V. Poireau

A Study of

The e(+)e(-) -> p (p) over bar cross section is determined over a range of p (p) over bar masses, from threshold to 4.5 GeV/c(2), by studying the e(+)e(-)-> p (p) over bar gamma process. The data set corresponds to an integrated luminosity of 232 fb(-1), collected with the BABAR detector at the PEP-II storage ring, at an e(+)e(-) center-of-mass energy of 10.6 GeV. The mass dependence of the ratio of electric and magnetic form factors, vertical bar G(E)/G(M)vertical bar, is measured for p (p) over bar masses below 3 GeV/c(2); its value is found to be significantly larger than 1 for masses up to 2.2 GeV/c(2). We also measure J/psi -> p (p) over bar and psi(2S) -> p (p) over bar branching fractions and set an upper limit on Y(4260) -> p (p) over bar production and decay.

e^ + e^ - \to p \bar p

Using a sample of 471 million B{bar B} events collected with the BABAR detector, we study the sum of seven exclusive final states B {yields} X{sub s(d){gamma}}, where X{sub s(d)} is a strange (non-strange) hadronic system with a mass of up to 2.0 GeV/c{sup 2}. After correcting for unobserved decay modes, we obtain a branching fraction for b {yields} d{gamma} of (9.2 {+-} 2.0(stat.) {+-} 2.3(syst.)) x 10{sup -6} in this mass range, and a branching fraction for b {yields} s{gamma} of (23.0 {+-} 0.8(stat.) {+-} 3.0(syst.)) x 10{sup -5} in the same mass range. We find {Beta}(b{yields}d{gamma})/{Beta}(b{yields}s{gamma}) = 0.040 {+-} 0.009(stat.) {+-} 0.010(syst.), from which we determine |V{sub td}/V{sub ts}| = 0.199 {+-} 0.022(stat.) {+-} 0.024(syst.) {+-} 0.002(th.).Using a sample of 471 x 10(6) B (B) over bar events collected with the BABAR detector, we study the sum of seven exclusive final states B -> X-s(d)gamma, where X-s(d) is a strange (nonstrange) hadronic system with a mass of up to 2.0 GeV/c(2). After correcting for unobserved decay modes, we obtain a branching fraction for b -> d gamma of (9.2 +/- 2.0(stat) +/- 2.3(syst) x 10(-6) in this mass range, and a branching fraction for b -> s gamma of (23.0 +/- 0.8(stat) +/- 3.0(syst) x 3.0(syst) x 10(-5) in the same mass range. We find B(b -> d gamma)/B(b -> s gamma) = 0.040 +/- 0.009(stat) +/- 0.010(syst), from which we determine vertical bar Vtd/Vts vertical bar = 0.199 +/- 0.022(stat) +/- 0.024(syst) +/- 0.002(th).

using initial state radiation with BABAR

We perform a time-dependent and time-integrated angular analysis of the B{sup 0} {yields} {psi}K*(892){sup 0}, {psi}K*{sub 2}(1430{sup 0}), and {psi}(K{pi}){sub S-wave}{sup 0} decays with the final sample of about 465 million B{bar B} pairs recorded with the BABAR detector. Overall, twelve parameters are measured for the vector-vector decay, nine parameters for the vector-tensor decay, and three parameters for the vector-scalar decay, including the branching fractions, CP-violation parameters, and parameters sensitive to final state interaction. We use the dependence on the K{pi} invariant mass of the interference between the scalar and vector or tensor components to resolve discrete ambiguities of the strong and weak phases. We use the time-evolution of the B {yields} {psi}K{sub S}{sup 0}{pi}{sup 0} channel to extract the CP-violation phase difference {Delta}{phi}{sub 00} = 0.28 {+-} 0.42 {+-} 0.04 between the B and {bar B} decay amplitudes. When the B {yields} {psi}K{sup {+-}}{pi}{sup {-+}} channel is included, the fractions of longitudinal polarization f{sub L} of the vector-vector and vector-tensor decay modes are measured to be 0.494 {+-} 0.034 {+-} 0.013 and 0.901{sub -0.058}{sup +0.046} {+-} 0.037, respectively. This polarization pattern requires the presence of a helicity-plus amplitude in the vector-vector decay from a presently unknown source.

