113 research outputs found
The decay omega(782) -> 5 pi in chiral theory
The arguments are put forward that the many pion decays omega ->2 pi^+ 2 pi^-
pi^0 and pi^+ pi^- 3 pi^0 provide an ideal test site for testing the
predictions of chiral models of the vector meson decays into many pions. Using
the approach based on the Weinberg Lagrangian or, in a new language, the
Lagrangian of hidden local symmetry added with the term induced by the
anomalous Lagrangian of Wess and Zumino, the partial widths of these decays are
evaluated, and their excitation curves in e^+e^- annihilation are obtained. The
discussed are the perspectives of the experimental study of the decays omega ->
5 pi in e^+e^- annihilation and photoproduction.Comment: revtex, 12 pages include 2 ps figures; clarifying remarks and
references added, 17-fold reduction of filesize of fig1.ps. Accepted in Phys.
Lett.
The decays omega(782), phi(1020) to 5 pi in the hidden local symmetry approach
The decays omega -> 2pi^+ 2pi^- pi^0 and omega -> pi^+ pi^- 3pi^0 are
reconsidered in the hidden local symmetry approach (HLS) added with the
anomalous terms. The decay amplitudes are analyzed in detail, paying the
special attention to the Adler condition of vanishing the whole amplitude at
vanishing momentum of any final pion. Combining the Okubo-Zweig-Iizuka (OZI)
rule applied to the five pion final state, with the Adler condition, we
calculate also the phi -> 2pi^+ 2pi^-pi^0 and phi -> pi^+ pi^- 3pi^0 decay
amplitudes. The partial widths of the above decays are evaluated, and the
excitation curves in e^+e^- annihilation are obtained, assuming reasonable
particular relations among the parameters characterizing the anomalous terms of
the HLS Lagrangian. The evaluated branching ratios B(phi -> pi^+ pi^-
3pi^0)~2x10^{-7} and B(phi -> 2pi^+ 2pi^- pi^0)~7x10^{-7} are such that with
the luminosity L=500 pb^{-1} attained at DAFNE phi factory, one may already
possess about 1685 events of the decays phi -> 5pi.Comment: 15 pages text, 12 pages of figures. Typos corrected, clarifying
remarks added. Accepted for publication in Phys.Rev.
The sigma term and the quark number operator in QCD
We discuss the relationship of the forward matrix element of the operator
, related to the so-called sigma term, to the quark number. We
show that in the naive quark model in the canonical formalism these quantities
coincide in the limit of small average quark momenta. In the QCD parton model
defined through light-front quantization this result is preserved at leading
perturbative order but it receives radiative corrections. We analyze the
theoretical and phenomenological consequences of this result, which provides a
bridge between a current algebra quantity, the sigma term, and a deep-inelastic
quantity, the parton number.Comment: 30 pages, 1 figure, DFTT-92-6 (April 1993
Why is CPT fundamental?
