arXiv subjects
Publications and source records attributed to CLEO Collaboration.
We have searched for the charmless hadronic decay of B0 mesons into two neutral pions. Using 9.13fb^-1 taken at the Upsilon(4S) with the CLEO detector, we obtain an improved upper limit for the branching fraction BR(B0-->pi0pi0) < 5.7*10^-6 at the 90% confidence level.
We use data collected with the CLEO II detector to perform a high-statistics measurement of the resonant substructure in $D^0 \to K^-π^+π^0$ decays. We find the Dalitz Plot is well represented by a combination of seven quasi-two-body decay channels ($\bar{K}^{*0} π^0$, $K^- ρ$, $K^{*-} π^+$, $K^*_0(1430)^-π^+$, $\bar{K}^*_0(1430)^0 π^0$, $K^- ρ^+(1700)$, and $K^*(1680)^- π^+$), plus a small non-resonant component. Using the amplitudes and phases from this analysis, we calculate an integrated CP asymmetry of $-0.031 \pm 0.086$.
We present preliminary results of several analyses searching for the effects of CP violation and mixing in the decay of D0 mesons. We find no evidence of CP asymmetry in five different two-body decay modes of the D0 to pairs of light pseudo-scalar mesons: A_CP(K+ K-) = (+0.05 +- 2.18 +- 0.84)%, A_CP(pi+ pi-) = (+2.0 +- 3.2 +- 0.8)%, A_CP(K0_S pi0) = (+0.1 +- 1.3)%, A_CP(pi0 pi0) = (+0.1 +- 4.8)% and A_CP(K0_S K0_S) = (-23 +- 19)%. We present the first measurement of the rate of wrong-sign D0 -> K+ pi- pi0 decay: R_WS = 0.0043 + 0.0011 - 0.0010 +- 0.0007. Finally, we describe a measurement of the mixing parameter y_CP= Delta Gamma / (2 Gamma) by searching for a lifetime difference between the CP neutral K+ pi- final state and the CP even K+K- and pi+pi- final states. Under the assumption that CP is conserved we find y_CP = -0.011 +- 0.025 +- 0.014.
We have made the first measurement of the D*+ width using 9/fb of e+e- data collected near the Upsilon(4S) resonance by the CLEO II.V detector. Our method uses advanced tracking techniques and a reconstruction method that takes advantage of the small vertical size of the CESR beam spot to measure the energy release distribution from the D*+ -> D0 pi+ decay. Our preliminary result is Gamma(D*+) = 96 +- 4 (Statistical) +- 22 (Systematic) keV.
We have studied two-body charmless hadronic decays of $B$ mesons into the final states phi K and phi K^*. Using 9.7 million $B\bar{B}$ pairs collected with the CLEO II detector, we observe the decays B- -> phi K- and B0 -> phi K*0 with the following branching fractions: BR(B- -> phi K-)=(5.5 +2.1-1.8 +- 0.6) x 10^{-6} and BR(B0 -> phi K*0)=(11.5 +4.5-3.7 +1.8-1.7) x 10^{-6}. We also see evidence for the decays B0 -> phi K0 and B- -> phi K*-. However, since the statistical significance is not overwhelming for these modes we determine upper limits of <12.3 x 10^{-6} and <22.5 x 10^{-6} (90% C.L.) respectively.
We have studied two-body charmless decays of the $B$ meson into the final states $ρ^0 ρ^0$, $K^{*0} ρ^0$, $K^{*0} K^{*0}$, $K^{*0} \bar{K^{*0}}$, $K^{*+} ρ^0$, $K^{*+} \bar{K^{*0}}$, and $K^{*+} K^{*-}$ using only decay modes with charged daughter particles. Using 9.7 million $B \bar{B}$ pairs collected with the CLEO detector, we place 90% confidence level upper limits on the branching fractions, $(0.46-7.0)\times 10^{-5}$, depending on final state and polarization.
We have searched for CP-violating asymmetries in neutral charm meson decays in 13.7 fb^-1 of e^+e^- collision data at sqrt{s} = 10.6 GeV with the CLEO detector. The measured asymmetries in the rate of D0 and D0bar decays to K0sPi0, Pi0Pi0 and K0sK0s final states are (+0.1 +- 1.3)%, (+0.1 +- 4.8)% and (-23 +- 19)%, respectively.
Using 13.7 $fb^{-1}$ of data recorded by the CLEO detector at CESR, we report evidence for two new charmed baryons: one decaying into $Ξ_c^{0 \prime}π^+$ with the subsequent decay $Ξ_c^{0 \prime} \to Ξ_c^0 γ$, and its isospin partner decaying into $Ξ_c^{+ \prime} π^-$ followed by $Ξ_c^{+\prime} \to Ξ_c^+γ$. We measure the following mass differences for the two states: $M(Ξ_c^0 γπ^+)-M(Ξ_c^0)$=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 $Λ_{c1}^+(2593)$.
Using the CLEO II detector at the Cornell Electron Storage Ring we have measured the $Ξ_c^{0}$ decay asymmetry parameter in the decay $Ξ_c^{0} \to Ξ^{-} π^+$. We find $α_{Ξ_c^{0}} α_Ξ = 0.26 \pm 0.18{(stat)}^{+0.05}_{-0.04}{(syst)}$, using the world average value of $α_Ξ = -0.456 \pm 0.014$ we obtain $α_{Ξ_c^{0}} = -0.56 \pm 0.39{(stat)}^{+0.10}_{-0.09}{(syst)}$. The physically allowed range of a decay asymmetry parameter is $-1<α<+1$. Our result prefers a negative value: $α_{Ξ_c^{0}}$ is $<0.1$ at the 90% CL. The central value occupies the middle of the theoretically expected range but is not yet precise enough to choose between models.
