21,286 research outputs found
The renormalized B-meson light-cone distribution amplitude
I discuss the renormalization-group equation governing the leading order
light-cone distribution amplitude of the B-meson phi^B_+(omega,mu) and its
exact analytic solution. The solution displays two features concerning the
asymptotic behaviour of phi^B_+(omega,mu) for small and large values of omega.
I comment on further applications and argue that the loss of normalizability is
not a problem in practice.Comment: 3 pages, 3 figures, invited talk at the international conference EPS
'03, Aachen, German
Development of the Saturn Space Vehicle
Space science - launch vehicle - saturn rocke
Unstable manifolds and Schroedinger dynamics of Ginzburg-Landau vortices
The time evolution of several interacting Ginzburg-Landau vortices according
to an equation of Schroedinger type is approximated by motion on a
finite-dimensional manifold. That manifold is defined as an unstable manifold
of an auxiliary dynamical system, namely the gradient flow of the
Ginzburg-Landau energy functional. For two vortices the relevant unstable
manifold is constructed numerically and the induced dynamics is computed. The
resulting model provides a complete picture of the vortex motion for arbitrary
vortex separation, including well-separated and nearly coincident vortices.Comment: 23 pages amslatex, 5 eps figures, minor typos correcte
Theory of Charmless Inclusive B Decays and the Extraction of V_{ub}
We present ``state-of-the-art'' theoretical expressions for the triple
differential B->X_u l^- nu decay rate and for the B->X_s gamma photon spectrum,
which incorporate all known contributions and smoothly interpolate between the
``shape-function region'' of large hadronic energy and small invariant mass,
and the ``OPE region'' in which all hadronic kinematical variables scale with
M_B. The differential rates are given in a form which has no explicit reference
to the mass of the b quark, avoiding the associated uncertainties. Dependence
on m_b enters indirectly through the properties of the leading shape function,
which can be determined by fitting the B->X_s gamma photon spectrum. This
eliminates the dominant theoretical uncertainties from predictions for B->X_u
l^- nu decay distributions, allowing for a precise determination of |V_{ub}|.
In the shape-function region, short-distance and long-distance contributions
are factorized at next-to-leading order in renormalization-group improved
perturbation theory. Higher-order power corrections include effects from
subleading shape functions where they are known. When integrated over
sufficiently large portions in phase space, our results reduce to standard OPE
expressions up to yet unknown O(alpha_s^2) terms. Predictions are presented for
partial B->X_u l^- nu decay rates with various experimental cuts. An elaborate
error analysis is performed that contains all significant theoretical
uncertainties, including weak annihilation effects. We suggest that the latter
can be eliminated by imposing a cut on high lepton invariant mass.Comment: 45 pages, 4 figures; several minor revisions, more systematic
treatment of subleading shape-function effects, numerical results and tables
updated; version to appear in Physical Review
An investigation of the suitability of white rats for sub-orbital studies of behavior in a gravity field
Suitability of white rats for suborbital studies of behavior in gravity field
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