G. L\"uders and W. Pauli proved the theorem based on
Lagrangian quantum field theory almost half a century ago. R. Jost gave a more
general proof based on ``axiomatic'' field theory nearly as long ago. The
axiomatic point of view has two advantages over the Lagrangian one. First, the
axiomatic point of view makes clear why is fundamental--because
it is intimately related to Lorentz invariance. Secondly, the axiomatic proof
gives a simple way to calculate the transform of any
relativistic field without calculating , and
separately and then multiplying them. The purpose of this
pedagogical paper is to ``deaxiomatize'' the theorem by
explaining it in a few simple steps. We use theorems of distribution theory and
of several complex variables without proof to make the exposition elementary.Comment: 17 pages, no figure
Spherical collapse with dark energy
I discuss the work of Maor and Lahav [1], in which the inclusion of dark
energy into the spherical collapse formalism is reviewed. Adopting a
phenomenological approach, I consider the consequences of - a) allowing the
dark energy to cluster, and, b) including the dark energy in the virialization
process. Both of these issues affect the final state of the system in a
fundamental way. The results suggest a potentially differentiating signature
between a true cosmological constant and a dynamic form of dark energy. This
signature is unique in the sense that it does not depend on a measurement of
the value of the equation of state of dark energy.Comment: To appear in the proceedings of the ``Peyresq Physics 10" Workshop,
19 - 24 June 2005, Peyresq, Franc
Differential Equations for Definition and Evaluation of Feynman Integrals
It is shown that every Feynman integral can be interpreted as Green function
of some linear differential operator with constant coefficients. This
definition is equivalent to usual one but needs no regularization and
application of -operation. It is argued that presented formalism is
convenient for practical calculations of Feynman integrals.Comment: pages, LaTEX, MSU-PHYS-HEP-Lu2/9
Weighted scale invariant quantum field theories
We study a class of Lorentz violating quantum field theories that contain
higher space derivatives, but no higher time derivatives, and become
renormalizable in the large N expansion. The fixed points of their
renormalization-group flows provide examples of exactly "weighted scale
invariant" theories, which are noticeable Lorentz violating generalizations of
conformal field theories. We classify the scalar and fermion models that are
causal, stable and unitary. Solutions exist also in four and higher dimensions,
even and odd. In some explicit four dimensional examples, we compute the
correlation functions to the leading order in 1/N and the critical exponents to
the subleading order. We construct also RG flows interpolating between pairs of
fixed points.Comment: 29 pages, 3 figures; v2: JHEP versio
Renormalization of gauge invariant composite operators in light-cone gauge
We generalize to composite operators concepts and techniques which have been
successful in proving renormalization of the effective Action in light-cone
gauge. Gauge invariant operators can be grouped into classes, closed under
renormalization, which is matrix-wise. In spite of the presence of non-local
counterterms, an ``effective" dimensional hierarchy still guarantees that any
class is endowed with a finite number of elements. The main result we find is
that gauge invariant operators under renormalization mix only among themselves,
thanks to the very simple structure of Lee-Ward identities in this gauge,
contrary to their behaviour in covariant gauges.Comment: 35100 Padova, Italy DFPD 93/TH/53, July 1993
documentstyle[preprint,aps]{revtex
Exploring \pp scattering in the \1N picture
In the large approximation to , the leading \pp scattering
amplitude is expressed as the sum of an infinite number of tree diagrams. We
investigate the possibility that an adequate approximation at energies up to
somewhat more than one can be made by keeping diagrams which involve the
exchange of resonances in this energy range in addition to the simplest chiral
contact terms. In this approach crossing symmetry is automatic but individual
terms tend to drastically violate partial wave unitarity. We first note that
the introduction of the meson in a chirally invariant manner
substantially delays the onset of drastic unitarity violation which would be
present for the {\it current algebra} term alone. This suggests a possibility
of local (in energy) cancellation which we then explore in a phenomenological
way. We include exchanges of leading resonances up to the region.
However, unitarity requires more structure which we model by a four derivative
contact term or by a low lying scalar resonance which is presumably subleading
in the \1N expansion, but may nevertheless be important. The latter two
flavor model gives a reasonable description of the phase shift up
until around , before the effects associated which the
threshold come into play.Comment: 27 LaTex pages + 13 figures (also available in hard-copy
Charge-conjugation violating neutrino interactions in supernovae
The well known charge conjugation violating interactions in the Standard
Model increase neutrino- and decrease anti-neutrino- nucleon cross sections.
This impacts neutrino transport in core collapse supernovae through "recoil"
corrections of order the neutrino energy over the nucleon mass . All
corrections to neutrino transport deep inside a protoneutron star are
calculated from angular integrals of the Boltzmann equation. We find these
corrections significantly modify neutrino currents at high temperatures. This
produces a large mu and tau number for the protoneutron star and can change the
ratio of neutrons to protons. In addition, the relative size of neutrino mean
free paths changes. At high temperatures, the electron anti-neutrino mean free
path becomes {\it longer} than that for mu or tau neutrinos.Comment: 14 pages, 2 included ps figures, subm. to Phys. Rev.
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