227 research outputs found
Top 2014: Theory Summary
This write-up is the summary of the theoretical presentations at the Top 2014
Workshop held in Mandelieu France from September 29 to October 3, 2014.Comment: 7 page
Dark Matter from Unification of Color and Baryon Number
We analyze a recently proposed extension of the Standard Model based on the
SU(4) x SU(2)_L x U(1)_X gauge group, in which baryon number is interpreted as
the fourth color and dark matter emerges as a neutral partner of the ordinary
quarks under SU(4). We show that under well-motivated minimal flavor-violating
assumptions the particle spectrum contains a heavy dark matter candidate which
is dominantly the partner of the right-handed top quark. Assuming a standard
cosmology, the correct thermal relic density through freeze-out is obtained for
dark matter masses around 2 - 3 TeV. We examine the constraints and future
prospects for direct and indirect searches for dark matter. We also briefly
discuss the LHC phenomenology, which is rich in top quark signatures, and
investigate the prospects for discovery at a 100 TeV hadron collider.Comment: 6 pages, 5 figure
A Fat Higgs with a Fat Top
A new variant of the supersymmetric Fat Higgs model is presented in which the
MSSM Higgses as well as the top quark are composite. The underlying theory is
an s-confining SU(3) gauge theory with the MSSM gauge groups realized as gauged
sub-groups of the chiral flavor symmetries. This motivates the large Yukawas
necessary for the large top mass and SM-like Higgs of mass>>M_Z in a natural
way as the residual of the strong dynamics responsible for the composites. This
removes fine-tuning associated with these couplings present in the original Fat
Higgs and New Fat Higgs models, respectively.Comment: 17 pages, 4 figures, Latex2e, uses JHEP3.cls and youngtab.sty, new
references adde
Sensitivity of a Future High Energy Collider to Bosons
We consider the capability of a future high energy collider to
search for the bosons associated with a gauge
extension of the Standard Model. Even for masses well above the
center of mass energy of the collider, the rates of production of ,
, unflavored jets, and -tagged jets can reveal the presence of
virtual exchange. We consider collider configurations with
center-of-mass energy 200, 300, and 500 GeV, and show how various classes of
model-lines can be probed with of integrated
luminosity. We find that for order one couplings, masses on the
order of several TeV can be discovered, depending on the collider energy. Our
results suggest that a 200 GeV collision energy is unlikely to discover any of
the models we consider that would not have already been visible in
late stages of LHC running, but could still help refine understanding of the
couplings and distinguish between different models. For collision
energies of 300 GeV, parameter space beyond the reach of the LHC becomes
accessible
Extended MSSM Neutralinos as the Source of the PAMELA Positron Excess
We consider a scenario within the Minimal Supersymmetric Standard Model
extended by a singlet chiral superfield, in which neutralino dark matter
annihilates to light singlet-like Higgs bosons, which proceed to decay to
either electron-positron or muon-antimuon pairs. Unlike neutralino
annihilations in the MSSM, this model can provide a good fit to the PAMELA
cosmic ray positron fraction excess. Furthermore, the singlet-like scalar Higgs
can induce a large Sommerfeld enhancement and provide an annihilation rate
sufficient to accommodate the observed positron excess
A High Quality Composite Axion
The strong CP problem is a compelling motivation for physics beyond the
Standard Model. The most popular solutions invoke a global Peccei-Quinn
symmetry, but are challenged by quantum gravitational corrections which are
thought to be incompatible with global symmetries, arguing that realistic
theories contain additional structure. We explore a construction in which the
Peccei-Quinn symmetry is protected to arbitrary order by virtue of a
supersymmetric, confining
product gauge group, achieving for an model
with GeV. This construction leads to low energy
predictions such as a gauge symmetry, and for engineers a
naturally order ~TeV value for the parameter of the MSSM.Comment: 17 pages, 2 figures, 3 table
Top Spin and Experimental Tests
We examine pair mass dependence near threshold as a means to measure the spin
of the top quark in hadron collisions, and we discuss the possibility that a
top squark signal could be hidden among the top events.Comment: 9 pages, RevTeX, 3 figures. Contribution to the Thinkshop on
Top-Quark Physics for the Tevatron Run II, Fermilab, October 16 - 18, 199
Triplet-Quadruplet Dark Matter
We explore a dark matter model extending the standard model particle content
by one fermionic triplet and two fermionic quadruplets,
leading to a minimal realistic UV-complete model of electroweakly interacting
dark matter which interacts with the Higgs doublet at tree level via two kinds
of Yukawa couplings. After electroweak symmetry-breaking, the physical spectrum
of the dark sector consists of three Majorana fermions, three singly charged
fermions, and one doubly charged fermion, with the lightest neutral fermion
serving as a dark matter candidate. A typical spectrum exhibits a
large degree of degeneracy in mass between the neutral and charged fermions,
and we examine the one-loop corrections to the mass differences to ensure that
the lightest particle is neutral. We identify regions of parameter space for
which the dark matter abundance is saturated for a standard cosmology,
including coannihilation channels, and find that this is typically achieved for
. Constraints from precision electroweak
measurements, searches for dark matter scattering with nuclei, and dark matter
annihilation are important, but leave open a viable range for a thermal relic.Comment: 27 pages, 6 figures. v2: minor revisions to match published versio
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