Search Results (54 total)

We present a study of the decay B^-→D_(CP)⁰K^- and its charge conjugate, where D_(CP)⁰ is reconstructed in both a non-CP flavor eigenstate and in CP (CP-even and CP-odd) eigenstates, based on a sample of 382 million Υ(4S)→BB̅ decays collected with the BABAR detector at the PEP-II e⁺e^- storage ring. We measure the direct CP asymmetries A_CP± and the ratios of the branching fractions R_CP±: A_CP+=0.27±0.09(stat)±0.04(syst), A_CP-=-0.09±0.09(stat)±0.02(syst), R_CP+=1.06±0.10(stat)±0.05(syst), R_CP-=1.03±0.10(stat)±0.05(syst). We also express the results in terms of the so-called Cartesian coordinates x₊, x_-, and r²: x₊=-0.09±0.05(stat)±0.02(syst), x_-=0.10±0.05(stat)±0.03(syst), r²=0.05±0.07(stat)±0.03(syst). These results will help to better constrain the phase parameter γ=arg⁡(-V_udV_ub^*/V_cdV_cb^*) of the Cabibbo-Kobayashi-Maskawa quark mixing matrix.

Using 226×10⁶ BB̅ events recorded on the Υ(4S) resonance with the BABAR detector at the SLAC e⁺e^- PEP-II storage rings, we reconstruct B^-→D^*0e^-ν̅ _e decays using the decay chain D^*0→D⁰π⁰ and D⁰→K^-π⁺. From the dependence of their differential rate on w, the dot product of the four velocities of B^- and D^*0, and using the form factor description by Caprini et al. with the parameters F(1) and ρ_A1², we obtain the results ρ_A1²=1.16±0.06±0.08, F(1)|V_cb|=(35.9±0.6±1.4)×10^-3, and B(B^-→D^*0e^-ν̅ _e)=(5.56±0.08±0.41)%.

We present measurements of the decays B⁺→X(3872)K⁺ and B⁰→X(3872)K⁰ with X(3872)→J/ψπ⁺π^-. The data sample used, collected with the BABAR detector at the PEP-II e⁺e^- asymmetric-energy storage ring, corresponds to 455×10⁶BB̅ pairs. Branching fraction measurements of B(B⁺→X(3872)K⁺)×B(X(3872)→J/ψπ⁺π^-)=(8.4±1.5±0.7)×10^-6 and B(B⁰→X(3872)K⁰)×B(X(3872)→J/ψπ⁺π^-)=(3.5±1.9±0.4)×10^-6 are obtained. We set an upper limit on the natural width of the X(3872) of Γ<3.3  MeV/c² at the 90% confidence level.

We present searches for the leptonic decays B⁺→ℓ⁺ν and the lepton flavor violating decays B⁰→ℓ^±τ^∓, where ℓ=e, μ, with data collected by the BABAR experiment at SLAC. This search demonstrates a novel technique in which we fully reconstruct the accompanying B̅ in Υ(4S)→BB̅ events, and look for a monoenergetic lepton from the signal B decay. The signal yield is extracted from a fit to the signal lepton candidate momentum distribution in the signal B rest frame. Using a data sample of approximately 378×10⁶ BB̅ pairs (342  fb^-1), we find no evidence of signal in any of the decay modes. Branching fraction upper limits of B(B⁺→e⁺ν)<5.2×10^-6, B(B⁺→μ⁺ν)<5.6×10^-6, B(B⁰→e⁺τ^-)<2.8×10^-5 and B(B⁰→μ⁺τ^-)<2.2×10^-5, are obtained at 90% confidence level.

We present for the first time a measurement of the weak phase 2β+γ obtained from a time-dependent Dalitz plot analysis of B⁰→D^∓K⁰π^± decays. Using a sample of approximately 347×10⁶ BB̅ pairs collected by the BABAR detector at the PEP-II asymmetric-energy storage rings and assuming the ratio r of the b→u and b→c decay amplitudes to be 0.3, we obtain 2β+γ=(83±53±20)° and the equivalent solution at +180°. The magnitudes and phases for the resonances associated with the b→c transitions are also extracted from the fit.

