Search Results (112 total)

We present a measurement of the parameters of the Υ(10580) resonance based on a dataset collected with the BABAR detector at the SLAC PEP-II asymmetric B factory. We measure the total width Γ_tot=(20.7±1.6±2.5)  MeV, the electronic partial width Γ_ee=(0.321±0.017±0.029)  keV and the mass M=(10579.3±0.4±1.2)  MeV/c².

We present a search for the decay B^-→τ^-ν_τ̅ in a sample of 88.9×10⁶ BB̅ pairs recorded with the BABAR detector at the Stanford Linear Accelerator Center B factory. One of the two B mesons from the Υ(4S) is reconstructed in a hadronic or a semileptonic final state, and the decay products of the other B in the event are analyzed for consistency with a B^-→τ^-ν̅ _τ decay. We find no evidence of a signal and set an upper limit on the branching fraction of B(B^-→τ^-ν̅ _τ)<4.2×10^-4 at the 90% confidence level.

We present a search for the decays B⁰→e⁺e^-, B⁰→μ⁺μ^-, and B⁰→e^±μ^∓ in data collected at the Υ(4S) resonance with the BABAR detector at the SLAC B Factory. Using a data set of 111  fb^-1, we find no evidence for a signal in any of the three channels investigated and set the following branching fraction upper limits at the 90% confidence level: B(B⁰→e⁺e^-)<6.1×10^-8, B(B⁰→μ⁺μ^-)<8.3×10^-8, and B(B⁰→e^±μ^∓)<18×10^-8.

We study the decay B^-→J/ψK^-π⁺π^- using 117×10⁶ BB̅ 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^-→h_cK^-, h_c→J/ψπ⁺π^- and for the decay B^-→J/ψD⁰π^-, with D⁰→K^-π⁺. We set the 90% C.L. limits B(B^-→h_cK^-)×B(h_c→J/ψπ⁺π^-)<3.4×10^-6 and B(B^-→J/ψD⁰π^-)<5.2×10^-5.

We present a measurement of the Cabibbo-Kobayashi-Maskawa matrix element |V_cb| based on a sample of about 53 700 B̅ ⁰→D^*+ℓ^-ν̅ _ℓ decays observed by the BABAR detector. We obtain the branching fraction averaged over ℓ=e,μ, B(B̅ ⁰→D^*+ℓ^-ν̅ _ℓ)=(4.90±0.07(stat.)_-0.35^+0.36(syst.))%. We measure the differential decay rate as a function of w, the relativistic boost γ of the D^*+ in the B̅ ⁰ rest frame. By extrapolating dΓ/dw to the kinematic limit w→1, we extract the product of |V_cb| and the axial form factor A₁(w=1). We combine this measurement with a lattice QCD calculation of A₁(w=1) to determine |V_cb|=(38.7±0.3(stat.)±1.7(syst.)_-1.3^+1.5(theory))×10^-3.

We present measurements of the branching fraction and CP-violating asymmetries in the decay B⁰→f₀(980)K_S⁰. The results are obtained from a data sample of 123×10⁶ Υ(4S)→BB̅ decays. From a time-dependent maximum likelihood fit, we measure the branching fraction B(B⁰→f₀(980)(→π⁺π^-)K⁰)=(6.0±0.9±0.6±1.2)×10^-6, the mixing-induced CP violation parameter S=-1.62_-0.51^+0.56±0.09±0.04, and the direct CP violation parameter C=0.27±0.36±0.10±0.07, where the first errors are statistical, the second systematic, and the third due to model uncertainties. We measure the f₀(980) mass and width to be m_f0(980)=(980.6±4.1±0.5±4.0)   MeV/c² and Γ_f0(980)=(43_-9⁺¹²±3±9)   MeV/c², respectively.

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<Δ_0-<0.146, both at the 90% confidence level.

