Neutrino mixing, interval matrices and singular values

We study the properties of singular values of mixing matrices embedded within an experimentally determined interval matrix. We argue that any physically admissible mixing matrix needs to have the property of being a contraction. This condition constrains the interval matrix, by imposing correlations on its elements and leaving behind only physical mixings that may unveil signs of new physics in terms of extra neutrino species. We propose a description of the admissible three-dimensional mixing space as a convex hull over experimentally determined unitary mixing matrices parametrized by Euler angles which allows us to select either unitary or nonunitary mixing matrices. The unitarity-breaking cases are found through singular values and we construct unitary extensions yielding a complete theory of minimal dimensionality larger than three through the theory of unitary matrix dilations. We discuss further applications to the quark sector.Comment: Misprints correcte

Heavy neutrinos and the pp→lljjpp\to lljj CMS data

We show that the excess in the $pp \to ee jj$ CMS data can be naturally interpreted within the Minimal Left Right Symmetric model (MLRSM), keeping $g_L = g_R$, if CP phases and non-degenerate masses of heavy neutrinos are taken into account. As an additional benefit, a natural interpretation of the reported ratio (14:1) of the opposite-sign (OS) $pp\to l^\pm l^\mp jj$ to the same-sign (SS) $pp\to l^\pm l^\pm jj$ lepton signals is possible. Finally, a suppression of muon pairs with respect to electron pairs in the $pp \to lljj$ data is obtained, in accordance with experimental data. If the excess in the CMS data survives in the future, it would be a first clear hint towards presence of heavy neutrinos in right-handed charged currents with specific CP phases, mixing angles and masses, which will have far reaching consequences for particle physics directions.Comment: 8 pages, 7 figures. v2: minor changes, refs added, typos corrected, version accepted for publication in PL

Single chargino production with R-parity lepton number violation in electron-electron and muon-muon collisions

We examine single chargino production in conjunction with R-parity lepton number violation in future lepton-lepton collisions. Present bounds on R-parity violating couplings allow for a production cross section of the order of ${\cal{O}} (10 {fb})$ for a wide range of sneutrino and chargino masses. Scenarios of chargino decay which lead to purely leptonic signals in the final state and without missing energy are also discussed.Comment: Unfortunate mistake in the list of authors corrected, 10 pages, 4 figure

Quantization and renormalization of the manifest left-right symmetric model of electroweak interactions

Quantization and renormalization of the left-right symmetric model is the main purpose of the paper. First the model at tree level with a Higgs sector containing one bidoublet and two triplets is precisely discussed. Then the canonical quantization and Faddeev-Popov Lagrangian are carried out ('t Hooft gauge). The BRST symmetry is discussed. Subsequently the on mass shell renormalization is performed and, as a test of consistency, the renormalization of the ZNiNj vertex is analyzed.Comment: 74 pages, 65 Postscript figures, submitted to Annals of Physic

Pion Pair Production with Higher Order Radiative Corrections in Low Energy e+e- Collisions

The complete one-loop QED initial state, final state and initial--final state interference corrections to the process e+e- -> pi+pi- are presented. Analytic formulae are given for the virtual and for the real photon corrections. The total cross section, the pion angular distribution and the pi+pi- invariant mass distribution are investigated in the regime of experimentally realistic kinematical cuts. It is shown that in addition to the full one-loop corrections also two-loop initial state corrections and even the resummation of higher order soft photon logarithms can be necessary if at least per cent accuracy is required. For the data analysis we focus on an inclusive treatment of all photons. The theoretical error concerning our treatment of radiative corrections is then estimated to be less than 2 per mille for both the measurement of the total cross section and the pi+pi- invariant mass distribution. In addition we discuss the model uncertainty due to the pion substructure. Altogether the precision of the theoretical prediction matches the requirements of low energy e+e- experiments like the ones going on at DAFNE or VEPP-2M.Comment: 16 pages 9 figures 7 tables; 6 figs added+text; modified Eqs.(56,68), enhanced appendice