11,564 research outputs found
Interference Phenomenon for the Faddeevian Regularization of 2D Chiral Fermionic Determinants
The classification of the regularization ambiguity of 2D fermionic
determinant in three different classes according to the number of second-class
constraints, including the new faddeevian regularization, is examined and
extended. We found a new and important result that the faddeevian class, with
three second-class constraints, possess a free continuous one parameter family
of elements. The criterion of unitarity restricts the parameter to the same
range found earlier by Jackiw and Rajaraman for the two-constraints class. We
studied the restriction imposed by the interference of right-left modes of the
chiral Schwinger model () using Stone's soldering formalism. The
interference effects between right and left movers, producing the massive
vectorial photon, are shown to constrain the regularization parameter to belong
to the four-constraints class which is the only non-ambiguous class with a
unique regularization parameter.Comment: 15 pages, Revtex. Final version to be published in Phys. Rev.
Limits on excited tau leptons masses from leptonic tau decays
We study the effects induced by excited leptons on the leptonic tau decay at
one loop level. Using a general effective lagrangian approach to describe the
couplings of the excited leptons, we compute their contributions to the
leptonic decays and use the current experimental values of the branching ratios
to put limits on the mass of excited states and the substructure scale.Comment: 10 pages, 6 figures, to be published in Phys. Rev.
New remarks on the linear constraint self-dual boson and Wess-Zumino terms
In this work we prove in a precise way that the soldering formalism can be
applied to the Srivastava chiral boson (SCB), in contradiction with some
results appearing in the literature. We have promoted a canonical
transformation that shows directly that the SCB is composed of two
Floreanini-Jackiw's particles with the same chirality which spectrum is a
vacuum-like one. As another conflictive result we have proved that a
Wess-Zumino term used in the literature consists of the scalar field, once
again denying the assertion that the WZ term adds a new degree of freedom to
the SCB theory in order to modify the physics of the system.Comment: 6 pages, Revtex. Final version to appear in Physical Review
Open charm and charmonium production at relativistic energies
We calculate open charm and charmonium production in reactions at
= 200 GeV within the hadron-string dynamics (HSD) transport approach
employing open charm cross sections from and reactions that are
fitted to results from PYTHIA and scaled in magnitude to the available
experimental data. Charmonium dissociation with nucleons and formed mesons to
open charm ( pairs) is included dynamically. The 'comover'
dissociation cross sections are described by a simple phase-space model
including a single free parameter, i.e. an interaction strength , that
is fitted to the suppression data for collisions at SPS
energies. As a novel feature we implement the backward channels for charmonium
reproduction by channels employing detailed balance. From our
dynamical calculations we find that the charmonium recreation is comparable to
the dissociation by 'comoving' mesons. This leads to the final result that the
total suppression at = 200 GeV as a function of centrality
is slightly less than the suppression seen at SPS energies by the NA50
Collaboration, where the 'comover' dissociation is substantial and the backward
channels play no role. Furthermore, even in case that all directly produced
mesons dissociate immediately (or are not formed as a mesonic state),
a sizeable amount of charmonia is found asymptotically due to the + meson channels in central collisions of at =
200 GeV which, however, is lower than the yield expected from binary
scaling of collisions.Comment: 42 pages, including 14 eps figures, discussions extended and
references added, to be published in Phys. Rev.
A Precision Calculation of the Next-to-Leading Order Energy-Energy Correlation Function
The O(alpha_s^2) contribution to the Energy-Energy Correlation function (EEC)
of e+e- -> hadrons is calculated to high precision and the results are shown to
be larger than previously reported. The consistency with the leading logarithm
approximation and the accurate cancellation of infrared singularities exhibited
by the new calculation suggest that it is reliable. We offer evidence that the
source of the disagreement with previous results lies in the regulation of
double singularities.Comment: 6 pages, uuencoded LaTeX and one eps figure appended Complete paper
as PostScript file (125 kB) available at:
http://www.phys.washington.edu/~clay/eecpaper1/paper.htm
Importance of reaction volume in hadronic collisions: Canonical enhancement
We study the canonical flavor enhancement arising from exact conservation of
strangeness, and charm flavor. Both the theoretical motivation, and the
practical consequences are explored. We argue using qualitative theoretical
arguments and quantitative evaluation, that this proposal to reevaluate
strangeness signature of quark--gluon plasma is not able to explain the
majority of available experimental results.Comment: 14 pages including 6 figures, submitted to Journal of Physics G
Presented at: Strange Quark Matter, September 2001, Frankfur
Colour reconnection and Bose-Einstein effects
Final-state interactions and interference phenomena that could affect the
value of the W mass reconstructed from hadronic WW decays at LEP2 are reviewed,
and possible areas for future investigation are identified.Comment: 14 pages, 5 figures, LaTeX, uses epsfig. Talk at Phenomenology
Workshop on LEP2 Physics, Oxford, April 199
Composite Scalars at LEP: Constraining Technicolor Theories
LEPI and LEPII data can be used to constrain technicolor models with light,
neutral pseudo-Nambu-Goldstone bosons, Pa. We use published limits on branching
ratios and cross sections for final states with photons, large missing energy,
jet pairs, and b bbar pairs to constrain the anomalous Pa Z0 Z0, Pa Z0 photon,
and Pa photon photon couplings. From these results, we derive bounds on the
size of the technicolor gauge group and the number of technifermion doublets in
models such as Low-scale Technicolor.Comment: 27 pages (including title page), 15 figures, 6 tables. version 2: In
addressing PRD referee comments, we have significantly expanded our
manuscript, to include detailed discussion of limits from LEP II data, as
well as expanding the number or specific models to which we apply our
results. As a result, we have changed the title from "Z0 decays to composite
scalars: constraining technicolor theories
Adaptabilidade e estabilidade de genótipos de milho avaliados pelo método de Annicchiarico.
bitstream/item/212040/1/ORAL12.pd
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