Observation of B→D(*) π^(+)π^(-)ℓ^(-)ν Decays in e^(+)e^(-) Collisions at the Υ(4S) Resonance.

We report on measurements of the decays of B¯ mesons into the semileptonic final states B¯→D^(*)π^(+)π^(-)ℓ^(-)ν¯, where D^(*) represents a D or D^(*) meson and ℓ^(-) is an electron or a muon. These measurements are based on 471×10^(6) BB ¯ pairs recorded with the BABAR detector at the SLAC asymmetric B factory PEP-II. We determine the branching fraction ratios R_{π^{+}π^{-}}^{(*)}=B(B[over ¯]→D^{(*)}π^{+}π^{-}ℓ^{-}ν[over ¯])/B(B[over ¯]→D^{(*)}ℓ^{-}ν[over ¯]) using events in which the second B meson is fully reconstructed.

First Observation of CP Violation in B[over ¯]^{0}→D_{CP}^{(*)}h^{0} Decays by a Combined Time-Dependent Analysis of BABAR and Belle Data.

We report a measurement of the time-dependent CP asymmetry of B[over ¯]^{0}→D_{CP}^{(*)}h^{0} decays, where the light neutral hadron h^{0} is a π^{0}, η, or ω meson, and the neutral D meson is reconstructed in the CP eigenstates K^{+}K^{-}, K_{S}^{0}π^{0}, or K_{S}^{0}ω. The measurement is performed combining the final data samples collected at the ϒ(4S) resonance by the BABAR and Belle experiments at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain (471±3)×10^{6} BB[over ¯] pairs recorded by the BABAR detector and (772±11)×10^{6} BB[over ¯] pairs recorded by the Belle detector.

Search for Long-Lived Particles in e+ e- Collisions.

We present a search for a neutral, long-lived particle L that is produced in e+ e- collisions and decays at a significant distance from the e+ e- interaction point into various flavor combinations of two oppositely charged tracks. The analysis uses an e+ e- data sample with a luminosity of 489.1  fb(-1) collected by the BABAR detector at the ϒ(4S), ϒ(3S), and ϒ(2S) resonances and just below the ϒ(4S).

Study of CP asymmetry in B^{0}-B[over ¯]^{0} mixing with inclusive dilepton events.

We present a measurement of the asymmetry A_{CP} between same-sign inclusive dilepton samples ℓ^{+}ℓ^{+} and ℓ^{-}ℓ^{-} (ℓ=e, μ) from semileptonic B decays in ϒ(4S)→BB[over ¯] events, using the complete data set recorded by the BABAR experiment near the ϒ(4S) resonance, corresponding to 471×10^{6} BB[over ¯] pairs. The asymmetry A_{CP} allows comparison between the mixing probabilities P(B[over ¯]^{0}→B^{0}) and P(B^{0}→B[over ¯]^{0}), and therefore probes CP and T violation. The result, A_{CP}=[-3.

Search for a dark photon in e(+)e(-) collisions at BABAR.

Dark sectors charged under a new Abelian interaction have recently received much attention in the context of dark matter models. These models introduce a light new mediator, the so-called dark photon (A^{'}), connecting the dark sector to the standard model. We present a search for a dark photon in the reaction e^{+}e^{-}→γA^{'}, A^{'}→e^{+}e^{-}, μ^{+}μ^{-} using 514  fb^{-1} of data collected with the BABAR detector.

Search for CP violation in B0-B0 mixing using partial reconstruction of B0→D*- Xℓ+ νℓ and a kaon tag.

We present results of a search for CP violation in B0- B0 mixing with the BABAR detector. We select a sample of B0→D*- Xℓ+ ν decays with a partial reconstruction method and use kaon tagging to assess the flavor of the other B meson in the event. We determine the CP violating asymmetry ACP≡[N(B0B0)-N(B0B0)]/[N(B0B0)+N(B0B0)]=(0.

Measurement of the D*(2010)+ meson width and the D*(2010)+ - D0 mass difference.

We measure the mass difference Δm0 between the D*(2010)+ and the D0 and the natural linewidth Γ of the transition D*(2010)+ → D0π+. The data were recorded with the BABAR detector at center-of-mass energies at and near the Υ(4S) resonance, and correspond to an integrated luminosity of approximately 477  fb(-1). The D0 is reconstructed in the decay modes D0 → K- π+ and D0 → K- π+ π- π+.