We report a measurement of the branching fractions for B̅ →D^(*)(π)ℓ^-ν̅ _ℓ decays based on 341.1  fb^-1 of data collected at the Υ(4S) resonance with the BABAR detector at the SLAC PEP-II e⁺e^- storage rings. Events are tagged by fully reconstructing one of the B mesons in a hadronic decay mode. We obtain B(B^-→D⁰ℓ^-ν̅ _ℓ)=(2.33±0.09_stat±0.09_syst)%, B(B^-→D^*0ℓ^-ν̅ _ℓ)=(5.83±0.15_stat±0.30_syst)%, B(B̅ ⁰→D⁺ℓ^-ν̅ _ℓ)=(2.21±0.11_stat±0.12_syst)%, B(B̅ ⁰→D^*+ℓ^-ν̅ _ℓ)=(5.49±0.16_stat±0.25_syst)%, B(B^-→D⁺π^-ℓ^-ν̅ _ℓ)=(0.42±0.06_stat±0.03_syst)%, B(B^-→D^*+π^-ℓ^-ν̅ _ℓ)=(0.59±0.05_stat±0.04_syst)%, B(B̅ ⁰→D⁰π⁺ℓ^-ν̅ _ℓ)=(0.43±0.08_stat±0.03_syst)%, and B(B̅ ⁰→D^*0π⁺ℓ^-ν̅ _ℓ)=(0.48±0.08_stat±0.04_syst)%.

We present a measurement of the branching fraction and photon-energy spectrum for the decay B→X_sγ using data from the BABAR experiment. The data sample corresponds to an integrated luminosity of 210  fb^-1, from which approximately 680 000 BB̅ events are tagged by a fully reconstructed hadronic decay of one of the B mesons. In the decay of the second B meson, an isolated high-energy photon is identified. We measure B(B→X_sγ)=(3.66±0.85_stat±0.60_syst)×10^-4 for photon energies E_γ above 1.9 GeV in the B rest frame. From the measured spectrum we calculate the first and second moments for different minimum photon energies, which are used to extract the heavy-quark parameters m_b and μ_π². In addition, measurements of the direct CP asymmetry and isospin asymmetry are presented.

A search for lepton flavor violating decays of a τ to a lighter-mass charged lepton and an ω vector meson is performed using 384.1  fb^-1 of e⁺e^- annihilation data collected with the BABAR detector at the Stanford Linear Accelerator Center PEP-II storage ring. No signal is found, and the upper limits on the branching ratios are determined to be B(τ^±→e^±ω)<1.1×10^-7 and B(τ^±→μ^±ω)<1.0×10^-7 at 90% confidence level.

We have studied two-body charmless decays of the B meson into the final states ρ⁰ρ⁰, K^*0ρ⁰, K^*0K^*0, K^*0K̅ ^*0, K^*+ρ⁰, K^*+K̅ ^*0, and K^*+K^*- using only decay modes with charged daughter particles. Using 9.7×10⁶ BB̅ pairs collected with the CLEO detector, we place 90% confidence level upper limits on the branching fractions (1.4–14.1)×10^-5, depending on final state and polarization.

We have measured the CP asymmetry A_CP≡[Γ(b→sγ)-Γ(b̅ →s̅ γ)]/[Γ(b→sγ)+Γ(b̅ →s̅ γ)] to be A_CP  =  (-0.079±0.108±0.022) (1.0±0.030), implying that, at 90% confidence level, A_CP lies between -0.27 and +0.10. These limits rule out some extreme non-standard-model predictions, but are consistent with most, as well as with the standard model.

Using 13.7 fb^-1 of data recorded by the CLEO detector at the Cornell Electron Storage Ring, we investigate the spectrum of charmed baryons which decay into Λ_c⁺π^-π⁺ and are more massive than the Λ_c⁺(2625) baryon. We find evidence for two new states: one is broad and has an invariant mass roughly 480 MeV above that of the Λ_c⁺ baryon; the other is narrow with an invariant mass of 596±1±2 MeV above the Λ_c⁺ mass.

The τ decays to six-pion final states have been studied with the CLEO detector at the Cornell Electron Storage Ring. The measured branching fractions are B(τ^-→2π^-π⁺3π⁰ν_τ)  =  (2.2±0.3±0.4)×10^-4 and B(τ^-→3π^-2π⁺π⁰ν_τ)  =  (1.7±0.2±0.2)×10^-4. A search for substructure in these decays shows that they are saturated by intermediate states with η or ω mesons. We present the first observation of the decay τ^-→2π^-π⁺ων_τ and the branching fraction is measured to be (1.2±0.2±0.1)×10^-4. The measured branching fractions are in good agreement with the isospin expectations but somewhat below the conserved-vector-current predictions.

