Browsing by Author "BaBar Collaboration"
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Item Amplitude Analysis and Measurement of the Time-Dependent CP Asymmetry of B⁰→K_S⁰K_S⁰K_S⁰ Decays(American Physical Society, 2012-03-27) Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Martinelli, M.; Milanes, D. A.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We present the first results on the Dalitz-plot structure and improved measurements of the time-dependent CP-violation parameters of the process B⁰→K_S⁰K_S⁰K_S⁰ obtained using 468×10⁶ BB̄ decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. The Dalitz-plot structure is probed by a time-integrated amplitude analysis that does not distinguish between B⁰ and B̅⁰ decays. We measure the total inclusive branching fraction ℬ(B⁰→K_S⁰K_S⁰K_S⁰)=(6.19 ± 0.48 ± 0.15 ± 0.12)×10⁻⁶, where the first uncertainty is statistical, the second is systematic, and the third represents the Dalitz-plot signal model dependence. We also observe evidence for the intermediate resonant states ʄ₀(980), ʄ₀(1710), and ʄ₂(2010). Their respective product branching fractions are measured to be (2.70_{-1.19}^{+1.25} ± 0.36 ± 1.17)×10⁻⁶, (0.50_{-0.24}^{+0.46 ± 0.04 ± 0.10)×10⁻⁶, and (0.54_{-0.20}^{+0.21} ± 0.03 ± 0.52)×10⁻⁶. Additionally, we determine the mixing-induced CP-violation parameters to be S = -0.94_{-0.21}^{+0.24 ± 0.06 and C = -0.17 ± 0.18 ± 0.04, where the first uncertainty is statistical and the second is systematic. These values are in agreement with the standard model expectation. For the first time, we report evidence of CP violation in B⁰→K_S⁰K_S⁰K_S⁰ decays; CP conservation is excluded at 3.8 standard deviations including systematic uncertainties.Item Antideuteron Production in ϒ(nS) Decays and in e⁺e⁻→qq̅ at √s ≈ 10.58 GeV(American Physical Society, 2014-06-24) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Stugu, B.; Lou, Xinchou; Izen, Joseph M.; BaBar Collaboration; 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We present measurements of the inclusive production of antideuterons in e+e- annihilation into hadrons at ≈ 10.58 GeV center-of-mass energy and in ϒ(1S,2S,3S) decays. The results are obtained using data collected by the BABAR detector at the PEP-II electron-positron collider. Assuming a fireball spectral shape for the emitted antideuteron momentum, we find ℬ(ϒ(1S) → d̅X) = (2. 81 ± 0.49 (stat) _{-0.24}^{+0.20} (syst)) x 10⁻⁵ ℬ(ϒ(2S) → d̅X) = (2. 64 ± 0.11 (stat) _{-0.21}^{+0.26} (syst)) x 10⁻⁵, B(ϒ(3S) → d̅X) = (2. 33 ± 0.15 (stat) _{-0.28}^{+0.31} (syst)) x 10⁻⁵, and σ(e⁺e⁻ → d̅X) = (9.63 ± 0.41 (stat) _{-1.01}^{+1.17} (syst) fb.Item Bottomonium Spectroscopy and Radiative Transitions Involving the χ_{bJ} (1p, 2p) States at BaBar(American Physical Society, 2014-12-24) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Stugu, B.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We use (121 ± 1) million ϒ(3S) and (98 ± 1) million ϒ(2S) mesons recorded by the BABAR detector at the PEP-II e⁺e⁻ collider at SLAC to perform a study of radiative transitions involving the χ_{bJ}(1P, 2P) states in exclusive decays with μ⁺μ⁻γγ final states. We reconstruct twelve channels in four cascades using two complementary methods. In the first we identify both signal photon candidates in the electromagnetic calorimeter (EMC), employ a calorimeter timing-based technique to reduce backgrounds, and determine branching-ratio products and fine mass splittings. These results include the best observational significance yet for the χ_{b0}(2P) → γϒ(2S) and χ_{b0}(1P) → γϒ(1S) transitions. In the second method, we identify one photon candidate in the EMC and one which has converted into an e⁺e⁻ pair due to interaction with detector material, and we measure absolute product branching fractions. This method is particularly useful for measuring ϒ(3S) → γχ_{b1,2}(1P) decays. Additionally, we provide the most up-to-date derived branching fractions, matrix elements and mass splittings for χ_b transitions in the bottomonium system. Using a new technique, we also measure the two lowest-order spin-dependent coefficients in the nonrelativistic QCD Hamiltonian.Item Branching Fraction and Form-Factor Shape Measurements of Exclusive Charmless Semileptonic B Decays, and Determination of |V_{ub}|(American Physical Society, 2012-11-05) Lees, J. P.; Poireau, V.; Tisserand, V.; Tico, J. Garra; Grauges, E.; Palano, A.; Eigen, G.