arXiv subjects
Publications and source records attributed to CLEO Collaboration.
We search and find no evidence for CP violation in tau decays into the K pi nu final state. We provide confidence limits on the imaginary part of the coupling constant Lambda, describing a relative contribution of the CP violating processes with respect to the Standard Model, to be -0.155 < Im(Lambda) < 0.047 at 90% C.L.
The Xi^+_c lifetime is measured using 9.0 fb^-1 of e+e- annihilation data collected on and just below the Upsilon(4S) resonance with the CLEO II.V detector at CESR. This is the first measurement of the Xi^+_c lifetime from a collider experiment. Using an unbinned maximum likelihood fit, the Xi^+_c lifetime is measured to be 503 +/- 47 (stat.) +/- 18 (syst.) fs. The precision of this measurement is comparable to previous measurements carried out by fixed target experiments with different sources of systematic uncertainties.
We describe several measurements using the decays D0->K+K- and pi+pi-. We find the ratio of partial widths, Gamma(D0->K+K-)/Gamma(D0->pi+pi-), to be 2.96+/-0.16+/-0.15, where the first error is statistical and the second is systematic. We observe no evidence for direct CP violation, obtaining A_CP(KK) = (0.0+/-2.2+/-0.8)% and A_CP(pipi = (1.9+/-3.2+/-0.8)%. In the limit of no CP violation we measure the mixing parameter y_CP = -0.012+/-0.025+/-0.014 by measuring the lifetime difference between D0->K+ K- or pi+pi- and the CP neutral state, D0->K-pi+. We see no evidence for mixing.
Using data recorded by the CLEO II and CLEO II.V detector configurations at CESR, we report new measurements of the masses of the Sigma_c^{++} and Sigma_c^0 charmed baryons, and the first measurements of their intrinsic widths. We find M(Sigma_c^{++}) - M(Lambda_c^+) = 167.4 +- 0.1 +- 0.2 MeV, Gamma(Sigma_c^{++}) = 2.3 +- 0.2 +- 0.3 MeV, and M(Sigma_c^0) - M(Lambda_c^+) = 167.2 +- 0.1 +- 0.2 MeV, Gamma(Sigma_c^0) = 2.5 +- 0.2 +- 0.3 MeV, where the uncertainties are statistical and systematic, respectively.
We have measured the branching fraction and photon energy spectrum for the radiative penguin process b -> s gamma. We find BR(b -> s gamma) = (3.21 +- 0.43 +- 0.27 +0.18 -0.10) 10^(-4), where the errors are statistical, systematic, and from theory corrections. We obtain first and second moments of the photon energy spectrum above 2.0 GeV, < E_γ> = 2.346 +- 0.032 +- 0.011 GeV, and - ^2 = 0.0226 +- 0.0066 +- 0.0020 GeV^2, where the errors are statistical and systematic. From the first moment we obtain (in MS[Bar], to order 1/M^3 and beta_0 alpha_s^2) the HQET parameter Lambda[Bar] = 0.35 +- 0.08 +- 0.10 GeV.
We have measured the first and second moments of the hadronic mass-squared distribution in B -> X_c l nu, for P(lepton) > 1.5 GeV/c. We find = 0.251 +- 0.066 GeV^2, < (M_X^2 - )^2 > = 0.576 +- 0.170 GeV^4, where M_D[Bar] is the spin-averaged D meson mass. From that first moment and the first moment of the photon energy spectrum in b -> s gamma, we find the HQET parameter lambda_1 (MS[Bar], to order 1/M^3 and beta_0 alpha_s^2) to be -0.24 +- 0.11 GeV^2. Using these first moments and the B semileptonic width, and assuming parton-hadron duality, we obtain |V_cb| = 0.0404 +- 0.0013.
We report on the observation of B0bar -> D*0 pi+ pi+ pi- pi- decays. The branching ratio is (0.30 +/- 0.07 +/- 0.06)%. Interest in this particular mode was sparked by Ligeti, Luke and Wise who propose it as a way to check the validity of factorization tests in B0bar -> D*+ pi+ pi- pi- pi0 decays.
