195 research outputs found
e+ e- -> t anti-t H including decays: on the size of background contributions
We present results for the lowest order cross sections, calculated with the
complete set of the standard model Feynman diagrams, of all possible detection
channels of the associated production of the top quark pair and the light Higgs
boson, which may be used for determination of the top-Higgs Yukawa coupling at
the future e+e- linear collider. We show that, for typical particle
identification cuts, the background contributions are large. In particular, the
QCD background contributions are much bigger than could be expected when taking
into account a possibly low virtuality of exchanged gluons. Moreover, we
include the initial state radiation effects and discuss the dependence of the
cross sections on the Higgs boson and top quark masses.Comment: 13 pages, 1 figure; substantially revised version, accepted for
publication in Eur.Phys.J.
An anomalous Wtb coupling at a linear collider
Differential cross sections of secondary particles in a process of top quark
pair production and decay into six fermions at a linear collider with an
unpolarized and a longitudinally polarized electron beam are computed to the
lowest order in the standard model and in the presence of an anomalous Wtb
coupling. It is illustrated that the latter has a little impact on the
differential cross sections. In particular, it is shown that the angular
distribution of a secondary lepton receives practically no contribution from
the anomalous Wtb coupling, even if the top quark is produced off shell and the
non-double resonance background contributions are taken into account. This
finding is in accordance with the decoupling theorem that has been proven in
literature in the narrow top quark width approximation.Comment: 11 pages, 9 figures, axodraw.st
On the energy dependence of hadronic production
An estimate is presented of the production cross section of mesons
between threshold and LHC energies using lowest-order perturbation theory and
non-relativistic bound state approximation. It is shown that the ratio of the
production cross sections for mesons and for quarks varies strongly
with energy.Comment: 5 pages, 1 figure, Latex; Contribution to the 5th International
Workshop on -Physics at Hadron Machines, 1997, Los Angeles, California,
US
Anomalous Wtb vertex in top quark production in e+e- colliders
The potential of high energy e+e- collisions to detect an anomalous
Wtb coupling is discussed. The anomalous Wtb coupling is implemented
in the calculation of cross sections of four fermion reactions containing a
single on-mass-shell top quark and numerical results for e+e- -+ tbp^PIÀ
are presented[…
Current status of CARLOMAT, a program for automatic computation of lowest order cross sections
The current status of CARLOMAT, a program for automatic computation of the
lowest order cross sections of multiparticle reactions is described, the
results of comparisons with other multipurpose Monte Carlo programs are shown
and some new results on e+e- -> b anti-b b anti-b u anti-d d anti-u are
presented.Comment: 6 pages, LaTeX, 3 postscript figures, to appear in proceedings of the
"9th Workshop on Elementary Particle Theory: Loops and Legs in Quantum Field
Theory", Sondershausen, Germany, April 20-25, 200
Microstructured reactor as a pre-turbo catalytic converter
The idea of a structured catalytic converter
placed immediately after engine exhaust valves, thus
operating on high gas temperature and velocity, is
explored. The assumption is that major part of the reactor
operates in the entry region where Nusselt and Sherwood
numbers are highly enhanced. In this work, flow resistances
as well as heat and mass transfer coefficients were studied
for gas velocities exceeding 50 m/s. Consequently, the
transition range (between laminar and turbulent flows) was
reached. The comparison with classic monolith has shown
significant improvement in heat or mass transfer paid by
slight increase in flow resistance
Top quark pair production and decay at linear colliders: signal vs. off resonance background
Standard Model predictions for the reactions with six fermions in the final
state relevant for top quark pair production and decay at linear colliders are
discussed. An issue of the double resonance signal versus non doubly resonant
background is addresed. Effects related to the off-mass-shell production of the
t\bar{t}-pair are discussed.Comment: 9 pages, talk presented by K. Kolodziej at 6th International
Symposium on Radiative Corrections RADCOR 2002 and 6th Zeuthen Workshop on
Elementary Particle Theory ``Loops and Legs in Quantum Field Theory'',
Kloster Banz, Germany, September 8--13, 200
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