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We report the results of a study of the exclusive charmless semileptonic decays, B0→π -+ν, B+ → π0⁺ν, B +→ω +ν, B +→η +ν, and B +→η ′+ν (=e or μ) undertaken with approximately 462×106 BB̄ pairs collected at the Υ(4S) resonance with the BABAR detector. The analysis uses events in which the signal B decays are reconstructed with a loose neutrino reconstruction technique. We obtain partial branching fractions in several bins of q2, the square of the momentum transferred to the lepton-neutrino pair, for B0→π - +ν, B +→π0 +ν, B +→ω +ν, and B +→η +ν. From these distributions, we extract the form-factor shapes f +(q2) and the total branching fractions B(B0→π -+ν)=(1.45±0.04 stat±0.06 syst)×10 -4 (combined π - and π0 decay channels assuming isospin symmetry), B(B +→ω +ν)=(1.19±0.16 stat±0.09 syst)×10 -4 and B(B +→η +ν)=(0.38±0.05 stat±0.05 syst)×10 -4. We also measure B(B +→η ′+ν)=(0.24±0. 08 stat±0.03 syst)×10 -4. We obtain values for the magnitude of the Cabibbo-Kobayashi-Maskawa (CKM) matrix element |V ub| by direct comparison with three different QCD calculations in restricted q2 ranges of B→π +ν decays. From a simultaneous fit to the experimental data over the full q2 range and the FNAL/MILC lattice QCD predictions, we obtain |V ub|=(3.25±0.31)×10 -3, where the error is the combined experimental and theoretical uncertainty. © 2012 American Physical Society.Item Branching fraction of τ-→π-Ks0Ks0(π0)ν τ decays(American Physical Society, 2012-11-26) Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Palano, A.; Eigen, G.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We present a study of τ -→π -KS0KS0(π0) ν τ and τ -→K -KS0KS0(π0) ν τ decays using a data set of 430 million tau lepton pairs, corresponding to an integrated luminosity of 468 fb(-1), collected with the BABAR detector at the PEP-II asymmetric energy e(+)e(-) storage rings. We measure branching fractions of (2.31 +/- 0.04 +/- 0.08) x 10(-4) and (1.60 +/- 0.20 +/- 0.22) x 10(-5) for the τ -→π -KS0KS0ν τ and τ -→π -KS0KS0π0ν τ decays, respectively. We find no evidence for τ -→K -KS0KS0ν τ and τ -→K -KS0KS0π0ν τ decays and place upper limits on the branching fractions of 6.3 x 10(-7) and 4.0 x 10(-7) at the 90% confidence level.Item Collins Asymmetries in Inclusive Charged KK and Kπ Pairs Produced in e⁺e⁻ Annihilation(American Physical Society, 2015-12-22) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Stugu, B.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We present measurements of Collins asymmetries in the inclusive process e⁺e⁻ → h₁h₂Χ, h₁h₂ = 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 h₁h₂ 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.Item Cross Sections for the Reactions e⁺e⁻ → K⁺ K⁻ π⁺π⁻, K⁺ K⁻ π⁰π⁰, and K⁺ K⁻K⁺ K⁻ Measured Using Initial-State Radiation Events(Amer Physical Soc, 2012-07-26) Lees, J. P.; Poireau, V.; Prencipe, E.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Martinelli, M.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 56366505900 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We study the processes e⁺e⁻ → K⁺ K⁻ π⁺π⁻γ, K⁺ K⁻ π⁰π⁰γ, and K⁺ K⁻ K⁺ K⁻ γ, where the photon is radiated from the initial state. About 84000, 8000, and 4200 fully reconstructed events, respectively, are selected from 454 fb⁻¹ of BABAR data. The invariant mass of the hadronic final state defines the e⁺e⁻ center-of-mass energy, so that the K⁺ K⁻ π⁺π⁻γ data can be compared with direct measurements of the e⁺e⁻ → K⁺ K⁻ π⁺π⁻ reaction. No direct measurements exist for the e⁺e⁻→ K ⁺K ⁻ π⁰π⁰ or e⁺e⁻ → K⁺ K⁻K⁺ K⁻ - reactions, and we present an update of our previous result based on a data sample that is twice as large. Studying the structure of these events, we find contributions from a number of intermediate states and extract their cross sections. In particular, we perform a more detailed study of the e⁺e⁻ → φ(1020)ππγ reaction and confirm the presence of the Y(2175) resonance in the φ(1020)f⁰(980) and K⁺ K⁻ f⁰ (980) modes. In the charmonium region, we observe the J/ψ in all three final states and in several intermediate states, as well as the ψ(2S) in some modes, and measure the corresponding products of branching fraction and electron width.Item Dalitz Plot Analyses of B⁰ → D⁻D⁰K⁺ and B⁺ → D̅⁰D⁰K⁺ Decays(American Physical Society, 2015-03-02) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Stugu, B.