1,421 research outputs found
One Loop Multiphoton Helicity Amplitudes
We use the solutions to the recursion relations for double-off-shell fermion
currents to compute helicity amplitudes for -photon scattering and
electron-positron annihilation to photons in the massless limit of QED. The
form of these solutions is simple enough to allow {\it all}\ of the
integrations to be performed explicitly. For -photon scattering, we find
that unless , the amplitudes for the helicity configurations (+++...+) and
(-++...+) vanish to one-loop order.Comment: 27 pages + 4 uuencoded figures (included), Fermilab-Pub-93/327-T,
RevTe
Multi-Parton Amplitudes in Gauge Theories
In this report we review recent developments in perturbation theory methods
for gauge theories. We present techniques and results that are useful in the
calculation of cross sections for processes with many final state partons which
have applications in the study of multi-jet phenomena in high-energy Colliders.Comment: 84 pages, 12 figures: Latex, preprint version of 1991 Physics Reports
article. Scanned Figure
Off shell W pair production in e+ e- annihilation: The CC11 process
The various four-fermion production channels in annihilation are
discussed and the {\tt CC11} process , {\mbox{}}, is studied in detail. The cross
section , with being the invariant masses squared
of the two fermion pairs, may be expressed by six generic functions. All but
one may be found in the literature. The cross section, including initial state
radiation and the Coulomb correction, is discussed and compared with other
calculations from low energies up to = 2 ~TeV.Comment: 28 pages, LaTex, 6 figures, 8 tables, a uuencoded file containing the
latex file and figures is available via anonymous ftp at
ftp://ftp.ifh.de/pub/preprint/desy95-167.uu and the complete ps file also
from http://www.ifh.de/~riemann/desy95-167.ps.g
Multigluon Helicity Amplitudes Involving a Quark Loop
We apply the solution to the recursion relation for the double-off-shell
quark current to the problem of computing one loop amplitudes with an arbitrary
number of gluons. We are able to compute amplitudes for photon-gluon
scattering, electron-positron annihilation to gluons, and gluon-gluon
scattering via a quark loop in the case of like-helicity gluons. In addition,
we present the result for the one-loop gluon-gluon scattering amplitude when
one of the gluons has opposite helicity from the others.Comment: 31 pages (RevTeX) + 2 uuencoded figures (included),
Fermilab-Pub-93/389-
How to Integrate Divergent Integrals: a Pure Numerical Approach to Complex Loop Calculations
Loop calculations involve the evaluation of divergent integrals.
Usually [1] one computes them in a number of dimensions different than four
where the integral is convergent and then one performs the analytical
continuation and considers the Laurent expansion in powers of epsilon =n-4. In
this paper we discuss a method to extract directly all coefficients of this
expansion by means of concrete and well defined integrals in a five dimensional
space. We by-pass the formal and symbolic procedure of analytic continuation;
instead we can numerically compute the integrals to extract directly both the
coefficient of the pole 1/epsilon and the finite part.Comment: 13 pages, 1 Postscript figur
Mathematical Formulas for Calculating Net Returns from Participation in Government Farm Programs: Provisions of the Food, Agricultural, Conservation and Trade Act of 1990
Agricultural and Food Policy, Agricultural Finance,
QED collinear radiation factors in the next-to-leading logarithmic approximation
The effect of the collinear photon radiation by charged particles is
considered in the second order of the perturbation theory. Double and single
photon radiation is evaluated. The corresponding radiation factors are
obtained. The QED renormalization group approach is exploited in the
next-to-leading order. The results are suited to perform a systematic treatment
of the second order next-to-leading logarithmic radiative corrections to
various processes either analytically or numerically.Comment: 8 page
ee4fgamma, A program for e+e- -> 4f, 4fgamma with nonzero fermion masses
A computer program ee4fgamma for calculating cross sections of any four
fermion final state of e+e--annihilation at high energy and the corresponding
bremsstrahlung reaction that is possible in the framework of the Standard Model
is presented. As the fermion masses are arbitrary, the cross sections can be
computed without any collinear cut, the on-shell top quark production can be
studied and the Higgs boson exchange can be incorporated in a consistent way.
The program can be used as a Monte Carlo generator of unweighted events as
well.Comment: 20 pages; version published in Computer Physics Communication
An Economic Comparison of Composted Manure and Commercial Nitrogen with Imperfect Information
The economic feasibility of fertilizing irrigated grain sorghum with compos ted manure is evaluated using net return budgeting and production function analysis. Although the use of compost is technically feasible, the economic analysis indicates that compost does not comprise a large percentage of the nitrogen source in the profit-maximizing combination with commercial fertilizer.Composted manure, commercial nitrogen, net returns budgeting, production function analysis, irrigated grain sorghum, Crop Production/Industries,
Helac-Phegas: a generator for all parton level processes
The updated version of the Helac-Phegas event generator is presented. The
matrix elements are calculated through Dyson-Schwinger recursive equations.
Helac-Phegas generates parton-level events with all necessary information, in
the most recent Les Houches Accord format, for the study of any process within
the Standard Model in hadron and lepton colliders
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