265 research outputs found
On Measuring the top quark mass using the dilepton decay modes
We demonstrate a new likelihood method for extracting the top quark mass from
events of the type ttbar-->bW(l+nu)bW(l+nu) This method estimates the top quark
mass correctly from an ensemble of dilepton events. The method proposed by
Dalitz and Goldstein [1] is shown to result in a systematic underestimation of
the top quark mass. Effects due to the spin correlations between the top and
anti-top quarks are shown to be unimportant in estimating the mass of the top
quark.Comment: To appear in the proceedings of the 1996 DPF/DPB study on new
directions for High Energy Physics, Snowmass, Colorad
Spinor techniques for massive fermions with arbitrary polarization
We present a new variant of the spinor techniques for calculating the
amplitudes of processes involving massive fermions with arbitrary polarization.
It is relatively simple and leads to basic spinor products. Our procedure is
not more complex than CALCUL spinor techniques for massless fermions. We obtain
spinor Chisholm identities for massive fermions. As an illustration,
expressions are given for the amplitudes of electron-positron annihilation into
fermions-pairs for several polarizations.Comment: 14 pages, 2 figure
Discrepancy-based error estimates for Quasi-Monte Carlo. II: Results in one dimension
The choice of a point set, to be used in numerical integration, determines,
to a large extent, the error estimate of the integral. Point sets can be
characterized by their discrepancy, which is a measure of its non-uniformity.
Point sets with a discrepancy that is low with respect to the expected value
for truly random point sets, are generally thought to be desirable. A low value
of the discrepancy implies a negative correlation between the points, which may
be usefully employed to improve the error estimate of a numerical integral
based on the point set. We apply the formalism developed in a previous
publication to compute this correlation for one-dimensional point sets, using a
few different definitions of discrepancy.Comment: 10 pages, 3 Encapsulated Postscript figures, uses
a4.sty,psfrag.sty+epsf.sty(coming with psfrag.sty
Discrepancy-based error estimates for Quasi-Monte Carlo. I: General formalism
We show how information on the uniformity properties of a point set employed
in numerical multidimensional integration can be used to improve the error
estimate over the usual Monte Carlo one. We introduce a new measure of
(non-)uniformity for point sets, and derive explicit expressions for the
various entities that enter in such an improved error estimate. The use of
Feynman diagrams provides a transparent and straightforward way to compute this
improved error estimate.Comment: 23 pages, uses axodraw.sty, available at
ftp://nikhefh.nikhef.nl/pub/form/axodraw Fixed some typos, tidied up section
3.
Higgs Search : Present and Future
In this talk I review theoretical bounds on mass of the Higgs scalar in the
Standard Model(SM) and then summarise current experimental limits from the LEP
experiments. Following this I discuss the search strategies for the SM Higgs at
LEP 200 and the TeV energy \eplem\ colliders which are under discussion. This
will be followed by a summary of the Higgs search potential of the pp
supercolliders such as SSC/LHC. I then close with a brief discussion of a `Dark
Higgs' whose dominant decay modes are into invisible channels.Comment: 22 pages, 14 figures, available on request. Latex, needs
equation.sty, added at the end of manuscript. BU-TH-93/
Thread-Scalable Evaluation of Multi-Jet Observables
A leading-order, leading-color parton-level event generator is developed for
use on a multi-threaded GPU. Speed-up factors between 150 and 300 are obtained
compared to an unoptimized CPU-based implementation of the event generator. In
this first paper we study the feasibility of a GPU-based event generator with
an emphasis on the constraints imposed by the hardware. Some studies of Monte
Carlo convergence and accuracy are presented for PP -> 2,...,10 jet observables
using of the order of 1e11 events.Comment: 16 pages, 5 figures, 3 table
Color-flow decomposition of QCD amplitudes
We introduce a new color decomposition for multi-parton amplitudes in QCD,
free of fundamental-representation matrices and structure constants. This
decomposition has a physical interpretation in terms of the flow of color,
which makes it ideal for merging with shower Monte-Carlo programs. The
color-flow decomposition allows for very efficient evaluation of amplitudes
with many quarks and gluons, many times faster than the standard color
decomposition based on fundamental-representation matrices. This will increase
the speed of event generators for multi-jet processes, which are the principal
backgrounds to signals of new physics at colliders.Comment: 23 pages, 11 figures, version to appear on Phys. Rev.
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-
Detecting the intermediate-mass Higgs boson through the associate production channel pp --> t + anti-t + H + X
We examine the detection of the intermediate-mass Higgs boson (IMH) at LHC
through the associate production channel pp-->t+(anti-t)+H+X-->l+photon+
photon+X'. It is shown that by applying kinematic cuts or b-tagging on the
final state jets, the main backgrounds of W(-->l+nu)+photon+photon+(n-jet) can
be reduced substantially without significant loss of signals. It is possible to
detect the Higgs boson at LHC through the pp-->t+(anti-t)+H+X channel using a
modest photon detector with mass resolution of about 3% of the photon pair
invariant mass.Comment: 10 pages, standard LaTex fil
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