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 $(179.6 \pm 6.9(stat.) \pm 4.4(syst.))$ fs. The precision of this colliding beam measurement is comparable to other measurements, which are based on fixed target experiments with different systematic errors.
Using 13.7 fb^{-1} of data recorded by the CLEO detector at CESR, we investigate the spectrum of charmed baryons which decay into Lambda_c^+ pi^- pi^+ and are more massive than the Lambda_{c1} baryons. We find evidence for two new states: one is broad and has an invariant mass roughly 480 MeV above that of the Lambda_c^+; the other is narrow with an invariant mass of 596 +- 1 +- 2 MeV above the Lambda_c^+ mass. These results are preliminary.
We report on a search for a supersymmetric $\tilde{B}$ meson with mass between 3.5 and 4.5 GeV/$c^2$ using 4.52 ${\rm fb}^{-1}$ of integrated luminosity produced at $\sqrt{s}=10.52$ GeV, just below the $e^+e^-\to B\bar{B}$ threshold, and collected with the CLEO detector. We find no evidence for a light scalar bottom quark.
The CLEO experiment at the CESR collider has used 13.7 fb$^{-1}$ of data to search for the production of the $Ω_c^0$ (css-ground state) in $e^{+}e^{-}$ collisions at $\sqrt{s} \simeq 10.6$ {\rm GeV}. The modes used to study the $Ω_c^0$ are $Ω^- π^+$, $Ω^- π^+ π^0$, $Ξ^- K^- pi^+ π^+$, $Ξ^0 K^- pi^+$, and $Ω^- π^+ π^- π^+$. We observe a signal of 40.4$\pm$9.0(stat) events at a mass of 2694.6$\pm$2.6(stat)$\pm$1.9(syst) {\rm MeV/$c^2$}, for all modes combined.
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 $B^+ \to ψ(2S) K^+$, $B^+ \to ψ(2S) K^*(892)^+$, $B^0 \to ψ(2S) K^0$, and $B^0 \to ψ(2S) K^*(892)^0$ 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 $B \to ψ(2S) K^*(892)$ candidates: $Γ_L / Γ= 0.45 +- 0.11 +- 0.04 $. Our measurements of the decays $B^0 \to ψ(2S) K^0$ and $B^+ \to ψ(2S) K^*(892)^+$ are first observations.
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 ${\cal B}(τ^-\to 2π^-π^+3π^0ν_τ)=(2.2 \pm 0.3 \pm 0.4)\times 10^{-4}$ and ${\cal B}(τ^-\to 3π^-2π^+π^0ν_τ)=(1.7 \pm 0.2 \pm 0.2)\times 10^{-4}$. 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 $τ^-\to 2π^-π^+ων_τ$ and the branching fraction is measured to be $(1.2 \pm 0.2 \pm 0.1) \times 10^{-4}$. The measured branching fractions are in good agreement with the isospin expectations but somewhat below the Conserved-Vector-Current predictions.
Using a sample of 9.7 million B meson pairs collected with the CLEO detector, we study B decays to the chi_c1 and chi_c2 charmonia states, which are reconstructed via their radiative decays to J/psi. We first measure the branching fraction for inclusive chi_c1 production in B decays to be Br(B->chi_c1 X)=(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 chi_c1 and chi_c2 production in B decays by subtracting the known contribution of the decay chain B->psi(2S)X with psi(2S)->chi_c1,2 gamma. We obtain Br[B->chi_c1(direct) X]=(3.83+-0.31+-0.40)*10^-3. No statistically significant signal for chi_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 Br(B->chi_c2 X), [0.0,1.7]*10^-3 for Br[B->chi_c2(direct) X], and [0.00,0.44] for the ratio Br[B->chi_c2(direct) X]/Br[B->chi_c1(direct) X]. We also measure the branching ratio Br[B->chi_c2(direct) X_s]/Br[B->chi_c1(direct) X_s] for different X_s configurations by reconstructing B decays into exclusive final states with J/psi, a photon, a kaon, and up to four pions. For all the X_s configurations we observe a strong chi_c1 signal yet no statistically significant chi_c2 signal. We discuss how our results compare with theoretical predictions in different models of charmonium production.
Using data collected with the CLEO II detector we have performed a search for direct CP violation in the $Ξ$ hyperon system. CP violation gives rise to an asymmetry, A, between the parity-violating angular distributions of the decay chains $Ξ^- \To Λpi^-$, $Λ\To p π^-$ and $\barΞ^+ \To \barΛ π^+$, $\barΛ \To \bar{p} π^+$. In the Standard Model, A is expected to be in the range $10^{-4}$ to $10^{-5}$. If CP violation were found at a higher level it could indicate the presence of new physics. We find no evidence for CP violation: A = -0.057 +- 0.064 +- 0.039. We also obtain $A_Ξ = -0.070 +- 0.064 +- 0.045$ and $α_{\barΞ}= 0.49^{+0.06}_{-0.05} +- 0.10$.
We report the first observation of exclusive decays of the type B to D^* N anti-N X, where N is a nucleon. Using a sample of 9.7 times 10^{6} B-Bbar pairs collected with the CLEO detector operating at the Cornell Electron Storage Ring, we measure the branching fractions B(B^0 \to D^{*-} proton antiproton π^+) = ({6.5}^{+1.3}_{-1.2} +- 1.0) \times 10^{-4} and B(B^0 \to D^{*-} proton antineutron) = ({14.5}^{+3.4}_{-3.0} +- 2.7) times 10^{-4}. Antineutrons are identified by their annihilation in the CsI electromagnetic calorimeter.