TopReX generator (version~3.25). Short manual

This is the manual of the specialized event generator TopReX 3.25. The generator provides the simulation of several important processes in pp and p pbar collisions, not implemented in PYTHIA (yet). Some of these processes include t-quarks whose spin polarizations are taken into account in the subsequent decay of the t-quarks. Several non-SM top quark decay channels are included, too. All calculated subprocesses can be accessed from PYTHIA as external processes. In addition, TopReX can be used as stand alone event generator, providing partonic final states before showering. In this mode the control of the event generation is taken by TopReX itself. A few simple examples of main routines, which show how to use TopReX in the different modes are discussed.Comment: 12 pages, 4 figures, LaTe

Double Top Production at Hadronic Colliders

We calculate the contribution of anomalous top-quark interaction with a gluon, photon, and $Z$-boson (FCNC) to $t \bar t$ pair production in hadronic collisions. Using the current data from Run~1 of the Tevatron we evaluate the upper limit on the the anomalous coupling of $t$-quark with gluon, $|\kappa_g/\Lambda| \le 0.52$ TeV$^{-1}$. We examine the production of double top ($t t$ or $\bar t \bar t$) at hadronic colliders as a result of FCNC interactions of the top quark. It is shown that the study of such reactions at LHC collider makes possible to obtain the constraint on strength of coupling at the level of $|\kappa_g /\Lambda| \le 0.09$ TeV$^{-1}$.Comment: 16 pages, LaTeX, epsfig, 12 figure

rho_T Production via W_L Z_L Fusion at Hadronic Colliders

Multiscale technicolor models predict the existence of high mass resonances at hadron colliders. Although the quark fusion process of production dominates, vector boson fusion offers the advantage of allowing forward jet tagging for background suppression. We calculate here the cross section and differential distributions for $\rho_T$ production in the vector boson fusion channel at the LHC.Comment: 9 pages, 6 figures, LaTe

The Constraint on FCNC Coupling of the Top Quark with a Gluon from ep Collisions

Using the constraint on the single top production cross-section obtained at the HERA collider, $\sigma(ep \to e t X)$, we evaluate an upper limit on oupling constant of the anomalous top quark interaction with a gluon via flavor-changing neutral current: $|\kappa_{tgq}/\Lambda| \le 0.4 {TeV}^{-1}$, BR$(t \to gq) < 13$Comment: Latex, 3 figures, missed references were adde

BcB_c Physics at Hadron Colliders

In this paper we summarize the results of the theory working group dedicated to the analysis of $B_c$ production at hadron colliders.Comment: 7 pages, LaTe

The Contribution of Bc Mesons to the Search for B->tau nu Decays at LEP

We study the contribution of B_c mesons to the search for B->tau nu decays. We find that at LEP the contributions from B_u and B_c mesons can be comparable. This observation can have a relevant impact on the extraction of constraints on new physics (such as charged-Higgs contributions) from current LEP limits on B->tau nu final states. Inclusion of the B_c contribution can reduce the current L3 limit on Tan(beta)/M_H from 0.38/GeV (90%CL) down to 0.27/GeV (90%CL).Comment: 8 pages, Latex, epsfig, 1 figur

New angles on top quark decay to a charged Higgs

To properly discover a charged Higgs Boson ($H^\pm$) requires its spin and couplings to be determined. We investigate how to utilize \ttbar spin correlations to analyze the $H^\pm$ couplings in the decay $t\to bH^+\to b\tau^+\nu_\tau$. Within the framework of a general Two-Higgs-Doublet Model, we obtain results on the spin analyzing coefficients for this decay and study in detail its spin phenomenology, focusing on the limits of large and small values for $\tan\beta$. Using a Monte Carlo approach to simulate full hadron-level events, we evaluate systematically how the $H^\pm\to\tau^\pm\nu_\tau$ decay mode can be used for spin analysis. The most promising observables are obtained from azimuthal angle correlations in the transverse rest frames of $t(\bar{t})$. This method is particularly useful for determining the coupling structure of $H^\pm$ in the large $\tan\beta$ limit, where differences from the SM are most significant.Comment: 28 pages, 13 figures. Uses JHEP forma

Study of ATLAS sensitivity to FCNC top decays

The ATLAS experiment sensitivity to top quark Flavour Changing Neutral Current (FCNC) decays was studied at LHC using ttbar events. While one of the top quarks is expected to follow the dominant Standard Model decay t->bW, the other decays through a FCNC channel, i.e. t-> Z u(c), t-> gamma u(c) or t-> g u(c). Different types of analyses, applied to each FCNC decay mode, were compared. The FCNC branching ratio sensitivity (assuming a 5sigma signal significance) and 95% confidence level limits on the branching ratios (in the hypothesis of signal absence) were obtained

Heavy Quark Fragmentation Functions for D-wave Quarkonium and Charmed Beauty Mesons

At the large transverse momentum region, the production of heavy-heavy bound-states such as charmonium, bottomonium, and $\bar bc$ mesons in high energy $e^+e^-$ and hadronic collisions is dominated by parton fragmentation. We calculate the heavy quark fragmentation functions into the D-wave quarkonium and $\bar bc$ mesons to leading order in the strong coupling constant and in the non-relativistic expansion. In the $\bar b c$ meson case, one set of its D-wave states is expected to lie below the open flavor threshold. The total fragmentation probability for a $\bar b$ antiquark to split into the D-wave $\bar b c$ mesons is about $2 \times 10^{-5}$, which implies that only 2\% of the total pseudo-scalar ground state $B_c$ comes from the cascades of these orbitally excited states.Comment: 26 pages in RevteX and 3 figures in postscript. Also available at http://www.ph.utexas.edu/~cheung/paper.htm

MEtop - a generator for single top production via FCNC interactions

We present a generator for single top quark production via flavour-changing neutral currents. The MEtop event generator allows for Next-to-Leading-Order direct top production $pp \to t$ and Leading-Order production of several other single top processes. A few packages with definite sets of dimension six operators are available. We discuss how to improve the bounds on the effective operators and how well new physics can be probed with each set of independent dimension six operators.Comment: 26 pages, 22 figure