Observation of time-reversal violation in the B0 meson system.

Although CP violation in the B meson system has been well established by the B factories, there has been no direct observation of time-reversal violation. The decays of entangled neutral B mesons into definite flavor states (B(0) or B(0)), and J/ψK(L)(0) or ccK(S)(0) final states (referred to as B(+) or B(-)), allow comparisons between the probabilities of four pairs of T-conjugated transitions, for example, B(0) → B(-) and B(-) → B(0), as a function of the time difference between the two B decays. Using 468 × 10(6) BB pairs produced in Υ(4S) decays collected by the BABAR detector at SLAC, we measure T-violating parameters in the time evolution of neutral B mesons, yielding ΔS(T)(+) = -1.

Precision measurement of the B → Xs γ photon energy spectrum, branching fraction, and direct CP asymmetry A(CP)((B → X(s+d)γ).

The photon spectrum in the inclusive electromagnetic radiative decays of the B meson, B → X(s)γ plus B → X(d)γ, is studied using a data sample of (382.8 ± 4.2) × 10(6)Υ(4S) → BB decays collected by the BABAR experiment at SLAC.

Evidence for an excess of B→D*τ(-)ν(τ) decays.

Based on the full BABAR data sample, we report improved measurements of the ratios R(D(*))=B(B[over ¯]→D(*)τ(-)ν[over ¯](τ))/B(B[over ¯]→D(*)ℓ(ℓ)(-)ν[over ¯](ℓ)), where ℓ is either e or μ. These ratios are sensitive to new physics contributions in the form of a charged Higgs boson. We measure R(D)=0.

Search for low-mass dark-sector Higgs bosons.

Recent astrophysical and terrestrial experiments have motivated the proposal of a dark sector with GeV-scale gauge boson force carriers and new Higgs bosons. We present a search for a dark Higgs boson using 516 fb(-1) of data collected with the BABAR detector. We do not observe a significant signal and we set 90% confidence level upper limits on the product of the standard model-dark-sector mixing angle and the dark-sector coupling constant.

Search for hadronic decays of a light Higgs boson in the radiative decay Υ→γA0.

We search for hadronic decays of a light Higgs boson (A(0)) produced in radiative decays of an Υ(2S) or Υ(3S) meson, Υ→γA(0). The data have been recorded by the BABAR experiment at the Υ(3S) and Υ(2S) center-of-mass energies and include (121.3±1.

Observation of the decay B- → D(s)((*)+) K- ℓ- ν(ℓ).

We report the observation of the decay B- → D(s)((*)+) K- ℓ- ν(ℓ) based on 342  fb(-1) of data collected at the Υ(4S) resonance with the BABAR detector at the PEP-II e+ e- storage rings at SLAC. A simultaneous fit to three D(s)(+) decay chains is performed to extract the signal yield from measurements of the squared missing mass in the B meson decay. We observe the decay B- → D(s)((*)+) K- ℓ- ν(ℓ) with a significance greater than 5 standard deviations (including systematic uncertainties) and measure its branching fraction to be B(B- → D(s)((*)+) K- ℓ- ν(ℓ)) = [6.

Search for production of invisible final states in single-photon decays of Υ(1S).

We search for single-photon decays of the Υ(1S) resonance, Υ → γ + invisible, where the invisible state is either a particle of definite mass, such as a light Higgs boson A⁰, or a pair of dark matter particles, χχ. Both A⁰ and χ are assumed to have zero spin. We tag Υ(1S) decays with a dipion transition Υ(2S) → π⁺π⁻Υ(1S) and look for events with a single energetic photon and significant missing energy.

A Scanning Transmission Electron Microscopy Method for Determining Manganese Composition in Welding Fume as a Function of Primary Particle Size.

Increasing evidence suggests that the physicochemical properties of inhaled nanoparticles influence the resulting toxicokinetics and toxicodynamics. This report presents a method using scanning transmission electron microscopy (STEM) to measure the Mn content throughout the primary particle size distribution of welding fume particle samples collected on filters for application in exposure and health research. Dark field images were collected to assess the primary particle size distribution and energy-dispersive X-ray and electron energy loss spectroscopy were performed for measurement of Mn composition as a function of primary particle size.

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 460  fb⁻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.

Measurement of D0-D0 mixing parameters using D0 → K(S)(0)π+ π- and D0 → 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.

