Search for the Decay B+-->K+ tau-/+ mu+/-

We present a search for the lepton flavor violating decay B+-->K+ tau-/+ mu+/- using 383 x 10;{6} BB[over ] events collected by the BABAR experiment. The branching fraction for this decay can be substantially enhanced in new physics models. The kinematics of the tau from the signal B decay are inferred from the K+, mu, and other B in the event, which is fully reconstructed in one of a variety of hadronic decay modes, allowing the signal B candidate to be fully reconstructed. We observe no excess of events over the expected background and set a limit of B(B+-->K+ tau mu)<7.7 x 10(-5) at 90% confidence level, where the branching fraction is for the sum of the K+ tau- mu+ and K+ tau+mu- final states. We use this result to improve a model-independent bound on the energy scale of flavor-changing new physics.

Improved measurement of CP violation in neutral B decays to cc[over]s

We present updated measurements of time-dependent CP asymmetries in fully-reconstructed neutral B decays to several CP eigenstates containing a charmonium meson. The measurements use a data sample of (383+/-4)x10(6) Upsilon(4S)-->BB[over] decays collected with the BABAR detector at the PEP-II B factory. We determine sin2beta = 0.714+/-0.032(stat)+/-0.018(syst) and |lambda|=0.952+/-0.022(stat)+/-0.017(syst).

Measurements of CP-violating asymmetries in the decay B0-->K+K-K0

We analyze the decay B0-->K+K-K0 using 383 x 10(6) BB events collected by the BABAR detector at SLAC to extract CP violation parameter values over the Dalitz plot. Combining all K+K-K0 events, we find ACP=-0.015+/-0.077+/-0.053 and beta eff = 0.352+/-0.076+/-0.026 rad, corresponding to a CP violation significance of 4.8 sigma. A second solution near pi/2-beta eff is disfavored with a significance of 4.5 sigma. We also report ACP and beta eff separately for decays to phi(1020)K0, f0(980)K0, and K+K-K0 with mK+K- > 1.1 GeV/c2.

Quantum Hall states near the charge-neutral Dirac point in graphene

We investigate the quantum Hall (QH) states near the charge-neutral Dirac point of a high mobility graphene sample in high magnetic fields. We find that the QH states at filling factors nu=+/-1 depend only on the perpendicular component of the field with respect to the graphene plane, indicating that they are not spin related. A nonlinear magnetic field dependence of the activation energy gap at filling factor nu=1 suggests a many-body origin. We therefore propose that the nu=0 and +/-1 states arise from the lifting of the spin and sublattice degeneracy of the n=0 Landau level, respectively.

Measurement of the Time-Dependent CP Asymmetry in B;{0}-->D_{CP};{(*)}h;{0} Decays

We report a measurement of the time-dependent CP-asymmetry parameters S and C in color-suppressed B{0}-->D{(*)0}h{0} decays, where h{0} is a pi{0}, eta, or omega meson, and the decays to one of the CP eigenstates K+K-, K{S}{0}pi{0}, or K{S}{0}omega. The data sample consists of 383 x 10{6} Upsilon(4S)-->BB decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. The results are S=-0.56+/-0.23+/-0.05 and C=-0.23+/-0.16+/-0.04, where the first error is statistical and the second is systematic.

Measurement of CP-violating asymmetries in B0-->D*(+/-)D(-/+)

We present updated measurements of CP-violating asymmetries in the decays B0-->D*(+/-)D(-/+) and B0-->D+D- using (383+/-4) x 10(6)B(B) pairs collected by the BABAR detector at the SLAC PEP-II B factory. We determine the time-integrated CP asymmetry A(D*(+/-)D(-/+))=0.12+/-0.06+/-0.02, and the time-dependent asymmetry parameters to be C(D*+D-)=0.18+/-0.15+/-0.04, S(D*+D-)=-0.79+/-0.21+/-0.06, C(D*-D+)=0.23+/-0.15+/-0.04, S(D*-D+)=-0.44+/-0.22+/-0.06, C(D+D-)=0.11+/-0.22+/-0.07, and S(D+D-)=-0.54+/-0.34+/-0.06, where the first uncertainty is statistical and the second is systematic.

Production and decay of Omegac0

We present an analysis of inclusive Omega(c)(0) baryon production and decays in 230.5 fb(-1) of data recorded with the BABAR detector. Omega(c)(0) baryons are reconstructed in four final states (Omega(-)pi(+), Omega(-)pi(+)pi(0), Omega(-)pi(+)pi(+)pi(-), Xi(-)K(-)pi(+)pi(+)) and the corresponding ratios of branching fractions are measured. We also measure the momentum spectrum in the e(+)e(-) center-of-mass frame. From the spectrum, we observe Omega(c)(0) production from B decays and in cc events, and extract the two rates of production.

