Higgs Bosons as Probes of Nonminimal Supersymmetric Models
May 18, 2017126 pages
Supervisor:
Thesis: PhD - Katri Huitu()
- Helsinki U.
- Published: May 18, 2017
URN/HDL:
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Abstract: (submitter)
The experiments at the Large Hadron Collider (LHC) have confirmed that the
Standard Model (SM) is a good description of particle physics at the electroweak
scale. The Standard Model is still incomplete, since it does not explain e.g.
neutrino masses, dark matter, dark energy or gravity.
Supersymmetry is a well motivated way to extend the Standard Model. The
minimal supersymmetric Standard Model (MSSM) has become somewhat finetuned
after the first run of the LHC and therefore the detailed study of nonminimal
supersymmetric models is highly motivated.
We studied phenomenological implications of some nonminimal supersymmetric
models especially in the light of the recent discovery of a Higgs boson.
Our studies focused on supersymmetry without R-parity and left-right symmetric
supersymmetric models.
In the MSSM a 125 GeV Higgs requires rather heavy superpartners. In
nonminimal models the Higgs mass can be lifted by contributions from new
particles at tree-level, loop-level or by mixing effects. We found that if we
introduce spontaneous R-parity violation, the mixing between the SM-like Higgs
and a right-handed sneutrino can increase the mass of the SM-like Higgs if
the sneutrino-like state is lighter than 125 GeV. One does not need as heavy
superpartners as in the MSSM and thus fine-tuning is not as severe.
If the Higgs mass gets additional contributions, the squarks of the third
generation can be more easily within the reach of the LHC. If R-parity is not
imposed, the squarks can have new decay modes, which can have a large branching
fraction. As an example we studied a model, where R-charges are identified
with the lepton number and found that the discovery potential for the t˜→ be+
mode is well beyond 1 TeV squark masses.
In left-right supersymmetry we studied the Higgs decay modes and the option
of having a right-handed sneutrino as a dark matter candidate. We found
that a loop-induced mixing of the bidoublets can either enhance or suppress the
Higgs coupling to bottom quarks and thus change the signal strengths considerably.
However, in the scan there was also a large number of points, where the
couplings behaved close to those of the SM.
The right-handed sneutrino is a part of a doublet in left-right symmetric
models. We found that sneutrinos may annihilate via a D-term coupling to the
Higgs and produce the observed relic density. If we assume the gauge coupling of
the right-handed gauge interactions to be the same as for the left-handed ones,
we were able to predict a range of masses for the sneutrino. We also showed
that with 100 fb−1 we could get a signal of superpartners from the sleptonic
decays of the right-handed WR-boson, if its mass is below 3 TeV.- sneutrino: right-handed
- Higgs particle: mass
- sparticle: heavy
- coupling: Higgs
- model: nonminimal
- squark: mass
- neutrino: mass
- coupling: gauge
- R parity: violation
- scale: electroweak interaction
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