First Observation of CP Violation in B^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^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^0_S π^0, or K^0_Sω. 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 pairs recorded by the BABAR detector and (772±11)×10^6 BB pairs recorded by the Belle detector. We measure the CP asymmetry parameters –η_fS=+0.66±0.10(stat)±0.06(syst) and C=−0.02±0.07(stat)±0.03(syst). These results correspond to the first observation of CP violation in B^0 →D(*)_(CP)h^0 decays. The hypothesis of no mixing-induced CP violation is excluded in these decays at the level of 5.4 standard deviations

Dalitz plot analyses of B^0 → D^−D^0K^+ and B^+ → D^0D^0K^+ decays

We present Dalitz plot analyses for the decays of B mesons to D^−D^0K^+ and D^0D^0K^+. We report the observation of the D^∗_(s1)(2700)^+ resonance in these two channels and obtain measurements of the mass M(D^∗_(s1)(2700)+)=2699^(+14)_(−7)  MeV/c^2 and of the width Γ(D^∗_(s1)(2700)+)=127^(+24)_(−19)  MeV, including statistical and systematic uncertainties. In addition, we observe an enhancement in the D^0K^+ invariant mass around 2350–2500  MeV/c^2 in both decays B^0→D^−D^0K^+ and B^+→D^0D^0K^+, which we are not able to interpret. The results are based on 429  fb^(−1) of data containing 471×10^6BB pairs collected at the Υ(4S) resonance with the BABAR detector at the SLAC National Accelerator Laboratory

Collins asymmetries in inclusive charged KK and Kπ pairs produced in e^+e^− annihilation

We present measurements of Collins asymmetries in the inclusive process e^+e^− → h_1h_2X, h_1h_2 = KK, Kπ, ππ, at the center-of-mass energy of 10.6 GeV, using a data sample of 468  fb^(−1) collected by the BABAR experiment at the PEP-II B factory at SLAC National Accelerator Center. Considering hadrons in opposite thrust hemispheres of hadronic events, we observe clear azimuthal asymmetries in the ratio of unlike sign to like sign, and unlike sign to all charged h_1h_2 pairs, which increase with hadron energies. The Kπ asymmetries are similar to those measured for the ππ pairs, whereas those measured for high-energy KK pairs are, in general, larger

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). Fitting the two-track mass distribution in search of a signal peak, we do not observe a significant signal, and set 90% confidence level upper limits on the product of the L production cross section, branching fraction, and reconstruction efficiency for six possible two-body L decay modes as a function of the L mass. The efficiency is given for each final state as a function of the mass, lifetime, and transverse momentum of the candidate, allowing application of the upper limits to any production model. In addition, upper limits are provided on the branching fraction B(B→X_sL), where X_s is a strange hadronic system

Measurement of the branching fractions of the radiative leptonic τ decays τ→eγνν[bar] and τ→μγνν[bar] at BABAR

We perform a measurement of the τ→lγνν [bar] (l=e,μ) branching fractions for a minimum photon energy of 10 MeV in the τ rest frame, using 431  fb^(−1) of e^+ e^− collisions collected at the center-of-mass energy of the Υ(4S) resonance with the BABAR detector at the PEP-II storage rings. We find B(τ→μγνν [bar])=(3.69±0.03±0.10)×10^(−3) and B(τ→eγνν[bar]¯ )=(1.847±0.015±0.052)×10^(−2), where the first quoted error is statistical and the second is systematic. These results are substantially more precise than previous measurements

Search for new π^0-like particles produced in association with a τ-lepton pair

We report on a search in e^+e^− annihilations for new π^0-like particles produced in association with a τ-lepton pair. These objects, with a similar mass and similar decay modes to π^0 mesons, could provide an explanation for the non-asymptotic behavior of the pion-photon transition form factor observed by the BABAR Collaboration. No significant signal is observed, and limits on the production cross section at the level of 73 fb or 370 fb, depending on the model parameters, are determined at 90% confidence level. These upper limits lie below the cross section values needed to explain the BABAR form factor data

Evidence for CP violation in B^+ → K∗(892)^+π^0 from a Dalitz plot analysis of B^+ → K^0_Sπ^+π^0 decays

We report a Dalitz plot analysis of charmless hadronic decays of charged B mesons to the final state K^0_Sπ^+π^0 using the full BABAR data set of 470.9±2.8  million BB[overbar] events collected at the Υ(4S)resonance. We measure the overall branching fraction and CP asymmetry to be B(B^+→K^0π^+π^0)=(31.8±1.8±2.1+^(6.0)_(−0.0))×10^(-6) and A_(CP)(B^+→K^0π^+π^0)=0.07±0.05±0.03^(+0.02)_(−0.03), where the uncertainties are statistical, systematic, and due to the signal model, respectively. This is the first measurement of the branching fraction for B^+→K^0π^+π^0. We find first evidence of a CP asymmetry in B^+→K∗(892)+π^0 decays: A_(CP)(B^+→K∗(892)^+π^0)=−0.52±0.14±0.04^(+0.04)_(−0.02). The significance of this asymmetry, including systematic and model uncertainties, is 3.4 standard deviations. We also measure the branching fractions and CP asymmetries for three other intermediate decay modes