Search for the rare decay B-->pil+ l-

We have performed a search for the flavor-changing neutral-current decays B-->pil+ l-, where l+ l- is either e+ e- or mu+ mu-, using a sample of 230 x 10(6) Upsilon(4S)-->BB decays collected with the BABAR detector. We observe no evidence of a signal and measure the upper limit on the isospin-averaged branching fraction to be B(B-->pil+ l-)<9.1 x 10(-8) at 90% confidence level. We also search for the lepton-flavor-violating decays B-->pie+/- mu-/+ and measure an upper limit on the isospin-averaged branching fraction of B(B-->pie+/- mu-/+)<9.2 x 10(-8) at 90% confidence level.

Observation of CP violation in B(0) --> K(+)pi(-) and B(0) --> pi(+)pi(-)

We report observations of CP violation in the decays B(0) --> K(+)pi(-) and B(0) --> pi(+)pi(-) in a sample of 383 x 10(6) Upsilon(4S) --> BB[over] events. We find 4372+/-82 B(0) --> K(+)pi(-) decays and measure the direct CP-violating charge asymmetry A(Kpi) = -0.107+/-0.018(stat)(-0.004)(+0.007)(syst), which excludes the CP-conserving hypothesis with a significance of 5.5 standard deviations. In the same sample, we find 1139+/-49 B(0) --> pi(+)pi(-) decays and measure the CP-violating asymmetries S(pipi) = -0.60+/-0.11(stat)+/-0.03(syst) and C(pipi) = -0.21+/-0.09(stat)+/-0.02(syst). CP conservation in B(0) --> pi(+)pi(-) (S(pipi) = C(pipi) = 0) is excluded at a confidence level 1-C.L. = 8 x 10(-8), corresponding to 5.4 standard deviations.

Evidence of a broad structure at an invariant mass of 4.32 GeV/c2 in the reaction e+e- --> pi+pi-psi(2S) measured at BABAR

We present a measurement of the cross section of the process e(+)e(-)-->pi(+)pi(-)psi(2S) from threshold up to 8 GeV center-of-mass energy using events containing initial-state radiation, produced at the SLAC PEP-II e(+)e(-) storage rings. The study is based on 298 fb(-1) of data recorded with the BABAR detector. A structure is observed in the cross section not far above threshold, near 4.32 GeV. We also investigate the compatibility of this structure with the Y(4260) previously reported by this experiment.

Measurement of branching fractions and mass spectra of B-->Kpipigamma

We present a measurement of the partial branching fractions and mass spectra of the exclusive radiative penguin processes B-->Kpipigamma in the range m(Kpipi)<1.8 GeV/c(2). We reconstruct four final states: K(+)pi(-)pi(+)gamma, K(+)pi(-)pi(0)gamma, K(S)(0)pi(-)pi(+)gamma, and K(S)(0)pi(+)pi(0)gamma, where K(S)(0)-->pi(+)pi(-). Using 232 x 10(6) e(+)e(-)-->BB events recorded by the BABAR experiment at the SLAC PEP-II asymmetric-energy storage ring, we measure the branching fractions B(B(+)-->K(+)pi(-)pi(+)gamma)=[2.95+/-0.13(stat)+/-0.20(syst)] x 10(-5), B(B(0)-->K(+)pi(-)pi(0)gamma)=[4.07+/-0.22(stat)+/-0.31(syst)] x 10(-5), B(B(0)-->K(0)pi(+)pi(-)gamma)=[1.85+/-0.21(stat)+/-0.12(syst)] x 10(-5), and B(B(+)-->K(0)pi(+)pi(0)gamma)=[4.56+/-0.42(stat)+/-0.31(syst)] x 10(-5).

Evidence for D0-D0 mixing

We present evidence for D0-D(0) mixing in D(0)-->K(+)pi(-) decays from 384 fb(-1) of e(+)e(-) colliding-beam data recorded near square root s=10.6 GeV with the BABAR detector at the PEP-II storage rings at the Stanford Linear Accelerator Center. We find the mixing parameters x('2)=[-0.22+/-0.30(stat)+/-0.21(syst)] x 10(-3) and y(')=[9.7+/-4.4(stat)+/-3.1(syst)] x 10(-3) and a correlation between them of -0.95. This result is inconsistent with the no-mixing hypothesis with a significance of 3.9 standard deviations. We measure R(D), the ratio of doubly Cabibbo-suppressed to Cabibbo-favored decay rates, to be [0.303+/-0.016(stat)+/-0.010(syst)]%. We find no evidence for CP violation.

Infrared spectroscopy of Landau levels of graphene

We report infrared studies of the Landau level (LL) transitions in single layer graphene. Our specimens are density tunable and show in situ half-integer quantum Hall plateaus. Infrared transmission is measured in magnetic fields up to B=18 T at selected LL fillings. Resonances between hole LLs and electron LLs, as well as resonances between hole and electron LLs, are resolved. Their transition energies are proportional to sqrt[B], and the deduced band velocity is (-)c approximately equal to 1.1 x 10(6) m/s. The lack of precise scaling between different LL transitions indicates considerable contributions of many-particle effects to the infrared transition energies.

