K. Hohenwarter-Sodek

The role of polarized positrons and electrons in revealing fundamental interactions at the Linear Collider

The proposed International Linear Collider (ILC) is well-suited for discovering physics beyond the Standard Model and for precisely unraveling the structure of the underlying physics. The physics return can be maximized by the use of polarized beams. This report shows the paramount role of polarized beams and summarizes the benefits obtained from polarizing the positron beam, as well as the electron beam. The physics case for this option is illustrated explicitly by analyzing reference reactions in different physics scenarios. The results show that positron polarization, combined with the clean experimental environment provided by the linear collider, allows to improve strongly the potential of searches for new particles and the identification of their dynamics, which opens the road to resolve shortcomings of the Standard Model. The report also presents an overview of possible designs for polarizing both beams at the ILC, as well as for measuring their polarization.

A T-odd asymmetry in neutralino production and decay

We study CP-violating effects in neutralino production and subsequent decay within the Minimal Supersymmetric Standard Model with complex parameters M1 and ?. The observable we propose is a T-odd asymmetry based on a triple product in neutralino production e+e??0i02, i = 1,...,4?, with subsequent leptonic three-body decay 02?01?+??, ? = e,?, at an e+e? linear collider with (s)1/2 = 500?GeV and polarised beams. We provide compact analytical formulae for the cross section and the T-odd asymmetry taking into account the complete spin correlations between production and decay. We give numerical predictions for the cross section and the T-odd asymmetry. The asymmetry can go up to 10 %.

Test of lepton flavour violation at the LHC

We study lepton flavour violating decays of neutralinos and sleptons within the minimal supersymmetric standard model, assuming two and three generation mixings in the slepton sector. We take into account the most recent bounds on flavour violating rare lepton decays. Taking the SPS1a’ scenario as an example, we show that some of the lepton flavour violating branching ratios of neutralinos and sleptons can be sizable (∼5–10%). We study the impact of the lepton flavour violating neutralino and slepton decays on the di-lepton mass distributions measured at the LHC. We find that they can result in novel and characteristic edge structures in the distributions. In particular, double-edge structures can appear in the eτ and μτ mass spectra if

CP-odd observables in neutralino production with transverse e + and e − beam polarization

\tilde{\tau}_1

CP-sensitive observables in chargino production with transverse

is the lightest slepton. The appearance of these remarkable structures provides a powerful test of supersymmetric lepton flavour violation at the LHC.

e^{\pm}

We consider neutralino production and decay e + e − → ˜ χ 0 ˜ χ 0 , ˜ χ 0 → ˜ χ 0 f ¯ f at a linear collider with transverse e + and e − beam polarization. We propose CP asymmetries by means of the azimuthal distribution of the produced neutralinos and of that of the final leptons, while taking also into account the subsequent decays of the neutralinos. We include the complete spin correlations between production and decay. Our framework is the Minimal Supersymmetric Standard Model with complex parameters. In a numerical study we show that there are good prospects to observe these CP asymmetries at the International Linear Collider and estimate the accuracy expected for the determination of the phases in the neutralino sector.

beam polarization

Abstract.We consider the process

CP asymmetries in scalar bottom quark decays

e^ + e^-\to\tilde{\chi}^ + _i\tilde{\chi}^-_j

CP asymmetries in chargino production and decay: the three-body decay case

at a linear collider with transverse

Impact of squark generation mixing on the search for gluinos at LHC

e^{\pm}