Searcharxiv⌕ Search

arXiv subjects

Goran Senjanovic

Publications and source records attributed to Goran Senjanovic.

At least 55 records · Page 3Linked to original sources
arXiv2005

Supersymmetric Grand Unification: the quest for the theory

With the advent of neutrino masses, it has become more and more acknowledged that SO(10) is a more suitable theory than SU(5): it leads naturally to small neutrino masses via the see-saw mechanism, it has a simpler and more predictive Yukawa sector. There is however a rather strong disagreement on what the minimal consistent SO(10) theory is, i.e. what the Higgs sector is. The issue is particularly sensitive in the context of low-energy supersymmetry.

hep-ph↗
arXiv2005

Radiative seesaw and degenerate neutrinos

The radiative see-saw mechanism of Witten generates the right-handed neutrino masses in SO(10) with the spinorial 16_H Higgs field. We study here analytically the 2nd and 3rd generations for the minimal Yukawa structure containing 10_H and 120_H Higgs representations. In the approximation of small 2nd generation masses and gauge loop domination we find the following results : (1) b-tau unification, (2) natural coexistence between large theta_l and small theta_q, (3) degenerate neutrinos.

hep-ph↗
arXiv2005

See-saw and grand unification

I review the profound connection between the see-saw mechanism for neutrino masses and grand unification. This connection points naturally towards SO(10) grand unified theory. The emphasis here is on the supersymmetric theory, but I also discuss salient features of its split supersymmetry version and ordinary non-supersymmetric SO(10). Particular attention is paid to the crucial issue of the minimal such theory, i.e. the question of the Higgs sector needed to break SO(10) down to the Minimal Supersymmetric Standard Model or the Standard Model. Some essential features of the see-saw mechanism are clarified, in particular its precise origin at the high scale.

hep-ph↗
arXiv2004

Radiative seesaw: a case for split supersymmetry

We revive Witten's mechanism for the radiative seesaw induced neutrino masses in SO(10) grand unified theory. We propose its extension to charged fermion masses as a possible cure for wrong tree level mass relations. We offer two simple realizations that can produce a realistic fermionic spectrum. The first one requires two 10 dimensional Higgses in the Yukawa sector and utilizes radiative effects for charged fermion masses. The second one trades one 10 for a 120 dimensional Higgs and leads to the SO(10) theory with less parameters in the Yukawa sector. The mechanism works only if supersymmetry is broken at the GUT scale while gauginos and higgsinos remain at TeV. This provides a strong rationale for the so called split supersymmetry.

hep-ph↗
arXiv2004

Probing the nature of the seesaw in renormalizable SO(10)

We study the nature of the see-saw mechanism in the context of renormalizable SO(10) with Higgs fields in the 10-plets and 126-plet representations, paying special attention to the supersymmetric case. We discuss analytically the situation for the second and third generations of fermions ignoring any CP violating phase. It is shown that b-tau unification and large atmospheric mixing angle strongly disfavor the dominance of the type I see-saw.

hep-ph↗
arXiv2003

Consequences of Triplet Seesaw for Leptogenesis

We present the various leptogenesis scenarios which may occur if, in addition to the ordinary heavy right-handed neutrinos, there exists a heavy scalar SU(2)_L triplet coupled to leptons. We show that the contributions of the right-handed neutrinos and the triplet to the lepton asymmetry are proportional to their respective contributions to the neutrino mass matrix. A consequence of the triplet contribution to the lepton asymmetry is that there is no more upper bound on the neutrino masses from leptogenesis due to the fact that the neutrino mass constraints do not necessarily induce asymmetry washout effects. We also show how such a triplet leptogenesis mechanism may emerge naturally in the framework of the left-right symmetric theories, such as Pati-Salam or SO(10).