Measurements of CP-violating asymmetries in B0-->a1+/-(1260)pi-/+ decays

We present measurements of CP-violating asymmetries in the decay B(0)-->a(1)(+/-)(1260)pi(-/+) with a(1)(+/-)(1260)-->pi(-/+)pi(+/-)pi(+/-). The data sample corresponds to 384x10(6) BB[over ] pairs collected with the BABAR detector at the PEP-II asymmetric B factory at SLAC. We measure the CP-violating asymmetry A(CP)(a(1)pi)=-0.07+/-0.07+/-0.02, the mixing-induced CP violation parameter S(a(1)pi)=0.37+/-0.21+/-0.07, the direct CP violation parameter C(a(1)pi)=-0.10+/-0.15+/-0.09, and the parameters DeltaC(a(1)pi)=0.26+/-0.15+/-0.07 and DeltaS(a(1)pi)=-0.14+/-0.21+/-0.06. From these measured quantities we determine the angle alpha(eff)=78.6 degrees +/-7.3 degrees.

Branching fraction measurements of B+-->rho+gamma, B0-->rho0gamma, and B0-->omegagamma

We present a study of the decays B+-->rho+gamma, B0-->rho0gamma, and B0-->omegagamma. The analysis is based on data containing 347 x 10(6) BB[over ] events recorded with the BABAR detector at the PEP-II asymmetric B factory. We measure the branching fractions B(B+-->rho+)gamma)=(1.10_(-0.33)(+0.37)+/-0.09)x10(-6) and B(B0-->rho0gamma)=(0.79(-0.20)(+0.22)+/-0.06)x10(-6), and set a 90% C.L. upper limit B(B0-->omegagamma)<0.78 x 10(-6). We also measure the isospin-averaged branching fraction B(B-->(rho/omega)gamma)=(1.25(-0.24)(+0.25)+/-0.09)x10(-6), from which we determine |Vtd/Vts|=0.200(-0.020)(+0.021)+/-0.015, where the first uncertainty is experimental and the second is theoretical.

Measurement of the pseudoscalar decay constant fDs using charm-tagged events in e+e- collisions at square root s=10.58 GeV

Using 230.2 fb-1 of e+e- annihilation data collected with the BABAR detector at and near the peak of the Upsilon(4S) resonance, 489+/-55 events containing the pure leptonic decay Ds+-->micro;+numicro have been isolated in charm-tagged events. The ratio of partial widths Gamma(D+-->micro+numicro)/Gamma(Ds+-->phipi+) is measured to be 0.143+/-0.018+/-0.006 allowing a determination of the pseudoscalar decay constant fDs=(283+/-17+/-7+/-14) MeV. The errors are statistical, systematic, and from the Ds+-->phipi+ branching ratio, respectively.

Evidence for B(0) --> rho(0)rho(0) decays and implications for the Cabibbo-Kobayashi-Maskawa angle alpha

We search for the decays B(0) --> rho(0)rho(0), B(0) --> rho(0)f(0)(980), and B(0) --> f(0)(980)f(0)(980) in a sample of about 384 x 10(6) Upsilon(4S) --> BB[over] decays collected with the BABAR detector at the PEP-II asymmetric-energy e(+)e(-) collider at Stanford Linear Accelerator Center. We find evidence for B(0) --> rho(0)rho(0) with 3.5 sigma significance and measure the branching fraction B = (1.07 +/- 0.33 +/- 0.19) x 10(-6) and longitudinal polarization fraction f(L) = 0.87 +/- 0.13 +/- 0.04, where the first uncertainty is statistical, and the second is systematic. The uncertainty on the Cabibbo-Kobayashi-Maskawa quark-mixing matrix unitarity angle alpha due to penguin contributions in B --> rho rho decays is 18 degrees at the 1 sigma level. We also set upper limits on the B(0) --> rho(0)f(0)(980) and B(0) --> f(0)(980)f(0)(980) decay rates.

Room-Temperature Quantum Hall Effect in Graphene

The quantum Hall effect (QHE), one example of a quantum phenomenon that occurs on a truly macroscopic scale, has attracted intense interest since its discovery in 1980 and has helped elucidate many important aspects of quantum physics. It has also led to the establishment of a new metrological standard, the resistance quantum. Disappointingly, however, the QHE has been observed only at liquid-helium temperatures. We show that in graphene, in a single atomic layer of carbon, the QHE can be measured reliably even at room temperature, which makes possible QHE resistance standards becoming available to a broader community, outside a few national institutions.