We have measured the charge asymmetry in like-sign dilepton yields from B^0 B^0-bar meson decays using the CLEO detector at the Cornell Electron Storage Ring. We find a_ll = [N(l+l+) - N(l-l-)]/[N(l+l+) + N[l-l-)] = +0.013 +/- 0.050 +/- 0.005 . We combine this result with a previous, independent measurement and obtain Re(epsilon_B)/(1+|epsilon_B|^2) = +0.0035 +/- 0.0103 +/- 0.0015 (uncertainties are statistical and systematic, respectively) for the CP impurity parameter, epsilon_B.
We have measured the CP asymmetry A_CP = [BF(b -> s gamma) - BF(bbar -> sbar gamma)]/ [BF(b -> s gamma) + BF(bbar -> sbar gamma)] 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.
The Xi_c+ lifetime is measured using 9.0 fb^{-1} of e+ e- annihilation data collected on and just below the Upsilon(4S) resonance with the CLEO II.V detector at CESR. The Xi_c+ lifetime is measured using an unbinned maximum likelihood fit. The preliminary result for the Xi_c+ lifetime is (503 +- 47 (stat.) +- 18 (syst.)) fs.
We report on the observation of B-> D(*) pi+ pi- pi- pi^o decays. The branching ratios for D*+ and D*o are (1.72+/-0.14+/-0.24)% and (1.80+/-0.24+/-0.27)%, respectively. Each final state has a D* omega pi- component, with branching ratios (0.29+/-0.03+/-0.04)% and (0.45+/-0.10+/-0.07)% for the D*+ and D*o modes, respectively. We also observe B -> D omega pi- decays. The branching ratios for D+ and Do are (0.28+/-0.05+/-0.04)% and (0.41+/-0.07+/-0.06)%, respectively. A spin parity analysis of the D omega pi- final state prefers a wide 1^- resonance. A fit to the omega pi- mass spectrum finds a central mass of (1349+/-25^{+10}_{-5}) MeV and width of (547+/-86^{+46}_{-45}) MeV. We identify this object as the rho(1450) or the ρ'.
We have searched a sample of 9.6 million BBbar events for the flavor-changing neutral current decays B -> K l^+ l^- and B -> K^*(892) l^+ l^-. We subject the latter decay to the requirement that the dilepton mass exceed 0.5 GeV. There is no indication of a signal. We obtain the 90% confidence level upper limits on the branching fractions Br(B -> K l^+ l^-) < 1.7 \times 10^{-6} and Br(B -> K^*(892) l^+ l^-) < 3.3 \times 10^{-6}. We also obtain an upper limit on the weighted average 0.65 Br(B -> K l^+ l^-) + 0.35 Br(B -> K^*(892) l^+ l^-) < 1.5 \times 10^{-6}. The weighted-average limit is only 50% above the Standard Model prediction.
We have searched for the two-body decay of the B meson to a light pseudoscalar meson $h = π^+, K^+, K^0_S$ and a massless neutral weakly-interacting particle $X^0$ such as the familon, the Nambu-Goldstone boson associated with a spontaneously broken global family symmetry. We find no significant signal by analyzing a data sample containing 9.7 million $B\bar{B}$ mesons collected with the CLEO detector at the Cornell Electron Storage Ring, and set a 90% C.L. upper limit of $4.9 \times 10^{-5}$ and $5.3 \times 10^{-5}$ on the branching fraction for the decays $B^+ \to h^+ X^0$ and $B^0 \to K^0_S X^0$, respectively. These upper limits correspond to a lower bound of about $10^{8}$ GeV on the family symmetry breaking scale involving the third generation of quarks.
