10 research outputs found
Bosonization in Particle Physics
Path integral techniques in collective fields are shown to be a useful
analytical tool to reformulate a field theory defined in terms of microscopic
quark (gluon) degrees of freedom as an effective theory of collective boson
(meson) fields. For illustrations, the path integral bosonization approach is
applied to derive a (non)linear sigma model from a Nambu-Jona-Lasinio (NJL)
quark model. The method can be extended to include higher order derivative
terms in meson fields or heavy-quark symmetries. It is also approximately
applicable to QCD.Comment: 12 pages, LaTeX, uses lamuphys.sty, 5 LaTeX figures, talk given at
the Workshop "Field Theoretical Tools in Polymer and Particle Physics",
University Wuppertal, June 17-19, 199
Theta angle versus CP violation in the leptonic sector
Assuming that the axion mechanism of solving the strong CP problem does not
exist and the vanishing of theta at tree level is achieved by some
model-building means, we study the naturalness of having large CP-violating
sources in the leptonic sector. We consider the radiative mechanisms which
transfer a possibly large CP-violating phase in the leptonic sector to the
theta parameter. It is found that large theta cannot be induced in the models
with one Higgs doublet as at least three loops are required in this case. In
the models with two or more Higgs doublets the dominant source of theta is the
phases in the scalar potential, induced by CP violation in leptonic sector.
Thus, in the MSSM framework the imaginary part of the trilinear soft-breaking
parameter A_l generates the corrections to the theta angle already at one loop.
These corrections are large, excluding the possibility of large phases, unless
the universality in the slepton sector is strongly violated.Comment: 5 pages, 2 figure
The Strong CP Problem and Axions
I describe how the QCD vacuum structure, necessary to resolve the
problem, predicts the presence of a P, T and CP violating term proportional to
the vacuum angle . To agree with experimental bounds, however,
this parameter must be very small ). After briefly
discussing some possible other solutions to this, so-called, strong CP problem,
I concentrate on the chiral solution proposed by Peccei and Quinn which has
associated with it a light pseudoscalar particle, the axion. I discuss in
detail the properties and dynamics of axions, focusing particularly on
invisible axion models where axions are very light, very weakly coupled and
very long-lived. Astrophysical and cosmological bounds on invisible axions are
also briefly touched upon.Comment: 14 pages, to appear in the Lecture Notes in Physics volume on Axions,
(Springer Verlag