Karl Matthew Ecklund

The CLEO III drift chamber

Abstract The CLEO group at the Cornell Electron Storage Ring has constructed and commissioned a new central drift chamber. With 9796 cells arranged in 47 layers ranging in radius from 13.2 to 79 cm , the new drift chamber has a smaller outer radius and fewer wires than the drift chamber it replaces, but allows the CLEO tracking system to have improved momentum resolution. Reduced scattering material in the chamber gas and in the inner skin separating the drift chamber from the silicon vertex detector provides a reduction of the multiple scattering component of the momentum resolution and an extension of the usable measurement length into the silicon. Momentum resolution is further improved through quality control in wire positioning and symmetry of the electric fields in the drift cells which have provided a reduction in the spatial resolution to 88 μm (averaged over the full drift range).

Branching fractions of τ Leptons to three charged Hadrons

From electron-positron collision data collected with the CLEO detector operating at Cornell Electron Storage Ring near sqrt[s]=10.6 GeV, improved measurements of the branching fractions for tau decays into three explicitly identified hadrons and a neutrino are presented as B(tau(-)-->pi(-)pi(+)pi(-)nu(tau))=(9.13+/-0.05+/-0.46)%, B(tau(-)-->K-pi(+)pi(-)nu(tau))=(3.84+/-0.14+/-0.38) x 10(-3), B(tau(-)-->K-K+pi(-)nu(tau))=(1.55+/-0.06+/-0.09) x 10(-3), and B(tau(-)-->K-K+K-nu(tau))<3.7 x 10(-5) at 90% C.L., where the uncertainties are statistical and systematic, respectively.

Measurement of exclusive B decays to final states containing a charmed baryon

Using data collected by the CLEO detector in the Upsilon(4S) region, we report new measurements of the exclusive decays of B mesons into final states of the type Lambda_c^+ p-bar n(pi), where n=0,1,2,3. We find signals in modes with one, two and three pions and an upper limit for the two body decay Lambda_c^+ pbar. We also make the first measurements of exclusive decays of B mesons to Sigma_c p-bar n(pi), where n=0,1,2. We find signals in modes with one and two pions and an upper limit for the two body decay Sigma_c p-bar. Measurements of these modes shed light on the mechanisms involved in B decays to baryons.

Search for baryons in the radiative penguin decay b→sγ

We have searched for the baryon-containing radiative penguin decays B^- -> \Lambda p-bar \gamma and B^- -> \Sigma^0 p-bar \gamma, using a sample of 9.7 million BBbar events collected at the \Upsilon(4S) with the CLEO detector. We find no evidence for either, and set 90% confidence level upper limits for photons with B rest frame energy greater than 2.0 GeV of [Br(B^- -> \Lambda p-bar \gamma) + 0.3 Br(B^- -> \Sigma^0 p-bar \gamma)] \Sigma^0 p-bar \gamma) + 0.4 Br(B^- -> \Lambda p-bar \gamma)] < 6.4 x 10^-6. From the latter, we estimate (for photons with B rest frame energy greater than 2.0 GeV) Br(B -> X_s \gamma, X_s containing baryons) s \gamma that are less than half the combined statistical and systematic errors quoted on these quantities.

Semileptonic B Decays from CLEO

I report recent results in semileptonic decays of B mesons from the CLEO collaboration. Results for exclusive reconstruction of B→Dlν and B→ρlν are given including the q2 dependence of the form factors. Two preliminary analyses using inclusive techniques measure the lepton momentum spectrum and hadronic recoil mass spectrum in B→Xclν decays, showing promise for future precision measurements of Vcb.

Measurement of B(D{sub s}{sup +}{yields}l{sup +}{nu}) and the decay constant f{sub D{sub S}{sup +}}

We examine e{sup +}e{sup -}{yields}D{sub s}{sup -}D{sub s}*{sup +} and D{sub s}*{sup -}D{sub s}{sup +} interactions at 4170 MeV using the CLEO-c detector in order to measure the decay constant f{sub D{sub s}{sup +}}. We use the D{sub s}{sup +}{yields}l{sup +}{nu} channel, where the l{sup +} designates either a {mu}{sup +} or a {tau}{sup +}, when the {tau}{sup +}{yields}{pi}{sup +}{nu}. Analyzing both modes independently, we determine B(D{sub s}{sup +}{yields}{mu}{sup +}{nu})=(0.594{+-}0.066{+-}0.031)%, and B(D{sub s}{sup +}{yields}{tau}{sup +}{nu})=(8.0{+-}1.3{+-}0.4)%. We also analyze them simultaneously to find an effective value of B{sup eff}(D{sub s}{sup +}{yields}{mu}{sup +}{nu})=(0.638{+-}0.059{+-}0.033)% and extract f{sub D{sub s}{sup +}}=274{+-}13{+-}7 MeV. Combining with our previous determination of B(D{sup +}{yields}{mu}{sup +}{nu}), we also find the ratio f{sub D{sub s}{sup +}}/f{sub D{sup +}}=1.23{+-}0.11{+-}0.04. We compare to current theoretical estimates. Finally, we find B(D{sub s}{sup +}{yields}e{sup +}{nu})<1.3x10{sup -4} at 90% confidence level.

CLEO results on |Vcb| and |Vub|

I report results from the CLEO collaboration on semileptonic B decays, highlighting measurements of the Cabibbo‐Kobayashi‐Maskawa matrix elements |Vcb| and |Vub|. I describe the techniques used to obtain the recent improvements in precision for these measurements, including the use of the b → sγ photon spectrum to reduce hadronic uncertainties in semileptonic B decays.

Recent CLEO Results

I report B physics results from the CLEO collaboration, highlighting measurements of the Cabibbo‐Kobayashi‐Maskawa matrix elements |Vcb| and |Vub|. I report a recent measurement of |Vub| through study of the q2 dependence of B → πlv and B → ρlv. I also describe new measurements of the inclusive semileptonic branching fraction B(B → Xev) and of moments of the hadronic invariant mass spectrum in B → Xlv, with impact on |Vcb|.

Measuring B(D{sup +}{yields}{mu}{sup +}{nu}) and the pseudoscalar decay constant f{sub D{sup +}}

In 60 inverse-pb of data taken on the psi(3770) resonance with the CLEO-c detector, we find 8 D+ -> mu+ nu decay candidates that are mostly signal, containing only 1 estimated background. Using this statistically compelling sample, we measure a value of B(D+ -> mu+ nu) = (3.5 +/- 1.4 +/- 0.6) x10^(-4), and determine fD+=(202 +/- 41 +/-17) MeV.

| V cb |, | V ub |, and HQET at CLEO

I report results from the CLEO collaboration on semileptonic B decays, highlighting measurements of the Cabibbo-Kobayashi-Maskawa matrix elements |Vcb| and |Vub|. I describe the techniques used to obtain the recent improvements in precision for these measurements, including the use of the b→ sγ photon spectrum to reduce hadronic uncertainties in semileptonic B decays. I also report new measurements of |Vcb| using the inclusive semileptonic branching fraction