Xuefei Li

Measurement of the branching fractions of the radiative charm decays D-0 ->(K)overbar(*0)gamma and D-0 ->phi gamma

We present a measurement of the branching fractions for the Cabibbo-favored radiative decay D^0→K ^(*0) γ and the Cabibbo-suppressed radiative decay D^0→ϕγ. These measurements are based on a data sample corresponding to an integrated luminosity of 387.1u2009u2009fb^(-1) and recorded with the BABAR detector at the PEP-II e^+e^- asymmetric-energy collider operating at center-of-mass energies 10.58 and 10.54 GeV. We measure the branching fractions relative to the well-studied decay D^0→K^-π^+ and find B(D^0→K ^(*0) γ)/B(D^0→K^-π^+)=(8.43±0.51±0.70)×10^(-3) and B(D^0→ϕγ)/B(D^0→K^-π^+)=(7.15±0.78±0.69)×10^(-4), where the first error is statistical and the second is systematic. This is the first observation of the decay mode D^0→K ^(*0) γ.

Observation of e(+)e(-)->rho(+)rho(-) near root s=10.58 GeV

We report the first observation of e^+e^- → ρ^+ρ^-, in a data sample of 379 fb^(-1) collected with the nBABAR detector at the PEP-II e+e- storage ring at center-of-mass energies near √s = 10:58 GeV. We nmeasure a cross section of σ(e^+e^- → ρ^+ρ^-)= 8:3 ± 0:7(stat)± 0:8(syst) fb within the range of n│cosθ^*│ < 0:8 and │ cosθ_±│ < 0:85, where θ^* is the center-of-mass polar angle of the ρ^± meson and nθ_± are the angles in the ρ^± rest frame between the direction of the boost from the laboratory frame and the ndirection of the π^±. Assuming production through single-photon annihilation, there are three independent nhelicity amplitudes. We measure the ratios of their squared moduli to be │F_(00)│^2:│F_(10)│^2:│F_(11)│^2 = n0:51 ± 0:14(stat) ± 0:07(syst):0:10 ± 0:04(stat) ± 0:01(syst):0:04 ± 0:03(stat) ± 0:01(syst). The │F_(00)│^2 nresult is inconsistent with the prediction of 1.0 made by QCD models with a significance of 3.1 standard ndeviations including systematic uncertainties.The authors report the first observation of e{sup +}e{sup -} {yields} {rho}{sup +}{rho}{sup -}, in a data sample of 379 fb{sup -1} collected with the BABAR detector at the PEP-II e{sup +}e{sup -} storage ring at center-of-mass energies near {radical}s = 10.58 GeV. The authors measure a cross section of {sigma}(e{sup +}e{sup -} {yields} {rho}{sup +}{rho}{sup -}) = 19.5 {+-} 1.6(stat) {+-} 3.2(syst) fb. Assuming production through single-photon annihilation, there are three independent helicity amplitudes. They measure the ratios of their squared moduli to be |F{sub 00}|{sup 2} : |F{sub 10}|{sup 2} : |F{sub 11}|{sup 2} = 0.51 {+-} 0.14(stat) {+-} 0.07(syst) : 0.10 {+-} 0.04(stat) {+-} 0.01(syst) : 0.04 {+-} 0.03(stat) {+-} 0.01(syst). The |F{sub 00}|{sup 2} result is inconsistent with the prediction of 1.0 made by QCD models with a significance of 3.1 standard deviations including systematic uncertainties.

Search for B -> K-*nu(nu)overbar decays

We present a search for the decays B -> K-*nu(nu)overbar using 454x10(6)B(B)overbar pairs collected at the Upsilon(4S) resonance with the BABAR detector at the SLAC PEP-II B-Factory. We first select an event sample where one B is reconstructed in a semileptonic or hadronic mode with one charmed meson. The remaining particles in the event are then examined to search for a B -> K-*nu(nu)overbar decay. The charged K-* is reconstructed as K*+-> K-S(0)pi(+) or K*+-> K+pi(0); the neutral K-* is identified in K-*0 -> K+pi(-) mode. We establish upper limits at 90% confidence level of B(B+-> K*+nu(nu)overbar>) K-*0 nu(nu)overbar) K-*nu(nu)overbar)< 8x10(-5).We present a search for the decays