2,786 research outputs found
Flavor Physics in the Randall-Sundrum Model: I. Theoretical Setup and Electroweak Precision Tests
A complete discussion of tree-level flavor-changing effects in the
Randall-Sundrum (RS) model with brane-localized Higgs sector and bulk gauge and
matter fields is presented. The bulk equations of motion for the gauge and
fermion fields, supplemented by boundary conditions taking into account the
couplings to the Higgs sector, are solved exactly. For gauge fields the
Kaluza-Klein (KK) decomposition is performed in a covariant R_xi gauge. For
fermions the mixing between different generations is included in a completely
general way. The hierarchies observed in the fermion spectrum and the quark
mixing matrix are explained naturally in terms of anarchic five-dimensional
Yukawa matrices and wave-function overlap integrals. Detailed studies of the
flavor-changing couplings of the Higgs boson and of gauge bosons and their KK
excitations are performed, including in particular the couplings of the
standard W and Z bosons. A careful analysis of electroweak precision
observables including the S and T parameters and the Zbb couplings shows that
the simplest RS model containing only Standard Model particles and their KK
excitations is consistent with all experimental bounds for a KK scale as low as
a few TeV, if one allows for a heavy Higgs boson and/or for an ultra-violet
cutoff below the Planck scale. The study of flavor-changing effects includes
analyses of the non-unitarity of the quark mixing matrix, anomalous
right-handed couplings of the W bosons, tree-level flavor-changing neutral
current couplings of the Z and Higgs bosons, the rare decays t-->c(u)+Z and
t-->c(u)+h, and the flavor mixing among KK fermions. The results obtained in
this work form the basis for general calculations of flavor-changing processes
in the RS model and its extensions.Comment: 70 pages, 12 figures. v2: Incorrect treatment of phases in zero-mode
approximation corrected, and discussion of electroweak precision tests
modified. v3: Additional minor modifications and typos corrected; version
published in JHE
Consistency and lattice renormalization of the effective theory for heavy quarks
The effective theory describing infinite mass particles with a given
velocity, has a great interest in heavy flavor physics. It has the unpleasant
characteristic that the energy spectrum is unbounded from below; this fact is
the source of the problems in the formulation of the euclidean theory. In this
paper we present an analysis of the euclidean effective theory, that is rather
complete and has positive conclusions. A proof of the consistency of the
euclidean theory is presented and a technique for the evaluation of the
amplitudes in perturbation theory is described. We compute also the one-loop
renormalization constants of the lattice effective theory and of the
heavy-heavy current that is needed for the determination of the Isgur-Wise
function. A variety of effects related to the explicit breaking of the Lorentz
symmetry of lattice regularization is demonstrated. The most peculiar
phenomenon is that the heavy quark velocity receives a finite renormalization.
Finally, we compute the lattice-continuum renormalization constant of the
Isgur-Wise current. It is needed for the conversion of the values of the matrix
elements computed with the lattice effective theory, to the values in the full
theory.Comment: 28 pages, Latex version 2.09, SISSA 56/93/E
Renormalization of the Lattice HQET Isgur-Wise Function
We compute the perturbative renormalization factors required to match to the
continuum Isgur-Wise function, calculated using lattice Heavy Quark Effective
Theory. The velocity, mass, wavefunction and current renormalizations are
calculated for both the forward difference and backward difference actions for
a variety of velocities. Subtleties are clarified regarding tadpole
improvement, regulating divergences, and variations of techniques used in these
renormalizations.Comment: 28 pages, 0 figures, LaTeX. Final version accepted for publication in
Phys. Rev. D. (Minor changes.
Radiatively corrected shape function for inclusive heavy hadron decays
We discuss the non-perturbative and the radiative corrections to inclusive B
decays from the point of view known from QED corrections to high energy e^+ e^-
processes. Here the leading contributions can be implemented through the so
called ``radiator function'' which corresponds to the shape function known in
heavy hadron decays. In this way some new insight into the origin of the shape
function is obtained. As a byproduct, a parameterization of the radiatively
corrected shape function is suggested which can be implemented in Monte Carlo
studies of inclusive heavy hadron decays.Comment: LaTeX, uses a4, graphicx and psfrag, 10 pages. The complete paper is
also available at http://www-ttp.physik.uni-karlsruhe.de/Preprints
Resummed B -> X_u l nu Decay Distributions to Next-to-Leading Order
We perform factorization of the most general distribution in semileptonic B
-> X_u decays and we resum the threshold logarithms to next-to-leading order.