Measurement of the B0-->pi(-l)(+nu) form-factor shape and branching fraction, and determination of /Vub/ with a loose neutrino reconstruction technique

We report the results of a study of the exclusive charmless semileptonic decay, B0-->pi(-l)(+nu), undertaken with approximately 227 x 10(6) BB pairs collected at the Upsilon(4S) resonance with the BABAR detector. The analysis uses events in which the signal B decays are reconstructed with an innovative loose neutrino reconstruction technique. We obtain partial branching fractions in 12 bins of q2, the momentum transfer squared, from which we extract the f + (q2) form-factor shape and the total branching fraction B(B0-->pi(-l)(+nu))=(1.46+/-0.07stat+/-0.08syst) x 10(-4). Based on a recent unquenched lattice QCD calculation of the form factor in the range q2>16 GeV2, we find the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element /Vub/ to be (4.1+/-0.2stat +/- 0.2syst(+0.6)-0.4_{FF}) x 10(-3), where the last uncertainty is due to the normalization of the form factor.

Observation of decays B0-->Ds(*)+ pi- and B0-->Ds(*)- K+

We report the observation of decays B{0}-->D{s}{(*)+}pi- and B{0}-->D{s}{(*)-}K+ in a sample of 230 x 10(6) Upsilon(4S)-->BB[over] events recorded with the BABAR detector at the SLAC PEP-II asymmetric-energy e+ e- storage ring. We measure the branching fractions B(B{0}-->D{s}{+}pi-)=(1.3+/-0.3(stat)+/-0.2(syst))x10(-5), B(B{0}-->D{s}{-} K+)=(2.5+/-0.4(stat)+/-0.4(syst))x10(-5), B(B{0}-->D{s}{*+}pi-)=(2.8+/-0.6(stat)+/-0.5(syst))x10(-5), and B(B{0}-->D{s}{*-}K+)=(2.0+/-0.5(stat)+/-0.4(syst))x10(-5). The significances of the measurements to differ from zero are 5, 9, 6, and 5 standard deviations, respectively. This is the first observation of B{0}-->D{s}{+}pi-, B{0}-->D{s}{*+}pi-, and B{0}-->D{s}{*-}K+ decays.

Search for lepton flavor violating decays tau(+/-) --> l(+/-)pi0, l(+/-)eta, l(+/-)eta'

A search for lepton flavor violating decays of the tau lepton to a lighter mass lepton and a pseudoscalar meson has been performed using 339 fb;{-1} of e;{+}e;{-} annihilation data collected at a center-of-mass energy near 10.58 GeV by the BABAR detector at the SLAC PEP-II storage ring. No evidence of a signal has been found, and upper limits on the branching fractions are set at the 10;{-7} level.

Vector-tensor and vector-vector decay amplitude analysis of B0-->phiK*0

We perform an amplitude analysis of the decays B(0)-->phiK*(2)(1430)(0), phiK*(892)(0), and phi(Kpi)(0)(S-wave) with a sample of about 384x10(6) BB[over ] pairs recorded with the BABAR detector. The fractions of longitudinal polarization f(L) of the vector-tensor and vector-vector decay modes are measured to be 0.853(-0.069+0.061)+/-0.036 and 0.506+/-0.040+/-0.015, respectively. Overall, twelve parameters are measured for the vector-vector decay and seven parameters for the vector-tensor decay, including the branching fractions and parameters sensitive to CP violation.

Measurement of the CP asymmetry and branching fraction of B0-->rho0K0

We present a measurement of the branching fraction and time-dependent CP asymmetry of B(0)-->rho0K0. The results are obtained from a data sample of 227x10(6) Upsilon(4S)-->BB decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at Stanford Linear Accelerator Center. From a time-dependent maximum likelihood fit yielding 111+/-19 signal events, we find B(B(0)-->rho0K0)=(4.9+/-0.8+/-0.9)x10(-6), where the first error is statistical and the second systematic. We report the measurement of the CP parameters S(rho)(0)K(0)S=0.20+/-0.52+/-0.24 and C(rho)(0)K(0)S=0.64+/-0.41+/-0.20.

Observation of B-->eta'K* and evidence for B+-->eta'rho+

We present an observation of B-->eta'K*. The data sample corresponds to 232x10(6) BB[over ] pairs collected with the BABAR detector at the PEP-II asymmetric-energy B factory at the Stanford Linear Accelerator Center. We measure the branching fractions (in units of 10(-6)) B(B(0)-->eta'K*0)=3.8+/-1.1+/-0.5 and B(B+-->eta'K*+)=4.9(1.7)(+1.9)+/-0.8, where the first error is statistical and the second systematic. A simultaneous fit results in the observation of B-->eta'K* with B(B-->eta'K*)=4.1(-0.9)(+1.0)+/-0.5. We also search for B-->eta'rho and eta'f(0)(980)(f(0)-->pi+pi-) with results and 90% confidence level upper limits B(B+-->eta'rho+)=8.7(-2.8-1.3)(+3.1+2.3) (<14), B(B(0)-->eta'rho0)<3.7, and B(B(0)-->eta'f(0)(980)(f(0)-->pi+pi-))<1.5. Charge asymmetries in the channels with significant yields are consistent with zero.

