483 research outputs found
Vector meson couplings to vector and tensor currents in extended NJL quark model
A simple explanation of the dynamic properties of vector mesons is given in
the framework of extended Nambu - Jona-Lasinio quark model. New mass relations
among the hadron vector resonances are derived. The results of this approach
are in good accordance with the QCD sum rules, the lattice calculations and the
experimental data.Comment: 4 pages, 2 figure
Formalism for dilepton production via virtual photon bremsstrahlung in hadronic reactions
We derive a set of new formulas for various distributions in dilepton
production via virtual photon bremsstrahlung from pseudoscalar mesons and
unpolarized spin-one-half fermions. These formulas correspond to the leading
and sub-leading terms in the Low-Burnett-Kroll expansion for real photon
bremsstrahlung. The relation of our leading-term formulas to previous works is
also shown. Existing formulas are examined in the light of Lorentz covariance
and gauge invariance. Numerical comparison is made in a simple example, where
an "exact" formula and real photon data exist. The results reveal large
discrepancies among different bremsstrahlung formulas. Of all the leading-term
bremsstrahlung formulas, the one derived in this work agrees best with the
exact formula. The issues of M_T-scaling and event generators are also
addressed.Comment: 37 pages, RevTeX, epsf.sty, 10 embedded figure
A Dependence of Hadron Production in Inelastic Muon Scattering and Dimuon Production by Protons
The A dependence of the production of hadrons in inelastic muon scattering
and of the production of dimuons in high proton interactions are simply
related. Feynman x distributions and z scaling distributions in nuclei are
compared with energy loss models. Suggestions for new data analyses are
presented.Comment: 14pp +13 figures, UPR report 607T (available from
ftp://dept.physics.upenn.edu/muhad
Pion and Rho Structure Functions from Lattice QCD
We calculate the lower moments of the deep-inelastic structure functions of
the pion and the rho meson on the lattice. Of particular interest to us are the
spin-dependent structure functions of the rho. The calculations are done with
Wilson fermions and for three values of the quark mass, so that we can perform
an extrapolation to the chiral limit.Comment: 30pp, LaTeX2e with 15 eps figures using epsfig. Postscript file also
available from ftp://ftp.th.physik.uni-frankfurt.de/pub/cbest/pionrho.ps or
http://www.th.physik.uni-frankfurt.de/~cbest/pionrho.p
Weak gauge principle and electric charge quantization
Starting from a weak gauge principle we give a new and critical revision of
the argument leading to charge quantization on arbitrary spacetimes. The main
differences of our approach with respect to previous works appear on spacetimes
with non trivial torsion elements on its second integral cohomology group. We
show that in these spacetimes there can be topologically non-trivial
configurations of charged fields which do not imply charge quantization.
However, the existence of a non-exact electromagnetic field always implies the
quantization of charges. Another consequence of the theory for spacetimes with
torsion is the fact that it gives rise to two natural quantization units that
could be identified with the electric quantization unit (realized inside the
quarks) and with the electron charge. In this framework the color charge can
have a topological origin, with the number of colors being related to the order
of the torsion subgroup. Finally, we discuss the possibility that the
quantization of charge may be due to a weak non-exact component of the
electromagnetic field extended over cosmological scales.Comment: Latex2e, 24 pages, no figure
Quaternion Gravi-Electromagnetism
Defining the generalized charge, potential, current and generalized fields as
complex quantities where real and imaginary parts represent gravitation and
electromagnetism respectively, corresponding field equation, equation of motion
and other quantum equations are derived in manifestly covariant manner. It has
been shown that the field equations are invariant under Lorentz as well as
duality transformations. It has been shown that the quaternionic formulation
presented here remains invariant under quaternion transformations.Comment: Key Words: Quaternion, dyons, gravito-dyons, gravi-electromagnetism.
PACS No.: 04.90. +e ; 14.80. H
Four Dimensional CFT Models with Rational Correlation Functions
Recently established rationality of correlation functions in a globally
conformal invariant quantum field theory satisfying Wightman axioms is used to
construct a family of soluble models in 4-dimensional Minkowski space-time. We
consider in detail a model of a neutral scalar field of dimension 2. It
depends on a positive real parameter c, an analogue of the Virasoro central
charge, and admits for all (finite) c an infinite number of conserved symmetric
tensor currents. The operator product algebra of is shown to coincide
with a simpler one, generated by a bilocal scalar field of
dimension (1,1). The modes of V together with the unit operator span an
infinite dimensional Lie algebra whose vacuum (i.e. zero energy lowest
weight) representations only depend on the central charge c. Wightman
positivity (i.e. unitarity of the representations of ) is proven to be
equivalent to .Comment: 28 pages, LATEX, amsfonts, latexsym. Proposition 2.3, and Conjecture
in Sec. 6 are revised. Minor errors are correcte
Worldline Approach to Forward and Fixed Angle fermion-fermion Scattering in Yang-Mills Theories at High Energies
Worldline techniques are employed to study the general behaviour of the
fermion-fermion collision amplitude at very high energies in a non-abelian
gauge field theory for the forward and fixed angle scattering cases. A central
objective of this work is to demonstrate the simplicity by which the worldline
methodology isolates that sector of the full theory which carries the soft
physics, relevant to each process. Anomalous dimensions pertaining to a given
soft sector are identified and subseuently used to facilitate the
renormalization group running of the respective four point functions. Gluon
reggeization is achieved for forward, while Sudakov suppression is established
for fixed angle scattering.Comment: 28 pages, 10 figures in three file
The generalized cusp in ABJ(M) N = 6 Super Chern-Simons theories
We construct a generalized cusped Wilson loop operator in N = 6 super
Chern-Simons-matter theories which is locally invariant under half of the
supercharges. It depends on two parameters and interpolates smoothly between
the 1/2 BPS line or circle and a pair of antiparallel lines, representing a
natural generalization of the quark-antiquark potential in ABJ(M) theories. For
particular choices of the parameters we obtain 1/6 BPS configurations that,
mapped on S^2 by a conformal transformation, realize a three-dimensional
analogue of the wedge DGRT Wilson loop of N = 4. The cusp couples, in addition
to the gauge and scalar fields of the theory, also to the fermions in the
bifundamental representation of the U(N)xU(M) gauge group and its expectation
value is expressed as the holonomy of a suitable superconnection. We discuss
the definition of these observables in terms of traces and the role of the
boundary conditions of fermions along the loop. We perform a complete two-loop
analysis, obtaining an explicit result for the generalized cusp at the second
non-trivial order, from which we read off the interaction potential between
heavy 1/2 BPS particles in the ABJ(M) model. Our results open the possibility
to explore in the three-dimensional case the connection between localization
properties and integrability, recently advocated in D = 4.Comment: 53 pages, 10 figures, added references, this is the version appeared
on JHE
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