Using 13.7 fb^-1 of data recorded by the CLEO detector at Cornell Electron Storage Ring, we report evidence of two new charmed baryons: one decaying into Ξ_c^0′π⁺ with the subsequent decay Ξ_c^0′→Ξ_c⁰γ, and its isospin partner decaying into Ξ_c^+′π^- followed by Ξ_c^+′→Ξ_c⁺γ. We measure the following mass differences for the two states: M(Ξ_c⁰γπ⁺)-M(Ξ_c⁰)  =  318.2±1.3±2.9 MeV and M(Ξ_c⁺γπ^-)-M(Ξ_c⁺)  =  324.0±1.3±3.0 MeV. We interpret these new states as the J^P  =  1 / 2^- Ξ_c1 particles, the charmed-strange analogs of the Λ_c1⁺(2593).

The CLEO experiment at the CESR collider has used 13.7 fb^-1 of data to search for the production of the Ω_c⁰ (css ground state) in e⁺e^- collisions at sqrt[s]≃10.6 GeV. The modes used to study the Ω_c⁰ are Ω^-π⁺, Ω^-π⁺π⁰, Ξ^-K^-π⁺π⁺, Ξ⁰K^-π⁺, and Ω^-π⁺π⁺π^-. We observe a signal of 40.4±9.0(stat) events at a mass of 2694.6±2.6(stat)±1.9(syst) MeV/c², for all modes combined.

We use data collected with the CLEO II detector to perform a high-statistics measurement of the resonant substructure in D⁰→K^-π⁺π⁰ decays. We find that the Dalitz plot is well represented by a combination of seven quasi-two-body decay channels [K^*0π⁰, K^-ρ, K^*-π⁺, K₀(1430)^-π⁺, K₀(1430)⁰π⁰, K^-ρ⁺(1700), and K^*(1680)^-π⁺], plus a small non-resonant component. We see no evidence of a scalar κ→K^-π⁺ resonance in the mass range recently reported by other groups. Using the amplitudes and phases from this analysis, we calculate an integrated CP asymmetry of -0.031±0.086.

We report results of a search for B→τν in a sample of 9.7×10⁶ charged B meson decays. We exclusively reconstruct the companion B̅ decay to suppress background. We set an upper limit on the branching fraction B(B→τν)<8.4×10^-4 at 90% confidence level. We also establish B(B^±→K^±νν̅ )<2.4×10^-4 at 90% confidence level.

We analyze 9.7×10⁶ BB̅ pairs recorded with the CLEO detector to determine the production ratio of charged to neutral B-meson pairs produced at the ϒ(4S) resonance. We measure the rates for B⁰→J/ψK^(*)0 and B⁺→J/ψK^(*)+ decays and use the world-average B-meson lifetime ratio to extract the relative widths f_+- / f₀₀  =  Γ(ϒ(4S)→B⁺B^-) / Γ(ϒ(4S)→B⁰B̅ ⁰)  =  1.04±0.07(stat)±0.04(syst). With the assumption that f_+-+f₀₀  =  1, we obtain f₀₀  =  0.49±0.02(stat)±0.01(syst) and f_+-  =  0.51±0.02(stat)±0.01(syst). This production ratio and its uncertainty apply to all exclusive B-meson branching fractions measured at the ϒ(4S) resonance.

We report the first observation of exclusive decays of the type B→D^*NN̅ X, where N is a nucleon. Using a sample of 9.7×10⁶BB̅ pairs collected with the CLEO detector operating at the Cornell Electron Storage Ring, we measure the branching fractions B(B⁰→D^*-pp̅ π⁺)  =  (6.5_-1.2^+1.3±1.0)×10^-4 and B(B⁰→D^*-pn̅ )  =  (14.5_-3.0^+3.4±2.7)×10^-4. Antineutrons are identified by their annihilation in the CsI electromagnetic calorimeter.

The Λ_c⁺ lifetime is measured using 9.0 fb^-1 of e⁺e^- annihilation data collected on or just below the ϒ(4S) resonance with the CLEO II.V detector at CESR. Using an unbinned maximum likelihood fit, the Λ_c⁺ lifetime is measured to be 179.6±6.9(stat)±4.4(syst) fs. The precision of this colliding beam measurement is comparable to other measurements, which are based on fixed-target experiments, with different systematic uncertainties.

Using data recorded with the CLEO II and CLEO II.V detector configurations at the Cornell Electron Storage Rings, we report the first observation and mass measurement of the Σ_c^*+ charmed baryon, and an updated measurement of the mass of the Σ_c⁺ baryon. We find M(Σ_c^*+)-M(Λ_c⁺)  =  (231.0±1.1±2.0)  MeV, and M(Σ_c⁺)-M(Λ_c⁺)  =  (166.4±0.2±0.3)  MeV, where the errors are statistical and systematic, respectively.

We report on a search for a supersymmetric B̃ meson with mass between 3.5 and 4.5 GeV/c² using 4.52 fb^-1 of integrated luminosity produced at sqrt[s]=10.52 GeV, just below the e⁺e^-→BB̅ threshold, and collected with the CLEO detector. We find no evidence for a light scalar bottom quark.

