Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userIntermediate Scale Dependence of Non-Universal Gaugino Masses in Supersymmetric SO(10)
232
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We calculate the dependence on intermediate scale of the gaugino mass ratios upon breaking of SO(10) into the SM via an intermediate group $H$. We see that the ratios change significantly when the intermediate scale is low (say, $10^8$ GeV or 1 Tev) compared to the case when the two breakings occur at the same scale.
rate research
Read More
We discuss the possibility of unifying in a simple and economical manner the Yukawa couplings of third generation fermions in a non-supersymmetric SO(10) model with an intermediate symmetry breaking, focusing on two possible patterns with intermediate Pati-Salam and minimal left-right groups. For this purpose, we start with a two Higgs doublet model at the electroweak scale and assume a minimal Yukawa sector at the high energy scales. We first enforce gauge coupling unification at the two-loop level by including the threshold corrections in the renormalisation group running which are generated by the heavy fields that appear at the intermediate symmetry breaking scale. We then study the running of the Yukawa couplings of the top quark, bottom quark and tau lepton at two-loops in these two breaking schemes, when the appropriate matching conditions are imposed. We find that the unification of the third family Yukawa couplings can be achieved while retaining a viable spectrum, provided that the ratio of the vacuum expectation values of the two Higgs doublet fields is large, $tanbeta approx 60$.
We demonstrate that natural supersymmetry is readily realized in the framework of SU(4)_c times SU(2)_L times SU(2)_R with non-universal gaugino masses. Focusing on ameliorating the little hierarchy problem, we explore the parameter space of this model which yields small fine-tuning measuring parameters (natural supersymmetry) at the electroweak scale (Delta_{EW}) as well as at high scale (Delta_{HS}). It is possible to have both Delta_{EW} and Delta_{HS} less than 100 in these models, (2 % or better fine-tuning), while keeping the light CP-even (Standard Model-like) Higgs mass in the 123 GeV-127 GeV range. The light stop quark mass lies in the range 700 GeV <m_{tilde{t}_{1}}< 1500 GeV, and the range for the light stau lepton mass is 900 GeV <m_{tilde{tau}_{1}}< 1300 GeV. The first two family squarks are in the mass range 3000 GeV <m_{tilde{t}_{1}}< 4500 GeV, and for the gluino we find 2500 GeV <m_{tilde{g}_{1}}< 3500 GeV. We do not find any solution with natural supersymmetry which yields significant enhancement for Higgs production and decay in the diphoton channel.
We study the supersymmetric spontaneous symmetry breaking of SO(10) into SU(3)xSU(2)xU(1) for the most physically interesting cases of SU(5) or flipped SU(5)xU(1) intermediate symmetries. The first case is more easily realized while the second one requires a fine-tuning condition on the parameters of the superpotential. This is because in the case of SU(5) symmetry there is at most one singlet of the residual symmetry in each SO(10) irreducible representation. We also point out on more general grounds in supersymmetric GUTs that some intermediate symmetries can be exactly realized and others can only be approximated by fine-tuning. In the first category, there could occur some tunneling between the vacua with exact and approximate intermediate symmetry. The flipped SU(5)xU(1) symmetry improves the unification of gauge couplings if (B-L) is broken by (B-L)=1 scalars yielding right handed neutrino masses below 10^{14} GeV}.
Despite the successes of the Standard Model of particle physics, it is known to suffer from a number of deficiencies. Several of these can be addressed within non-supersymmetric theories of grand unification based on $mathrm{SO}(10)$. However, achieving gauge coupling unification in such theories is known to require additional physics below the unification scale, such as symmetry breaking in multiple steps. Many such models are disfavored due to bounds on the proton lifetime. Corrections arising from threshold effects can, however, modify these conclusions. We analyze all seven relevant breaking chains with one intermediate symmetry breaking scale, assuming the survival hypothesis for the scalar masses. Two are allowed by proton lifetime and two are disfavored by a failure to unify the gauge couplings. The remaining three unify at a too low scale, but can be salvaged by various amounts of threshold corrections. We parametrize this and thereby rank the models by the size of the threshold corrections required to save them.
Assuming a Zee-like matrix for the right-handed neutrino Majorana masses in the see-saw mechanism, one gets maximal mixing for vacuum solar oscillations, a very small value for $U_{e3}$ and an approximate degeneracy for the two lower neutrino masses. The scale of right-handed neutrino Majorana masses is in good agreement with the value expected in a SO(10) model with Pati-Salam $SU(4)ts SU(2)ts SU(2)$ intermediate symmetry.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
