B and B_s decay constants from QCD Duality at three loops

Using special linear combinations of finite energy sum rules which minimize the contribution of the unknown continuum spectral function, we compute the decay constants of the pseudoscalar mesons B and B_s. In the computation, we employ the recent three loop calculation of the pseudoscalar two-point function expanded in powers of the running bottom quark mass. The sum rules show remarkable stability over a wide range of the upper limit of the finite energy integration. We obtain the following results for the pseudoscalar decay constants: f_B=178 \pm 14 MeV and f_{B_s}=200 \pm 14 MeV. The results are somewhat lower than recent predictions based on Borel transform, lattice computations or HQET. Our sum rule approach of exploiting QCD quark hadron duality differs significantly from the usual ones, and we believe that the errors due to theoretical uncertainties are smaller

Dynamical zeros in neutrino-electron elastic scattering at leading order

We show the existence of dynamical zeros in the helicity amplitudes for neutrino-electron elastic scattering at lowest order in the standard theory. In particular, the $\lambda=1/2$ non-flip electron helicity amplitude in the electron antineutrino process vanishes for an incident neutrino energy $E_{\nu}=m_{e}/(4sin^{2}\theta_{W})$ and forward electrons (maximum recoil energy). The rest of helicity amplitudes show kinematical zeros in this configuration and therefore the cross section vanishes. Prospects to search for neutrino magnetic moment are discussed.Comment: 9 pg.+ 2 figures (not included available upon request

A Novel Kind of Neutrino Oscillation Experiment

A novel method to look for neutrino oscillations is proposed based on the elastic scattering process $\bar{\nu}_{i} e^{-}\rightarrow \bar{\nu}_{i} e^{-}$, taking advantage of the dynamical zero present in the differential cross section for $\bar{\nu}_{e} e^{-}\rightarrow \bar{\nu}_{e} e^{-}$. An effective tunable experiment between the "appearance" and "disappearance" limits is made possible. Prospects to exclude the allowed region for atmospheric neutrino oscillations are given.Comment: 11 pages (+3 figures, available upon request),Standard Latex, FTUV/94-3

B and B_S decay constants from moments of Finite Energy Sum Rules in QCD

We use an appropriate combination of moments of finite energy sum rules in QCD in order to compute the B_q-meson decays constants f_B and f_{B_s}.We perform the calculation using a two-loop computation of the imaginary part of the pseudoscalar two point function in terms of the running bottom quark mass. The results are stable with the so called QCD duality threshold and they are in agreement with the estimates obtained from Borel transform QCD sum rules and lattice computations.Comment: 11 pages, 2 figure

Resonance estimates for single spin asymmetries in elastic electron-nucleon scattering

We discuss the target and beam normal spin asymmetries in elastic electron-nucleon scattering which depend on the imaginary part of two-photon exchange processes between electron and nucleon. We express this imaginary part as a phase space integral over the doubly virtual Compton scattering tensor on the nucleon. We use unitarity to model the doubly virtual Compton scattering tensor in the resonance region in terms of $\gamma^* N \to \pi N$ electroabsorption amplitudes. Taking those amplitudes from a phenomenological analysis of pion electroproduction observables, we present results for beam and target normal single spin asymmetries for elastic electron-nucleon scattering for beam energies below 1 GeV and in the 1-3 GeV region, where several experiments are performed or are in progress.Comment: 36 pages, 16 figure

Charm-quark mass from weighted finite energy QCD sum rules

The running charm-quark mass in the $\bar{MS}$ scheme is determined from weighted finite energy QCD sum rules (FESR) involving the vector current correlator. Only the short distance expansion of this correlator is used, together with integration kernels (weights) involving positive powers of $s$, the squared energy. The optimal kernels are found to be a simple {\it pinched} kernel, and polynomials of the Legendre type. The former kernel reduces potential duality violations near the real axis in the complex s-plane, and the latter allows to extend the analysis to energy regions beyond the end point of the data. These kernels, together with the high energy expansion of the correlator, weigh the experimental and theoretical information differently from e.g. inverse moments FESR. Current, state of the art results for the vector correlator up to four-loop order in perturbative QCD are used in the FESR, together with the latest experimental data. The integration in the complex s-plane is performed using three different methods, fixed order perturbation theory (FOPT), contour improved perturbation theory (CIPT), and a fixed renormalization scale $\mu$ (FMUPT). The final result is $\bar{m}_c (3\, {GeV}) = 1008\,\pm\, 26\, {MeV}$, in a wide region of stability against changes in the integration radius $s_0$ in the complex s-plane.Comment: A short discussion on convergence issues has been added at the end of the pape

Radiological assessment of peri-implant bone loss: a 12-month retrospective study

Introduction: Following dental implant loading, marginal bone loss after one year must be evaluated to check correct maintenance of the bone levels. Objectives: To assess implant treatment success and quantify marginal bone loss 6 and 12 months after loading. Material and method: Sixty-one MIS® implants with a 1.8 mm machined neck were placed in 26 patients. Implant success was based on the criteria of Buser. Radiological controls were made 6 and 12 months after loading, measuring bone loss mesial and distal. Results: Twenty-two patients with 56 implants were included: 32 in the maxilla and 24 in the mandible. Two implants failed in two patients during the osseointegration phase (both in the maxilla), yielding an implant success rate of 96.4%. After 6 months, bone loss was 0.80±1.04 mm mesial and 0.73±1.08 mm distal, while after 12 months bone loss was 0.92±1.02 mesial and 0.87±1.01 distal. Conclusions: Bone loss 6 and 12 months after machined neck implant placement was within the normal ranges described in the literature