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 rare leptonic decay B--->tau-nutau.

We present a search for the decay B(-)--> tau(-)nu(tau) in a sample of 88.9 x 10(6) BB pairs recorded with the BABAR detector at the Stanford Linear Accelerator Center B factory. One of the two B mesons from the Gamma(4S) is reconstructed in a hadronic or a semileptonic final state, and the decay products of the other B in the event are analyzed for consistency with a B(-) --> tau(-)nu(tau) decay. We find no evidence of a signal and set an upper limit on the branching fraction of B(B(-) --> tau(-) nu(tau)) < 4.2 x 10(-4) at the 90% confidence level.

Improved measurement of CP asymmetries in B0 --> (cc)K(0(*)) decays.

We present results on time-dependent CP asymmetries in neutral B decays to several CP eigenstates. The measurements use a data sample of about 227 x 10(6) upsilon(4S) --> BB decays collected by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. The amplitude of the CPasymmetry, sin2beta in the standard model, is derived from decay-time distributions from events in which one neutral B meson is fully reconstructed in a final state containing a charmonium meson and the other B meson is determined to be either a B0 or B0 from its decay products. We measure sin2beta = 0.722 +/- 0.040(stat) +/- 0.023(syst) in agreement with the standard model expectation.

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.

Measurements of the branching fraction and CP-violation asymmetries in B0-->f0(980)K0S.

We present measurements of the branching fraction and CP-violating asymmetries in the decay B0-->f0(980)K0S. The results are obtained from a data sample of 123 x 10(6) Upsilon(4S)-->BB decays. From a time-dependent maximum likelihood fit, we measure the branching fraction B(B0-->f0(980)(-->pi+pi-)K0)=(6.0+/-0.9+/-0.6+/-1.2)x10(-6), the mixing-induced CP violation parameter S=-1.62(+0.56)(-0.51)+/-0.09+/-0.04, and the direct CP violation parameter C=0.27+/-0.36+/-0.10+/-0.07, where the first errors are statistical, the second systematic, and the third due to model uncertainties. We measure the f0(980) mass and width to be mf0(980)=(980.6+/-4.1+/-0.5+/-4.0) MeV/c2 and Gammaf0(980)=(43(+12)(-9)+/-3+/-9) MeV/c2, respectively.

Search for radiative penguin decays B(+)-->rho(+)gamma, B(0)-->rho(0)gamma, and B(0)-->omegagamma.

A search for the decays B-->rho(770)gamma and B0-->omega(782)gamma is performed on a sample of 211 x 10(6) Upsilon(4S)-->BB events collected by the BABAR detector at the SLAC PEP-II asymmetric-energy e(+)e(-) storage ring. No evidence for the decays is seen. We set the following limits on the individual branching fractions: B(B+-->rho(+)gamma)<1.8 x 10(-6), B(B0-->rho(0)gamma)<0.4 x 10(-6), and B(B0-->omegagamma)<1.0 x 10(-6) at the 90% confidence level. We use the quark model to limit the combined branching fraction B [B-->(rho/omega)gamma]<1.2 x 10(-6), from which we determine a constraint on the ratio of Cabibbo-Kobayashi-Maskawa matrix elements |V(td)|/|V(ts)|.

Search for flavor-changing neutral current and Lepton-flavor violating decays of D0-->l+l-.

We report on a search for the flavor-changing neutral current decays D0-->e(+)e(-) and D0-->mu(+)mu(-), and the lepton-flavor violating decay D0-->e(+/-)mu(-/+). The measurement is based on 122 fb(-1) of data collected by the BABAR detector at the SLAC PEP-II asymmetric e(+)e(-) collider. No evidence is found for any of the decays. The upper limits on the branching fractions, at the 90% confidence level, are 1.2x10(-6) for D0-->e(+)e(-), 1.3x10(-6) for D0-->mu(+)mu(-), and 8.1x10(-7) for D0-->e(+/-)mu(-/+).

Measurement of time-dependent CP-violating asymmetries in B0-->K*0gamma(K*0-->K(0)Spi0) decays.

We present a measurement of the time-dependent CP-violating asymmetries in B0-->K(*0)gamma(K(*0)-->K(0)(S)pi(0)) decays based on 124 x 10(6) Upsilon(4S)-->BB decays collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at the Stanford Linear Accelerator Center. In a sample containing 105+/-14 signal decays, we measure S(K(*)gamma)=0.25+/-0.63+/-0.14 and C(K(*)gamma)=-0.57+/-0.32+/-0.09, where the first error is statistical and the second, systematic.

Study of the decay B0(B- 0)-->rho+rho-, and constraints on the Cabibbo-Kobayashi-Maskawa angle alpha.

