53 research outputs found
Vector Meson Masses in Chiral Perturbation Theory
We discuss the vector meson masses within the context of Chiral Perturbation
Theory performing an expansion in terms of the momenta, quark masses and 1/Nc.
We extend the previous analysis to include isospin breaking effects and also
include up to order . We discuss vector meson chiral perturbation theory
in some detail and present a derivation from a relativistic lagrangian. The
unknown coefficients are estimated in various ways. We also discuss the
relevance of electromagnetic corrections and the implications of the present
calculation for the determination of quark masses.Comment: 17 pages, LaTeX, 2 figures. Revised version to appear in Nuclear
Physics B. One reference added, some misprints, mainly in the appendix,
correcte
Matching the Heavy Vector Meson Theory
We show how to obtain a ``heavy'' meson effective lagrangian for the case
where the number of heavy particles is not conserved. We apply the method in a
simple example at tree level and perform then the reduction for the case of
vector mesons in Chiral Perturbation Theory in a manifestly chiral invariant
fashion. Some examples showing that ``heavy'' meson effective theory also works
at the one-loop level are included.Comment: 11 pages, 2 figures, revte
Charm Quark Mass Dependence of QCD Corrections to Nonleptonic Inclusive B Decays
We calculate the radiative corrections to the nonleptonic inclusive B decay
mode taking into account the charm quark mass.
Compared to the massless case, corrections resulting from a nonvanishing c
quark mass increase the nonleptonic rate by (4--8)\%, depending on the
renormalization point. As a by--product of our calculation, we obtain an
analytic expression for the radiative correction to the semileptonic decay
taking into account the lepton mass, and
estimate the c quark mass effects on the nonleptonic decay mode .Comment: 38 pages, TUM-T31-67/94/R (to be published in Nuclear Physics) (one
reference added and used for an improved phenomenological analysis
Galilean Lee Model of the Delta Function Potential
The scattering cross section associated with a two dimensional delta function
has recently been the object of considerable study. It is shown here that this
problem can be put into a field theoretical framework by the construction of an
appropriate Galilean covariant theory. The Lee model with a standard Yukawa
interaction is shown to provide such a realization. The usual results for delta
function scattering are then obtained in the case that a stable particle exists
in the scattering channel provided that a certain limit is taken in the
relevant parameter space. In the more general case in which no such limit is
taken finite corrections to the cross section are obtained which (unlike the
pure delta function case) depend on the coupling constant of the model.Comment: 7 pages, latex, no figure
Two-dimensional electron gas in a uniform magnetic field in the presence of a delta-impurity
The density of states and the Hall conductivity of a two-dimensional electron
gas in a uniform magnetic field and in the presence of a delta impurity are
exactly calculated using elementary field theoretic techniques. Although these
results are not new, our treatment is explicitly gauge-invariant, and can be
easily adapted to other problems involving a delta potential.Comment: 12+1 pages, 1 ps figure, REVTEX. Corrigendum adde
The regulated four parameter one dimensional point interaction
The general four parameter point interaction in one dimensional quantum
mechanics is regulated. It allows the exact solution, but not the perturbative
one. We conjecture that this is due to the interaction not being asymptotically
free. We then propose a different breakup of unperturbed theory and
interaction, which now is asymptotically free but leads to the same physics.
The corresponding regulated potential can be solved both exactly and
perturbatively, in agreement with the conjecture.Comment: 17 pages, no figures, Tex fil
The Isgur-Wise Function to from Sum Rules in the Heavy Quark Effective Theory
Radiative corrections to both perturbative and non-perturbative contributions
are added to existing calculations of the Isgur-Wise function . To
this end, we develop a method for calculating two-loop integrals in the heavy
quark effective theory involving two different scales. The inclusion of
terms causes to decrease as compared to the lowest
order result and shows the importance of quantum effects. The slope parameter
violates the bound given by de Rafael and Taron.Comment: 11 pages, 2 figures (not included), (LaTeX), HD-THEP-92-4
Renormalizabilty of TH Heavy Quark Effective Theory
We show that the Heavy Quark Effective Theory is renormalizable
perturbatively. We also show that there exist renormalization schemes in which
the infinite quark mass limit of any QCD Green function is exactly given by the
corresponding Green function of the Heavy Quark Effective Theory. All this is
accomplished while preserving BRS invariance.Comment: LATEX/10 pages/ UAB-FT-314/ (References have been added.) figures
(PS) available on request. Unfortunately some mails asking for copies by
conventional mail were lost. Please resend request
Theoretical Update of the Semileptonic Branching Ratio of B Mesons
We reconsider the prediction of the semileptonic branching ratio of B mesons,
using a recent calculation of the radiative corrections with account for finite
quark masses in nonleptonic decays and taking into account 1/m_b^2 corrections.
For the semileptonic branching ratio we obtain B_SL =(11.8\pm 1.6)% using pole
quark masses and B_SL = (11.0\pm 1.9)% using running MS-bar quark masses. The
uncertainty is dominated by unknown higher order perturbative corrections. We
conclude that the present accuracy of the theoretical analysis does not allow
to state a significant disagreement with the experimental results. However, our
re-analysis of the decay b->ccs yields an increase of (35\pm 11)% due to
next-to-leading order corrections including mass dependent terms, which further
emphasizes the problem of the average charm quark content of the final states
in B decays. Abstract of the erratum: Some of the numerical results presented
in our paper PLB 342 (1995) 362 are affected by an error in the computer
program and need to be revised. The numerical changes are, however, marginal.
We take the opportunity to incorporate the complete results for the quark mass
dependence of the radiative corrections to the subprocess b->ccs and enlarge
the discussion of the average charm quark content in the final state, giving
the results in two different renormalization schemes and adding a figure with
charm quark content plotted vs. the semileptonic branching ratio.Comment: 14 pages latex plus one PS figure, uses epsf.sty and a4wide.sty;
Erratum to published version appende
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