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 BcB_c production

An estimate is presented of the production cross section of $B_c$ 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 $B_c$ mesons and for $b$ quarks varies strongly with energy.Comment: 5 pages, 1 figure, Latex; Contribution to the 5th International Workshop on $B$-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

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

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