We present a search for B decays to charmless final states involving charged or neutral a₀ mesons. The data sample corresponds to 89×10⁶ BB̅ pairs collected with the BABAR detector operating at the PEP-II asymmetric-energy B Factory at Stanford Linear Accelerator Center. We find no significant signals and determine the following 90% C.L. upper limits: B(B⁰→a₀^-π⁺)<5.1×10^-6, B(B⁰→a₀^-K⁺)<2.1×10^-6, B(B^-→a₀^-K̅ ⁰)<3.9×10^-6, B(B⁺→a₀⁰π⁺)<5.8×10^-6, B(B⁺→a₀⁰K⁺)<2.5×10^-6, and B(B⁰→a₀⁰K⁰)<7.8×10^-6, where in all cases B indicates the product of branching fractions for B→a₀X and a₀→ηπ, where X indicates K or π.

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 f_L=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 C_L=-0.17±0.27(stat)±0.14(syst) and S_L=-0.42±0.42(stat)±0.14(syst). We exclude values of α between 19° and 71° (90% C.L.).

We have investigated the exclusive, radiative B meson decays to K₂^*(1430) in 89×10⁶ BB̅ events with the BABAR detector at the PEP-II storage ring. We measure the branching fractions B(B⁰→K₂^*(1430)⁰γ)=(1.22±0.25±0.10)×10^-5 and B(B⁺→K₂^*(1430)⁺γ)=(1.45±0.40±0.15)×10^-5, where the first error is statistical and the second systematic. In addition, we measure the CP-violating asymmetry A_CP[B⁰→K₂^*(1430)⁰γ]=-0.08±0.15±0.01.

We present the results of a search for the radiative decay B⁰→J/ψγ in a data set containing 123.0×10⁶ Υ(4S)→BB̅ decays, collected by the BABAR detector at the PEP-II asymmetric-energy e⁺e^- storage ring at SLAC. We find no evidence for a signal and place an upper limit of B(B⁰→J/ψγ)<1.6×10^-6 at 90% confidence level.

We present results of searches for B-meson decays to K⁺π^-π⁺ with the BABAR detector. With a data sample of 61.6×10⁶ BB̅ 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)π⁺]=(15.5±1.8_-4.0^+1.5)×10^-6, B[B⁺→f₀(980)K⁺,f₀→π⁺π^-]=(9.2±1.2_-2.6^+2.1)×10^-6, B[B⁺→D̅ ⁰π⁺,D̅ ⁰→K⁺π^-]=(184.6±3.2±9.7)×10^-6, B[B⁺→ρ⁰(770)K⁺]<6.2×10^-6 and B[B⁺→K⁺π^-π⁺ nonresonant]<17×10^-6.

We present a measurement of the time-dependent CP-violating asymmetries in B⁰→K^*0γ(K^*0→K_S⁰π⁰) decays based on 124×10⁶ Υ(4S)→BB̅ decays collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at the Stanford Linear Accelerator Center. In a sample containing 105±14 signal decays, we measure S_K^*γ=0.25±0.63±0.14 and C_K^*γ=-0.57±0.32±0.09, where the first error is statistical and the second, systematic.

We search for B meson decays into two-body combinations of η,η^′,ω, and ϕ mesons from 89×10⁶ BB̅ pairs collected with the BABAR detector at the PEP-II asymmetric-energy e⁺e^- collider at SLAC. We find the branching fraction B(B⁰→ηω)=(4.0_-1.2^+1.3±0.4)×10^-6 with a significance of 4.3σ. For the other decay modes we set the following 90% confidence level upper limits on the branching fractions, in units of 10^-6: B(B⁰→ηη)<2.8, B(B⁰→ηη^′)<4.6, B(B⁰→η^′η^′)<10, B(B⁰→η^′ω)<2.8, B(B⁰→ηϕ)<1.0, B(B⁰→η^′ϕ)<4.5, and B(B⁰→ϕϕ)<1.5.

We measure the branching fractions and CP asymmetries in the decays B⁰→K⁺K^-K_S⁰ and B⁺→K⁺K_S⁰K_S⁰ using a sample of approximately 122×10⁶ BB̅ pairs collected by the BABAR detector. From a time-dependent analysis of the K⁺K^-K_S⁰ sample that excludes ϕK_S⁰, 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 A_CP(B⁺→K⁺K_S⁰K_S⁰)=-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⁺K_S⁰K_S⁰)=(10.7±1.2±1.0)×10^-6.