Observation of CP violation in B --> eta'K0 decays

We present measurements of the time-dependent CP-violation parameters S and C in B(0) --> eta(')K(0) decays. The data sample corresponds to 384 x 10(6) BB pairs produced by e(+)e(-) annihilation at the Upsilon(4S). The results are S=0.58+/-0.10+/-0.03 and C=-0.16+/-0.07+/-0.03. We observe mixing-induced CP violation with a significance of 5.5 standard deviations in this b --> s penguin dominated mode.

Observation of a Charmed Baryon Decaying to D;{0}p at a Mass Near 2.94 GeV/c;{2}

A search for charmed baryons decaying to D(0)p reveals two states: the Lambdac(2880)+ baryon and a previously unobserved state at a mass of [2939.8+/-1.3(stat)+/-1.0(syst)] MeV/c2 and with an intrinsic width of [17.5+/-5.2(stat)+/-5.9(syst)] MeV. Consistent and significant signals are observed for the K(-)pi(+) and K(-)pi(+)pi(-)pi(+) decay modes of the D0 in 287 fb(-1) annihilation data recorded by the BABAR detector at a center-of-mass energy of 10.58 GeV. There is no evidence in the D+p spectrum of doubly charged partners. The mass and intrinsic width of the Lambdac(2880)+ baryon and relative yield of the two baryons are also measured.

Measurements of branching fraction, polarization, and charge asymmetry of B(+/-)-->rho(+/-)rho(0) and a search for B(+/-)-->rho(+/-)f(0)(980)

We measure the branching fraction (B), polarization (f(L)), and CP asymmetry (A(CP)) of B(+/-)-->rho(+/-)rho(0) decays and search for the decay B(+/-)-->rho(+/-)f(0)(980) based on a data sample of 231.8 x 10(6) Upsilon(4S)-->BB decays collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B factory. In B(+/-)-->rho(+/-)rho(0) decays we measure B=(16.8+/-2.2+/-2.3) x 10(-), f(L)=0.905+/-0.042(-0.027)(+0.023), and A(CP)=-0.12+/-0.13+/-0.10, and find an upper limit on the branching fraction of B(+/-)-->rho(+/-)f(0)(980)(-->pi(+)pi(-)) decays of 1.9 x 10(-6) at 90% confidence level.

Observation of B(+)-->phiphiK(+) and evidence for B(0)-->phiphiK(0) below eta(c) threshold

We report measurements of the decays B(+)-->phiphiK(+) and B(0)-->phiphiK(0) using a sample of 231 x 10(6) BB pairs collected with the BABAR detector at the PEP-II asymmetric-energy B factory at the Stanford Linear Accelerator Center. The branching fractions are measured to be B(B(+)-->phiphiK(+))=(7.5+/-1.0(stat)+/-0.7(syst)) x 10(-6) and B(B(0)-->phiphiK(0))=(4.1(-1.4)(+1.7)(stat)+/-0.4(syst)) x 10(-6) for a phiphi invariant mass below 2.85 GeV/c(2).

Observation of an excited charm baryon Omega c* decaying to Omega c0gamma

We report the first observation of an excited singly charmed baryon Omega c* (css) in the radiative decay Omega c0gamma, where the Omega c0 baryon is reconstructed in the decays to the final states Omega(-)pi+, Omega(-)pi+pi0, Omega(-)pi+pi(-)pi+, and Xi(-)K(-)pi+pi+. This analysis is performed using a data set of 230.7 fb(-1) collected by the BABAR detector at the PEP-II asymmetric-energy B factory at the Stanford Linear Accelerator Center. The mass difference between the Omega c* and the Omega c0 baryons is measured to be 70.8+/-1.0(stat)+/-1.1(syst) MeV/c2. We also measure the ratio of inclusive production cross sections of Omega c* and Omega c0 in e+e(-) annihilation.

Search for D0-D0 mixing and branching-ratio measurement in the decay D0-->K+ pi- pi0

We analyze 230.4 fb;{-1} of data collected with the BABAR detector at the PEP-II e;{+}e;{-} collider at SLAC to search for evidence of D0-D[over ];{0} mixing using regions of phase space in the decay D;{0}-->K;{+}pi;{-}pi;{0}. We measure the time-integrated mixing rate R_{M}=(0.023_{-0.014};{+0.018}(stat.)+/-0.004(syst.))%, and R_{M}<0.054% at the 95% confidence level, assuming CP invariance. The data are consistent with no mixing at the 4.5% confidence level. We also measure the branching ratio for D;{0}-->K;{+}pi;{-}pi;{0} relative to D;{0}-->K;{-}pi;{+}pi;{0} to be (0.214+/-0.008(stat.)+/-0.008(syst.))%.

