1,168 research outputs found
Multiloop String-Like Formulas for QED
Multiloop gauge-theory amplitudes written in the Feynman-parameter
representation are poised to take advantage of two important developments of
the last decade: the spinor-helicity technique and the superstring
reorganization. The former has been considered in a previous article; the
latter will be elaborated in this paper. We show here how to write multiloop
string-like formulas in the Feynman-parameter representation for any process in
QED, including those involving other non-electromagnetic interactions. The
general connection between the Feynman-parameter approach and the
superstring/first-quantized approach is discussed. In the special case of a
one-loop multi-photon amplitude, these formulas reduce to the ones obtained by
the superstring and the first quantized methods. The string-like formulas
exhibits a simple gauge structure which makes the Ward-Takahashi identity
apparent, and enables the integration-by-parts technique of Bern and Kosower to
be applied, so that gauge-invariant parts can be extracted diagram-by-diagram
with the seagull vertex neglected.Comment: 25 pages in Plain Tex, plus four figures in a postscript file;
McGill/92-5
Charge asymmetry in hadroproduction of heavy quarks
A sizeable difference in the differential production cross section of top and
antitop quarks, respectively, is predicted for hadronically produced heavy
quarks. It is of order and arises from the interference between
charge odd and even amplitudes respectively. For the TEVATRON it amounts to
approximately 5-10% in the region where the cross section is large and could
therefore be measured in the next round of experiments. At the LHC the
asymmetry can be studied by selecting appropriately chosen kinematical regions.Comment: LaTeX, 5pp, 5 figures, uses revtex. The complete paper, including
figures, is also available via anonymous ftp at
ftp://ttpux2.physik.uni-karlsruhe.de/ , or via www at
http://www-ttp.physik.uni-karlsruhe.de/cgi-bin/preprints/ Final version as
published in Phys.Rev.Let
A dual lagrangian for non-Abelian tensor gauge fields
For non-Abelian tensor gauge fields of the lower rank we have found an
alternative expression for the field strength tensors, which transform
homogeneously with respect to the complementary gauge transformations and allow
us to construct the dual Lagrangian.Comment: 13 pages, LaTex fil
Heavy Top Quark Searches in the Di-Lepton Mode at the Tevatron
We present the results of a detailed study of the effects of -tagging on
the heavy top-quark signal and backgrounds for the modes of the di-lepton plus
two high transverse energy jets at the Fermilab Tevatron. The general
characteristics of the heavy top-quark signal events are also discussed so that
a comparison can be made between -tagging and imposing stringent kinematical
cuts to eliminate backgrounds.Comment: uses PHYZZX and TABLES macros, 10 pages, four figures not included
(available by request), FERMILAB-Pub-93/105-
Knowledge integration by thinking along
Organizing depends on the integration of specialized knowledge that lies distributed across individuals. There are benefits from specialization, and, yet, the integration of knowledge across boundaries is critical for organizational vitality. How do organizations benefit from knowledge that lies in different domains without having to transfer knowledge? This paper describes results of two exploratory ethnographic studies of knowledge integration in industrial research organizations. It introduces a knowledge integration mechanism - ‘thinking along’ – that has not received much attention by researchers before. Thinking along is a mechanism that allows for knowledge integration without the need for transfer. As a consequence, benefits of specialization obtain even as knowledge from one domain informs knowledge from another. The paper describes how researchers use thinking along to integrate knowledge within and across boundaries. It concludes with implications for knowledge management and future research
Finite calculation of divergent selfenergy diagrams
Using dispersive techniques, it is possible to avoid ultraviolet divergences
in the calculation of Feynman diagrams, making subsequent regularization of
divergent diagrams unnecessary. We give a simple introduction to the most
important features of such dispersive techniques in the framework of the
so-called finite causal perturbation theory. The method is also applied to the
'divergent' general massive two-loop sunrise selfenergy diagram, where it leads
directly to an analytic expression for the imaginary part of the diagram in
accordance with the literature, whereas the real part can be obtained by a
single integral dispersion relation. It is pointed out that dispersive methods
have been known for decades and have been applied to several nontrivial Feynman
diagram calculations.Comment: 15 pages, Latex, one figure, added reference
Four-pion production in tau decays and e+e- annihilation: an update
An improved description of four-pion production in electron-positron
annihilation and in tau lepton decays is presented. The model amplitude is
fitted to recent data from BaBar which cover a wide energy range and which were
obtained exploiting the radiative return. Predicting tau decay distributions
from e+e- data and comparing these predictions with ALEPH and CLEO results, the
validity of isospin symmetry is confirmed within the present experimental
errors. A good description of two- and three-pion sub-distributions is
obtained. Special emphasis is put on the predictions for omega pi (->
pi+pi-pi0) in e+e- annihilation and in tau decay. The model amplitude is
implemented in the Monte Carlo generator PHOKHARA.Comment: a few typos correcte
Data taking strategy for the phase study in
The study of the relative phase between strong and electromagnetic amplitudes
is of great importance for understanding the dynamics of charmonium decays. The
information of the phase can be obtained model-independently by fitting the
scan data of some special decay channels, one of which is . To find out the optimal data taking strategy for a scan experiment
in the measurement of the phase in , the
minimization process is analyzed from a theoretical point of view. The result
indicates that for one parameter fit, only one data taking point in the
vicinity of a resonance peak is sufficient to acquire the optimal precision.
Numerical results are obtained by fitting simulated scan data. Besides the
results related to the relative phase between strong and electromagnetic
amplitudes, the method is extended to analyze the fits of other resonant
parameters, such as the mass and the total decay width of .Comment: 13 pages, 7 figure
Heavy boson production through the collision of an ultrahigh-energy neutrino on a target nucleon
We discuss W and Z production through the deep inelastic neutrino-nucleon
scattering in the context of the standard model SU(3)x SU(2)x U(1) of the
strong and electroweak interactions. We find the cross section rates for the
process neutrino + nucleon --> lepton(-) + W(+) + X for the case of
ultrahigh-energy neutrinos colliding on a target nucleon.Comment: 20 pages, 6 figure
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