1,495 research outputs found
The problem of roughness drag at supersonic speeds
Methods of estimating roughness drag at supersonic speed
Techniques for computing two-loop QCD corrections to b-->c transitions
We have recently presented the complete O(alpha_s^2) corrections to the
semileptonic decay width of the b quark at maximal recoil. Here we discuss
various technical aspects of that calculation and further applications of
similar methods. In particular, we describe an expansion which facilitates the
phase space integrations and the treatment of the mixed real-virtual
corrections, for which Taylor expansion does not work and the so-called eikonal
expansion must be employed. Several terms of the expansion are given for the
O(alpha_s^2) QCD corrections to the differential semileptonic decay width of
the b --quark at maximal recoil. We also demonstrate how the light quark loop
corrections to the top quark decay rate can be obtained using the same methods.
We briefly discuss the application of these techniques to the calculation of
the O(alpha_s^2) correction to zero recoil sum rules for heavy flavor
transitions.Comment: 22 pages, revte
Theoretical face pressure and drag characteristics of forward-facing steps in supersonic turbulent boundary layers
A theoretical investigation of the pressure distributions and drag characteristics was made for forward facing steps in turbulent flow at supersonic speeds. An approximate solution technique proposed by Uebelhack has been modified and extended to obtain a more consistent numerical procedure. A comparison of theoretical calculations with experimental data generally indicated good agreement over the experimentally available range of ratios of step height to boundary layer thickness from 7 to 0.05
Unparticle Searches Through Low Energy Parity Violating Asymmetry
In this paper, we study the effects of the unparticles on the
parity-violating asymmetry for the low energy electron-electron scattering,
. Using the data from the E158 experiment at SLAC we
extract the limits on the unparticle coupling , and on the the
energy scale at 95% C.L. for various values of the scaling dimension
Theoretical pressure distributions over arbitrarily shaped periodic waves in subsonic compressible flow and comparison with experiment
Theoretical solution for pressure distribution over arbitrarily shaped periodic waves using Fourier serie
Analysis of pressure distributions for a series of tip and trailing-edge controls on a 60 deg wing at Mach numbers of 1.61 and 2.01
Supersonic pressure distributions for tip and trailing edge controls on 60 deg delta win
Pressure drags due to two-dimensional fabrication-type surface roughness on an ogive cylinder at transonic speeds
Pressure drags due to two-dimensional fabrication- type surface roughness on ogive cylinder at transonic speed
Threshold expansion for heavy-light systems and flavor off-diagonal current-current correlators
An expansion scheme is developed for Feynman diagrams describing the
production of one massive and one massless particle near the threshold. As an
example application, we compute the correlators of heavy-light quark currents,
(\bar b gamma_mu u) and (\bar b gamma_5 u), through O(alpha_s^2).Comment: 4 pages, revtex
Semileptonic b --> u decays: lepton invariant mass spectrum
We compute O(alpha_s^2) QCD corrections to the lepton invariant mass spectrum
in the decay b --> u l nu_l, relevant for the determination of the CKM matrix
element |V_{ub}|. Our method can also be used to evaluate moments of the lepton
energy distribution with an O(alpha_s^2) accuracy. The abelian part of our
result gives the neutrino invariant mass spectrum in the muon decay and, upon
integration, the O(alpha^2) correction to the muon lifetime.Comment: 5 pages, revte
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