Browsing by Author "Brown, D. N."
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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 the D*(2010)⁺ –D⁺ Mass Difference(American Physical Society, 2018-08-24) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Brown, D. N.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); Izen, Joseph M.; Lou, XinchouWe measure the mass difference, Δm₊, between the D*(2010)⁺ and the D⁺ using the decay chain D*(2010)⁺ → D⁺π⁰ 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 Δm₀ ≡ m(D*(2010)⁺) - m(D⁰) 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.Item Measurement of the e⁺e⁻ → K_s⁰ K^± π^∓ π⁰ and K_s⁰ K^± π^∓η Cross Sections Using Initial-State Radiation(American Physical Society, 2017-05-30) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Brown, D. N.; Izen, Joseph M.; Lou, Xinchou; BaBaR Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); Izen, Joseph M.; Lou, XinchouThe processes e⁺e⁻ → K_s⁰ K^± π^∓ π⁰ and e⁺e⁻ → K_s⁰ K^± π^∓η are studied over a continuum of energies from threshold to 4 GeV with the initial-state photon radiation method. Using 454 fb⁻¹ of data collected with the BABAR detector at the SLAC PEP-II storage ring, the first measurements of the cross sections for these processes are obtained. The intermediate resonance structures from K*⁰ (Kπ)⁰, K*(892)^±(Kπ)^∓, and K_s⁰ K^± ρ^∓ are studied. The J/ψ is observed in all of these channels, and corresponding branching fractions are measured.Item Measurement of the e⁺e⁻ → π⁺π⁻π⁰π⁰ Cross Section Using Initial-State Radiation at BABAR(Amer Physical Soc, 2018-10-22) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Brown, D. N.; BaBar Collaboration; 250674117 (Izen, JM); Lou, XinchouThe process e⁺e⁻ → π⁺π⁻ 2π⁰γ is investigated by means of the initial-state radiation technique, where a photon is emitted from the incoming electron or positron. Using 454.3 fb⁻¹ of data collected around a center of- mass energy of √s = 10.58 GeV by the BABAR experiment at SLAC, approximately 150000 signal events are obtained. The corresponding nonradiative cross section is measured with a relative uncertainty of 3.6% in the energy region around 1.5 GeV, surpassing all existing measurements in precision. Using this new result, the channel's contribution to the leading order hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon is calculated as (g(μ)(π⁺π⁻ 2π⁰) - 2)/2 = (17.9 ± 0.1(stat) ± 0.6(syst)) x 10⁻¹⁰ in the energy range 0.85 < E(CM) < 1.8 GeV. In the same energy range, the impact on the running of the fine-structure constant at the Z⁰-pole is determined as Δα(π⁺π⁻ 2π⁰) (M(z)²) = (4.44 ± 0.02 (stat) ± 0.14 (syst)) x 10⁻⁴. Furthermore, intermediate resonances are studied and especially the cross section of the process e⁺e⁻ → ωπ⁰ → π⁺π⁻ 2π⁰ is measured.Item Measurement of the I = 1/2 Kπ S-Wave Amplitude from Dalitz Plot Analyses of η_c → KK̅π in Two-Photon Interactions(American Physical Society, 2016-01-20) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; 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 study the processes γγ→K(S)⁰ K^± π^∓ and γγ→K⁺K⁻π⁰ using a data sample of 519 fb⁻¹ recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy e⁺e⁻ collider at center-of-mass energies at and near the Υ(nS) (n=2, 3, 4) resonances. We observe η(c) decays to both final states and perform Dalitz plot analyses using a model-independent partial wave analysis technique. This allows a model-independent measurement of the mass-dependence of the I = 1/2 KπS-wave amplitude and phase. A comparison between the present measurement and those from previous experiments indicates similar behavior for the phase up to a mass of 1.5 GeV/c². In contrast, the amplitudes show very marked differences. The data require the presence of a new a₀(1950) resonance with parameters m=1931 ±14 ± 22 MeV/c² and Γ=271 ± 22 ± 29 MeV.Item Measurement of the Spectral Function for the τ- →k-ksντ Decay(American Physical Society) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Brown, D. N.