Observation of a new Ds meson decaying to DK at a mass of 2.86 GeV/c2

We observe a new D_{s} meson with mass (2856.6+/-1.5_{stat}+/-5.0_{syst}) MeV/c;{2} and width (48+/-7_{stat}+/-10_{syst}) MeV/c;{2} decaying into D0K+ and D;{+}K_{S};{0}. In the same mass distributions, we also observe a broad structure with mass (2688+/-4_{stat}+/-3_{syst}) MeV/c;{2} and width (112+/-7_{stat}+/-36_{syst}) MeV/c;{2}. To obtain this result, we use 240 fb;{-1} of data recorded by the BABAR detector at the PEP-II asymmetric-energy e;{+}e;{-} storage rings at the Stanford Linear Accelerator Center running at center-of-mass energies near 10.6 GeV.

Measurement of the B-->pi l nu branching fraction and determination of absolute value of V(ub) with tagged B mesons

We report a measurement of the B-->pi l nu branching fraction based on 211 fb(-1) of data collected with the BABAR detector. We use samples of B0 and B+ mesons tagged by a second B meson reconstructed in a semileptonic or hadronic decay and combine the results assuming isospin symmetry to obtain B(B(0)-->pi- l+ nu) = (1.33+/-0.17stat+/-0.11syst) x 10(-4). We determine the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element absolute value V(ub) by combining the partial branching fractions measured in ranges of the momentum transfer squared and theoretical calculations of the form factor. Using a recent lattice QCD calculation, we find absolute value V(ub) = (4.5+/-0.5stat+/-0.3syst(+0.7) -0.5FF x 10(-3), where the last error is due to the normalization of the form factor.

Measurements of branching fractions, polarizations, and direct CP-violation asymmetries in B-->rhoK* and B-->f0(980)K* decays

We report searches for B-meson decays to the charmless final states rhoK* and f0(980)K* with a sample of 232x10(6) BB pairs collected with the BABAR detector at the PEP-II e+e- collider. We measure in units of 10(-6) the following branching fractions, where the first error quoted is statistical and the second systematic, or upper limits are given at the 90% confidence level: B(B+-->rho0K*+)<6.1, B(B+-->rho+K*0)=9.6+/-1.7+/-1.5, B(B0-->rho-K*+)<12.0, B(B0-->rho0K*0)=5.6+/-0.9+/-1.3, B(B+-->f0(980)K*+)=5.2+/-1.2+/-0.5, and B(B0-->f0(980)K*0)<4.3. For the significant modes, we also measure the fraction of longitudinal polarization and the charge asymmetry: fL(B+-->rho+K*0)=0.52+/-0.10+/-0.04, fL(B0-->rho0K*0)=0.57+/-0.09+/-0.08, ACP(B+-->rho+K*0)=-0.01+/-0.16+/-0.02, ACP(B0-->rho0K*0)=0.09+/-0.19+/-0.02, and ACP(B+-->f0(980)K*+)=-0.34+/-0.21+/-0.03.

Measurement of branching fractions and charge asymmetries in B decays to an eta meson and a K* meson

We present measurements of branching fractions and charge asymmetries for the decays B-->etaK*, where K* indicates a spin 0, 1, or 2 Kpi system. The data sample corresponds to 344x10(6) BB pairs collected with the BABAR detector at the PEP-II asymmetric-energy e+ e- collider at SLAC. We measure the branching fractions (in units of 10(-6): B(B0-->etaK*0(892))=16.5+/-1.1+/-0.8, B(B+-->etaK*+(892))=18.9+/-1.8+/-1.3, B(B0-->eta(Kpi)0*0)=11.0+/-1.6+/-1.5, B(B+-->eta(Kpi)0*+)=18.2+/-2.6+/-2.6, B(B0-->etaK2*0(1430))=9.6+/-1.8+/-1.1, and B(B+-->etaK2*+(1430))=9.1+/-2.7+/-1.4. We also determine the charge asymmetries for all decay modes.

Transforming growth factor beta and monocyte chemotactic protein-1 are elevated in cerebrospinal fluid of immunocompromised patients with HIV-1 infection

Monocyte infiltration of the brain is central to the pathogenesis of HIV-1 encephalitis. The cytokines promoting recruitment of monocytes into the central nervous system during HIV-1 infection are not established. In this study, we evaluated human cerebrospinal fluid from patients with HIV-1 infection for transforming growth factor beta1 (TGFbeta1) and monocyte chemotactic protein-1 (MCP-1) using a quantitative sandwich enzyme-linked immunoassays. Cytokine levels were compared to those from patients with multiple sclerosis and normal controls. In cerebrospinal fluid of patients with HIV-1 infection and CD4<500 cells/mm3, both TGFbeta1 and MCP-1 were significantly elevated compared to those with CD4>500 cells/mm3, multiple sclerosis, and controls.

