The solar wind is slowed, deflected, and heated as it encounters Venus's induced magnetosphere. The importance of kinetic plasma processes to these interactions has not been examined in detail, due to a lack of constraining observations. In this study, kinetic-scale electric field structures are identified in the Venusian magnetosheath, including plasma double layers. The double layers may be driven by currents or mixing of inhomogeneous plasmas near the edge of the magnetosheath. Estimated double-layer spatial scales are consistent with those reported at Earth. Estimated potential drops are similar to electron temperature gradients across the bow shock. Many double layers are found in few high cadence data captures, suggesting that their amplitudes are high relative to other magnetosheath plasma waves. These are the first direct observations of plasma double layers beyond near-Earth space, supporting the idea that kinetic plasma processes are active in many space plasma environments.

We present a measurement of the branching fractions for B → D/D */D(*)πℓ-̄νℓ decays based on 341.1 fb-1 of data collected at the γ(4S) resonance with the BABAR detector at the PEP-II e+e- storage rings. Events are tagged by fully reconstructing one of the B mesons in a hadronic decay mode. We obtain B(B- → D0ℓ-̄νℓ) = (2.33 ± 0.09 (stat.) ± 0.09 (syst.))%, B(B- → D*0ℓ-̄νℓ) = (5.83±0.15 (stat.)±0.30 (syst.))%, B(B0 → D+ℓ-̄νℓ) = (2.21±0.11 (stat.)±0.12 (syst.))%, B(B0 → D*+ℓ-̄νℓ) = (5.49 ± 0.16 (stat.) ± 0.25 (syst.))%, B(B- → D+π-ℓ-̄νℓ) = (0.42 ± 0.06 (stat.) ± 0.03 (syst.))%, B(B- → D *+π-ℓ-̄νℓ) = (0.59±0.05 (stat.)±0.04 (syst.))%, B(B0 → D*π+ℓ- ̄νℓ) = (0.43±0.08 (stat.)±0.03 (syst.))% and B(B0 → D*0π+ℓ-̄νℓ) = (0.48±0.08 (stat.)±0.04 (syst.))%.

We study the decay B 0 → ρ 0 ρ 0 in a sample of about 427 million γ(4S) → BB decays collected with the BABAR detector at the PEP-II asymmetric-energy e + e - collider at SLAC. We find the branching fraction B = (0.84 ± 0.29 ± 0.17) × 10-6 and longitudinal polarization fraction of fL = 0.70 ± 0.14 ± 0.05, where the first uncertainty is statistical, and the second is systematic. The evidence for the B 0 → ρ 0 ρ 0 signal has 3.6σ significance. We investigate the proper-time dependence of the longitudinal component in the decay and measure the CP-violating coefficients S00 L = (0.5± 0.9 ± 0.2) and C00 L = (0.4 ± 0.9 ± 0.2), corresponding to the sine and cosine terms in the time evolution of asymmetry. We study the implication of these results for penguin contributions in B → ρρ decays and for the CKM unitarity angle α.

We present updated measurements of time-dependent CP asymmetries in fully reconstructed neutral B decays containing a charmonium meson. The measurements reported here use a data sample of (465±5)×106 Υ(4S) →BB̄ decays collected with the BABAR detector at the PEP-II asymmetric energy e+e- storage rings operating at the SLAC National Accelerator Laboratory. The time-dependent CP asymmetry parameters measured from JψKS0, JψKL0, ψ(2S)KS0, ηcKS0, χc1KS0, and J/ψK*(892)0 decays are: Cf=0.024±0.020(stat)±0.016(syst) and -ηfSf=0. 687±0.028(stat)±0.012(syst). © 2009 The American Physical Society.

We present a search for B decays to a charged scalar meson a0+ and a π0 where the a0+ decays to an η meson and a π+. The analysis was performed on a data sample consisting of 383×106 BB̄ pairs collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We find no significant signal and set an upper limit on the product branching fraction B(B+→a0+π0)×B(a0+→ηπ+) of 1.4×10-6 at the 90% confidence level. © 2008 The American Physical Society.