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 56366505900 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We present Dalitz plot analyses for the decays of B mesons to D⁻D⁰K⁺ and D̅⁰D⁰K⁺. 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{₋₇}⁺¹⁴ MeV/c² and of the width Γ(D*{s1} (2700)⁺) = 127{₋₁₉}⁺²⁴ MeV, including statistical and systematic uncertainties. In addition, we observe an enhancement in the D⁰K⁺ invariant mass around 2350-2500 MeV/c² in both decays B⁰ → D⁻D⁰K⁺ and B⁺ → D̅⁰D⁰K⁺, which we are not able to interpret. The results are based on 429 fb⁻¹ of data containing 471 x10⁶ BB̅ pairs collected at the ϒ(4S) resonance with the BABAR detector at the SLAC National Accelerator Laboratory.Item Evidence for an excess of B̄ → D^(*)_τ⁻ ν̅_τ decays(Amer Physical Soc, 2012-09-06) Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Palano, A.; Eigen, G.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 56366505900 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.Based on the full BABAR data sample, we report improved measurements of the ratios R(D^( *) = ℬ(B̄→D^( *)τ -ν {̄τ}) / ℬ(B̄→D^( *)ℓe̅ν ̅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*) = 0.440 ± 0.058 ± 0.042 and R(D*) = 0.332 ± 0.024 ± 0.018, which exceed the standard model expectations by 2.0σ and 2.7σ, respectively. Taken together, our results disagree with these expectations at the 3.4σ level. This excess cannot be explained by a charged Higgs boson in the type II two-Higgs-doublet model.Item Evidence for CP Violation in B⁺ → K*(892)⁺π⁰ from a Dalitz Plot Analysis of B⁺ → K_s⁰π⁺π⁰ Decays(American Physical Society, 2017-10-02) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Stugu, B.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); Izen, Joseph M.; Lou, XinchouWe report a Dalitz plot analysis of charmless hadronic decays of charged B mesons to the final state K_s⁰ π⁺π⁰ using the full BABAR data set of 470.9 ± 2.8 million BB̅ events collected at the Υ(4S) resonance. We measure the overall branching fraction and CP asymmetry to be Β(B⁺ → K⁰ π⁺π⁰) = (31.8 ± 1.8 ± 2.1_{-0.0}^{+6.0}) x 10⁻⁶ and A_{CP}(B⁺ → K⁰ π⁺π⁰) = 0.07 ± 0.05 ± 0.03_{-0.03}^{+0.02}, where the uncertainties are statistical, systematic, and due to the signal model, respectively. This is the first measurement of the branching fraction for B⁺ → K⁰ π⁺π⁰. We find first evidence of a CP asymmetry in B⁺ → K*(892)⁺π⁰ decays: A_{CP}(B⁺ → K*(892)⁺π⁰) = -0.52 ± 0.14 ± 0.04_{-0.02}^{+0.04}. 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.Item Evidence for the Baryonic Decay B̅→ D⁰ΛΛ̅(2014-06-06) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Stugu, B.; Lou, Xinchou; Izen, Joseph M.; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.Evidence is presented for the baryonic B meson decay B̅⁰ → D⁰ΛΛ̅ based on a data sample of 471 x 10⁶ BB̅ pairs collected with the BABAR detector at the PEP-II asymmetric e⁺e⁻ collider located at the SLAC National Accelerator Laboratory. The branching fraction is determined to beℬ(B̅⁰ → D⁰ΛΛ̅) = (9.8_{-2.6}^{+2.9} ± 1.9) x 10⁻⁶, corresponding to a significance of 3.4 standard deviations including additive systematic uncertainties. A search for the related baryonic B meson decay B̅⁰ → D⁰Σ⁰Λ̅ with Σ⁰ → Λγ is performed and an upper limit ℬ(B̅⁰ → D⁰Σ⁰Λ̅ + B̅⁰ → D⁰ΛΣ̅⁰ < 3.1 x 10⁻⁵ is determined at 90% confidence level.Item Evidence for the Decay B⁰ → ωω and Search for B⁰ → ωφ(American Physical Society, 2014-03-05) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Stugu, B.; Lou, Xinchou; Izen, Joseph M.; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We describe searches for B meson decays to the charmless vector-vector final states ωω and ωφ with 471 x 10⁶ BB̅ pairs produced in e⁺e⁻ annihilation at √s̅ = 10.58 GeV using the BABAR detector at the PEP-II collider at the SLAC National Accelerator Laboratory. We measure the branching fraction ℬ(B⁰ → ωω) = (1.2 ± 0.3_{-0.2}^{+0.3}) x 10⁻⁶, where the first uncertainty is statistical and the second is systematic, corresponding to a significance of 4.4 standard deviations. We also determine the upper limit ℬ(B⁰ → ωφ) < 0.7 x 10⁻⁶ at 90% confidence level. These measurements provide the first evidence for the decay B⁰ → ωω, and an improvement of the upper limit for the decay B⁰ → ωφ.Item Exclusive Measurements of b → sγ Transition Rate and Photon Energy Spectrum(American Physical Society, 2012-10-17) Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Palano, A.; Eigen, G.