Malcolm John

Abstract:

We present results on time-dependent CP asymmetries in neutral B decays to several CP eigenstates. The measurements use a data sample of about 227 × 10⁶ Y(4S) → BB̄ decays collected by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. The amplitude of the CPasymmetry, sin2β in the standard model, is derived from decay-time distributions from events in which one neutral B meson is fully reconstructed in a final state containing a charmonium meson and the other B meson is determined to be either a B0 or B0 from its decay products. We measure sir2β = 0.722 ±0.040(stat) ±0.023(syst) in agreement with the standard model expectation. © 2005 The American Physical Society.

Abstract:

We report measurements of branching fractions and charge asymmetries of exclusive decays of neutral and charged B mesons into two-body final states containing a charmonium state and a light strange meson. The charmonium mesons considered are J/ψ, ψ(2S) and χc1, and the light meson is either K or K*. We use a sample of about 124 × 10⁶ BB̄ pairs collected with the BABAR detector at the PEP-II storage ring at the Stanford Linear Accelerator Center. © 2005 The American Physical Society.

Abstract:

We search for the decay B⁰ → ρ⁰ρ ⁰ in a data sample of about 227 × 10⁶ Γ(4S) → B B̄ decays collected with the BABAR detector at the PEP-II asymmetric-energy e⁺ e^- collider at SLAC. We find no significant signal and set an upper limit of 1.1 × 10^-6 at 90% C.L. on the branching fraction. As a result, the uncertainty due to penguin contributions on the Cabibbo-Kobayashi-Maskawa unitarity angle α measured in B → ρρ decays is decreased to 11° at 68% C.L. © 2005 The American Physical Society.

Abstract:

We study the decay B^- → J/ΨK ^-π⁺π^- using 117×10⁶ BB̄ events collected at the Y(4S) resonance with the BABAR detector at the PEP-II e⁺e^- asymmetric-energy storage ring. We measure the branching fractions ℬ (B^- → J/ΨK ^-π⁺π^-) = (116±7(stat.) ±9(syst.))×10^-5 and ℬ (B^- → X(3872)K^-) × ℬ (X(3872) → J/Ψπ⁺π ^-) = (1.28±0.41)×10^-5 and find the mass of the X(3872) to be 3873.4±1.4 MeV/c². We search for the h c narrow state in the decay B^- → hcK ^-, hc → J/Ψπ⁺π^- and for the decay B^- → J/ΨD⁰π^-, with D⁰ → K^-π⁺. We set the 90% C.L. limits ℬ(B^- → hcK^-) × ℬ(h c → J/Ψπ⁺π^-)<3. 4×10^-6 and ℬ(B^- → J/ΨD ⁰π^-)<5.2×10^-5. © 2005 The American Physical Society.

Abstract:

We search for the rare flavor-changing neutral-current decay B⁺ → K⁺ νν̄ in a data sample of 82 fb^-1 collected with the BABAR detector at the PEP-II S-factory. Signal events are selected by examining the properties of the system recoiling against either a reconstructed hadronic or semileptonic charged-B decay. Using these two independent samples we obtain a combined limit of ℬ(B⁺ →K⁺ νν̄) ≤ 5.2 × 10^-5 at the 90% confidence level In addition, by selecting for pions rather than kaons, we obtain a limit of ℬ(B⁺ → π⁺ νν̄) < 1.0 × 10^-4 using only the hadronic B reconstruction method. © 2005 The American Physical Society.