2,044 research outputs found
BHAGEN-1PH: A Monte Carlo event generator for radiative Bhabha scattering
BHAGEN-1PH is a FORTRAN program providing fast Monte Carlo event generation
of the process , within electroweak theory, for
both unpolarized beams and also for the longitudinally polarized electron beam.
The program is designed for final leptons outside a small cone around the
initial leptons direction and has a new algorithm allowing also for a fast
generation of non collinear initial and final emission, as well as for
asymmetric and different angular cuts for final leptons.Comment: 23 pages, plain Tex, no figure
Simulation of the process within electroweak theory with longitudinally polarized initial electrons
We present simple analytic expressions for the distributions of the Bhabha
scattering process with emission of one hard photon, including weak boson
exchanges, and with longitudinal polarization of the initial electron. The
results from the Monte Carlo generator BHAGEN-1PH, based on these expressions,
are presented and compared, for the unpolarized case, with those existing in
literature.Comment: 9 pages, plain Tex, no figures, small change in Table
Production of a Higgs pseudoscalar plus two jets in hadronic collisions
We consider the production of a Higgs pseudoscalar accompanied by two jets in
hadronic collisions. We work in the limit that the top quark is much heavier
than the Higgs pseudoscalar and use an effective Lagrangian for the
interactions of gluons with the pseudoscalar. We compute the amplitudes
involving: 1) four gluons and the pseudoscalar, 2) two quarks, two gluons and
the pseudoscalar and 3) four quarks and the pseudoscalar. We find that the
pseudoscalar amplitudes are nearly identical to those for the scalar case, the
only differences being the overall size and the relative signs between terms.
We present numerical cross sections for proton-proton collisions with
center-of-mass energy 14 TeV.Comment: 12 pages, LaTeX, 4 Postscript figures, submitted to Phys. Rev.
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
Analytical and numerical methods for massive two-loop self-energy diagrams
Motivated by the precision results in the electroweak theory studies of
two-loopFeynman diagrams are performed. Specifically this paper gives a
contribution to the knowledge of massive two-loop self-energy diagrams in
arbitrary and especially four dimensions.This is done in three respects firstly
results in terms of generalized, multivariable hypergeometric functions are
presented giving explicit series for small and large momenta. Secondly the
imaginary parts of these integrals are expressed as complete elliptic
integrals.Finally one-dimensional integral representations with elementary
functions are derived.They are very well suited for the numerical evaluations.Comment: 24 page
Competing communities of users and developers of computer software: competition between open source software and commercial software
The open source movement is a group of volunteer programmers that has recently caused quite a stir in the software market. The volunteers of this group develop computer operating systems, programming languages, and other software. They work together in teams that communicate via the Internet. Their goal is to develop useful software that is available for free and that users can change at will. To enable users to change and improve the software, they distribute their software not only in compiled form (that a computer needs to actually run the software), but also in its source code (the lines of code that programmers write). This cooperation breaks through the usual barriers that separate corporate suppliers from their buyers. This may represent the first example where the Internet enables cooperation on a scale that changes market dynamics. This paper studies the interaction between the network dynamics of the open source movement and the dynamics of a commercial software supplier. It makes our first step in identifying conditions that support a successful development of open source software. We focus on one particular set of projects within the open source movement, namely the Linux computer operating system.management and organization theory ;
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
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-
Generalized Gluon Currents and Applications in QCD
We consider the process containing two quark lines and an arbitrary number of
gluons in a spinor helicity framework. A current with two off-shell gluons
appears in the amplitude. We first study this modified gluon current using
recursion relations. The recursion relation for the modified gluon current is
solved for the case of like-helicity gluons. We apply the modified gluon
current to compute the amplitude for in the like-helicity gluon case.Comment: 80 pages, 2 figures (appended in pictex), CLNS 91/112
The Pseudothreshold Expansion of the 2-loop Sunrise Selfmass Master Amplitudes
The values at pseudothreshold of two loop sunrise master amplitudes with
arbitrary masses are obtained by solving a system of differential equations.
The expansion at pseudothreshold of the amplitudes is constructed and some
lowest terms are explicitly presented.Comment: 1+22 pages, Latex, no figures, changes in Eq.(41),(44),(47
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