Color-suppressed decays of B mesons to final states with ψ(2S) mesons have been observed with the CLEO detector. The branching fractions for the decays B⁺→ψ(2S)K⁺, B⁺→ψ(2S)K^*(892)⁺, B⁰→ψ(2S)K⁰, and B⁰→ψ(2S)K^*(892)⁰ are measured to be (7.8±0.7±0.9)×10^-4, (9.2±1.9±1.2)×10^-4, (5.0±1.1±0.6)×10^-4, and (7.6±1.1±1.0)×10^-4, respectively, where the first uncertainty is statistical and the second is systematic. The first measurement of the longitudinal polarization fraction is extracted from the angular analysis of the B→ψ(2S)K^*(892) candidates: Γ_L/Γ=0.45±0.11±0.04. Our measurements of the decays B⁰→ψ(2S)K⁰ and B⁺→ψ(2S)K^*(892)⁺ are first observations.

Using a sample of 9.7×10⁶ BB̅ meson pairs collected with the CLEO detector, we study B decays to the χ_c1 and χ_c2 charmonia states, which are reconstructed via their radiative decays to J/ψ. We first measure the branching fraction for inclusive χ_c1 production in B decays to be B(B→χ_c1X)=(4.14±0.31±0.40)×10^-3, where the first uncertainty is statistical and the second one is systematic. We derive the branching fractions for direct χ_c1 and χ_c2 production in B decays by subtracting the known contribution of the decay chain B→ψ(2S)X with ψ(2S)→χ_c1,2γ. We obtain B[B→χ_c1(direct)X]=(3.83±0.31±0.40)×10^-3. No statistically significant signal for χ_c2 production is observed in either case. Using the Feldman-Cousins approach, we determine the 95% confidence intervals to be [0.2,2.0]×10^-3 for B(B→χ_c2X), [0.0,1.7]×10^-3 for B[B→χ_c2(direct)X], and [0.00,0.44] for the ratio Γ[B→χ_c2(direct)X]/Γ[B→χ_c1(direct)X]. We also measure the branching ratio Γ[B→χ_c2(direct)X_s]/Γ[B→χ_c1(direct)X_s] for different X_s configurations by reconstructing B decays into exclusive final states with J/ψ, γ, a kaon, and up to four pions. For all the X_s configurations, we observe a strong χ_c1 signal yet no statistically significant χ_c2 signal. We discuss how our results compare with theoretical predictions in different models of charmonium production.

In a sample of 9.66×10⁶BB̅ pairs collected with the CLEO detector we make the first observation of B decays to an η_c and a kaon. We measure branching fractions B(B⁺→η_cK⁺)  =  (0.69_-0.21^+0.26±0.08±0.20)×10^-3 and B(B°→η_cK°)  =  (1.09_-0.42^+0.55±0.12±0.31)×10^-3, where the first error is statistical, the second is systematic, and the third is from the η_c branching fraction uncertainty. From these we extract the η_c decay constant in the factorization approximation, f_ηc  =  335±75 MeV. We also search for B decays to a χ_c0 and a kaon. No evidence for a signal is found and we set 90% C.L. upper limits: B(B⁺→χ_c0K⁺)<4.8×10^-4 and B(B°→χ_c0K°)<5.0×10^-4.

This article describes improved measurements by CLEO of the B⁰→D_s⁺D^*- and B⁰→D_s^*+D^*- branching fractions, and first evidence for the decay B⁺→D_s^(*)+D^**0, where D^**0 represents the sum of the D₁(2420)⁰, D₂^*(2460)⁰, and D₁(j=1/2)⁰ L=1 charm meson states. Also reported is the first measurement of the D_s^*+ polarization in the decay B⁰→D_s^*+D^*-. A partial reconstruction technique, employing only the fully reconstructed D_s⁺ and slow pion π_s^- from the D^*-→D⁰π_s^- decay, enhances sensitivity. The observed branching fractions are B(B⁰→D_s⁺D^*-)=(1.10±0.18±0.10±0.28)%, B(B⁰→D_s^*+D^*-)=(1.82±0.37±0.24±0.46)%, and B(B⁺→D_s^(*)+D^**0)=(2.73±0.78±0.48±0.68)%, where the first error is statistical, the second systematic, and the third is the uncertainty in the D_s⁺→φπ⁺ branching fraction. The measured D_s^*+ longitudinal polarization, Γ_L/Γ=(50.6±13.9±3.6)%, is consistent with the factorization prediction of 54%.