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688 records were found.

We present a new measurement of the time-dependent CP asymmetry of B^0→D^(*+)D^(*-) decays using (471±5) million BB pairs collected with the BABAR detector at the PEP-II B Factory at the SLAC National Accelerator Laboratory. Using the technique of partial reconstruction, we measure the time-dependent CP asymmetry parameters S = -0.34 ± 0.12 ± 0.05 and C = +0.15 ± 0.09 ± 0.04. Using the value for the CP-odd fraction R_⊥ = 0.158 ± 0.028 ± 0.006, previously measured by BABAR with fully reconstructed B^0→D^(*+)D^(*-) events, we extract the CP-even components S_+= -0.49 ± 0.18 ± 0.07 ± 0.04 and C_+ = +0.15 ± 0.09 ± 0.04. In each case, the first uncertainty is statistical and the second is systematic; the third uncertainty on S_+ is the contribution from the uncertainty on R_⊥. The measured value of the CP-even component S_+ is consistent wi...
The photon spectrum in B → X_sγ decay, where X_s is any strange hadronic state, is studied using a data sample of (382.8±4.2) × 10^6 e^+e^- → Υ(4S) → BB events collected by the BABAR experiment at the PEP-II collider. The spectrum is used to measure the branching fraction B(B → X_sγ)=(3.21±0.15±0.29±0.08) × 10^(-4) and the first, second, and third moments ⟨E_γ⟩=2.267±0.019±0.032±0.003  GeV, ⟨(E_γ-⟨E_γ⟩)^2⟩=0.0484±0.0053±0.0077±0.0005  GeV^2, and ⟨(E_γ-⟨E_γ⟩)^3⟩=-0.0048±0.0011±0.0011±0.0004  GeV^3, for the range E_γ > 1.8  GeV, where E_γ is the photon energy in the B-meson rest frame. Results are also presented for narrower E_γ ranges. In addition, the direct CP asymmetry A_(CP)(B → X_(s+d)γ) is measured to be 0.057±0.063. The spectrum itself is also unfolded to the B-meson rest frame; that is the frame in which theoretical predictions ...
We present a measurement of D^0-D^0 mixing and CP violation using the ratio of lifetimes simultaneously extracted from a sample of D^0 mesons produced through the flavor-tagged process D^(*+)→D^0π^+, where D^0 decays to K^∓π^±, K^-K^+, or π^-π^+, along with the untagged decays D^0→K^∓π^± and D^0→K^-K^+. The lifetimes of the CP-even, Cabibbo-suppressed modes K^-K^+ and π^-π^+ are compared to that of the CP-mixed mode K^∓π^± in order to measure y_(CP) and ΔY. We obtain y_(CP)=[0.72±0.18(stat)±0.12(syst)]% and ΔY=[0.09±0.26(stat)±0.06(syst)]%, where ΔY constrains possible CP violation. The y_(CP) result excludes the null mixing hypothesis at 3.3σ significance. This analysis is based on an integrated luminosity of 468  fb^(-1) collected with the BABAR detector at the PEP-II asymmetric-energy e^+e^- collider.
We search for di-muon decays of a low-mass Higgs boson (A^0) produced in radiative Υ(1S) decays. The Υ(1S) sample is selected by tagging the pion pair in the Υ(2S,3S) → π^+ π^-Υ(1S) transitions, using a data sample of 92.8 × 10^6 Υ(2S) and 116.8 × 10^6 Υ(3S) events collected by the BABAR detector. We find no evidence for A^0 production and set 90% confidence level upper limits on the product branching fraction B(Υ(1S) → γA^0) × B(A^0 → μ^ +μ^-) in the range of (0.28-9.7) × 10^(-6) for 0.212 ≤ m_A^0 ≤ 9.20  GeV/c^2. The results are combined with our previous measurements of Υ(2S,3S) → γA^0, A^0 → μ^+μ^- to set limits on the effective coupling of the b quark to the A^0.
We present a measurement of the B^+ → ωℓ^+ν branching fraction based on a sample of 467 million BB pairs recorded by the BABAR detector at the SLAC PEP-II e+e- collider. We observe 1125±131 signal decays, corresponding to a branching fraction of B(B^+ → ωℓ^+ν)=(1.21±0.14±0.08)×10^(-4), where the first error is statistical and the second is systematic. The dependence of the decay rate on q^2, the invariant mass squared of the leptons, is compared to QCD predictions of the form factors based on a quark model and light-cone sum rules.
We present improved measurements of CP-violation parameters in the decays B^0→π^+π^-, B^0→K^+π^-, and B^0→π^0π^0, and of the branching fractions for B^0→π^0π^0 and B^0→K^0π^0. The results are obtained with the full data set collected at the Υ(4S) resonance by the BABAR experiment at the PEP-II asymmetric-energy B factory at the SLAC National Accelerator Laboratory, corresponding to (467±5)×10^6 BB pairs. We find the CP-violation parameter values and branching fractions: S_(π^+π^-)=-0.68±0.10±0.03, C_(π^+π^-)=-0.25±0.08±0.02, A_(K^-π^+)=-0.107±0.016_(-0.004)^(+0.006), C_(π^0π^0)=-0.43±0.26±0.05, B(B^0→π^0π^0)=(1.83±0.21±0.13)×10^(-6),  B(B^0→K^0π^0)= (10.1±0.6±0.4)×10^(-6), where in each case, the first uncertainties are statistical and the second are systematic. We observe CP violation with a significance of 6.7 standard deviations for...
We report on a search for direct CP violation in the singly Cabibbo-suppressed decay D^+→K^+K^-π^+ using a data sample of 476  fb^(-1) of e^+e^- annihilation data accumulated with the BABAR detector at the SLAC PEP-II electron-positron collider, running at and just below the energy of the Υ(4S) resonance. The integrated CP-violating decay rate asymmetry A_(CP) is determined to be (0.37±0.30±0.15)%. Model-independent and model-dependent Dalitz plot analysis techniques are used to search for CP-violating asymmetries in the various intermediate states. We find no evidence for CP-violation asymmetry.
We report a search for CP violation in the decay modes D^±→K_S^0K^±, D_s^±→K_S^0K^±, and D_s^±→K_S^0π^± using a data set corresponding to an integrated luminosity of 469  fb^(-1) collected with the BABAR detector at the PEP-II asymmetric energy e^+e^- storage rings. The decay rate CP asymmetries, A_(CP), are determined to be (+0.13±0.36(stat)±0.25(syst))%, (-0.05±0.23(stat)±0.24(syst))%, and (+0.6±2.0(stat)±0.3(syst))%, respectively. These measurements are consistent with zero, and also with the Standard Model prediction [(-0.332±0.006)% for the D^±→K_S^0K^± and D_s^±→K_S^0K^± modes, and (+0.332±0.006)% for the D_s^±→K_S^0π^± mode]. They are the most precise determinations to date.
We report the determination of the Cabibbo-Kobayashi-Maskawa CP-violating angle γ through the combination of various measurements involving B^± → DK^±, B^± → D^*K^±, and B^± → DK^(*±) decays performed by the BABAR experiment at the PEP-II e^+e^- collider at SLAC National Accelerator Laboratory. Using up to 474 million BB pairs, we obtain γ=(69_(-16)^(+17))° modulo 180°. The total uncertainty is dominated by the statistical component, with the experimental and amplitude-model systematic uncertainties amounting to ±4°. The corresponding two-standard-deviation region is 41° < γ < 102°. This result is inconsistent with γ=0 with a significance of 5.9 standard deviations.
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