We present a measurement of the time-dependent CP-violating (CPV) asymmetries in B⁰→K_S⁰π⁰ decays based on 124×10⁶ Υ(4S)→BB̅ decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. In a sample containing 122±16 signal decays, we obtain the magnitudes of the direct CPV asymmetry C_KS⁰π⁰=0.40_-0.28^+0.27±0.09 and of the CPV asymmetry in the interference between mixing and decay S_KS⁰π⁰=0.48_-0.47^+0.38±0.06 where the first error is statistical and the second systematic.

We search for B^±→[K^∓π^±]_DK^± decays, where [K^∓π^±]_D indicates that the K^∓π^± pair originates from the decay of a D⁰ or D̅ ⁰. Results are based on 120×10⁶ Υ(4S)→BB̅ decays collected with the BABAR detector at SLAC. We set an upper limit on the ratio R_Kπ≡  [Γ(B⁺→[K^-π⁺]_DK⁺)+Γ(B^-→[K⁺π^-]_DK^-)] / [Γ(B⁺→[K⁺π^-]_DK⁺)+Γ(B^-→[K^-π⁺]_DK^-)]<0.026 (90%   C.L.). This constrains the amplitude ratio r_B≡  |A(B^-→D̅ ⁰K^-)/A(B^-→D⁰K^-)|<0.22 (90% C.L.), consistent with expectations. The small value of r_B favored by our analysis suggests that the determination of the Cabibbo-Kobayashi-Maskawa phase γ from B→DK will be difficult.

We present measurements of the branching fractions and charge asymmetries (where appropriate) of two-body B decays to η^(′)K^*, η^(′)ρ, η^(′)π⁰, ωπ⁰, and φπ⁰. The data were recorded with the BABAR detector at PEP-II and correspond to 89×10⁶ BB̅ pairs produced in e⁺e^- annihilation through the Υ(4S) resonance. We find significant signals for two decay modes and measure the branching fractions B(B⁺→ηK^*+)=(25.6±4.0±2.4)×10^-6 and B(B⁰→ηK^*0)=(18.6±2.3±1.2)×10^-6, where the first error is statistical and the second systematic. We also find evidence with significance 3.5σ for a third decay mode and measure B(B⁺→ηρ⁺)=(9.2±3.4±1.0)×10^-6. For other channels, we set 90% C.L. upper limits of B(B⁰→ηρ⁰)<1.5×10^-6, B(B⁺→η^′K^*+)<14×10^-6, B(B⁰→η^′K^*0)<7.6×10^-6, B(B⁺→η^′ρ⁺)<22×10^-6, B(B⁰→η^′ρ⁰)<4.3×10^-6, B(B⁰→ηπ⁰)<2.5×10^-6, B(B⁰→η^′π⁰)<3.7×10^-6, B(B⁰→ωπ⁰)<1.2×10^-6, and B(B⁰→φπ⁰)<1.0×10^-6. For self-flavor-tagging modes with significant signals, the time-integrated charge asymmetries are A_ch(ηK^*+)=+0.13±0.14±0.02 and A_ch(ηK^*0)=+0.02±0.11±0.02.

We establish 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 B⁰ decays to νν̅ γ. Within the standard model, these decays have branching fractions that are below current experimental sensitivity, but various models of physics beyond the standard model predict significant contributions from these channels. Using 88.5×10⁶ BB̅ pairs collected at the Υ(4S) resonance by the BABAR experiment at the PEP-II e⁺e^- storage ring at the Stanford Linear Accelerator Center, we establish upper limits at the 90% confidence level of 22×10^-5 for the branching fraction of B⁰→invisible and 4.7×10^-5 for the branching fraction of B⁰→νν̅ γ.

We measure the branching fraction for the flavor-changing neutral-current process B→X_sℓ⁺ℓ^- with a sample of 89×10⁶ Υ(4S)→BB̅ events recorded with the BABAR detector at the PEP-II e⁺e^- storage ring. The final state is reconstructed from e⁺e^- or μ⁺μ^- pairs and a hadronic system X_s consisting of one K^± or K_S⁰ and up to two pions, with at most one π⁰. We observe a signal of 40±10(stat)±2(syst) events and extract the inclusive branching fraction B(B→X_sℓ⁺ℓ^-)=(5.6±1.5(stat)±0.6(exp   syst)±1.1(model   syst))×10^-6 for m_ℓ⁺ℓ^->0.2   GeV/c².

