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Register a new userProton Lifetime in Minimal SUSY SU(5) in Light of LHC Results
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We examine proton decay mediated by color-triplet Higgsinos in minimal supersymmetric $SU(5)$ grand unified theory in light of the discovery of the Higgs boson and the absence of SUSY signals at the LHC. We pay special attention to various threshold effects arising from Planck-suppressed operators that affect the color-triplet Higgsino mass and also correct the wrong mass relations for the light fermions. Our analysis allows for a non-universal SUSY spectrum with the third family scalars having a separate mass compared to the first two families. We identify the allowed parameter space of the model and show that the SUSY scalar masses are constrained by current limits from proton lifetime to be above 5 TeV, while the glunio, Wino and the Higgsinos may be within reach of the LHC. When the SUSY scalar masses are required to be $leq 20$ TeV, so that they are within reach of next generation collider experiments, we find that proton lifetime for the decay $p rightarrow overline{ u} K^+$ is bounded by $tau(p rightarrow overline{ u} K^+) leq 1.1 times 10^{35}$ yrs.
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We study the influence of messenger Yukawa couplings and top, bottom and $tau$ Yukawa couplings on the proton lifetime in SU(5) Supersymmetric GUT with dynamical supersymmetry breaking mechanism due to Dine and Nelson.
We study CP-conserving non-minimal flavour violation in $A_4 times SU(5)$ inspired Supersymmetric Grand Unified Theories (GUTs), focussing on the regions of parameter space where dark matter is successfully accommodated due to a light right-handed smuon a few GeV heavier than the lightest neutralino. We find that it is necessary to scan over all NMFV parameters simultaneously in order to properly constrain the space of the model.
The SU(5) GUT model extended with fermions in the adjoint $24_F$ representation predicts triplet fermions in the 100 GeV mass range, opening up the possibility of testing seesaw at LHC. However, once the model is supersymmerized, the triplet fermion mass is constrained to be close to the GUT scale for the gauge couplings to unify. We propose an extension of the SUSY SU(5) model where type II seesaw can be tested at LHC. In this model we add a matter chiral field in the adjoint $hat{24}_F$ representation and Higgs chiral superfields in the symmetric $hat{15}_H$ and $hat{bar{15}}_H$ representations. We call this the symmetric adjoint SUSY SU(5) model. The triplet scalar and triplet fermion masses in this model are predicted to be in the 100 GeV and $10^{13}$ GeV range respectively, while the mass of the singlet fermion remains unconstrained. This gives a type I plus type II plus type III seesaw mass term for the neutrinos. The triplet scalars with masses $sim 100$ GeV range can be produced at the LHC. We briefly discuss the collider phenomenology and predictions for proton decay in this model.
We propose an extension of the SUSY SU(5) which predicts LHC testable type-III seesaw. The supersymmetric SU(5) GUT model is extended by adding a 24-plet matter superfield along with a pair of $10_H$-plet and $bar{10}_H$-plet Higgs superfields. The 24-plet carries a triplet and a singlet fermion multiplet of SU(2)$_L$, which leads to type I+III seesaw. The additional $10_H$ (and $bar{10}_H$) multiplets help in achieving gauge coupling unification while keeping the triplet fermion mass in the TeV range, making them accessible at LHC. We study the phenomenology of this model in detail. Large lepton flavor violation predicted in this model puts severe constraints on the Yukawa couplings of the triplet fermion. We show that this smothers the possibility of observing the contribution of the heavy fermions in neutrinoless double beta decay experiments. The presence of the additional $10_H$ and $bar{10}_H$ in this model not only gives gauge coupling unification, it also leads to very large lepton flavor violation.
We study CP-conserving non-minimal flavour violation in $A_4 times SU(5)$ inspired Supersymmetric Grand Unified Theories (GUTs), focussing on the regions of parameter space where dark matter is successfully accommodated due to a light right-handed smuon a few GeV heavier than the lightest neutralino. In this region of parameter space we find that some of the flavour-violating parameters are constrained by the requirement of the dark matter relic density, due to the delicate interplay between the smuon and neutralino masses. By scanning over GUT scale flavour violating parameters, constrained by low-energy quark and lepton flavour violating observables, we find a striking difference in the results in which individual parameters are varied to those where multiple parameters are varied simultaneously, where the latter relaxes the constraints on flavour violating parameters due to cancellations and/or correlations. Since charged lepton-flavour violation provides the strongest constraints within a GUT framework, due to relations between quark and lepton flavour violation, we examine in detail a prominent correlation between some of the flavour violating parameters at the GUT scale consistent with the stringent lepton flavour violating process $mu rightarrow e gamma$. We also examine the relation between GUT scale and low scale flavour violating parameters, for both quarks and leptons, and show how the usual expectations may be violated due to the correlations when multiple parameters are varied simultaneously.
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