A search for the decay B+→K+ννˉB^+ \to K^+ \nu \bar{\nu}

We search for the rare flavor-changing neutral-current decay $B^+ \to K^+ \nu \bar{\nu}$ in a data sample of 82 fb$^{-1}$ collected with the {\sl BABAR} detector at the PEP-II B-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 ${\mathcal B}(B^+ \to K^+ \nu \bar{\nu})<5.2 \times 10^{-5}$ at the 90% confidence level. In addition, by selecting for pions rather than kaons, we obtain a limit of ${\mathcal B}(B^+ \to \pi^+ \nu \bar{\nu})<1.0 \times 10^{-4}$ using only the hadronic B reconstruction method.Comment: 7 pages, 8 postscript figures, submitted to Phys. Rev. Let

High-reflectivity broadband distributed Bragg reflector lattice matched to ZnTe

We report on the realization of a high quality distributed Bragg reflector with both high and low refractive index layers lattice matched to ZnTe. Our structure is grown by molecular beam epitaxy and is based on binary compounds only. The high refractive index layer is made of ZnTe, while the low index material is made of a short period triple superlattice containing MgSe, MgTe, and ZnTe. The high refractive index step of Delta_n=0.5 in the structure results in a broad stopband and the reflectivity coefficient exceeding 99% for only 15 Bragg pairs.Comment: 4 pages, 3 figure

Improved measurement of CP asymmetries in B-0 ->(c(c)over-bar)K0((*)) decays

We present results on time-dependent CP asymmetries in neutral B decays to several CP eigenstates. The measurements use a data sample of about 227x10(6) Upsilon(4S)-> B (B) over bar decays collected by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. The amplitude of the CPasymmetry, sin2 beta 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 B-0 or (0) from its decay products. We measure sin2 beta=0.722 +/- 0.040(stat)+/- 0.023(syst) in agreement with the standard model expectation

Branching Fractions and CP Asymmetries in B0→K+K-KS0 and B+→K+KS0KS0

We measure the branching fractions and CP asymmetries in the decays B0→K+K-KS0 and B+→K+KS0KS0 using a sample of approximately 122×106 BB̅ pairs collected by the BABAR detector. From a time-dependent analysis of the K+K-KS0 sample that excludes ϕKS0, the values of the CP-violation parameters are S=-0.56±0.25±0.04 and C=-0.10±0.19±0.10, where the first uncertainty is statistical and the second is systematic. We confirm that the final state is nearly purely CP even and extract the standard model parameter sin⁡2β=0.57±0.26±0.04-0+0.17 where the last error is due to uncertainty on the CP content. We present the first measurement of the CP-violating charge asymmetry ACP(B+→K+KS0KS0)=-0.04±0.11±0.02. The branching fractions are B(B0→K+K-K0)=(23.8±2.0±1.6)×10-6 and B(B+→K+KS0KS0)=(10.7±1.2±1.0)×10-6

Study of the Decay B0(B¯0)→ρ+ρ-, and Constraints on the Cabibbo-Kobayashi-Maskawa Angle α

Using a data sample of 89×106 Υ(4S)→BB̅ decays collected with the BABAR detector at the PEP-II asymmetric B Factory at SLAC, we measure the B0(B̅ 0)→ρ+ρ- branching fraction as [30±4(stat)±5(syst)]×10-6 and a longitudinal polarization fraction of fL=0.99±0.03(stat)-0.03+0.04(syst). We measure the time-dependent-asymmetry parameters of the longitudinally polarized component of this decay as CL=-0.17±0.27(stat)±0.14(syst) and SL=-0.42±0.42(stat)±0.14(syst). We exclude values of α between 19° and 71° (90% C.L.)

Measurement of the B0→ϕK*0 Decay Amplitudes

With a sample of about 227×106 BB̅ pairs recorded with the BABAR detector we perform a full angular analysis of the decay B0→ϕK*0(892). We make novel measurements of five parameters sensitive to CP violation. We also measure the branching fraction to be (9.2±0.9±0.5)×10-6 and determine the fractions of longitudinal and parity-odd transverse contributions as fL=0.52±0.05±0.02 and f⊥=0.22±0.05±0.02. The phases of the parity-even and parity-odd transverse amplitudes relative to the longitudinal amplitude are found to be ϕ∥=2.34-0.20+0.23±0.05  rad and ϕ⊥=2.47±0.25±0.05  rad. We also observe the decay B0→ϕK*0(1430)

Measurements of neutral B decay branching fractions to K-S(0)pi(+)pi(-) final states

Branching fraction measurements using B-meson decays to K(S)(0)pi(+)pi(-) are presented. These measurements were obtained by analyzing a data sample of 88.9x10(6) Y(4S)--&gt;B (B) over bar decays collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B factory. Using a maximum likelihood fit, the following branching fraction results were obtained: B(B-0--&gt;K(0)pi(+)pi(-))=(43.7+/-3.8+/-3.4)x10(-6), B(B-0--&gt;K(*+)pi(-))=(12.9+/-2.4+/-1.4)x10(-6), and B(B-0--&gt;D-(--&gt;K(S)(0)pi(-))pi(+))=(42.7+/-2.1+/-2.2)x10(-6). The CP violating charge asymmetry A(K)(*)pi for the decay B-0--&gt;K(*+)pi(-) was measured to be A(K)(*)pi=0.23+/-0.18(-0.06)(+0.09). For all these measurements the first error is statistical and the second is systematic

Measurement of branching fractions and CP and isospin asymmetries for B→K^{*}γ

The branching fractions of the decays B0→K*0γ and B+→K*+γ are measured using a sample of 88×106BB̅ events collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider. We find B(B0→K*0γ)=[3.92±0.20(stat)±0.24(syst)]×10-5, B(B+→K*+γ)=[3.87±0.28(stat)±0.26(syst)]×10-5. Our measurements also constrain the direct CP asymmetry to be -0.074<A(B→K*γ)<0.049 and the isospin asymmetry to be -0.046<Δ0-<0.146, both at the 90% confidence level

Measurements of the branching fractions of charged B decays to K+- pi-+ pi+- final states

We present results of searches for B-meson decays to K(+)pi(-)pi(+) with the BABAR detector. With a data sample of 61.6x10(6) B (B) over bar pairs, we measure the branching fractions and 90% confidence-level upper limits averaged over charge-conjugate states (the first error is statistical and the second is systematic): B[B+-->K-*0(892)pi(+)]=(15.5+/-1.8(-4.0)(+1.5))x10(-6), B[B+-->f(0)(980)K+,f(0)-->pi(+)pi(-)]=(9.2+/-1.2(-2.6)(+2.1))x10(-6), B[B+-->(D) over bar (0)pi(+),(D) over bar (0)-->K(+)pi(-)]=(184.6+/-3.2+/-9.7)x10(-6), B[B+-->rho(0)(770)K+]K(+)pi(-)pi(+)nonresonant]<17x10(-6)