Associated production of the top-pions and single top at hadron colliders

In the context of topcolor assisted technicolor(TC2) models, we study the production of the top-pions $\pi_{t}^{0,\pm}$ with single top quark via the processes $p\bar{p} \to t\pi_{t}^{0}+X$ and $p\bar{p} \to t\pi_{t}^{\pm}+X$, and discuss the possibility of detecting these new particles at Tevatron and LHC. We find that it is very difficult to observe the signals of these particles via these processes at Tevatron, while the neutral and charged top-pions $\pi_{t}^{0}$ and $\pi_{t}^{\pm}$ can be detecting via considering the same sign top pair $tt\bar{c}$ event and the $tt\bar{b}$ (or $t\bar{t}b$) event at LHC, respectively.Comment: latex files,14 pages, 7 figures. Accepted for publication in Phys. Rev.

Single-shot carrier-envelope phase determination of long superintense laser pulses

The impact of the carrier-envelope phase (CEP) of an intense multi-cycle laser pulse on the radiation of an electron beam during nonlinear Compton scattering is investigated. An interaction regime of the electron beam counterpropagating to the laser pulse is employed, when pronounced high-energy x-ray double peaks emerge at different angles near the backward direction relative to the initial electron motion. This is achieved in the relativistic interaction domain, with the additional requirements that the electron energy is much lower than that necessary for the electron reflection condition at the laser peak, and the stochasticity effects in the photon emission are weak. The asymmetry parameter of the double peaks in the angular radiation distribution is shown to serve as a sensitive and uniform measure for the CEP of the laser pulse. The method demonstrates unprecedented sensitivity to subtle CEP-effects up to 10-cycle laser pulses and can be applied for the characterization of extremely strong laser pulses in present and near future laser facilities

Retardation Terms in The One-Gluon Exchange Potential

It is pointed out that the retardation terms given in the original Fermi-Breit potential vanish in the center of mass frame. The retarded one-gluon exchange potential is rederived in this paper from the three-dimensional one-gluon exchange kernel which appears in the exact three-dimensional relativistic equation for quark-antiquark bound states. The retardation part of the potential given in the approximation of order $p^2/m^2$ is shown to be different from those derived in the previous literature. This part is off-shell and does no longer vanish in the center of mass frame