Tania Robens (Aachen):

NLO Event Generation for Chargino Production at the ILC

Abstract:

In the chargino and neutralino sector of the MSSM, the electroweak SUSY parameters can be determined by a small number of measurements of masses and cross sections. At the ILC, these parameters can be determined with an experimental accuracy matching the precision of NLO and higher-order theoretical predictions. The higher order contributions therefore need to be included in the analysis of the parameters of the SUSY sector. We present a NLO Monte-Carlo event generator for simulating chargino pair-production at the ILC. We consider two approaches of including photon radiation. A strict fixed-order approach allows for comparison and consistency checks with published semianalytic results in the literature, but suffers from negative weights in certain points of phase space. A version with soft- and hard-collinear resummation of photon radiation, which combines photon resummation with the inclusion of the NLO matrix element for the production process,avoids negative event weights, so the program can simulate physical (unweighted) event samples. Photons are explicitly generated throughout the range where they can be experimentally resolved. We evaluate the systematic errors due to softand collinear approximations. In the resummation approach, the residual uncertainty can be brought down to the per-mil level, coinciding with the expected statistical uncertainty at the ILC. We show results for cross sections and event generation for both approaches.

download document (pdf, 877 kB)