30 research outputs found
Constraints on Neutralino masses and mixings from Cosmology and Collider Physics
Bounds on cross section measurements of chargino pair production at LEP yield
a bound on the chargino mass. If the GUT relation is assumed, the lightest
neutralino must be heavier than \approx 45 -50\GeV. If no GUT relation is
assumed, no lower bound on the neutralino mass exists. I derive mass bounds on
the lightest neutralino from relic density measurements for relativistic and
non-relativistic neutralinos and I derive bounds on the selectron mass from the
observed limits on the cross section of the neutralino pair production process
e^+e^-\to \x{1}\x{2} at LEP, if the lightest neutralino is massless. I
further discuss radiative neutralino production and its background at the
future ILC. Finally, I present a method to determine the neutralino couplings
to right and left handed selectrons and Z bosons from cross section
measurements of radiative neutralino production and neutralino pair production
at the ILC.Comment: PhD-Thesis, 101 page
Measurement of radiative neutralino production
We perform the first experimental study with full detector simulation for the
radiative production of neutralinos at the linear collider, at sqrt{s} = 500
GeV and realistic beam polarizations. We consider all relevant backgrounds,
like the Standard Model background from radiative neutrino production. The
longitudinal polarized beams enhance the signal and simultaneously reduce the
background, such that statistical errors are significantly reduced. We find
that the photon spectrum from the signal process can be well isolated. The
neutralino mass and the cross section can be measured at a few per-cent level,
with the largest systematic uncertainties from the measurement of the beam
polarization and the beam energy spectrum.Comment: 6 pages, 2 figures, to appear in the proceedings of the 2011
International Workshop on Future Linear Colliders (LCWS11), Sept. 26-30,
Granada, Spai
Model-independent WIMP Characterisation using ISR
The prospects of measuring the parameters of WIMP dark matter in a model
independent way at the International Linear Collider are investigated. The
signal under study is direct WIMP pair production with associated initial state
radiation. The analysis is performed in full simulation of the ILD detector
concept. With an integrated luminosity of L = 500 fb-1 and realistic beam
polarizations the helicity structure of the WIMP couplings to electrons can be
determined, and the masses and cross sections can be measured to the percent
level. The systematic uncertainties are dominated by the polarization
measurement and the luminosity spectrum.Comment: 7 pages, 4 figures, International Workshop on Future Linear Colliders
LCWS1
QCD threshold corrections for gluino pair production at hadron colliders
We present the complete threshold enhanced predictions in QCD for the total cross section of gluino pair production at hadron colliders at next-to-next-to-leading order. Thanks to the computation of the required one-loop hard matching coefficients our results are accurate to the next-to-next-to-leading logarithm. In a brief phenomenological study we provide predictions for the total hadronic cross sections at the LHC and we discuss the uncertainties arising from scale variations and the parton distribution functions
Mass Bounds on a Very Light Neutralino
Within the Minimal Supersymmetric Standard Model (MSSM) we systematically
investigate the bounds on the mass of the lightest neutralino. We allow for
non-universal gaugino masses and thus even consider massless neutralinos, while
assuming in general that R-parity is conserved. Our main focus are laboratory
constraints. We consider collider data, precision observables, and also rare
meson decays to very light neutralinos. We then discuss the astrophysical and
cosmological implications. We find that a massless neutralino is allowed by all
existing experimental data and astrophysical and cosmological observations.Comment: 36 pages, 13 figures, minor modification in astro-physical bounds.
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