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CLEO Collaboration

Publications and source records attributed to CLEO Collaboration.

At least 253 records · Page 14Linked to original sources
arXiv1997

New Limits for Neutrinoless Tau Decays

Neutrinoless 3-prong tau lepton decays into a charged lepton and either two charged particles or one neutral meson have been searched for using 4.79 fb^{-1} of data collected with the CLEO II detector at CESR. This analysis represents an update of a previous study and the addition of six decay channels. In all channels the numbers of events found are compatible with background estimates and branching fraction upper limits are set for 28 different decay modes. These limits are either more stringent than those set previously or represent the first attempt to find these decays.

hep-ex↗
arXiv1997

Study of Semileptonic Decays of B Mesons to Charmed Baryons

Using data collected by the CLEO II detector at the center-of-mass energy on or near the Upsilon(4S) resonance, we have determined the 90% confidence level upper limit B(Bbar --> Lambda_c^+ e- X)/B(Bbar --> Lambda_c^+ X, Lambdabar_c^- X) < 0.05 for electrons with momentum above 0.6 GeV/c. We have also derived the ratio B(B^- --> Lambda_c^+ pbar e- nubar_e)/B(Bbar --> Lambda_c^+ pbar X) < 0.04 at the 90% confidence level and measured the ratio B(Bbar --> Lambda_c^+ pbar X)/B(Bbar --> Lambda_c^+ X, Lambdabar_c^- X) = 0.57 +- 0.05 +- 0.05.

hep-ex↗
arXiv1997

Observation of the Radiative Decay $D^{*+}\to D^{+}γ$

We have observed a signal for the decay D*+ -> D+ gamma at a significance of 4 standard deviations. From the measured branching ratio B(D*+ -> D+ gamma)/B(D*+ -> D+ pi0)=0.055 +- 0.014 +- 0.010 we find B(D*+ -> D+ gamma)= 0.017 +- 0.004 +- 0.003, where the first uncertainty is statistical and the second is systematic. We also report the highest precision measurements of the remaining D*+ branching fractions.

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arXiv1997

Observation of Exclusive Two-Body B Decays to Kaons and Pions

We have studied two-body charmless hadronic decays of B mesons into the final states $ππ$, $K π$, and $KK$. Using 3.3 million $B\bar{B}$ pairs collected with the CLEO-II detector, we have made the first observation of the decays $B^0\to K^+π^-$, $B^+\to K^0π^+$, and the sum of $B^+ \to π^+π^0$ and $B^+ \to K^+π^0$ decays (an average over charge-conjugate states is always implied). We place upper limits on branching fractions for the remaining decay modes.

hep-ex↗
arXiv1997

Flavor-Specific Inclusive B Decays to Charm

We have measured the branching fractions for B -> D_bar X, B -> D X, and B -> D_bar X \ell^+ ν, where ``B'' is an average over B^0 and B^+, ``D'' is a sum over D^0 and D^+, and``D_bar'' is a sum over D^0_bar and D^-. From these results and some previously measured branching fractions, we obtain Br(b -> c c_bar s) = (21.9 $\pm$ 3.7)%, Br(b -> s g) < 6.8% @ 90% c.l, and Br(D^0 -> K^- π^+) = (3.69 $\pm$ 0.20)%. Implications for the ``B semileptonic decay problem'' (measured branching fraction being below theoretical expectations) are discussed. The increase in the value of Br(b -> c c_bar s) due to $B -> D X$ eliminates 40% of the discrepancy.

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arXiv1997

Search for Inclusive $b\to sl^{+]l^{-}$

We have searched for the effective FCNC decays b->s l+l- using an inclusive method. We set upper limits on the branching ratios B(b->s e+e-) < 5.7 10^{-5}, B(b->s mu+mu-) < 5.8 10^{-5}, and B(b->s e+-mu-+) < 2.2 10^{-5} (at 90 %\ C.L.). Combining the di-electron and di-muon decay modes we find: B(b->s l+l-) < 4.2 10^{-5} (at 90 % C.L.).

hep-ex↗
arXiv1997

Measurement of the Branching Fractions of $Λ_{c}^{+}\to p\bar{K}n(π)$

Using data recorded by the CLEO-II detector at CESR, we report new measurements of the branching fractions for the decays of the charmed baryon $Λ_c^+$ into $pK^-π^+π^0$, $p\bar{K}^0$, $p\bar{K}^0π^+π^-$, and $p\bar{K}^0π^0$, all measured relative to $pK^-π^+$. The relative branching fractions are $0.67\pm0.04\pm0.11, 0.46\pm0.02\pm0.04,0.52\pm0.04\pm0.05$, and $0.66\pm0.05\pm0.07$ respectively.

