Effects of heavy Majorana neutrinos at lepton-proton colliders

We discuss the prospects of detecting the processes $e^+p\to\bar\nu_e\ell^+\ell'^+X$ and $\nu_ep\to e\ell^+\ell'^+X$ ($\ell,\ell'=e,\mu,\tau$) under the conditions of the present $ep$ collider HERA and of future colliders. These high-energy processes are assumed to be mediated by the exchange of heavy Majorana neutrinos (HMN). We consider two simple scenarios for the HMN mass spectrum: the effective singlet ($m_1\ll m_2<m_3...$) and the effective doublet ($m_1<m_2\ll m_3...$). For the latter case, the cross section includes information about CP-violating phases.Comment: 5pages, 2 figures; published in conference proceedings: Particle Physics in Laboratory, Space and Universe, 11th. Lomonosov Conf. on Elementary Particle Physics (Moscow, 21-27 August 2003) (Singapore, World Scientific, 2005

Electron angular correlation in neutrinoless double beta decay and new physics

The angular correlation of the electrons in the neutrinoless double beta decay ($0\nu2\beta$) is calculated taking into account the nucleon recoil, the $S$ and $P$-waves for the electrons and the electron mass using a general Lorentz invariant effective Lagrangian. We show that the angular coefficient is essentially independent of the nuclear matrix element models. We work out the angular coefficient in several scenarios for new physics, in particular, in the left-right symmetric models.Comment: 5 pages, 1 figure; to appear in the Proceedings of the 13th Lomonosov Conference on Elementary Particle Physics, 23 --29 August 2007, Moscow, Russi

Radiative neutrino mass generation and dark energy

We study the models with radiative neutrino mass generation and explore the relation between the neutrino masses and dark energy. In these models, the pseudo-Nambu-Goldston bosons (pNGBs) arise at two-loop level via the Majorana neutrino masses. In particular, we demonstrate that the potential energy of the pNGB can be the dark energy potential and the observed value of the equation of state (EoS) parameter of the universe, $i.e.$, $w\simeq -1$, can be realized.Comment: 10 pages, 1 figure, a minor correction in Eq. (17

Neutrinoless double-beta decay and physics beyond the standard model

Neutrinoless double-beta decay is the most powerful tool to probe not only for Majorana neutrino masses but for lepton number violating physics in general. We discuss relations between lepton number violation, double-beta decay and neutrino mass, review a general Lorentz-invariant parametrization of the double-beta decay rate, highlight a number of different new physics models showing how different mechanisms can trigger double-beta decay and, finally, discuss possibilities of discriminating and testing these models and mechanisms in complementary experiments

Resolving Fermi, PAMELA and ATIC anomalies in split supersymmetry without R-parity

A long-lived decaying dark matter as a resolution to Fermi, PAMELA and ATIC anomalies is investigated in the framework of split supersymmetry (SUSY) without R-parity, where the neutralino is regarded as the dark matter and the extreme fine-tuned couplings for the long-lived neutralino are naturally evaded in the usual approach.Comment: 14 pages, 6 figures. Erroneous results concerning the cascade processes removed. Main results unchange

Searching for doubly charged Higgs bosons in M\"{o}ller scattering by resonance effects at linear e−e−e^-e^- collider

We discuss the parity-violating left-right asymmetries (LRAs) in M\"{o}ller scattering at the International Linear Collider (ILC) induced by doubly charged Higgs bosons in models with $SU(2)_L$ triplet and singlet scalar bosons, which couple to the left- and right-handed charged leptons, respectively. These bosons are important in the scenarios for the generation of the neutrino mass. We demonstrate that the contributions to the LRAs from the triplet and singlet bosons are opposite to each other. In particular, we show that the doubly charged Higgs boson from the singlet scalar can be tested at the ILC by using the resonance effect.Comment: 12 pages, 5 figures; version published in Eur.Phys.J.C60:119-124,200

A novel Q-limit guided continuation power flow method for voltage stability analysis

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Voltage security assessment is becoming a more and more important issue due to the fact that electrical power systems are more prone to voltage instability under increased demand, and it can be time-consuming to determine the actual level of voltage security in large power systems. For this reason, this thesis presents a novel method for calculating the margin of voltage collapse that is based on the Continuation Power Flow (CPF) method. The method offers a flexible and reliable solution procedure without suffering from divergence problems even when near the bifurcation point. In addition, the new method accounts for reactive power limits. The algorithmic continuation steps are guided by the prediction of Q-limit breaking point. A Lagrange polynomial interpolation formula is used in this method in order to find the Q-limit breaking point indices that determine when the reactive power output of a generator has reached its limit. The algorithmic continuation steps will then be guided to the closest Q-limit breaking point, consequently reducing the number of continuation steps and saving computational time. The novel method is compared with alternative conventional and enhanced CPF methods. In order to improve CPF further, studies comparing the performance of using direct and iterative solvers in a power flow calculation have also been performed. I first attempt to employ the column approximate minimum degree (AMD) ordering scheme to reset the permutation of the coefficient matrix, which decreases the number of iterations required by iterative solvers. Finally, the novel method has been applied to a range of power system case studies including a 953 bus national grid transmission case study. The results are discussed in detail and compared against exiting CPF methods