Measuring sigma(e^+e^- \to hadrons) using tagged photon

We propose to use events with radiated photons in e^+e^- collisions to measure the total cross section of e^+ e^- \to hadrons as a function of the center of mass energy. The Monte Carlo simulation for the collider DAPHNE shows that a competitive accuracy can be achieved with this method.Comment: revtex, 13 page

The Impact of σ(e+e−→hadrons)\sigma(e^+e^-\to {hadrons}) Measurements at Intermediate Energies on the Parameters of the Standard Model

We discuss the impact of precision measurements of $\sigma(e^+e^-\to {hadrons})$ in the center-of-mass range between 3 and 12 GeV, including improvements in the electronic widths of the narrow charmonium and bottonium resonances, on the determination of parameters of the Standard Model. In particular we discuss the impact of potential improvements on the extraction of the strong coupling constant $\alpha_s$, on the evaluation of the hadronic contributions to the electromagnetic coupling $\alpha(M_Z)$, and the determination of the charm and bottom quark masses.Comment: 8 page

Fermionic and Scalar Corrections for the Abelian Form Factor at Two Loops

Two-loop corrections for the form factor in a massive Abelian theory are evaluated, which result from the insertion of massless fermion or scalar loops into the massive gauge boson propagator. The result is valid for arbitrary energies and gauge boson mass. Power-suppressed terms vanish rapidly in the high energy region where the result is well approximated by a polynomial of third order in ln(s/M^2). The relative importance of subleading logarithms is emphasised.Comment: Latex, 10 pages, 5 figures. B. Feucht is B. Jantzen in later publications. (The contents of the paper is unchanged.

Electroweak effects in top-quark pair production at Hadron Colliders

Top-quark physics plays an important role at hadron colliders such as the Tevatron collider at Fermilab or the upcoming Large Hadron Collider (LHC) at CERN. Given the planned experimental precision, detailed theoretical predictions are mandatory. In this article we present analytic results for the complete electroweak corrections to gluon induced top-quark pair production, completing our earlier results for the quark-induced reaction. As an application we discuss top-quark pair production at Tevatron and at LHC. In particular we show that, although small for inclusive quantities, weak corrections can be sizeable for differential distribution