9 research outputs found
Low Scale Left-Right Symmetry and Warm Dark Matter
We study the scenario of dark matter in the minimal left-right symmetric
theory at the TeV scale. The only viable candidate is found to be the lightest
right-handed neutrino with a mass of keV. To satisfy the dark matter relic
abundance, the relic yield is diluted by late decays of the two heavier
neutrinos. We point out that the QCD phase transition temperature coincidences
with the typical freeze-out temperature governed by right-handed interactions,
which helps to alleviate the problem of overproduction. A careful numerical
study reveals a narrow window for the mass of the right-handed gauge boson,
within the reach of the LHC.Comment: Article in proceedings of the CETUP* 2012 workshop in Lead, South
Dakota; 10 pages, 5 figures, v2: references adde
Lepton flavor violation in type I + III seesaw
In the presence of a low scale seesaw of type I + III, flavor violating
effects in the leptonic sector are expected. Their presence in the charged
sector is due to the mixing of the fermionic vector-like weak triplets with the
chiral doublets, which cause non-universality of the tree-level Z coupling. We
investigate the bounds on the Yukawa couplings which are responsible for the
mixing and present the results for two minimal cases, a fermionic triplet with
a singlet or two fermionic triplets. Different channels for these processes are
considered and their current and future potential to probe these couplings is
discussed.Comment: 20 pages, 2 figures; corrected misprints, conclusions unchange
Minimal SO(10) splits supersymmetry
A good fit of the fermion masses and mixings has been found in the minimal
renormalizable supersymmetric SO(10). This solution needs a strongly split
supersymmetry breaking scenario with gauginos and higgsinos around 100 TeV,
sfermions close to 10^14 GeV and a low GUT scale of around 6 10^15 GeV. We
predict fast proton decays through SO(10) type of d=6 operators and the
leptonic mixing angle theta_13 approximately 0.1.Comment: 26 pages, 3 figure
Neutrino Mass and the LHC
We discuss the possibility of probing physics behind the generation of neutrino mass and its observability at the LHC. We focus on TeV scale tree-level see-saw mechanisms and their natural origin from the minimal left-right symmetric model or grand unified theories, such as the minimal SU(5). The fundamental aspect related to the Majorana nature of neutrinos is the breaking of lepton number, which can manifest itself at high energies via same-sign leptons and jets. Final states differ for different see-saw mediators and data from the LHC provide significantly improved or novel bounds on all three tree-level realisations. Simultaneously, searches for lepton number (and flavour) violation at low energies provide complementary information to colliders
Inert Doublet Dark Matter and Mirror/Extra Families after Xenon100
It was shown recently that mirror fermions, naturally present in a number of
directions for new physics, seem to require an inert scalar doublet in order to
pass the electroweak precision tests. This provides a further motivation for
considering the inert doublet as a dark matter candidate. Moreover, the
presence of extra families enhances the Standard Model Higgs-nucleon coupling,
which has crucial impact on the Higgs and dark matter searches. We study the
limits on the inert dark matter mass in view of recent Xenon100 data. We find
that the mass of the inert dark matter must lie in a very narrow window 74-76
GeV while the Higgs must weigh more than 400 GeV. For the sake of completeness
we discuss the cases with fewer extra families, where the possibility of a
light Higgs boson opens up, enlarging the dark matter mass window to m_h/2-76
GeV. We find that Xenon100 constrains the DM-Higgs interaction, which in turn
implies a lower bound on the monochromatic gamma-ray flux from DM annihilation
in the galactic halo. For the mirror case, the predicted annihilation cross
section lies a factor of 4-5 below the current limit set by Fermi LAT, thus
providing a promising indirect detection signal.Comment: 10 pages, 7 figures; reference adde
Left-Right Symmetry at LHC
We revisit the issue of the limit on the scale of Left-Right symmetry breaking. We focus on the minimal SU(2)_L x SU(2)_R x U(1)_B-L gauge theory with the seesaw mechanism and discuss the two possibilities of defining Left-Right symmetry as parity or charge conjugation. In the commonly adopted case of parity, we perform a complete numerical study of the quark mass matrices and the associated left and right mixing matrices without any assumptions usually made in the literature about the ratio of vacuum expectation values. We find that the usual lower limit on the mass of the right-handed gauge boson from the K mass difference, M_WR>2.5TeV, is subject to a possible small reduction due to the difference between right and left Cabibbo angles. In the case of charge conjugation the limit on M_WR is somewhat more robust. However, the more severe bounds from CP-violating observables are absent in this case. In fact, the free phases can also resolve the present mild discrepancy between the Standard Model and CP-violation in the -sector. Thus, even in the minimal case, both charged and neutral gauge bosons may be accessible at the Large Hadron Collider with spectacular signatures of lepton number violation