Measurements of charged current lepton universality and |Vus| using tau lepton decays to e- ν(e) ν(τ), μ- ν(μ) ν(τ), π- ν(τ), and K- ν(τ).

Using 467  fb(-1) of e+e- annihilation data collected with the BABAR detector, we measure (B(τ- → μ- ν(μ) ν(τ)))/(B(τ- → e- ν(e) ν(τ))) =(0.9796±0.0016±0.

Evidence for direct CP violation in the measurement of the Cabbibo-Kobayashi-Maskawa angle γ with B∓ → D(*)K(*)∓ decays.

We report the measurement of the Cabibbo-Kobayashi-Maskawa CP-violating angle γ through a Dalitz plot analysis of neutral D-meson decays to K(S)(0) π+ π- and K(S)(0) K+ K- produced in the processes B∓ → DK∓, B∓ D* K∓ with D* → Dπ(0), Dγ, and B∓ → DK*∓ with K*∓ → K(S)(0) π∓, using 468 million BB pairs collected by the BABAR detector at the PEP-II asymmetric-energy e+ e- collider at SLAC. We measure γ = (68 ± 14 ± 4 ± 3)° (modulo 180°), where the first error is statistical, the second is the experimental systematic uncertainty, and the third reflects the uncertainty in the description of the neutral D decay amplitudes. This result is inconsistent with γ = 0 (no direct CP violation) with a significance of 3.

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.

Search for charged lepton flavor violation in narrow upsilon decays.

Charged-lepton flavor-violating processes are unobservable in the standard model, but they are predicted to be enhanced in several extensions to the standard model, including supersymmetry and models with leptoquarks or compositeness. We present a search for such processes in a sample of 99x10(6)Upsilon(2S) decays and 117x10(6)Upsilon(3S) decays collected with the BABAR detector. We place upper limits on the branching fractions B(Upsilon(nS)-->e(+/-)tau(-/+)) and B(Upsilon(nS)-->mu(+/-)tau(-/+)) (n=2,3) at the 10(-6) level and use these results to place lower limits of order 1 TeV on the mass scale of charged-lepton flavor-violating effective operators.

Searches for Lepton flavor violation in the decays tau{+/-}-->e{+/-}gamma and tau{+/-}-->mu{+/-}gamma.

Searches for lepton-flavor-violating decays of a tau lepton to a lighter mass lepton and a photon have been performed with the entire data set of (963+/-7)x10{6} tau decays collected by the BABAR detector near the Upsilon(4S), Upsilon(3S) and Upsilon(2S) resonances. The searches yield no evidence of signals and we set upper limits on the branching fractions of B(tau{+/-}-->e{+/-}gamma)<3.3x10{-8} and B(tau{+/-}-->mu{+/-}gamma)<4.

Measurement of |V(cb)| and the form-factor slope in B --> Dl- nu(l) decays in events tagged by a fully reconstructed B meson.

We present a measurement of the Cabibbo-Kobayashi-Maskawa matrix element |V(cb)| and the form-factor slope rho2 in B --> Dl- nu(l) decays based on 460x10(6) BB events recorded at the Upsilon(4S) resonance with the BABAR detector. B --> Dl- nu(l) decays are selected in events in which a hadronic decay of the second B meson is fully reconstructed. We measure B(B- --> D0 l- nu(l))/B(B- --> Xl- nu(l)) = (0.

Search for invisible decays of the Upsilon(1S).

We search for invisible decays of the Upsilon(1S) meson using a sample of 91.4 x 10(6) Upsilon(3S) mesons collected at the BABAR/PEP-II B factory. We select events containing the decay Upsilon(3S) --> pi(+)pi(-)Upsilon(1S) and search for evidence of an undetectable Upsilon(1S) decay recoiling against the dipion system.

Precise measurement of the e+e- --> pi+pi-(gamma) cross section with the initial state radiation method at BABAR.

A precise measurement of the cross section of the process e(+)e(-) --> pi(+)pi(-)(gamma) from threshold to an energy of 3 GeV is obtained with the initial state radiation (ISR) method using 232 fb(-1) of data collected with the BABAR detector at e(+)e(-) center-of-mass energies near 10.6 GeV. The ISR luminosity is determined from a study of the leptonic process e(+)e(-) --> mu(+)mu(-)gamma(gamma).