Evaluation of Compton scattering sequence reconstruction algorithms for a portable position sensitive radioactivity detector based on pixelated Cd(Zn)Te crystals

We present extensive simulation studies on the performance of algorithms for the Compton sequence reconstruction used for the development of a portable spectroscopic instrument (COCAE), with the capability to localize and identify radioactive sources, by exploiting the Compton scattering imaging. Various Compton Sequence reconstruction algorithms have been compared using a large number of simulated events. These algorithms are based on Compton kinematics, as well as on statistical test criteria that exploit the redundant information of events having two or more photon interactions in the active detector's volume. The efficiency of the best performing technique is estimated for a wide range of incident gamma-ray photons emitted from point-like gamma sources.Comment: 16 pages, 17 figure

Little Higgs Model and Top-like Heavy Quark at CMS

The Little Higgs model gives an alternative solution to the fine-tuning problem present in the Standard Model (SM) of strong and electroweak interactions. The model invokes several new particles of TeV mass range, the lightest among them being a heavy quark (T) of charge +2/3. The CMS potential to discover this particle during intial years of LHC running is investigated

Study of Flavour Changing Neutral Currents in Top Quark Decays with the CMS Detector

This paper contains the first realistic estimate for the CMS sensitivity to Flavour Changing Neutral Currents (FCNC) in the top quark sector. The non Standard Model decays t -> Zq and t -> gamma q (q represents c or u quarks) have been studied at sqrts = 14 TeV exploiting leptonic decays of the Z boson and the photon. A realistic detector simulation has been adopted and the most relevant systematic effects have been addressed. The 5- sigma discovery limits for the two decays are BR(t-> qZ) =11.4 x 10^ -4 and BR(t -> gamma q ) =5.7 x 10^ -4, allowing some models of new physics to be tested

Simulated Performance Of Algorithms For The Localization Of Radioactive Sources From A Position Sensitive Radiation Detecting System (COCAE)

Simulation studies are presented regarding the performance of algorithms that localize point-like radioactive sources detected by a position sensitive portable radiation instrument (COCAE). The source direction is estimated by using the List Mode Maximum Likelihood Expectation Maximization (LM-ML-EM) imaging algorithm. Furthermore, the source-to-detector distance is evaluated by three different algorithms based on the photo-peak count information of each detecting layer, on the quality of the reconstructed source image as well as on the triangulation method. These algorithms have been tested on a large number of simulated photons in a wide energy range (from 200keV up to 2MeV) emitted by point-like radioactive sources located at different orientation and source-to-detector distances.Comment: 8 pages, 7 figures, 11th International Conference on Applications of Nuclear Techniques, Crete, Greece, June 12-18, 201

Search for composite and exotic fermions at LEP 2

A search for unstable heavy fermions with the DELPHI detector at LEP is reported. Sequential and non-canonical leptons, as well as excited leptons and quarks, are considered. The data analysed correspond to an integrated luminosity of about 48 pb^{-1} at an e^+e^- centre-of-mass energy of 183 GeV and about 20 pb^{-1} equally shared between the centre-of-mass energies of 172 GeV and 161 GeV. The search for pair-produced new leptons establishes 95% confidence level mass limits in the region between 70 GeV/c^2 and 90 GeV/c^2, depending on the channel. The search for singly produced excited leptons and quarks establishes upper limits on the ratio of the coupling of the excited fermio