10,733 research outputs found
Yukawa Unification and the Superpartner Mass Scale
Naturalness in supersymmetry (SUSY) is under siege by increasingly stringent
LHC constraints, but natural electroweak symmetry breaking still remains the
most powerful motivation for superpartner masses within experimental reach. If
naturalness is the wrong criterion then what determines the mass scale of the
superpartners? We motivate supersymmetry by (1) gauge coupling unification, (2)
dark matter, and (3) precision b-tau Yukawa unification. We show that for an
LSP that is a bino-Higgsino admixture, these three requirements lead to an
upper-bound on the stop and sbottom masses in the several TeV regime because
the threshold correction to the bottom mass at the superpartner scale is
required to have a particular size. For tan beta about 50, which is needed for
t-b-tau unification, the stops must be lighter than 2.8 TeV when A_t has the
opposite sign of the gluino mass, as is favored by renormalization group
scaling. For lower values of tan beta, the top and bottom squarks must be even
lighter. Yukawa unification plus dark matter implies that superpartners are
likely in reach of the LHC, after the upgrade to 14 (or 13) TeV, independent of
any considerations of naturalness. We present a model-independent, bottom-up
analysis of the SUSY parameter space that is simultaneously consistent with
Yukawa unification and the hint for m_h = 125 GeV. We study the flavor and dark
matter phenomenology that accompanies this Yukawa unification. A large portion
of the parameter space predicts that the branching fraction for B_s to mu^+
mu^- will be observed to be significantly lower than the SM value.Comment: 34 pages plus appendices, 20 figure
Towards the minimal renormalizable supersymmetric model
We find an explicit renormalizable supersymmetric model with all the
ingredients for being realistic. It consists of the Higgs sector
, which breaks directly to the
Standard Model gauge group. Three copies of dimensional representations
then describe the matter sector, while an extra pair is
needed to successfully split the Standard Model Higgs doublet from the heavy
Higgs triplet. We perform the analysis of the vacuum structure and the Yukawa
sector of this model, as well as compute contributions to proton decay. Also,
we show why some other simpler models fail to be realistic at the
renormalizable level.Comment: 36 pages, a new section on proton decay added, new reference, results
unchanged. To be published in JHE
A Little Solution to the Little Hierarchy Problem: A Vector-like Generation
We present a simple solution to the little hierarchy problem in the MSSM: a
vector-like fourth generation. With O(1) Yukawa couplings for the new quarks,
the Higgs mass can naturally be above 114 GeV. Unlike a chiral fourth
generation, a vector-like generation can solve the little hierarchy problem
while remaining consistent with precision electroweak and direct production
constraints, and maintaining the success of the grand unified framework. The
new quarks are predicted to lie between ~ 300 - 600 GeV and will thus be
discovered or ruled out at the LHC. This scenario suggests exploration of
several novel collider signatures.Comment: 19 pages, 3 figures. v2: Section 3 modified, version to appear in
PRD
Unification of gauge and Yukawa couplings
The unification of gauge and top Yukawa couplings is an attractive feature of
gauge-Higgs unification models in extra-dimensions. This feature is usually
considered difficult to obtain based on simple group theory analyses. We
reconsider a minimal toy model including the renormalisation group running at
one loop. Our results show that the gauge couplings unify asymptotically at
high energies, and that this may result from the presence of an UV fixed point.
The Yukawa coupling in our toy model is enhanced at low energies, showing that
a genuine unification of gauge and Yukawa couplings may be achieved.Comment: 5 pages, 2 figure; new results, extended discussion, conclusions
unchange
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