Measurement of the D^0→π^−e^+ν_e differential decay branching fraction as a function of q^2 and study of form factor parametrizations

Based on a sample of 500 million e^+e^−→cc events recorded by the BABAR detector at c.m. energies of close to 10.6 GeV, we report on a study of the decay D^0→π^−e^+ν_e. We measure the ratio of branching fractions, R_D=B(D^0→π^−e^+ν_e)/B(D^0→K^−π^+)=0.0713±0.0017_(stat)±0.0024_(syst), and use the present world average for B(D^0→K^−π^+) to obtain B(D^0→π^−e^+ν_e)= 2.770±0.068_(stat)±0.092_(syst)±0.037_(ext))×10^(−3) where the third error accounts for the uncertainty on the branching fraction for the reference channel. The measured dependence of the differential branching fraction on q^2, the four-momentum transfer squared between the D and the π meson, is compared to various theoretical predictions for the hadronic form factor, f^π_+,D(q^2), and the normalization V_(cd)|×f^π_+,D(q^2=0)=0.1374±0.0038_(stat)±0.0022_(syst)±0.0009_(ext). is extracted from a fit to data. Using the most recent LQCD prediction of f^π_(+,D)(q^2=0)=0.666±0.029, we obtain |V_(cd)|=0.206±0.007_(exp)±0.009_(LQCD). Assuming, instead, |V_(cd)|=|V_(us)|=0.2252±0.0009, we obtain f^π_(+,D)(q^2=0)=0.610±0.020_(exp)±0.005_(ext). The q^2 dependence of f^π_(+,D)(q^2) is compared to a variety of multipole parametrizations. This information is applied to B^0→π^−e^+ν_e decays and, combined with an earlier B^0→π^−e^+ν_e measurement by BABAR, is used to derive estimates of |V_(ub)|

Measurement of the D*(2010)^+−D^+ Mass Difference

We measure the mass difference, Δm_+, between the D*(2010)^+ and the D^+ using the decay chain D*(2010)^+→D^+π^0 with D^+→K−π^+π^+. 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 468  fb^(-1). We measure Δm_+=(140 601.0±6.8[stat]±12.9[syst])  keV. We combine this result with a previous BABAR measurement of Δm_0≡m(D*(2010)^+)−m(D^0) to obtain Δm_D=m(D^+)−m(D0)=(4824.9±6.8[stat]±12.9[syst])  keV. These results are compatible with and approximately five times more precise than the Particle Data Group averages

Measurement of the inclusive electron spectrum from B meson decays and determination of │V_(ub)│

Based on the full BABAR data sample of 466.5 million BB pairs, we present measurements of the electron spectrum from semileptonic B meson decays. We fit the inclusive electron spectrum to distinguish Cabibbo-Kobayashi-Maskawa (CKM) suppressed B → X_ueν decays from the CKM-favored B → X_ceν decays, and from various other backgrounds, and determine the total semileptonic branching fraction B(B → Xeν) = (10.34 ± 0.04_(stat) ± 0.26_(syst) %, averaged over B^± and B^0 mesons. We determine the spectrum and branching fraction for charmless B → X_ueν decays and extract the CKM element |V_ub|, by relying on four different QCD calculations based on the heavy quark expansion. While experimentally, the electron momentum region above 2.1 GeV/c is favored, because the background is relatively low, the uncertainties for the theoretical predictions are largest in the region near the kinematic endpoint. Detailed studies to assess the impact of these four predictions on the measurements of the electron spectrum, the branching fraction, and the extraction of the CKM matrix element |V_ub| are presented, with the lower limit on the electron momentum varied from 0.8  GeV/c to the kinematic endpoint. We determine |V_ub| using each of these different calculations and find, |V_ub|= (3.794 ± 0.107_(exp) ^(+0.292)_(−0.219) SF ^(+0.078) _(−0.068) theory) × 10^(−3) (De Fazio and Neubert), (4.563 ± 0.126_(exp) ^(+0.230)_(−0.208) SF ^(+0.162) _(−0.163) theory) × 10^(−3) (Bosch, Lange, Neubert, and Paz), (3.959 ± 0.104_(exp)^(+0.164)_(−0.154) SF ^(+0.042) _(−0.079) theory) × 10^(−3) (Gambino, Giordano, Ossola, and Uraltsev), (3.848 ± 0.108_(exp)^(+0.084)_^(−0.070) theory) × 10^(−3) (dressed gluon exponentiation), where the stated uncertainties refer to the experimental uncertainties of the partial branching fraction measurement, the shape function parameters, and the theoretical calculations