110 research outputs found
Contact Interactions Probe Effective Dark Matter Models at the LHC
Effective field theories provide a simple framework for probing possible dark
matter (DM) models by reparametrising full interactions into a reduced number
of operators with smaller dimensionality in parameter space. In many cases
these models have four particle vertices, e.g. qqXX, leading to the pair
production of dark matter particles, X, at a hadron collider from initial state
quarks, q. In this analysis we show that for many fundamental DM models with
s-channel DM couplings to qq-pairs, these effective vertices must also produce
quark contact interactions (CI) of the form qqqq. The respective effective
couplings are related by the common underlying theory which allows one to
translate the upper limits from one coupling to the other. We show that at the
LHC, the experimental limits on quark contact interactions give stronger
translated limits on the DM coupling than the experimental searches for dark
matter pair production.Comment: 6 pages, 3 figure
Froggatt-Nielsen models with a residual Z_4^R symmetry
The Froggatt-Nielsen mechanism provides an elegant explanation for the
hierarchies of fermion masses and mixings in terms of a U(1) symmetry.
Promoting such a family symmetry to an R-symmetry, we explicitly construct
supersymmetric Froggatt-Nielsen models which are gauged, family dependent
U(1)_R completions of the Z_4^R symmetry proposed by Lee, Raby, Ratz, Ross,
Schieren, Schmidt-Hoberg and Vaudrevange in 2010. Forbidden by Z_4^R, the
mu-term is generated around the supersymmetry breaking scale m_3/2 from either
the Kahler potential or the superpotential. Neutrinos acquire their mass via
the type I seesaw mechanism with three right-handed neutrino superfields.
Taking into account the Green-Schwarz anomaly cancellation conditions, we
arrive at a total of 3 x 34 distinct phenomenologically viable charge
assignments for the standard model fields, most of which feature highly
fractional charges.Comment: 19 page
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