We have measured the time-dependent decay rate for the process B→J/ψK^*0(892) in a sample of about 88×10⁶ Υ(4S)→BB̅ decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. In this sample we study flavor-tagged events in which one neutral B meson is reconstructed in the J/ψK^*0 or J/ψK̅ ^*0 final state. We measure the coefficients of the cosine and sine terms in the time-dependent asymmetries for J/ψK^*0 and J/ψK̅ ^*0, find them to be consistent with the standard model expectations, and set upper limits at 90% confidence level (C.L.) on the decay amplitude ratios |A(B̅ ⁰→J/ψK^*0)|/|A(B⁰→J/ψK^*0)|<0.26 and |A(B⁰→J/ψK̅ ^*0)|/|A(B̅ ⁰→J/ψK̅ ^*0)|<0.32. For a single ratio of wrong-flavor to favored amplitudes for B⁰ and B̅ ⁰ combined, we obtain an upper limit of 0.25 at 90% C.L.

We present a measurement of the time-dependent CP asymmetry for the neutral B-meson decay B⁰→ϕK⁰. We use a sample of approximately 114×10⁶ B-meson pairs taken at the Υ(4S) resonance with the BABAR detector at the PEP-II B-meson factory at SLAC. We reconstruct the CP eigenstates ϕK_S⁰ and ϕK_L⁰, where ϕ→K⁺K^-, K_S⁰→π⁺π^-, and K_L⁰ is observed via its hadronic interactions. The other B meson in the event is tagged as either a B⁰ or B̅ ⁰ from its decay products. The values of the CP-violation parameters are S_ϕK=0.47±0.34(stat)_-0.06^+0.08(syst) and C_ϕK=0.01±0.33(stat)±0.10(syst).

We measure the branching fraction for the charmless semi-inclusive process B→η^′X_s, where the η^′ meson has a momentum in the range 2.0 to 2.7  GeV/c in the Υ(4S) center-of-mass frame and X_s represents a system comprising a kaon and zero to four pions. We find B(B→η^′X_s)=[3.9±0.8(stat)±0.5(syst)±0.8(model)]×10^-4. We also obtain the X_s mass spectrum and find that it fits models predicting high masses.

We present measurements of branching fractions and charge asymmetries in B-meson decays to ρ⁺π⁰, ρ⁰π⁺, and ρ⁰π⁰. The data sample comprises 89×10⁶ Υ(4S)→BB̅ decays collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We find the charge-averaged branching fractions B(B⁺→ρ⁺π⁰)=[10.9±1.9(stat)±1.9(syst)]×10^-6 and B(B⁺→ρ⁰π⁺)=(9.5±1.1±0.9)×10^-6, and we set a 90% confidence-level upper limit B(B⁰→ρ⁰π⁰)<2.9×10^-6. We measure the charge asymmetries A_CP^ρ+π0=0.24±0.16±0.06 and A_CP^ρ0π+=-0.19±0.11±0.02.

Using events in which one of two neutral B mesons from the decay of an Υ(4S) resonance is fully reconstructed, we set limits on the difference between the decay rates of the two neutral B mass eigenstates and on CP, T, and CPT violation in B⁰B⁰ mixing. The reconstructed decays, comprising both CP and flavor eigenstates, are obtained from 88 million Υ(4S)→BB̅ decays collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We determine six independent parameters governing oscillations (Δm,ΔΓ/Γ), CPT and CP violation (Re z,Im z), and CP and T violation (Im λ_CP,|q/p|), where λ_CP characterizes B⁰ and B⁰ decays to states of charmonium plus K_S⁰ or K_L⁰. The results are sgn(Re λ_CP)ΔΓ/Γ=-0.008±0.037(stat.)±0.018(syst.)[-0.084,0.068],|q/p|=1.029±0.013(stat.)±0.011(syst.)[1.001,1.057],(Re λ_CP/|λ_CP|)Re z=0.014±0.035(stat.)±0.034(syst.)[-0.072,0.101],Im z=0.038±0.029(stat.)±0.025(syst.)[-0.028,0.104].The values inside square brackets indicate the 90% confidence-level intervals. The values of Im λ_CP and Δm are consistent with previous analyses and are used as cross checks. These measurements are in agreement with standard model expectations.