3,746 research outputs found
Diffractive eta_c photo-and electroproduction with the perturbative QCD Odderon
Using a set of new odderon states, we calculate their contribution to the
diffractive eta_c photo- and electroproduction process. Compared to previous
simple 3-gluon exchange calculations we find an enhancement of about one order
of magnitude in the cross section. The t-dependence of the cross section
exhibits a dip structure in the small t region.Comment: 16 pages, 3 eps figure
Numerical simulation tests with light dynamical quarks
Two degenerate flavours of quarks are simulated with small masses down to
about one fifth of the strange quark mass by using the two-step multi-boson
(TSMB) algorithm. The lattice size is 8^3 x 16 with lattice spacing about
0.27fm which is not far from the N_t=4 thermodynamical cross-over line.
Autocorrelations of different physical quantities are estimated as a function
of the quark mass. The eigenvalue spectra of the Wilson-Dirac operator are
investigated.Comment: 14 pages, 7 figures, uses svjour.cls; mistake in the autocorrelation
of the pion mass corrected, version accepted for publication on Eur. Phys. J.
Search for the QCD Ground State
Within the Euclidean effective action approach we propose criteria for the
ground state of QCD. Despite a nonvanishing field strength the ground state
should be invariant with respect to modified Poincar\'e transformations
consisting of a combination of translations and rotations with suitable gauge
transformations. We have found candidate states for QCD with four or more
colours. The formation of gluon condensates shows similarities with the Higgs
phenomenon.Comment: 17 pages, latex, DESY 94-081, HD-THEP-94-
Non-invariant two-loop counterterms for the three-gauge-boson vertices
Some practical applications of algebraic renormalization are discussed. In
particular we consider the two-loop QCD corrections to the three-gauge-boson
vertices involving photons, Z and W bosons. For this purpose also the
corresponding two-point functions have to be discussed. A recently developed
procedure is used to analyze the breaking terms of the functional identities
and explicit formulae for the universal counterterms are provided. Special
attention is devoted to the treatment of infra-red divergences.Comment: Some minor corrections and improved discussion in the one-loop
sectio
Chiral Fermions on the Lattice
A recently proposed method for regularizing chiral gauge theories
non-perturbatively is discussed in detail. The result is an effective action
which can be computed from the lattice gauge field, and which is suited for
numerical simulations.Comment: Talk given by G. Schierholz at Yukawa International Seminar on
Non-Perturbative QCD: Structure of the QCD Vacuum (YKIS97), Kyoto, December
1997; typos correcte
Global Power Counting Analysis On Probing Electroweak Symmetry Breaking Mechanism At High Energy Colliders
We develop a precise power counting rule (a generalization of Weinberg's
counting method for the nonlinear sigma model) for the electroweak theories
formulated by chiral Lagrangians. Then we estimate the contributions of ``all''
next-to-leading order (NLO) bosonic operators to the amplitudes of the relevant
scattering processes which can be measured at high energy colliders, such as
the LHC and future Linear Colliders. Based upon these results, we globally
classify the sensitivities of testing all NLO bosonic operators for probing the
electroweak symmetry breaking mechanism at high energy colliders.Comment: Version Published in Physics Letters B. Latex, 12 pages, minor typos
correcte
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