conservation in neutral weak interactions

The natural conservation of flavours to O(G_F²) in neutral weak interactions severely constrains choices of gauge groups as well as their fermion representations. In the absence of exactly conserved quantum numbers other than charge, and of |ΔQ| ? 2 charged currents, essentially the only weak and electromagnetic gauge groups whose neutral interactions naturally conserve all flavours are SU(2)_L ? U(1) and SU(2)_L ? [U(1)]². The plausible extensions of these gauge groups to grand unified models including the strong interactions are based on SU(5) and SO(10) respectively. Making the SU(5) model completely natural, including in the Higgs sector, gives the prediction $\text{m}{}_{\mathrm{<mtext>d</mtext>}}\text{/m}{}_{\mathrm{<mtext>e</mtext>}}\text{? m}{}_{\mathrm{<mtext>s</mtext>}}\text{/m}{}_{\mathrm{\mu }}\text{? m}{}_{\mathrm{<mtext>b</mtext>}}\text{/m}{}_{\mathrm{\tau }}\text{? 2605}$ where τ is the probable new heavy lepton and b is the conjectured third flavour of charge $\text{?1}\text{3}\text{quark}$. The SO(10) model contains a potential SU(2)_L ? SU(2)_R ? U(1) weak and electromagnetic gauge group, and has a complicated Higgs structure which does not naturally conserve quark flavours.