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Izen, Joseph M.; Lou, XinchouWe use 429 fb⁻¹ of e⁺e⁻ collision data collected at the Υ(4S) resonance with the BABAR detector to measure the radiative transition rate of b → sγ with a sum of 38 exclusive final states. The inclusive branching fraction with a minimum photon energy of 1.9 GeV is found to be ℬ(B̅ → Χ_sγ) = (3.29 ± 0.19 ± 0.48) x 10⁻⁴ where the first uncertainty is statistical and the second is systematic. We also measure the first and second moments of the photon energy spectrum and extract the best-fit values for the heavy-quark parameters, m_b and μ_π², in the kinetic and shape function models.Item First Observation of CP Violation in B̅⁰ → D{CP}^{*}h⁰ Decays by a Combined Time-Dependent Analysis of BABAR and Belle Data(American Physical Society, 2015-05) Abdesselam, A.; Adachi, I.; Adametz, A.; Adye, T.; Ahmed, H.; Aihara, H.; Akar, S.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; Belle Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We report a measurement of the time-dependent CP asymmetry of B̅⁰ → D{CP}^*h⁰ decays, where the light neutral hadron h⁰ is a π⁰, η, or ω meson, and the neutral D meson is reconstructed in the CP eigenstates K⁺K⁻, K⁰{s}π⁰ or K{s}⁰ω. 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) x 10⁻⁶ BB̅ pairs recorded by the BABAR detector and (772 ± 11) x 10⁶ BB̅ pairs recorded by the Belle detector. We measure the CP asymmetry parameters -η{f}S = +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 B̅⁰ → D{CP}^*h⁰ decays. The hypothesis of no mixing-induced CP violation is excluded in these decays at the level of 5.4 standard deviations.Item Improved Limits on B⁰ Decays to Invisible (+γ) Final States(American Physical Society, 2012-09-27) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Stugu, B.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Izen, Joseph M.; Lou, XinchouWe establish improved upper limits on branching fractions for B⁰ decays to final states where the decay products are purely invisible (i.e., no observable final state particles) and for final states where the only visible product is a photon. Within the Standard Model, these decays have branching fractions that are below the current experimental sensitivity, but various models of physics beyond the Standard Model predict significant contributions for these channels. Using 471 x 10⁶ BB̅ pairs collected at the Υ(4S) resonance by the BABAR experiment at the PEP-II e⁺e⁻ storage ring at the SLAC National Accelerator Laboratory, we establish upper limits at the 90% onfidence level of 2.4 x 10⁻⁵ for the branching fraction of B⁰ → invisible and1.7 x 10⁻⁵ for the branching fraction of B⁰ → invisible + γ.Item Measurement of Branching Fractions and Rate Asymmetries in the Rare Decays B → K^{(*)}ℓ⁺ℓ⁻(American Physical Society, 2012-08-24) Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Palano, A.; Eigen, G.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.In a sample of 471 x 106 BB̅ events collected with the BABAR detector at the PEP-II e⁺e⁻ collider we study the rare decays B → K^{(*)}ℓ⁺ℓ⁻, where ℓ⁺ℓ⁻ is either e⁺e⁻ or μ⁺μ⁻. We report results on partial branching fractions and isospin asymmetries in seven bins of dilepton mass-squared. We further present CP and lepton-flavor asymmetries for dilepton masses below and above the J/ψ resonance. We find no evidence for CP or lepton-flavor violation. The partial branching fractions and isospin asymmetries are consistent with the Standard Model predictions and with results from other experiments.Item Measurement of Collins Asymmetries in Inclusive Production of Charged Pion Pairs in e⁺e⁻ Annihilation at BaBar(American Physical Society, 2014-09-09) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Stugu, B.