From this (triple-differential) distribution, any other distribution is
obtained by integration. As an application of our method, we derive simple
analytical expressions for a few distributions, resummed to leading
approximation. It is shown that the shape function can be directly determined
by measuring the distribution in m_X^2/E_X^2, not in m_X^2/m_B^2. We compute
the resummed hadron energy spectrum, which has a ``Sudakov shoulder'', and we
show how the distribution in the singular region is related to the shape
function. We also present an improved formula for the photon spectrum in B->X_s
gamma which includes soft-gluon resummation and non-leading operators in the
effective hamiltonian. We explicitly show that the same non-perturbative
function - namely the shape function - controls the non-perturbative effects in
all the distributions in the semi-leptonic and in the rare decay.Comment: LaTex file, 19 pages, 3 postscript figures; minor changes, some typos
correcte
Transverse Momentum Distributions in B-Decays
We consider transverse momentum distributions in B-decays. The O(alpha_S)
coefficients for soft and collinear logarithms are computed to next-to-leading
accuracy. Resummation of large logarithmic contributions is performed in impact
parameter space within the general formalism for transverese momentum
distributions. It is shown that the shape-function approach as used for the
threshold distribution case cannot be extended to the transverse momentum one.Comment: LaTex file, 8 pages, 1 postscript figur
A heavy quark effective field lagrangian keeping particle and antiparticle mixed sectors
We derive a tree-level heavy quark effective Lagrangian keeping
particle-antiparticle mixed sectors allowing for heavy quark-antiquark pair
annihilation and creation. However, when removing the unwanted degrees of
freedom from the effective Lagrangian one has to be careful in using the
classical equations of motion obeyed by the effective fields in order to get a
convergent expansion on the reciprocal of the heavy quark mass. Then the
application of the effective theory to such hard processes should be sensible
for special kinematic regimes as for example heavy quark pair production near
threshold.Comment: LaTeX, 14 pages, 1 EPS figure
Damage estimation of subterranean building constructions due to groundwater inundation – the GIS-based model approach GRUWAD
The analysis and management of flood risk commonly focuses on surface water floods, because these types are often associated with high economic losses due to damage to buildings and settlements. The rising groundwater as a secondary effect of these floods induces additional damage, particularly in the basements of buildings. Mostly, these losses remain underestimated, because they are difficult to assess, especially for the entire building stock of flood-prone urban areas. For this purpose an appropriate methodology has been developed and lead to a groundwater damage simulation model named GRUWAD. The overall methodology combines various engineering and geoinformatic methods to calculate major damage processes by high groundwater levels. It considers a classification of buildings by building types, synthetic depth-damage functions for groundwater inundation as well as the results of a groundwater-flow model. The modular structure of this procedure can be adapted in the level of detail. Hence, the model allows damage calculations from the local to the regional scale. Among others it can be used to prepare risk maps, for ex-ante analysis of future risks, and to simulate the effects of mitigation measures. Therefore, the model is a multifarious tool for determining urban resilience with respect to high groundwater levels
A new formulation of the effective theory for heavy particles
We derive the effective theories for heavy particles with a functional
integral approach by integrating away the states with high velocity and with
high virtuality. This formulation is non-perturbative and has a close
connection with the Wilson renormalization group transformation. The fixed
point hamiltonian of our transformation coincides with the static hamiltonian
and irrelevant operators can be identified with the usual corrections to
the static theory. No matching condition has to be imposed between the full and
the static theory operators with our approach. The values of the matching
constants come out as a dynamical effect of the renormalization group flow.Comment: 26 pages, plain Latex + 4 postscript figures (appended at the end),
Preprint Roma1 993-94 (some missing lines in a few formulas have been
restored; minor changes
- …