743 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
Massive Feynman integrals and electroweak corrections
There are steady advances in the calculation of electroweak corrections to
massive scattering problems at colliders, from the very beginning in the
nineteen seventies until contemporary developments. Recent years brought a
remarkable progress due to new calculational technologies. This was motivated
by demands from phenomenological applications at particle accelerators: higher
multiplicities of the final states, extreme kinematics, need of higher
precision and thus of higher orders in perturbation theory. We describe
selected contributions from the project "Massive particle production" of
Sonderforschungsbereich/Transregio 9 of Deutsche Forschungsgemeinschaft.Comment: Material presented at the final Workshop of Sonderforschungsbereich
Transregio 9 "Advances in Computational Physics" of Deutsche
Forschungsgemeinschaft (DFG), 15-19 Sep 2014, Durbach, Germany, to appear in
the proceedings, 16 pages, 16 figures, 3 tables; references added in v
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
Analytical two-loop soft mass terms of sfermions in Extended GMSB models
Analytical two-loop contributions to soft masses of sfermions are derived in
the Extended GMSB (EGMSB) model with one superpotential coupling between matter
and messenger superfields. Analytical results allows to study in detail the
whole range of the ratio of the spurion -term, , to the messenger
scale . It is shown that if is of the order of , then one- and
two-loop contributions to soft masses are of the same magnitude and their
interplay leads to novel sfermion mass patterns.Comment: 8 pages, 5 figures. v2: typos corrected, figures added, discussion in
the Sec. 5 extende
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
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