Subproject C3: Threshold production of top-quark pairs and other heavy particles

Project leader:
Prof. Dr. Matthias Steinhauser, Institute of Theoretical Particle Physics, Karlsruhe Institute of Technology (KIT)

The common features of the physical phenomena investigated in this project are massive particles --- top and bottom quarks, new heavy particles such as squarks and gluinos, and weakly interacting dark matter particles at freeze-out or in the late universe --- moving at relative velocities much smaller than the speed of light. The method is non-relativistic effective field theory, appropriately matched to the full theory in the perturbative regime.

The mass of the top quark is a fundamental parameter of the Standard Model (SM). Since many observables of the electroweak sector depend sensitively on this parameter, its precise knowledge is important for precision tests of the SM and its extensions. Similarly, the bottom quark mass is an important input to B meson physics. In this project we calculate pair production of top and bottom quarks near threshold in e⁺ e^- collisions by applying non-relativistic effective field theory with the primary aim of a precise mass determination.

Threshold enhancements in the production of pairs of heavy particles are also relevant to precise calculations of production cross sections in hadronic collisions at the LHC with the added theoretical complication of enhanced soft gluon radiation. In the continuation of the project its scope is therefore extended from e⁺ e^- collisions to hadronic collisions with particular emphasis on combined soft-gluon and non-relativistic resummation.

The methods used in this project apply directly to the ``Sommerfeld enhancement'' of the dark matter annihilation cross section either due to new forces or the electroweak force for TeV scale dark matter. We address this effect model-independently in non-relativistic effective field theory, and specifically in the minimal supersymmetric standard model.

Last Change: 12th April 2012