hep-ph↗
arXiv2003

The minimal supersymmetric grand unified theory

We show that the minimal renormalizable supersymmetric SO(10) GUT with the usual three generations of spinors has a Higgs sector consisting only of a "light" 10-dimensional and "heavy" 126, 126-bar and 210 supermultiplets. The theory has only two sets of Yukawa couplings with fifteen real parameters and ten real parameters in the Higgs superpotential. It accounts correctly for all the fermion masses and mixings. The theory predicts at low energies the MSSM with exact R-parity. It is arguably the minimal consistent supersymmetric grand unified theory.

hep-ph↗
arXiv2003

Proton decay and fermion masses in supersymmetric grand unified theories

We briefly review the issues of proton decay and fermion masses and mixings in minimal supersymmetric grand unified theories. We argue that minimal SU(5), although tightly constrained by proton decay data, is still not ruled out. However, we outline the advantages of SO(10) unification, in particular in the model with renormalizable see-saw mechanism and its remarkable predictions of (a) exact R-parity at low energies, (b) large atmospheric neutrino angle as a consequence of b-tau unification and (c) 1-3 leptonic mixing angle close to its upper limit.

hep-ph↗
arXiv2003

Minimal Supersymmetric Pati-Salam Theory: Determination of Physical Scales

We systematically study the minimal supersymmetric Pati-Salam theory, paying special attention to the unification constraints. We find that the SU(4)_c scale M_c and the Left-Right scale M_R lie in the range 10^{10} GeV < M_c < 10^{14} GeV, 10^{3} GeV < M_R <10^{10} GeV (with single-step breaking at 10^{10} GeV), giving a potentially accessible scale of parity breaking. The theory includes the possibility of having doubly-charged supermultiplets at the supersymmetry breaking scale; color octet states with mass of order M_R^2/M_c; magnetic monopoles of intermediate mass that do not conflict with cosmology, and a 'clean' (type I) form for the see-saw mechanism of neutrino mass.

hep-ph↗
arXiv2002

Proton Decay in Minimal Supersymmetric SU(5)

We systematically study proton decay in the minimal supersymmetric SU(5) grand unified theory. We find that although the available parameter space of soft masses and mixings is quite constrained, the theory is still in accord with experiment.

hep-ph↗
arXiv2002

Minimal supersymmetric SU(5) theory and proton decay: where do we stand?

We review the situation regarding d=5 proton decay in the minimal supersymmetric SU(5) GUT. The minimal theory is defined as the theory with the minimal matter and Higgs content all the way up to the Planck scale; of course, this allows for the possible presence of Planck induced physics. It can be said that either higher dimensional operators must be present or/and some fine-tuning of O(1%) of the Higgs mass must be tolerated in order to save the theory.

hep-ph↗
arXiv2001

How Neutrino and Charged Fermion Masses Are Connected Within Minimal Supersymmetric SO(10)

Massive neutrinos are a generic prediction of SO(10), and models of unification cry for supersymmetry. Since we have a rather detailed information on neutrino and charged fermion masses, the real question is: how/whether it is possible to build a SO(10) supersymmetric model, that correctly incorporates fermion masses. We show that a simple construction is possible in the context of a minimal theory. We concentrate on the two heaviest generations, discuss the predictions of the model, and briefly comment on open questions.

hep-ph↗
arXiv2001

Flat directions in susy guts

It is shown that a realistic SUSY SU(6) GUT can dynamically generate the GUT scale and solve at the same time the doublet-triplet splitting problem. The cosmological implications of such a model are briefly reviewed.

hep-ph↗
arXiv2000

SO(10) theory of R-parity and neutrino mass

We study the Higgs sector of a SO(10) grand unified theory which predicts exact conservation of R-parity at all scales and incorporates the see-saw mechanism. We find possible intermediate scales and light states compatible with the constraints coming from the running of the gauge couplings. Such a pattern could lower the SO(10) breaking scale, allowing the d=6 proton decay operators to be comparable in magnitude to the d=5 ones.

hep-ph↗