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, $e^-e^-\to e^-e^-$. Using the data from the E158 experiment at SLAC we extract the limits on the unparticle coupling $\lambda_{AV}$, and on the the energy scale $\Lambda$ at 95% C.L. for various values of the scaling dimension $d$

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