45,056 research outputs found
Atmospheric and Solar Neutrinos with a Heavy Singlet
We follow a minimalistic approach to neutrino masses, by introducing a single
heavy singlet into the standard model (or supersymmetric standard model)
with a heavy Majorana mass , which couples as a single right-handed neutrino
in a Dirac fashion to leptons, and induces a single light see-saw mass
, leaving two neutrinos massless. This trivial
extension to the standard model may account for the atomospheric neutrino data
via oscillations with near maximal mixing angle
and . In order to account for the solar neutrino data the model is extended to
SUSY GUT/ string-inspired type models which can naturally yield an additional
light tau neutrino mass leading to
oscillations with and a mixing angle in the correct range for the small angle MSW
solution to the solar neutrino problem. The model predicts oscillations with a
similar angle but a larger splitting .Comment: 10 pages, Latex. Expanded discussion of mixing angles mainly in an
Appendi
Flavour from the Planck scale to the electroweak scale
We discuss a theory of flavour in which Higgs Yukawa couplings are related to
those of the new scalar triplet leptoquark and/or responsible for
, with all couplings arising effectively from mixing with a
vector-like fourth family, whose mass may be anywhere from the Planck scale to
the electroweak scale for the leptoquarks explanation, but is pinned down to
the TeV scale if the exchange plays a role. However, in this particular
model, only leptoquark exchange can contribute significantly to ,
since exchange is too constrained from mixing and , although other Higgs Yukawa matrix structures may allow it.Comment: 6 pages, 11 figures. Contribution to the 2019 EW session of the 54th
Rencontres de Morion
Minimal see-saw model predicting best fit lepton mixing angles
We discuss a minimal predictive see-saw model in which the right-handed
neutrino mainly responsible for the atmospheric neutrino mass has couplings to
(nu_e, nu_mu, nu_tau) proportional to (0,1,1) and the right-handed neutrino
mainly responsible for the solar neutrino mass has couplings to (nu_e, nu_mu,
nu_tau) proportional to (1,4,2), with a relative phase eta = -2pi/5. We show
how these patterns of couplings could arise from an A_4 family symmetry model
of leptons, together with Z_3 and Z_5 symmetries which fix eta = -2pi/5 up to a
discrete phase choice. The PMNS matrix is then completely determined by one
remaining parameter which is used to fix the neutrino mass ratio m_2/m_3. The
model predicts the lepton mixing angles theta12=34 degrees, theta23=41 degrees,
theta13=9.5 degrees, which exactly coincide with the current best fit values
for a normal neutrino mass hierarchy, together with the distinctive prediction
for the CP violating oscillation phase delta =106 degrees.Comment: 15 pages. arXiv admin note: substantial text overlap with
arXiv:1304.626
Jason L. Powell, Social Theory and Aging, Rowman and Littlefield, Lanham, Maryland, 2005, 157 pp., pbk $16.95, ISBN 0 7425 1954 6.
We construct a realistic Supersymmetric Grand Unified Theory of Flavour based on PSL(7)×SO(10), where the quarks and leptons in the 16 of SO(10) are assigned to the complex triplet representation of PSL(7), while the flavons are assigned to a combination of sextets and anti-triplets of PSL(7). Using a D-term vacuum alignment mechanism, we require the flavon sextets of PSL(7) to be aligned along the 3-3 direction leading to the third family Yukawa couplings, while the flavon anti-triplets describe the remaining Yukawa couplings. Other sextets are aligned along the neutrino flavour symmetry preserving directions leading to tri-bimaximal neutrino mixing via a type II see-saw mechanism, with predictions for neutrinoless double beta decay and cosmology. <br/
750 GeV Diphoton Resonance from Singlets in an Exceptional Supersymmetric Standard Model
The 750-760 GeV diphoton resonance may be identified as one or two scalars
and/or one or two pseudoscalars contained in the two singlet superfields
S_{1,2} arising from the three 27-dimensional representations of E_6 . The
three 27s also contain three copies of colour-triplet charge \mp 1/3
vector-like fermions D,\bar{D} and two copies of charged inert Higgsinos
\tilde{H}^{+},\tilde{H}^{-} to which the singlets S_{1,2} may couple. We
propose a variant of the E_6SSM where the third singlet S_3 breaks a gauged
U(1)_N above the TeV scale, predicting Z'_N, D,\bar{D},
\tilde{H}^{+},\tilde{H}^{-} at LHC Run 2, leaving the two lighter singlets
S_{1,2} with masses around 750 GeV. We calculate the branching ratios and
cross-sections for the two scalar and two pseudoscalar states associated with
the S_{1,2} singlets, including possible degeneracies and maximal mixing,
subject to the constraint that their couplings remain perturbative up to the
unification scale.Comment: 22 pages, 4 figures, some minor changes to the text, references adde
LHC Signatures of the Constrained Exceptional Supersymmetric Standard Model
We discuss two striking Large Hadron Collider (LHC) signatures of the
constrained version of the exceptional supersymmetric standard model (cE6SSM),
based on a universal high energy soft scalar mass m_0, soft trilinear coupling
A_0 and soft gaugino mass M_{1/2}. The first signature we discuss is that of
light exotic colour triplet charge 1/3 fermions, which we refer to as
D-fermions. We calculate the LHC production cross section of D-fermions, and
discuss their decay patterns. Secondly we discuss the E6 type U(1)_N spin-1 Z'
gauge boson and show how it may decay into exotic states, increasing its width
and modifying the line shape of the dilepton final state. We illustrate these
features using two representative cE6SSM benchmark points, including an "early
LHC discovery" point, giving the Feynman rules and numerical values for the
relevant couplings in order to facilitate further studies.Comment: 30 pages, 5 figures, corrections to figure caption
Spectrum of Higgs particles in the Exceptional Supersymmetric Standard Model
We discuss the spectrum of Higgs bosons in the framework of the exceptional
supersymmetric standard model. The presence of a and exotic particles
predicted by the exceptional SUSY model allows the lightest Higgs particle to
be significantly heavier than in the MSSM and NMSSM. When the mass of the
lightest Higgs boson is larger than the heaviest scalar,
pseudoscalar and charged Higgs states lie beyond the range.Comment: Presented at 12th Lomonosov Conference on Elementary Particle
Physics, Moscow, Russia, 25-31 August 2005, some minor changes to the text,
references adde
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