LHC/ILC Interplay in SUSY Searches

Combined analyses at the Large Hadron Collider and at the International Linear Collider are important to reveal precisely the new physics model as, for instance, supersymmetry. Examples are presented where ILC results as input for LHC analyses could be crucial for the identification of signals as well as of the underlying model. The synergy of both colliders leads also to rather accurate SUSY parameter determination and powerful mass constraints even if the scalar particles have masses in the multi-TeV range.Comment: 5 pages, contribution to the proceedings of EPS0

The Challenge of Determining SUSY Parameters in Focus-Point-Inspired Cases

We discuss the potential of combined LHC and ILC experiments for SUSY searches in a difficult region of the parameter space, in which all sfermion masses are above the TeV scale. Precision analyses of cross sections of light chargino production and forward--backward asymmetries of decay leptons and hadrons at the ILC, together with mass information on \tilde{\chi}^0_2 and squarks from the LHC, allow us to fit rather precisely the underlying fundamental gaugino/higgsino MSSM parameters and to constrain the masses of the heavy virtual sparticles. For such analyses the complete spin correlations between the production and decay processes have to be taken into account. We also took into account expected experimental uncertainties.Comment: 4 pages, talk given at XLI Rencontres de Moriond on Electroweak Interactions and Unified Theories, La Thuile, Italy, 11-18 Mar 200

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

We study CP violation in chargino production and decay in the Minimal Supersymmetric Standard Model (MSSM) with complex parameters at an e^+ e^- linear collider with longitudinally polarized beams. We investigate CP-sensitive asymmetries by means of triple product correlations and study their dependence on the complex parameters M_1 and mu. We give numerical predictions for the asymmetries and their measurability at the future International Linear Collider. Our results show that the CP asymmetries can be measured in a large region of the MSSM parameter space.Comment: 22 pages, LaTeX, 8 figures; v2: structural changes and references added, main conclusions unchanged, published versio

Normal tau polarisation as a sensitive probe of CP violation in chargino decay

CP violation in the spin-spin correlations in chargino production and subsequent two-body decay into a tau and a tau-sneutrino is studied at the ILC. From the normal polarisation of the tau, an asymmetry is defined to test the CP-violating phase of the higgsino mass parameter \mu. Asymmetries of more than \pm70% are obtained, also in scenarios with heavy first and second generation sfermions. Bounds on the statistical significances of the CP asymmetries are estimated. As a result, the normal tau polarisation in the chargino decay is one of the most sensitive probes to constrain or measure the phase \phi_\mu at the ILC, motivating further detailed experimental studies.Comment: 20 pages, 10 figures, gzipped tar fil

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

We consider neutralino production and decay e^+e^ --> chi^0_i chi^0_j, chi^0_j --> chi^0_1 f \bar{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.Comment: 30 pages, minor changes in the introduction, references adde

How light can the lightest neutralino be?

In this talk we summarize previous work on mass bounds of a light neutralino in the Minimal Supersymmetric Standard Model. We show that without the GUT relation between the gaugino mass parameters M_1 and M_2, the mass of the lightest neutralino is essentially unconstrained by collider bounds and precision observables. We conclude by considering also the astrophysics and cosmology of a light neutralino.Comment: 6 pages, 3 figures, to appear in the proceedings of the 16th International Symposium on Particles, Strings and Cosmology (PASCOS2010), Valencia (Spain), July 19th - 23rd, 201