Ulrich Langenfeld

Measuring the running top-quark mass

We present the first direct determination of the running top-quark mass based on the total cross section of top-quark pair production as measured at the Tevatron. Our theory prediction for the cross section includes various next-to-next-to-leading order QCD contributions, in particular, all logarithmically enhanced terms near threshold, the Coulomb corrections at two loops and all explicitly scale-dependent terms at next-to-next-to-leading order accuracy. The result allows for an exact and independent variation of the renormalization and factorization scales. For Tevatron and LHC we study its dependence on all scales, on the parton luminosity and on the top-quark mass using both the conventional pole mass definition as well as the running mass in the

Mass Bounds on a Very Light Neutralino

\overline{\mathrm{MS}}

Higher-order soft corrections to squark hadro-production

scheme. We extract for the top quark an

Discovery potential of radiative neutralino production at the ILC

\overline{\mathrm{MS}}

QCD threshold corrections for gluino pair production at hadron colliders

mass of

The top-quark's running mass

m(\ensuremath{\mu}=m)={160.0}_{\ensuremath{-}3.2}^{+3.3}\text{ }\text{ }\mathrm{GeV}

New results for t bar t production at hadron colliders

, which corresponds to a pole mass of

The role of beam polarization for radiative neutralino production at the ILC

{m}_{t}={168.9}_{\ensuremath{-}3.4}^{+3.5}\text{ }\text{ }\mathrm{GeV}

Model-independent WIMP Characterisation using ISR

.

Measurement of Radiative Neutralino Production

Within the Minimal Supersymmetric Standard Model (MSSM) we systematically investigate the bounds on the mass of the lightest neutralino. We allow for non-universal gaugino masses and thus even consider massless neutralinos, while assuming in general that R-parity is conserved. Our main focus is on laboratory constraints. We consider collider data, precision observables, and also rare meson decays to very light neutralinos. We then discuss the astrophysical and cosmological implications. We find that a massless neutralino is allowed by all existing experimental data and astrophysical and cosmological observations.