104 research outputs found
Mixing of fermion fields of opposite parities and baryon resonances
We consider a loop mixing of two fermion fields of opposite parities whereas
the parity is conserved in a Lagrangian. Such kind of mixing is specific for
fermions and has no analogy in boson case. Possible applications of this effect
may be related with physics of baryon resonances. The obtained matrix
propagator defines a pair of unitary partial amplitudes which describe the
production of resonances of spin and different parity or
. The use of our amplitudes for joint description of
partial waves and shows that the discussed effect is clearly
seen in these partial waves as the specific form of interference between
resonance and background. Another interesting application of this effect may be
a pair of partial waves and where the picture is more
complicated due to presence of several resonance states.Comment: 22 pages, 6 figures, more detailed comparison with \pi N PW
Fermion resonance in quantum field theory
We derive accurately the fermion resonance propagator by means of Dyson
summation of the self-energy contribution. It turns out that the relativistic
fermion resonance differs essentially from its boson analog.Comment: 8 pages, 2 figures, revtex4 class; references added, style
correction
and Polarizabilities from {} Data on the Base of S-Matrix Approach
We suggest the most model-independent and simple description of the
process near threshold in framework of S-matrix
approach. The amplitudes contain the pion polarizabilities and rather
restricted information about interaction. Application of these
formulae for description of MARK-II \cite{M2} and Crystal Ball \cite{CB} data
gives: ,
(in units system ) at the experimental values of scattering lengths. Both
values are compartible with current algebra predictions.Comment: LaTeX, 14 pages plus 6 figures (not included, available upon request)
, ISU-IAP.Th93-03, Irkuts
The Rarita--Schwinger field: renormalization and phenomenology
We discuss renormalization of propagator of interacting Rarita--Schwinger
field. Spin-3/2 contribution after renormalization takes usual resonance form.
For non-leading spin-1/2 terms we found procedure, which guarantees absence of
poles in energy plane. The obtained renormalized propagator has one free
parameter and is a straight generalization of the famous free propagator of
Moldauer and Case. Application of this propagator for production of
in \pi^{+}\particle{p}\to \pi^{+}\particle{p} leads to
good description of total cross-section and to reasonable agreement with
results of partial wave analysis.Comment: 19 pages, 3 figures, revtex4; misprints, min editorial change
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