hep-ex↗
arXiv1997

Investigation of Semileptonic $B$ Meson Decay to P-Wave Charm Mesons

We have studied semileptonic $B$ meson decays with a P-wave charm meson in the final state using 3.29 x 10^6 B\bar{B} events collected by the CLEO~II detector at the Cornell Electron-positron Storage Ring. We find a value for the exclusive semileptonic product branching fraction: Br(B^- -> D_1^0 l^- \barν) x Br(D_1^0 -> D^{*+}π^-) = (0.373 \pm 0.085 \pm 0.052 \pm 0.024)% and an upper limit for Br(B^- -> D_2^{*0} l^- \barν) x Br(D_2^{*0} -> D^{*+}π^-) < 0.16%$ (90% C.L.). These results indicate that at least 20% of the total B^- semileptonic rate is unaccounted for by the observed exclusive decays, B^- -> D^0 l^- \barν, B^- -> D^{*0} l^- \barν, B^- -> D_1^0 l^- \barν, and B^- -> D_2^{*0} l^- \barν.

hep-ex↗
arXiv1997

Search for Color-Suppressed $B$ Hadronic Decay Processes with CLEO

Using 3.1 fb$^{-1}$ of data accumulated at the $Υ$(4S) by the CLEO-II detector, corresponding to 3.3 million $B\bar{B}$ pairs, we have searched for the color-suppressed $B$ hadronic decay processes: $\bar{B}^0 \to D^0 (D^{*0}) X^0$, where $X^0$ is a light neutral meson $π^0$, $ρ^0$, $η$, $η'$ or $ω$. No obvious signal is observed. We set 90 % C.L. upper limits on these modes, varying from $1.2 \times 10^{-4}$ for $\bar{B}^0 \to D^0 π^0$ to $1.9 \times 10^{-3}$ for $\bar{B}^0 \to D^{*0} η'$.

hep-ex↗
arXiv1997

Measurements of the Meson-Photon Transition Form Factors of Light Pseudoscalar Mesons at Large Momentum Transfer

Using the CLEO~II detector, we have measured the differential cross sections for exclusive two-photon production of light pseudoscalar mesons $π^0$, $η$, and $η^{\prime}$. From our measurements we have obtained the form factors associated with the electromagnetic transitions $γ^*γ$ $\to$ meson. We have measured these form factors in the momentum transfer ranges from 1.5 to 9, 20, and 30 GeV$^2$ for $π^0$, $η$, and $η^{\prime}$, respectively, and have made comparisons to various theoretical predictions.

hep-ex↗
arXiv1997

Search for the Decay $τ^{-}\to 4pi^{-}3π^{+}(π^{0})ν_τ$

We have searched for the decay of the tau lepton into seven charged particles and zero or one pi0. The data used in the search were collected with the CLEO II detector at the Cornell Electron Storage Ring (CESR) and correspond to an integrated luminosity of 4.61 fb^(-1). No evidence for a signal is found. Assuming all the charged particles are pions, we set an upper limit on the branching fraction, B(tau- -> 4pi- 3pi+ (pi0) nu_tau) < 2.4 x 10^(-6) at the 90% confidence level. This limit represents a significant improvement over the previous limit.

hep-ex↗
arXiv1997

Study of the Decay tau^- \to 2pi^- pi^+ 3pi^0 nu_{tau}$

The decay tau- -> 2pi- pi+ 3pi0 nu_tau has been studied with the CLEO II detector at the Cornell Electron Storage Ring (CESR). The branching fraction is measured to be (2.85 +/- 0.56 +/- 0.51) x 10^(-4). The result is in good agreement with the isospin expectation but somewhat below the Conserved-Vector-Current (CVC) prediction. We have searched for resonance substructure in the decay. Within the statistical precision, the decay is saturated by the channels tau- -> pi- 2pi0 omega nu_tau, 2pi- pi+ eta nu_tau, and pi- 2pi0 eta nu_tau. This is the first observation of this omega decay mode and the branching fraction is measured to be (1.89 +0.74/-0.67 +/- 0.40) x 10^(-4).