We analyze the three-body charmless decay B±→K±K± K using a sample of 226.0±2.5 million BB̄ pairs collected by the BABAR detector. We measure the total branching fraction and CP asymmetry to be B=(35.2±0.9±1.6)×10-6 and ACP=(-1.7±2.6±1.5)%. We fit the Dalitz plot distribution using an isobar model and measure the magnitudes and phases of the decay coefficients. We find no evidence of CP violation for the individual components of the isobar model. The decay dynamics is dominated by the K+K- S-wave, for which we perform a partial-wave analysis in the region m(K+K-)<2GeV/c2. Significant production of the f0(980) resonance, and of a spin zero state near 1.55GeV/c2 are required in the isobar model description of the data. The partial-wave analysis supports this observation. © 2006 The American Physical Society.

We report a measurement of the branching fractions of B̄→D* *ℓ-ν̄ℓ decays based on 417fb-1 of data collected at the Υ(4S) resonance with the BABAR detector at the PEP-II e+e- storage rings. Events are selected by fully reconstructing one of the B mesons in a hadronic decay mode. A fit to the invariant mass differences m(D(*)π)- m(D(*)) is performed to extract the signal yields of the different D** states. We observe the B̄→D**ℓ- ν̄ℓ decay modes corresponding to the four D** states predicted by heavy quark symmetry with a significance greater than 5 standard deviations including systematic uncertainties. © 2008 The American Physical Society.

We present the first measurement of the B0 → X-u ℓ+νℓ partial branching fraction in the endpoint region of the lepton momentum spectrum, above the threshold for B → Xcℓνℓ decays. The analysis is based on a sample of 383 million γ(4S) decays into BB pairs collected with the BABAR detector at the PEP-II e+e- storage rings. We select B0B0 events by partially reconstructing one B meson via the B0 → Dz.ast;+ℓ- ̄νℓ decays then select B0 → X- u ℓ+νℓ decays identifying a second high momentum lepton. In the momentum interval ranging from 2.3 to 2.6 GeV/c we measure the partial branching fraction πB(B0 → Xuℓν) = (1.30 ± 0.21stat ± 0.07syst) × 10-4 where the first error is statistical and the second is systematic. By comparing this measurement with the one obtained from untagged B decays we obtain R+/0 = ΔB(B0 → Xuℓν)/ ΔB(B+ → Xuℓν) = 1.18 ± 0.35stat ± 0.17syst. Using this measurement we extract a limit on the contributions from processes breaking isospin symmetry in charmless semileptonic B decays.

We present a preliminary study of B- → D 0 (CP)π- and B- → D 0 (CP)K- decays, with the D 0 (CP)reconstructed in the CP-odd eigenstates Ksπ0, Ks, in the CP-even eigenstates K+K-, π+π-, and in the (non-CP) flavor eigenstate K ± π ± . Using a sample of about 382 million γ(4S) decays into BB pairs, collected with the BABAR detector operating at the PEP-II asymmetric-energy B Factory at SLAC, we measure the ratios of the branching fractions B(B- → D 0 CP±K-) + B(B+ → D 0 CP±K+) [B(B- → D 0 K-) + B(B+ → D 0 K+)]/2 and the direct CP asymmetry ACP± Ξ B(B-→D 0 CP±K-) - B(B+→D 0 CP±K+) B(B-→D 0 CP±K-) + B(B+→D 0 CP±K+) . The results are: RCP- = 0.81 ± 0.10(stat) ± 0.05(syst) RCP+ = 1.07 ± 0.10(stat) ± 0.04(syst) ACP- = -0.19 ± 0.12(stat) ± 0.02(syst) ACP+ = 0.35 ± 0.09(stat) ± 0.05(syst).

We present preliminary results of a search for B → Xdγ decays with a hadronic mass 1.0 GeV/c2 < M(Xd) < 1.8 GeV/c2. We consider seven final states with up to four charged pions and one neutral pion or η, which correspond to about 50% of the total Xd fragmentation in this mass range. Based on a sample of 383 million B ̄B events collected by the BaBar experiment at PEPII, we measure a partial branching fraction P7 Xd=1 B(B → Xdγ)|(1.0GeV/c2 < M(Xd) < 1.8GeV/c2) = (3.1±0.9+0.6 -0.5 ±0.5) · 10-6, where the uncertainties are statistical, systematic and model-dependent respectively.