Observation of B+ --> K0K+ and B0 --> K0K0

We report observations of the b --> d penguin-dominated decays B+ --> K0K+ and B0 --> K0K0 in 316 fb(-1) of e+ e- collision data collected with the BABAR detector. We measure the branching fractions B(B+ --> K0K+) = (1.61+/-0.44+/-0.09) x 10(-6) and B(B0 --> K0K0 = (1.08+/-0.28+/-0.11) x 10(-6) and the CP-violating charge asymmetry A(CP)(K0K+) = 0.10+/-0.26+/-0.03. Using a vertexing technique previously employed in several analyses of all-neutral final states containing kaons, we report the first measurement of time-dependent CP-violating asymmetries in B0 --> K(S)0K(S)0, obtaining S = -1.28(-0.73-0.16)(+0.80+0.11) and C = -0.40+/-0.41+/-0.06. We also report improved measurements of the branching fraction B(B+ --> K0 pi+) = (23.9+/-1.1+/-1.0) x 10(-6) and CP-violating charge asymmetry A(CP)(K0 pi+) = -0.029+/-0.039+/-0.010.

Measurement of the branching fraction and photon energy moments of B-->Xs gamma and A(CP)(B --> X(s+d gamma))

The photon spectrum in B-->Xs gamma decay, where Xs is any strange hadronic state, is studied using a data sample of 88.5 x 10(6) e+ e- --> Upsilon(4S) --> BB decays collected by the BABAR experiment at the Stanford Linear Accelerator Center. The partial branching fraction, DeltaB(B --> Xs gamma) = (3.67+/-0.29(stat)+/-0.34(syst)+/-0.29(model)) x 10(-4), the first moment <E gamma> = 2.288+/-0.025+/-0.017+/-0.015 GeV, and the second moment E2(gamma) = 0.0328+/-0.0040+/-0.0023+/-0.0036 GeV2 are measured for the photon energy range 1.9 GeV < E gamma < 2.7 GeV. They are also measured for narrower E gamma ranges. The moments are then fit to recent theoretical calculations to extract the heavy quark expansion parameters m(b) and mu2(pi) and to extrapolate the partial branching fraction to E gamma > 1.6 GeV. In addition, the direct CP asymmetry A(CP)(B-->X(s+d gamma) is measured to be -0.110+/-0.115(stat)+/-0.017(syst).

Observation of e(+)e(-) annihilation into the C = +1 hadronic final states rho(0)rho(0) and phirho(0)

We report the first observation of e(+)e(-) annihilation into states of positive C parity, namely, rho(0)rho(0) and phirho(0). The two states are observed in the pi(+)pi(-)pi(+)pi(-) and K(+)K(-)pi(+)pi(-) final states, respectively, in a data sample of 225 fb(-1) collected by the BABAR experiment at the Positron-Electron Project II e(+)e(-) storage rings at energies near sqrt[s]=10.58 GeV. The distributions of costheta(*), where theta(*) is the center-of-mass polar angle of the phi meson or the forward rho(0) meson, suggest production by two-virtual-photon annihilation. We measure cross sections within the range |costheta(*)|<0.8 of sigma(e(+)e(-)-->rho(0)rho(0))=20.7+/-0.7(stat)+/-2.7(syst) fb and sigma(e(+)e(-)-->phirho(0))=5.7+/-0.5(stat)+/-0.8(syst) fb.

Measurement of the spin of the omega(-) hyperon

A measurement of the spin of the Omega(-) hyperon produced through the exclusive process Xi(c)(0)-->Omega(-)K(+) is presented using a total integrated luminosity of 116 fb(-1) recorded with the BABAR detector at the e(+)e(-) asymmetric-energy B factory at SLAC. Under the assumption that the Xi(c)(0) has spin 1/2, the angular distribution of the Lambda from Omega(-)-->LambdaK(-) decay is inconsistent with all half-integer Omega(-) spin values other than 3/2. Lower statistics data for the process Omega(c)(0)-->Omega(-)pi(+) from a 230 fb(-1) sample are also found to be consistent with Omega(-) spin 3/2. If the Xi(c)(0) spin were 3/2, an Omega(-) spin of 5/2 could not be excluded.

Observation of B0 meson decay to a 1 +/(1260)pi /+

We present a measurement of the branching fraction of the decay B(0)-->a1 (+/)(1260)pi(/+) with a1 (+/)(1260)-->pi(/+)pi(+/)pi(+/). The data sample corresponds to 218 x 10(6) BB[over ] pairs produced in e+e- annihilation through the Upsilon(4S) resonance. We measure the branching fraction Beta(B(0)-->a1(+/)(1260)pi(/+))Beta(a1(+/)(1260)-->pi(/+)pi(+/)pi(+/)) = (16.6+/1.9+/1.5) x 10(-6), where the first error quoted is statistical and the second is systematic.

