445 research outputs found
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 CMS data
We show that the excess in the CMS data can be naturally
interpreted within the Minimal Left Right Symmetric model (MLRSM), keeping , 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) to the
same-sign (SS) lepton signals is possible. Finally, a
suppression of muon pairs with respect to electron pairs in the
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
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
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