Aspects of the cosmology of right-handed sneutrinos without lepton-number violation

In this work we add a Dirac right-handed neutrino superfield to the Minimal Supersymmetric Standard Model (MSSM). We discuss the interactions of the right- handed (RH) sneutrino and its mixing with its left-handed counterpart. We study the possibility of this RH sneutrino to be the lightest supersymmetrie particle (LSP). We obtain that this dark matter candidate is a non-thermal relic, and generally has a small relic density. This we argue makes it an interesting candidate for addressing the Ω(_DM)/ Ω(_b) problem. We then discuss a lepton-number conserving leptogenesis scenario, in which an Affleck-Dine inspired mechanism generates a left-right asymmetry in the sneutrino sector. The left-handed part of this asymmetry eventually genesis mechanism, as the right-handed part of the left-right asymmetry becomes the observed dark matter density

Obtaining the Full Unitarity Triangle from B -> pi K Decays

We present a method of obtaining the entire unitarity triangle from measurements of B -> pi K decay rates alone. Electroweak penguin amplitudes are included, and are related to tree operators. Discrete ambiguities are removed by comparing solutions with independent experimental data. The theoretical uncertainty in this method is rather small, in the range 5--10%.Comment: 4 pages, RevTeX, no figures. Clarifying remarks and references adde

New Physics Signals through CP Violation in B -> rho,pi

We describe here a method for detecting physics beyond the standard model via CP violation in B->rho,pi decays. Using a Dalitz-plot analysis to obtain alpha, along with an analytical extraction of the various tree (T) and penguin (P) amplitudes, we obtain a criterion for the absence of new physics (NP). This criterion involves the comparison of the measured |P/T| ratio with its value as predicted by QCD factorization. We show that the detection of NP via this method has a good efficiency when compared with the corresponding technique using B->pi,pi decays.Comment: 8 pages, 4 figures, talk given at MRST 2004: From Quarks to Cosmology, Concordia University, Montreal, May 200

Methods for Measuring New-Physics Parameters in B Decays

Recently, it was argued that new-physics (NP) effects in B decays can be approximately parametrized in terms of a few quantities. As a result, CP violation in the $B$ system allows one not only to detect the presence of new physics (NP), but also to measure its parameters. This will allow a partial identification of the NP, before its production at high-energy colliders. In this paper, we examine three methods for measuring NP parameters. The first uses a technique involving both \btos and \btod penguin B decays. Depending on which pair of decays is used, the theoretical error is in the range 5--15%. The second involves a comparison of $B\to \pi K$ and $B\to\pi\pi$ decays. Although the theoretical error is large (\gsim 25%), the method can be performed now, with presently-available data. The third is via a time-dependent angular analysis of \bvv decays. In this case, there is no theoretical error, but the technique is experimentally challenging, and the method applies only to those NP models whose weak phase is universal to all NP operators. A reliable identification of the NP will involve the measurement of the NP parameters in many different ways, and with as many B decay modes as possible, so that it will be important to use all of these methods.Comment: 33 pages, latex, no figures. Appendix added. Analysis and conclusions unchange

Affleck-Dine (Pseudo)-Dirac Neutrinogenesis

We consider the Affleck-Dine mechanism for leptogenesis in the minimal MSSM with Dirac or Pseudo-Dirac neutrinos. The rolling of scalars along D-flat directions generates a left-right asymmetry in the sneutrino sector, only the left part of which is transferred to a baryon asymmetry via sphaleron transitions. In the pure Dirac case the baryon asymmetry of the Universe is thus mirrored by an equal and opposite asymmetry in the leptons. The mechanism is also found to work when the neutrinos are pseudo-Dirac. No additional field needs to be added to the MSSM other than the right-handed neutrino.Comment: Latex, 3 figures, 1 bib file, 2 added reference, 1 minor correction, 1 added commen

Non-thermal right-handed sneutrino dark matter and the Omega_DM/Omega_b problem

We argue that the superpartner of the Dirac right-handed neutrino is a prime candidate for dark matter created from a 'mattergenesis' mechanism. We show that due to the smallness of the Yukawa couplings, a right-handed sneutrino density created in the early Universe would not be erased by annihilations, which remain out of thermal equilibrium. It would also not be drowned by a later, additional production of right-handed sneutrinos, as the relic density of the non-thermal right-handed sneutrinos is found to be generally negligible compared to the observed dark matter density. Mild constraints on sneutrino masses and trilinear SUSY-breaking couplings are obtained. Possible mattergenesis scenarios are also mentionedComment: 11 pages, 2 figures, 2 typos added, 1 reference added, minor corrections in section

Utilisation de la violation CP dans la désintégration [B en rhô pi] pour la recherche de nouvelle physique

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal

Design and applications of a tunable multi-wavelength SFL

Multi-wavelength laser sources have attracted much interest in the last decade as new photonic technologies have enabled the realization of such sources with much improved characteristics. Tunable continuous-wave multi-wavelength fiber lasers may now offer, for example, the ability to tune the wavelength spacing between the lasing lines and, also at times, the possibility to control the individual output peak powers. The more flexible and low-cost solutions benefiting from higher optical spectrum bandwidths also attract the most interest for future applications. These lasers find clients in so many fields such as optical test and measurement, optical communications, sensing, and processing like microwave photonic filtering. The search for such a flexible, stable and affordable laser source has fueled the investigation presented in this thesis. We first analyze the different approaches taken in the past for the implementation of tunable continuous-wave multi-wavelength lasers and follow with the development of a novel, relatively low-cost, tunable multi-wavelength semiconductor fiber laser (SFL). All the design steps are clearly explained and characterized. The final SFL is then used for the demonstration of two applications: chromatic dispersion measurements in long fiber spools, and the new design of a photonic microwave filter