Search for T, CP, and CPT violation in B0-B0 mixing with inclusive dilepton events

We report the results of a search for T, CP, CPT, and violation in B0-B0 mixing using an inclusive dilepton sample collected by the BABAR experiment at the PEP-II factory. Using a sample of 232 x 10(6) BB pairs, we measure the T and CP violation parameter |q/p| - 1 = (-0.8 +/- 2.7(stat) +/- 1.9(syst) x 10(-3), and the CPT and CP parameters Imz = (13.9 +/- 7.3(stat) +/- 3.2(syst)) x 10(-3) and Delta Gamma x Rez = (7.1 +/- 3.9(stat) +/- 2.0(stat)) x 10(-3) ps(-1). The statistical correlation between the measurements of Imz and Delta Gamma x Rez is 76%.

Search for the rare decay B0-->tau+tau- at BABAR

We present the results of a search for the decay B0-->tau+tau- in a data sample of (232+/-3)x10(6) Upsilon(4S)-->BB decays using the BABAR detector. Certain extensions of the standard model predict measurable levels of this otherwise rare decay. We reconstruct fully one neutral B meson and seek evidence for the signal decay in the rest of the event. We find no evidence for signal events and obtain Beta(B0->tau+tau-)<4.1x10(-3) at the 90% confidence level.

Observation of Upsilon(4S) decays to pi(+)pi(-)Upsilon(1S) and pi(+)pi(-)Upsilon(2S)

Observation of Upsilon(4S) decays to pi(+)pi(-)C and pi(+)pi(-)Upsilon(2S)We present the first measurement of Upsilon(4S) decays to pi(+)pi(-)Upsilon(1S) based on a sample of 230 x 106(4S) mesons collected with the BABAR detector. We measure the product branching fractions Beta(Upsilon(4S) --> pi(+)pi(-)Upsilon(1S)) x BetaUpsilon(1S) --> mu(+)mu(-) = (2.23 +/- 0.25(stat) +/- 0.27(syst))x 10(-6) and Beta(Upsilon(4S) --> pi(+)pi(-)Upsilon(2S) x Beta(Upsilon(2S) --> mu(+)mu(-))=(1.69 +/-0.26(stat) +/- 0.20(syst)) x 10(-)6, from which we derive the partial widths Gamma(Upsilon(4S) --> pi(+)pi(-)Upsilon(1S))=(1.8 +/-0.4) keV and Gamma(Upsilon(4S) --> pi(+)pi(-)Upsilon(2S))=(2.7 +/- 0.8) keV.

Determinations of from inclusive semileptonic decays with reduced model dependence

We report two novel determinations of /|Vub/ with reduced model dependence, based on measurements of the mass distribution of the hadronic system in semileptonic B decays. Events are selected by fully reconstructing the decay of one B meson and identifying a charged lepton from the decay of the other B meson from Upsilon(4S)-->BB events. In one approach, we combine the inclusive B-->Xulambdav rate, integrated up to a maximum hadronic mass mX<1.67 GeV/c2, with a measurement of the inclusive B-->Xsgamma photon energy spectrum. We obtain /Vub/=(4.43+/-0.38stat+/-0.25syst+/-0.29theo) x 10-3. In another approach we measure the total B-->Xulambdav rate over the full phase space and find /Vub/=(3.84+/-0.70stat+/-0.30syst+/-0.10theo) x 10-3.

Landau-level splitting in graphene in high magnetic fields

The quantum Hall (QH) effect in two-dimensional electrons and holes in high quality graphene samples is studied in strong magnetic fields up to 45 T. QH plateaus at filling factors nu = 0, +/-1, +/-4 are discovered at magnetic fields B > 20 T, indicating the lifting of the fourfold degeneracy of the previously observed QH states at nu = +/-4(absolute value(n) + 1/2), where n is the Landau-level index. In particular, the presence of the nu = 0, +/-1 QH plateaus indicates that the Landau level at the charge neutral Dirac point splits into four sublevels, lifting sublattice and spin degeneracy. The QH effect at nu = +/-4 is investigated in a tilted magnetic field and can be attributed to lifting of the spin degeneracy of the n = 1 Landau level.

Measurements of the absolute branching fractions of B+/- --> K+/-X(cc)

We study the two-body decays of B+/- mesons to K+/- and a charmonium state X(cc) in a sample of 210.5 fb(-1) of data from the BABAR experiment. We perform measurements of absolute branching fractions beta(B+/- --> K+/-X(cc)) using a missing mass technique, and report several new or improved results. In particular, the upper limit beta(B+/- --> K+/- X(3872)) < 3.2 x 10(-4) at 90% C.L. and the inferred lower limit beta(X(3872)J/psipi+ pi-) > 4.2% will help in understanding the nature of the recently discovered X(3872).

Search for lepton flavor violation in the decay tau+/--->e+/-gamma

A search for the nonconservation of lepton flavor in the decay tau+/--->e+/-gamma has been performed with 2.07x10(8) e+e--->tau+tau- events collected by the BABAR detector at the SLAC PEP II storage ring at a center-of-mass energy near 10.58 GeV. We find no evidence for a signal and set an upper limit on the branching ratio of Beta(tau+/--->e+/-gamma)<1.1x10(-7) at 90% confidence level.