hep-ex↗
arXiv1997

First Observation of $τ\to 3πην_τ$ and $τ\to f_{1}πν_τ$ Decays

We have observed new channels for $τ$ decays with an $η$ in the final state. We study 3-prong tau decays, using the $η\toγγ$ and $η\to 3\piz$ decay modes and 1-prong decays with two $\piz$'s using the $η\toγγ$ channel. The measured branching fractions are $\B(τ^{-}\to π^{-}π^{-}π^{+}ην_τ) =(3.4^{+0.6}_{-0.5}\pm0.6)\times10^{-4}$ and $\B(τ^{-}\to π^{-}2\pizην_τ =(1.4\pm0.6\pm0.3)\times10^{-4}$. We observe clear evidence for $f_1\toηππ$ substructure and measure $\B(τ^{-}\to f_1π^{-}ν_τ)=(5.8^{+1.4}_{-1.3}\pm1.8)\times10^{-4}$. We have also searched for $η'(958)$ production and obtain 90% CL upper limits $\B(τ^{-}\to π^{-}η'ν_τ)<7.4\times10^{-5}$ and $\B(τ^{-}\to π^{-}\pizη'ν_τ)<8.0\times10^{-5}$.

hep-ex↗
arXiv1997

A New Upper Limit on the Decay $η\to e^{+}e^{-}$

We have searched for the rare decay of the eta meson $η\to e^{+}e^{-}$ using the CLEO II detector. The $η$'s were produced in $e^{+}e^{-}$ collisions with 10 GeV center-of-mass energy at the Cornell Electron Storage Ring (CESR). We find with 90% confidence the upper limit on the branching fraction $B(η\to e^{+}e^{-}) < 7.7\times 10^{-5}$. The application of conventional elementary particle theory to this decay predicts a branching fraction of about $10^{-9}$.

hep-ex↗
arXiv1997

Measurement of the $\bar{B}\to D\ell\barν$ Partila Width and Form Factor Parameters

We have studied the decay $\bar{B} \to D\ell\barν$, where $\ell=e or μ$. From a fit to the differential decay rate $dΓ/dw$ we measure the rate normalization ${\cal F}_D(1)|V_{cb}|$ and form factor slope $\hatρ^2_D$, and, using measured values of $τ_B$, find $Γ(\bar{B} \to D\ell\barν) = (12.0 \pm 0.9 \pm 2.1) ns^{-1}$. The resulting branching fractions are ${\cal B}(\bar{B}^0 \to D^+\ell^-\barν)=(1.87 \pm 0.15 \pm 0.32)%$ and ${\cal B}(B^- \to D^0\ell^-\barν)=(1.94 \pm 0.15 \pm 0.34)%$. The form factor parameters are in agreement with those measured in $\bar{B} \to D^*\ell\barν$ decays, as predicted by heavy quark effective theory.

hep-ex↗
arXiv1997

Determination of the Michel Parameters and the tau Neutrino Helicity in tau Decay

Using the CLEO II detector at the $e^+e^-$ storage ring CESR, we have determined the Michel parameters $ρ$, $ξ$, and $δ$ in $τ^\mp \to l^\mpν\barν$ decay as well as the tau neutrino helicity parameter $h_{ν_τ}$ in $τ^\mp \to π^\mpπ^0ν$ decay. From a data sample of $3.02\times 10^6$ tau pairs produced at $\sqrt{s}=10.6 GeV$, using events of the topology $e^+e^- \to τ^+τ^- \to (l^\pmν\barν) (π^\mpπ^0ν)$ and $e^+e^- \to τ^+τ^- \to (π^\pmπ^0\barν) (π^\mpπ^0ν)$, and the determined sign of $h_{ν_τ}$, the combined result of the three samples is: $ρ= 0.747\pm 0.010\pm 0.006$, $ξ= 1.007\pm 0.040\pm 0.015$, $ξδ= 0.745\pm 0.026\pm 0.009$, and $h_{ν_τ} = -0.995\pm 0.010\pm 0.003$. The results are in agreement with the Standard Model V-A interaction.

hep-ex↗
arXiv1997

Observation of the Decay $D_{s}^{+}\to ωπ^{+}$

Using e+e- annihilation data collected by the CLEO~II detector at CESR, we have observed the decay Ds+ to omega pi+. This final state may be produced through the annihilation decay of the Ds+, or through final state interactions. We find a branching ratio of [Gamma(Ds+ to omega pi+)/Gamma(Ds+ to eta pi+)]=0.16+-0.04+-0.03, where the first error is statistical and the second is systematic.

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