D. G. Hitlin

Measurement of CP observables in B^± → D_(CP)K^± decays and constraints on the CKM angle γ

Using the entire sample of 467 million Y(4S) --> BBbar decays collected with the BaBar detector at the PEP-II asymmetric-energy B factory at SLAC, we perform a GLW analysis of B+- --> D K+- decays, using decay modes in which the neutral D meson decays to either CP-eigenstates or non-CP-eigenstates. We measure the partial decay rate charge asymmetries for CP-even and CP-odd D final states to be A_CP+ = 0.25+-0.06+-0.02 and A_CP- = -0.09+-0.07+-0.02, respectively, where the first error is the statistical and the second is the systematic uncertainty. The parameter A_CP+ is different from zero with a significance of 3.6 standard deviations, constituting evidence for direct CP violation. We also measure the ratios of the charged-averaged B partial decay rates in CP and non-CP decays, R_CP+ = 1.18+-0.09+-0.05 and R_CP- = 1.07+-0.08+-0.04. We infer frequentist confidence intervals for the angle gamma of the (db) unitarity triangle, for the strong phase difference delta_B, and for the amplitude ratio r_B, which are related to the B- --> DK- decay amplitude by r_Be^{i(delta_B-gamma)} = A(B- --> anti-D0 K^-)/A(B- --> D0 K-). Including statistical and systematic uncertainties, we obtain 0.24<r_B<0.45 (0.06<r_B<0.51) and, modulo 180 degrees, 11.3 degrees < gamma < 22.7 degrees or 80.9 degrees < gamma < 99.1 degrees or 157.3 degrees < gamma < 168.7 degrees (7.0 degrees < gamma < 173.0 degrees) at the 68% (95%) confidence level.

Observation and Study of the Baryonic B-meson Decays B to D(*) p pbar (pi) (pi)

We present results for B-meson decay modes involving a charm meson, protons, and pions using 455 x 10{sup 6} B{bar B} pairs recorded by the BABAR detector at the SLAC PEP-II asymmetric-energy e{sup +}e{sup -} collider. The branching fractions are measured for the following ten decays: {bar B}{sup 0} {yields} D{sup 0}p{bar p}, {bar B}{sup 0} {yields} D*{sup 0}p{bar p}, {bar B}{sup 0} {yields} D{sup +}p{bar p}{pi}{sup -}, {bar B}{sup 0} {yields} D*{sup +}p{bar p}{pi}{sup -}, B{sup -} {yields} D{sup 0}p{bar p}{pi}{sup -}, B{sup -} {yields} D*{sup 0}pp{pi}{sup -}, {bar B}{sup 0} {yields} D{sup 0}p{bar p}{pi}{sup -}{pi}{sup +}, {bar B}{sup 0} {yields} D*{sup 0}p{bar p}{pi}{sup -}{pi}{sup +}, B{sup -} {yields} D{sup +}p{bar p}{pi}{sup -}{pi}{sup -}, and B{sup -} {yields} D*{sup +}p{bar p}{pi}{sup -}{pi}{sup -}. The four B{sup -} and the two five-body B{sup 0} modes are observed for the first time. The four-body modes are enhanced compared to the three- and the five-body modes. In the three-body modes, the M(p{bar p}) and M(D{sup (*)0}p) invariant mass distributions show enhancements near threshold values. In the four-body mode {bar B}{sup 0} {yields} D{sup +}p{bar p}{pi}{sup -}, the M(p{pi}{sup -}) distribution shows a narrow structure of unknown origin near 1.5GeV/c{sup 2}. The distributions for the five-body modes, in contrast to the others, are similar to the expectations from uniform phase-space predictions.We present a study of ten B-meson decays to a D{sup (*)}, a proton-antiproton pair, and a system of up to two pions using BABARs data set of 455 x 10{sup 6} B{bar B} pairs. Four of the modes {bar B}{sup 0} {yields} D{sup 0}p{bar p}, {bar B}{sup 0} {yields} D*{sup 0}p{bar p}, {bar B}{sup 0} {yields} D{sup +}p{bar p}{pi}{sup -}, {bar B}{sup 0} {yields} D{sup ast+}p{bar p}{pi}{sup -} are studied with improved statistics compared to previous measurements; six of the modes (B{sup -} {yields} D{sup 0}p{bar p}{pi}{sup -}, B{sup -} {yields} D*{sup 0}p{bar p}{pi}{sup -}, {bar B}{sup 0} {yields} D{sup 0}p{bar p}{pi}{sup -}{pi}{sup +}, {bar B}{sup 0} {yields} D*{sup 0}p{bar p}{pi}{sup -}{pi}{sup +}, B{sup -} {yields} D{sup +}p{bar p}{pi}{sup -}{pi}{sup -}, B{sup -} {yields} D{sup ast+}p{bar p}{pi}{sup -}{pi}{sup -}) are first observations. The branching fractions for 3- and 5-body decays are suppressed compared to 4-body decays. Kinematic distributions for 3-body decays show non-overlapping threshold enhancements in m(p{bar p}) and m(D{sup (*)0}p) in the Dalitz plots. For 4-body decays, m(p{pi}{sup -}) mass projections show a narrow peak with mass and full width of (1497.4 {+-} 3.0 {+-} 0.9)MeV/c{sup 2} and (47 {+-} 12 {+-} 4)MeV/c{sup 2}, respectively, where the firstmorexa0» (second) errors are statistical (systematic). For 5-body decays, mass projections are similar to phase space expectations. All results are preliminary.«xa0less

