Flavour physics and CP violation in supersymmetric theories

With the start of the Large Hadron Collider LHC (CERN, Geneva) in September 2008 a new era of elementary particle physics is arising. Most likely, at the LHC signals of physics beyond the Standard Model of particle physics will be discovered. Supersymmetry is one of the most promising extensions of the Standard Model. The search for supersymmetric particles has a very high priority at LHC. The research project "Flavour physics and CP violation in supersymmetric theories" is a joint research project of the University of Vienna (Austria) and the University of Würzburg (Germany). Up to now most studies concerning supersymmetry at future colliders have been performed in the Minimal Supersymmetric Standard Model under the assumption that flavour mixing can be neglected and that R-parity is conserved. The main purpose of the present research project is to explore the flavour sector of supersymmetric extensions of the Standard Model, with and without R-parity conservation. We plan to investigate on the one hand the Minimal Supersymmetric Standard Model with intergenerational mixing in the supersymmetry breaking terms and on the other hand models with R- parity violation. In a systematic study we want to consider the most general case including CP violating phases as well as flavour violating parameters. In order to work out the implications of flavour and CP violating parameters for the determination of the underlying supersymmetric parameters, we are going to analyze in a systematic way production and decay processes of supersymetric particles at colliders. We want to take into account the existing experimental and theoretical constraints for the flavour violating parameters and the constraints from the dark matter density. In spite of the severe restrictions we expect large flavour violating signals in the supersymmetric production and decay processes. Therefore, the results of the research project "Flavour physics and CP violation in supersymmetric theories" will play an important role for the experiments at the LHC and other future colliders.

The first run of the experiments at the Large Hadron Collider (LHC) at CERN, Geneva, started in March 2010 and had its culmination point in the detection of the Higgs boson in July 2012. This marked the onset of a new era in particle physics. The second run of the LHC is scheduled to start in 2015. It is very probable that in the second run signals of new physics beyond the Standard Model will be discovered. Supersymmetry is one of the most promising candidates for an extension of the Standard Model, because it provides a framework for the unification of the fundamental forces of nature at a high-energy scale and for the solution of the so-called hierarchy problem. Moreover, the lightest supersymmetric particle could be an excellent candidate for dark matter. The additional supersymmetric complex parameters might be necessary to explain the observed baryon-antibaryon asymmetry of the Universe. Therefore, the search for supersymmetric particles has had a high priority at all colliders so far and is going to be one of the main goals in the second run of the LHC as well.If supersymmetric particles are found, the next important step will be the determination of the fundamental parameters of the underlying supersymmetric theory. In this spirit, the main aim of our research project has been to study the influence of new sources of quark flavour violation. These can occur in the sector of the squarks, the supersymmetric partners of the quarks. The flavour structure of the squark sector can be completely unrelated to the known flavour structure of the quark sector of the Standard Model. In our analyses we have assumed that the second and third generations of squarks can mix and have calculated their impact on the production and decay rates of the squarks and gluinos (the supersymmetric partners of the gluons) at the LHC. The parameters of this squark mixing are only constrained by the very precisely measured decay probabilities of the K mesons and B mesons, and from the data on the searches of Higgs bosons and supersymmetric particles. We have taken into account these experimental constraints according to the latest data available. We have shown that the rates for the quark flavour violating decays can be quite large (up to 50%), which means that the effects of squark mixing have to be taken into account in the determination of the supersymmetric parameters. We have published our results in international journals for high energy physics.Furthermore, we have completed the calculation of the full one-loop radiative corrections to the decay rates of sfermions and Higgs bosons in the flavour conserving case. We have written two program packages, SFOLD and HFOLD, which have been released to the public. The extension of these program packages to the flavour violating case will be an essential part of our follow-up FWF Project P 26338-N27.