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We present measurements of Collins asymmetries in the inclusive process e⁺e⁻ → ππX, where π stands for charged pions, at a center-of-mass energy of 10.6 GeV. We use a data sample of 468 fb⁻¹ collected by the BABAR experiment at the PEP-II B factory at SLAC, and consider pairs of charged pions produced in opposite hemispheres of hadronic events. We observe clear asymmetries in the distributions of the azimuthal angles in two distinct reference frames. We study the dependence of the asymmetry on several kinematic variables, finding that it increases with increasing pion momentum and momentum transverse to the analysis axis, and with increasing angle between the thrust and beam axis.Item Measurement of CP-Violating Asymmetries in B⁰ → (ρπ)⁰ Decays Using a Time-Dependent Dalitz Plot Analysis(American Physical Society, 2013-07-19) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Stugu, B.; Brown, D. N.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We present results for a time-dependent Dalitz plot measurement of CP-violating asymmetries in the mode B⁰ → π⁺π⁻π⁰. The data set is derived from the complete sample of 471 x 10⁶ BB̅ meson pairs collected with the BABAR detector at the PEP-II asymmetric-energy e⁺e⁻ collider at the SLAC National Accelerator Laboratory operating on the Υ(4S) resonance. We extract parameters describing the time-dependent B⁰ → ρπθ decay probabilities and CPθ asymmetries, including C=0.016 ± 0.059 ± 0.036, ΔC=0.234 ± 0.061 ± 0.048, S=0.053 ± 0.081 ± 0.034, and ΔS=0.054 ± 0.082 ± 0.039, where the uncertainties are statistical and systematic, respectively. We perform a two-dimensional likelihood scan of the direct CP-violation asymmetry parameters for B⁰ → ρ^± π^∓ decays, finding the change in χ² between the minimum and the origin (corresponding to no direct CPθ violation) to be Δχ² = 6.42. We present information on the CP-violating parameter αθ in a likelihood scan that incorporates B^± → ρπθ measurements. To aid in the interpretation of our results, statistical robustness studies are performed to assess the reliability with which the true values of the physics parameters can be extracted. Significantly, these studies indicate that αθ cannot be reliably extracted with our current sample size, though the other physics parameters are robustly extracted.Item Measurement of D⁰-D̅⁰ Mixing and CP Violation in Two-Body D⁰ Decays(American Physical Society, 2013-01-03) Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Palano, A.; Eigen, G.; Izen, Joseph M .; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We present a measurement of D⁰-D̅⁰ mixing and CP violation using the ratio of lifetimes simultaneously extracted from a sample of D⁰ mesons produced through the flavor-tagged process D*⁺ → D⁰π⁺, where D⁰ decays to K^∓ π^±, K⁻ K⁺, or π⁻ π⁺, along with the untagged decays D⁰ → K^∓ π^± and D⁰ → 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.Item Measurement of Initial-State-Final-State Radiation Interference in the Processes e⁺e⁻ → μ⁺μ⁻γ and e⁺e⁻ → π⁺π⁻γ(2015-10-28) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Stugu, B.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 56366505900 (Lou, X); 250674117 (Izen, JM); Lou, XinchouCharge asymmetry in the processes e⁺e⁻ → μ⁺μ⁻γ and e⁺e⁻ → π⁺π⁻γ is measured using 232 fb⁻¹ of data collected with the BABAR detector at e⁺e⁻ center-of-mass energies near 10.58 GeV. An observable is introduced and shown to be very robust against detector asymmetries while keeping a large sensitivity to the physical charge asymmetry that results from the interference between initial-and final-state radiation (FSR). The asymmetry is determined as a function of the invariant mass of the final-state tracks from production threshold to a few GeV/c². It is compared to the expectation from QED for e⁺e⁻ → μ⁺μ⁻γ, and from theoretical models for e⁺e⁻ → π⁺π⁻γ. A clear interference pattern is observed in e⁺e⁻ → π⁺π⁻γ, particularly in the vicinity of the f₂(1270) resonance. The inferred rate of lowest-order FSR production is consistent with the QED expectation for e⁺e⁻ → μ⁺μ⁻γ, and is negligibly small for e⁺e⁻ → π⁺π⁻γ.