Search for the decay B^0 → γγ

We present a limit on the branching fraction for the decay B0 -> gg using data collected at the U(4S) resonance with the BABAR detector at the PEP-II asym. energy e+e- collider. Based on the observation of one event in the signal region, out of a sample of 21.3*106 e+e- -> U(4S) -> B-B decays, we establish an upper limit on the branching fraction of B(B0 -> gg)< 1.7*10-6 at the 90% confidence level. This result substantially improves upon existing limits. [on SciFinder (R)]

Search for CP violation in the decay D^(±) → K_(S)^(0)π^±

We report on a search for CP violation in the decay D^(±) → K_(S)^(0)π^± using a data set corresponding to an integrated luminosity of 469 u2009fb^(-1) collected with the BABAR detector at the PEP-II asymmetric energy e+e- storage rings. The CP-violating decay rate asymmetry A_(CP) is determined to be (-0.44 ± 0.13(stat)±0.10(syst))%, consistent with zero at 2.7σ and with the standard model prediction of (-0.332±0.006)%. This is currently the most precise measurement of this parameter.

Measurement of D^0-D(overbar)^(0) Mixing Parameters Using D^0 → K_(S)^(0)π^(+)π^(-) and D^0 → K_(S)^(0)K^(+)K^(-) Decays

We report a direct measurement of D0-D0 mixing parameters through a time-dependent amplitude analysis of the Dalitz plots of D(0) → K(S)(0) π+ π- and, for the first time, D0 → K(S)(0)K+ K- decays. The low-momentum pion π(s)(+) in the decay D*+ → D0 π(s)(+) identifies the flavor of the neutral D meson at its production. Using 468.5 fb(-1) of e+ e- colliding-beam data recorded near square root(s)=10.6 GeV by the BABAR detector at the PEP-II asymmetric-energy collider at SLAC, we measure the mixing parameters x = [1.6 ± 2.3(stat) ± 1.2(syst) ± 0.8(model)] × 10(-3), and y = [5.7 ± 2.0(stat) ± 1.3(syst) ± 0.7(model)] × 10(-3). These results provide the best measurement to date of x and y. The knowledge of the value of x, in particular, is crucial for understanding the origin of mixing.

Search for f_{J}(2220) in Radiative J/ψ Decays

We present a search for f(J)(2220) production in radiative J/ψ→γf(J)(2220) decays using 460u2009u2009fb⁻¹ of data collected with the BABAR detector at the SLAC PEP-II e(+)e⁻ collider. The f(J)(2220) is searched for in the decays to K(+)K⁻ and K(S)⁰K(S)⁰. No evidence of this resonance is observed, and 90% confidence level upper limits on the product of the branching fractions for J/ψ→γf(J)(2220) and f(J)(2220)→K(+)K⁻(K(S)⁰K(S)⁰) as a function of spin and helicity are set at the level of 10⁻⁵, below the central values reported by the Mark III experiment.

Test of Lepton Universality in Υ(1S) Decays at BABAR

The ratio R(τμ)(Υ(1S))=Γ(Υ(1S)→τ+ τ-)/Γ(Υ(1S)→μ+ μ-) is measured using a sample of (121.8±1.2)×10(6)Υ(3S) events recorded by the BABAR detector. This measurement is intended as a test of lepton universality and as a search for a possible light pseudoscalar Higgs boson. In the standard model (SM) this ratio is expected to be close to 1. Any significant deviations would violate lepton universality and could be introduced by the coupling to a light pseudoscalar Higgs boson. The analysis studies the decays Υ(3S)→Υ(1S)π+ π-, Υ(1S)→l+ l-, where l=μ, τ. The result, R(τμ)(Υ(1S))=1.005±0.013(stat)±0.022(syst), shows no deviation from the expected SM value, while improving the precision with respect to previous measurements.