Study of B to X \gamma Decays and Determination of |V_{td}/V_{ts}|

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.

Time-dependent and time-integrated angular analysis of B -> phi K-S(0)pi(0) and phi K-+/-pi(-/+)

We present the results of a search for the decay B{sup 0} {yields} {tau}{sup +}{tau}{sup -} in a data sample of (232 {+-} 3) x 10{sup 6} {Upsilon}(4S) {yields} B{bar B} 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}(B{sup 0} {yields} {tau}{sup +}{tau}{sup -}) < 3.2 x 10{sup -3} at the 90% confidence level.

Search for Lepton Flavor Violation in the Decay tau -> electron gamma

We measure the time-dependent CP asymmetry in B^0→K_S^0π^0γ decays for two regions of K_S^0-π^0 invariant mass, m(KS0π0), using the final BABAR data set of 467×10^6 BB pairs collected at the PEP-II e^+e^- collider at SLAC. We find 339±24 B^0→K^(*0)γ candidates and measure S_(K*γ)=-0.03±0.29±0.03 and C_(K*_γ)=-0.14±0.16±0.03. In the range 1.1<m(K_S^0π^0)<1.8  GeV/c^2 we find 133±20 B^0→K_S^0π^0γ candidates and measure S_(KS^0π^0γ)=-0.78±0.59±0.09 and C_(KS^0π^0γ)=-0.36±0.33±0.04. The uncertainties are statistical and systematic, respectively.

A Search for the Rare Decay B0 to tau+tau- atBaBar

We report an analysis of charmless hadronic decays of neutral B mesons to the final state KsK+/-pi-/+, using a data sample of (465 +/- 5) x 10^6 BB-bar events collected with the BABAR detector at the Y(4S) resonance. We observe an excess of signal events with a significance of 5.2 standard deviations including systematic uncertainties and measure the branching fraction to be BF(B0 --> KsK+/-pi-/+) = (3.2 +/- 0.5 +/- 0.3) x 10^-6, where the uncertainties are statistical and systematic, respectively.

Measurement of Time-Dependent CP Asymmetry in B0 --> KS pi0 gamma Decays

We present measurements of the branching fraction and time-dependent CP asymmetries in B0-->J/psipi0 decays based on 466 x 10(6) Upsilon(4S)-->BB over events collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B factory. We measure the CP asymmetry parameters S= -1.23+/-0.21(stat)+/-0.04(syst) and C= -0.20+/-0.19(stat)+/-0.03(syst), where the measured value of (S, C) is 4.0 standard deviations from (0, 0) including systematic uncertainties. The branching fraction is determined to be B(B0-->J/psipi0)=[1.69+/-0.14(stat)+/-0.07(syst)]x10(-5).

Observation of the rare decay B0 --> KsK+-pi-+

We present searches for the leptonic decays B{sup +} {yields} {ell}{sup +}{nu} and the lepton flavor violating decays B{sup 0} {yields} {ell}{sup {+-}}{tau}{sup {-+}}, where {ell} = e, {mu}, with data collected by the BABAR experiment at SLAC. This search demonstrates a novel technique in which we fully reconstruct the accompanying {bar B} in {Upsilon}(4S) {yields} B{bar B} events, and look for a monoenergetic lepton from the signal B decay. The signal yield is extracted from a fit to the signal lepton candidate momentum distribution in the signal B rest frame. Using a data sample of approximately 378 million B{bar B} pairs (342 fb{sup -1}), we find no evidence of signal in any of the decay modes. Branching fraction upper limits of {Beta}(B{sup +} {yields} e{sup +}{nu}) < 5.2 x 10{sup -6}, {Beta}(B{sup +} {yields} {mu}{sup +}{nu}) < 5.6 x 10{sup -6}, {Beta}(B{sup 0} {yields} e{sup +}{tau}{sup -}) < 2.8 x 10{sup -5} and {Beta}(B{sup 0} {yields} {mu}{sup +}{tau}{sup -}) < 2.2 x 10{sup -5}, are obtained at 90% confidence level.

Evidence for CP violation in B0 to J/Psi pi0 Decays

Searches for