Precision Measurement of a Particle Mass at the Linear Collider

Precision measurement of the stop mass at the ILC is done in a method based on cross-sections measurements at two different center-of-mass energies. This allows to minimize both the statistical and systematic errors. In the framework of the MSSM, a light stop, compatible with electro-weak baryogenesis, is studied in its decay into a charm jet and neutralino, the Lightest Supersymmetric Particle(LSP), as a candidate of dark matter. This takes place for a small stop-neutralino mass difference.Comment: 6 pages, 4 figures, 3tables, Conference(Workshop)-LCWS/ILC2007-June,2,200

A Method for the Precision Mass Measurement of the Stop Quark at the International Linear Collider

Many supersymmetric models predict new particles within the reach of the next generation of colliders. For an understanding of the model structure and the mechanism(s) of symmetry breaking, it is important to know the masses of the new particles precisely. In this article the measurement of the mass of the scalar partner of the top quark (stop) at an e+e- collider is studied. A relatively light stop is motivated by attempts to explain electroweak baryogenesis and can play an important role in dark matter relic density. A method is presented which makes use of cross-section measurements near the pair-production threshold as well as at higher center-of-mass energies. It is shown that this method not only increases the statistical precision, but also greatly reduces the systematic uncertainties, which can be important. Numerical results are presented, based on a realistic event simulation, for two signal selection strategies: using conventional selection cuts, and using an Iterative Discriminant Analysis (IDA). Our studies indicate that a precision of \Delta\mstop = 0.42 GeV can be achieved, representing a major improvement over previous studies. While the analysis of stops is particularly challenging due to the possibility of stop hadronization, the general procedure could be applied to the mass measurement of other particles as well. We also comment on the potential of the IDA to discover a stop quark in this scenario, and we revisit the accuracy of the theoretical predictions for the neutralino relic densityComment: 41 pages, 14 figures, in JHEP forma

Reconstructing Supersymmetry at ILC/LHC

Coherent analyses of experimental results from LHC and ILC will allow us to draw a comprehensive and precise picture of the supersymmetric particle sector. Based on this platform the fundamental supersymmetric theory can be reconstructed at the high scale which is potentially close to the Planck scale. This procedure will be reviewed for three characteristic examples: minimal supergravity as the paradigm; a left-right symmetric extension incorporating intermediate mass scales; and a specific realization of string effective theories.Comment: published in Proceedings of the Ustron Conference 2005; technical LaTeX problem correcte

Reconstruction of Fundamental SUSY Parameters

We summarize methods and expected accuracies in determining the basic low-energy SUSY parameters from experiments at future e$^+$e$^-$ linear colliders in the TeV energy range, combined with results from LHC. In a second step we demonstrate how, based on this set of parameters, the fundamental supersymmetric theory can be reconstructed at high scales near the grand unification or Planck scale. These analyses have been carried out for minimal supergravity [confronted with GMSB for comparison], and for a string effective theory.Comment: 8 pages, latex, 7 figures, expanded version of contributions to the proceedings of ICHEP.2002 (Amstersdam) and LCWS.2002 (Jeju Island

SUSY Parameter Analysis at TeV and Planck Scales

Coherent analyses at future LHC and LC experiments can be used to explore the breaking mechanism of supersymmetry and to reconstruct the fundamental theory at high energies, in particular at the grand unification scale. This will be exemplified for minimal supergravity.Comment: 7 pages, 3 figures, uses espcrc2.sty (included), Proceedings, Loops and Legs 2004, Zinnowitz on Usedo

Temperature dependent photoluminescence of organic semiconductors with varying backbone conformation

We present photoluminescence studies as a function of temperature from a series of conjugated polymers and a conjugated molecule with distinctly different backbone conformations. The organic materials investigated here are: planar methylated ladder type poly para-phenylene, semi-planar polyfluorene, and non-planar para hexaphenyl. In the longer-chain polymers the photoluminescence transition energies blue shift with increasing temperatures. The conjugated molecules, on the other hand, red shift their transition energies with increasing temperatures. Empirical models that explain the temperature dependence of the band gap energies in inorganic semiconductors can be extended to explain the temperature dependence of the transition energies in conjugated molecules.Comment: 8 pages, 9 figure