We have made the first measurement of the D*+ width using 9/fb of e+e- data collected near the Y4S 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 present an observation and rate measurement of the decay D0 -> K+pi-pi0 produced in 9/fb of e+e- collisions near the Upsilon(4S) resonance. The signal is inconsistent with an upward fluctuation of the background by 4.9 standard deviations. We measured the rate of D0 -> K+pi-pi0 normalized to the rate of D0bar -> K+pi-pi0 to be 0.0043 +0.0011 -0.0010 (stat) +/- 0.0007 (syst). This decay can be produced by doubly-Cabibbo-suppressed decays or by the D0 evolving into a D0bar through mixing, followed by a Cabibbo-favored decay to K+pi-pi0. We also found the CP asymmetry A=(8 +25 -22)% to be consistent with zero.
Using 12.7 $fb^{-1}$ of data collected with the CLEO detector at CESR, we observed two-photon production of the $c \bar c$ states $χ_{c0}$ and $χ_{c2}$ in their decay to $π^+ π^- π^+ π^-$. We measured $Γ_{γγ}(χ_{c}) \times {\mathcal B}(χ_{c} \to π^+π^-π^+π^-)$ to be 75 +- 13 (stat) +- 8 (syst) eV for the $χ_{c0}$ and 6.4 +- 1.8 (stat) +- 0.8 (syst) eV for the $χ_{c2}$, implying $Γ_{γγ}(χ_{c0})$ = 3.76 +- 0.65 (stat) +- 0.41 (syst) +- 1.69 (br) keV and $Γ_{γγ}(χ_{c2})$ = 0.53 +- 0.15 (stat) +- 0.06 (syst) +- 0.22 (br) keV. Also, cancelation of dominant experimental and theoretical uncertainties permits a precise comparison of $Γ_{γγ}(χ_{c0})/Γ_{γγ}(χ_{c2})$, evaluated to be 7.4 +- 2.4 (stat) +- 0.5 (syst) +- 0.9 (br), with QCD-based predictions.
We search for CP non-conservation in the decays of tau leptons produced via $e^+ e^-$ annihilation at $\sqrt{s}\sim$ 10.6 GeV. The method uses correlated decays of pairs of tau leptons, each decaying to the $ππ^0 ν_τ$ final state. The search is done within the framework of a model with a scalar boson exchange. In an analysis of a data sample corresponding to 12.2 million produced tau pairs collected with the CLEO detector, we find no evidence of violation of CP symmetry. We obtain a limit on the imaginary part of the coupling constant parameterizing the relative contribution of diagrams that would lead to CP violation to be $-0.046 <\Im(Λ) < 0.022$ at 90% C.L. This result provides a restriction on CP non-conservation in the tau lepton decays. As a cross check, we study the decay angular distribution and perform a model-independent search for a CP violation effect of a scalar exchange in single $τ\to ππ^0ν_τ$ decays. The limit on the imaginary part of the $τ$ scalar coupling is $-0.033 < \Im(Λ) < 0.089$ at 90% C.L.
We present preliminary results of several analyses searching for the effects of CP violation and mixing in the decay of $D^0$ mesons. We find no evidence of CP asymmetry in five different two-body decay modes of the $D^0$ to pairs of light pseudo-scalar mesons: $A_{CP}(K^+ K^-) = (+0.05 \pm 2.18 \pm 0.84)% $, $A_{CP}(π^+ π^-) = (+2.0 \pm 3.2 \pm 0.8)% $, $A_{CP}(K^0_{\rm S} π^0) = (+0.1 \pm 1.3)%$, $A_{CP}(π^0 π^0) = (+0.1 \pm 4.8)%$, and $A_{CP}(K^0_{\rm S} K^0_{\rm S}) = (-23 \pm 19)%$. We present the first measurement of the rate of wrong-sign $D^0 \to K^+ π^- π^0$ decay: $R = 0.0043^{+0.0011}_{-0.0010} \pm 0.0007$. We also describe a measurement of the mixing parameter $y_{CP}= {ΔΓ\over 2 Γ}$ by searching for a lifetime difference between the CP neutral $K^{-}π^{+}$ final state and the CP even $K^+K^-$ and $π^+π^-$ final states. Under the assumption that CP is conserved we find $y_{CP} = -0.011 \pm 0.025 \pm 0.014$. Finally, we present our measurement of the \dstarp width: $96 \pm 4 \pm 22$~k$e$V.