Using a data sample of 89 x 10(6) Upsilon(4S)-->BB decays collected with the BABAR detector at the PEP-II asymmetric B Factory at SLAC, we measure the B0(B (0))-->rho(+)rho(-) branching fraction as [30+/-4(stat)+/-5(syst)]x10(-6) and a longitudinal polarization fraction of f(L)=0.99+/-0.03(stat)+0.04-0.03(syst). We measure the time-dependent-asymmetry parameters of the longitudinally polarized component of this decay as C(L)=-0.17+/-0.27(stat)+/-0.14(syst) and S(L)=-0.42+/-0.42(stat)+/-0.14(syst). We exclude values of alpha between 19 degrees and 71 degrees (90% C.L.).

Measurement of the B0-->phiK*0 decay amplitudes.

With a sample of about 227x10(6) BB pairs recorded with the BABAR detector we perform a full angular analysis of the decay B0-->phiK(*0)(892). We make novel measurements of five parameters sensitive to CP violation. We also measure the branching fraction to be (9.2+/-0.9+/-0.5)x10(-6) and determine the fractions of longitudinal and parity-odd transverse contributions as f(L)=0.52+/-0.05+/-0.02 and f( perpendicular)=0.22+/-0.05+/-0.02. The phases of the parity-even and parity-odd transverse amplitudes relative to the longitudinal amplitude are found to be phi( parallel)=2.34(+0.23)(-0.20)+/-0.05 rad and phi( perpendicular)=2.47+/-0.25+/-0.05 rad. We also observe the decay B0-->phiK(*0)(1430).

Direct CP violating asymmetry in B0-->K+pi- decays.

We present a measurement of the direct CP violating asymmetry in the decay B0-->K+pi(-) using a data sample of 227x10(6) Upsilon(4S)-->BB decays collected with the BABAR detector at the PEP-II asymmetric-energy e(+)e(-) collider at SLAC. We observe a total signal yield of nK-(pi(+))+nK+(pi(-))=1606+/-51 decays and measure the asymmetry (nK-(pi(+))-nK+(pi(-)))/(nK-(pi(+))+nK+(pi(-)))=-0.133+/-0.030(stat)+/-0.009(syst). The probability of observing such an asymmetry in the absence of direct CP violation is 1.3x10(-5), corresponding to 4.2 standard deviations.

Measurements of CP-violating asymmetries in B0-->K(0)(s)pi(0) decays.

We present a measurement of the time-dependent CP-violating (CPV) asymmetries in B0-->K(0)(S)pi(0) decays based on 124x10(6) Upsilon(4S)-->BB decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. In a sample containing 122+/-16 signal decays, we obtain the magnitudes of the direct CPV asymmetry CK(0)(S)(pi(0))=0.40(+0.27)(-0.28)+/-0.09 and of the CPV asymmetry in the interference between mixing and decay SK(0)(S)(pi(0))=0.48(+0.38)(-0.47)+/-0.06 where the first error is statistical and the second systematic.

Search for B+/--->[K(-/+)pi(+/-)](D)K+/- and upper limit on the b-->u amplitude in B+/--->DK+/-.

We search for B+/--->[K(-/+)pi(+/-)](D)K+/- decays, where [K(-/+)pi(+/-)](D) indicates that the K-/+pi(+/-) pair originates from the decay of a D0 or D (0). Results are based on 120x10(6) Upsilon(4S)-->BB decays collected with the BABAR detector at SLAC. We set an upper limit on the ratio R(Kpi) identical with[Gamma(B+-->[K(-)pi(+)](D)K+)+Gamma(B--->[K(+)pi(-)](D)K-)][Gamma(B+-->[K(+)pi(-)](D) / K+)+Gamma(B--->[K(-)pi(+)](D)K-)]<0.026 (90% C.L.). This constrains the amplitude ratio r(B) identical with|A(B--->D 0K-)/A(B--->D0K-)|<0.22 (90% C.L.), consistent with expectations. The small value of r(B) favored by our analysis suggests that the determination of the Cabibbo-Kobayashi-Maskawa phase gamma from B-->DK will be difficult.

Study of B-->D(*)sJ +-D(*) decays.

We report a study of D(*)(sJ)(2317)(+) and D(sJ)(2460)(+) meson production in B decays. We observe the decays B+-->D((*)+)(sJ)D ((*)0) and B0-->D((*)+)(sJ)D((*)-) with the subsequent decays D(*)(sJ)(2317)(+)-->D(+)(s)pi(0), D(sJ)(2460)(+)-->D(+)(s)gamma, and D(sJ)(2460)(+)-->D(*+)(s)pi(0). Based on a data sample of 122.1 x 10(6) BB pairs collected with the BABAR detector at the PEP-II B factory, we obtain branching fractions for these modes, including the previously unseen decays B-->D((*)+)(sJ)D(*). In addition, we perform an angular analysis of D(sJ)(2460)(+)-->D(+)(s)gamma decays to test the different D(sJ)(2460)(+) spin hypotheses.

Branching fractions and CP asymmetries in B0-->K+ K- K0 S and B+-->K+ K0 S K0 S.

