Browsing by Author "Cheung, KM"

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Comparison of high-energy galactic and atmospheric tau neutrino flux
(2003-01-01)
Athar, H
;
Cheung, KM
;
Lin, GL
;
Tseng, JJ
;
物理研究所
We compare the tau neutrino flux arising from the galaxy and the earth atmosphere for 10(3) <= E/GeV <= 10(11). The intrinsic and oscillated tau neutrino fluxes from both sources are calculated. The intrinsic galactic v(tau) flux (E >= 10(3) GeV) is calculated by considering the interactions of high-energy cosmic-rays with the matter present in our galaxy, whereas the oscillated galactic v, flux is coming from the oscillation of the galactic v(mu), flux. For the intrinsic atmospheric v, flux, we extend the validity of a previous calculation from E <= 10(6) GeV up to E <= 10(11) GeV. The oscillated atmospheric v, flux is, on the other hand, rather suppressed. We find that, for 10(3) <= E/GeV <= 5.10(7), the oscillated v(tau) flux along the galactic plane dominates over the maximal intrinsic atmospheric v(tau) flux, i.e., the flux along the horizontal direction.
Phenomenology of a TeV right-handed neutrino and the dark matter model
(2004-06-01)
Cheung, KM
;
Seto, O
;
物理研究所
;
Institute of Physics
In a model of a TeV right-handed (RH) neutrino by Krauss, Nasri, and Trodden, the sub-eV scale neutrino masses are generated via a three-loop diagram with the vanishing seesaw mass forbidden by a discrete symmetry, and the TeV mass RH neutrino is simultaneously a novel candidate for cold dark matter. However, we show that with a single RH neutrino it is not possible to generate two mass-square differences as required by the oscillation data. We extend the model by introducing one more TeV RH neutrino and show that it is possible to satisfy the oscillation pattern within the modified model. After studying in detail the constraints coming from the dark matter, lepton flavor violation, the muon anomalous magnetic moment, and the neutrinoless double beta decay, we explore the parameter space and derive predictions of the model. Finally, we study the production and decay signatures of the TeV RH neutrinos at TeV e(+)e(-)/mu(+)mu(-) colliders.