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); Izen, Joseph M.; Lou, XinchouThe decay τ⁻→ K⁻K_Sν_τ has been studied using 430×106e⁺e⁻ → τ⁺τ⁻ events produced at a center-of-mass energy around 10.6 GeV at the PEP-II collider and studied with the BABAR detector. The mass spectrum of the K⁻K_S system has been measured and the spectral function has been obtained. The measured branching fraction B(τ⁻ → K⁻K_Sν_τ)=(0.739±0.011(stat)±0.020(syst))×10⁻³ is found to be in agreement with earlier measurements.Item Search for B⁺→ K⁺τ⁺τ⁻ at the Babar Experiment(American Physical Society, 2018-08-24) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Brown, D. N.; Izen, Joseph M.; Lou, Xinchou; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); Izen, Joseph M.; Lou, XinchouWe search for the rare flavor-changing neutral current process B⁺→ K⁺τ⁺τ⁻ using data from the BABAR experiment. The data sample, collected at the center-of-mass energy of the Υ(4S) resonance, corresponds to a total integrated luminosity of 424 fb⁻¹ and to 471 x 10⁶ BB̅ pairs. We reconstruct one B meson, produced in the Υ(4S) → B⁺B⁻ decay, in one of many hadronic decay modes and search for activity compatible with a B⁺→ K⁺τ⁺τ⁻ decay in the rest of the event. Each τ lepton is required to decay leptonically into an electron or muon and neutrinos. Comparing the expected number of background events with the data sample after applying the selection criteria, we do not find evidence for a signal. The resulting upper limit, at the 90% confidence level, is 𝓑(B⁺→ K⁺τ⁺τ⁻) < 2.25 x 10⁻³.Item Search for Invisible Decays of a Dark Photon Produced in e⁺e⁻ Collisions at Babar(American Physical Society, 2017-09) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Brown, D. N.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); Izen, Joseph M.; Lou, XinchouWe search for single-photon events in 53 fb⁻¹ of e⁺e⁻ collision data collected with the BABAR detector at the PEP-II B-Factory. We look for events with a single high-energy photon and a large missing momentum and energy, consistent with production of a spin-1 particle A' through the process e⁺e⁻ → γA'; A' → invisible. Such particles, referred to as "dark photons," are motivated by theories applying a U(1) gauge symmetry to dark matter. We find no evidence for such processes and set 90% confidence level upper limits on the coupling strength of A' to e⁺e⁻ in the mass range m_{A'} ≤ 8 GeV. In particular, our limits exclude the values of the A' coupling suggested by the dark-photon interpretation of the muon (g - 2)_μ anomaly, as well as a broad range of parameters for the dark-sector models.Item Study of the Process e⁺e⁻ → π⁺π⁻η Using Initial State Radiation(Amer Physical Soc) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Brown, D. N.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); Izen, Joseph M.; Lou, XinchouWe study the process e⁺e⁻ → π⁺π⁻ηγ, where the photon is radiated from the initial state. About 8000 fully reconstructed events of this process are selected from the BABAR data sample with an integrated luminosity of 469 fb⁻¹. Using the π⁺π⁻η invariant mass spectrum, we measure the e⁺e⁻ → π⁺π⁻η cross section in the e⁺e⁻ center-of-mass energy range from 1.15 to 3.5 GeV. The cross section is well described by the Vector-Meson dominance model with four ρ-like states. We observe 49 ± 9 events of the J/ψ decay to π⁺π⁻η and measure the product Γ_{J/ψ → e⁺e⁻}ℬ_{J/ψ → π⁺π⁻η) = 2.34 ± 0.43(stat) ± 0.16(syst) eV.