We measure the branching fractions and CP asymmetries in the decays B0-->K(+)K(-)K(0)(S) and B+-->K(+)K(0)(S)K(0)(S) using a sample of approximately 122x10(6) BB pairs collected by the BABAR detector. From a time-dependent analysis of the K(+)K(-)K(0)(S) sample that excludes phiK(0)(S), the values of the CP-violation parameters are S=-0.56+/-0.25+/-0.04 and C=-0.10+/-0.19+/-0.10, where the first uncertainty is statistical and the second is systematic. We confirm that the final state is nearly purely CP even and extract the standard model parameter sin(2beta=0.57+/-0.26+/-0.04(+0.17)(-0) where the last error is due to uncertainty on the CP content. We present the first measurement of the CP-violating charge asymmetry A(CP)(B+-->K(+)K(0)(S)K(0)(S))=-0.04+/-0.11+/-0.02. The branching fractions are B(B0-->K+K-K0)=(23.8+/-2.0+/-1.6)x10(-6) and B(B+-->K(+)K(0)(S)K(0)(S))=(10.7+/-1.2+/-1.0)x10(-6).

Searches for B0 decays to combinations of two charmless isoscalar mesons.

We search for B meson decays into two-body combinations of eta, eta', omega, and phi mesons from 89 x 10(6) BB pairs collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider at SLAC. We find the branching fraction B(B0-->etaomega)=(4.0(+1.3)(-1.2)+/-0.4)x10(-6) with a significance of 4.3 sigma. For the other decay modes we set the following 90% confidence level upper limits on the branching fractions, in units of 10(-6): B(B0-->etaeta)<2.8, B(B0-->etaeta')<4.6, B(B0-->eta'eta')<10, B(B0-->eta'omega)<2.8, B(B0-->etaphi)<1.0, B(B0-->eta'phi)<4.5, and B(B0-->phiphi)<1.5.

Search for B0 decays to invisible final states and to nunugamma.

We establish upper limits on branching fractions for B0 decays to final states where the decay products are purely invisible (i.e., no observable final state particles) and for B0 decays to nunugamma. Within the standard model, these decays have branching fractions that are below current experimental sensitivity, but various models of physics beyond the standard model predict significant contributions from these channels. Using 88.5 x 10(6) BB pairs collected at the Upsilon(4S) resonance by the BABAR experiment at the PEP-II e(+)e- storage ring at the Stanford Linear Accelerator Center, we establish upper limits at the 90% confidence level of 22 x 10(-5) for the branching fraction of B0-->invisible and 4.7 x 10(-5) for the branching fraction of B0-->nunugamma.

Bound on the ratio of decay amplitudes for -B0-->J/psiK*0 and B0-->J/psiK*0.

We have measured the time-dependent decay rate for the process B-->J/psiK(*0) (892) in a sample of about 88x10(6) Upsilon(4S)-->B(-)B decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. In this sample we study flavor-tagged events in which one neutral B meson is reconstructed in the J/psiK(*0) or J/psi(-)K(*0) final state. We measure the coefficients of the cosine and sine terms in the time-dependent asymmetries for J/psiK(*0) and J/psi(-)K(*0), find them to be consistent with the standard model expectations, and set upper limits at 90% confidence level (C.L.) on the decay amplitude ratios |A((-)B(0)-->J/psiK(*0))|/|A(B0-->J/psiK(*0))|<0.26 and |A(B0-->J/psi(-)K(*0))|/|A((-)B(0)-->J/psi(-)K(*0))|<0.32. For a single ratio of wrong-flavor to favored amplitudes for B0 and (-)B(0) combined, we obtain an upper limit of 0.25 at 90% C.L.

Measurement of the B-->Xsl+l- branching fraction with a sum over exclusive modes.

We measure the branching fraction for the flavor-changing neutral-current process B-->X(s)l(+)l(-) with a sample of 89x10(6) Upsilon(4S)-->BBmacr; events recorded with the BABAR detector at the PEP-II e(+)e(-) storage ring. The final state is reconstructed from e(+)e(-) or micro(+)micro(-) pairs and a hadronic system X(s) consisting of one K+/- or K(0)(S) and up to two pions, with at most one pi(0). We observe a signal of 40+/-10(stat)+/-2(syst) events and extract the inclusive branching fraction B(B-->X(s)l(+)l(-))=(5.6+/-1.5(stat)+/-0.6(exp syst)+/-1.1(model syst))x10(-6) for ml(+)(l(-))>0.2 GeV/c(2).

Study of high momentum eta' production in B --> eta'Xs.

We measure the branching fraction for the charmless semi-inclusive process B --> eta'Xs, where the eta' meson has a momentum in the range 2.0 to 2.7 GeV/c in the upsilon4S center-of-mass frame and Xs represents a system comprising a kaon and zero to four pions. We find B(B --> eta'Xs) = [3.9 +/- 0.8(stat) +/- 0.5(syst) +/- 0.8(model)] x 10(-4). We also obtain the Xs mass spectrum and find that it fits models predicting high masses.