arXiv subjects

D. V. Gioutsos

Publications and source records attributed to D. V. Gioutsos.

5 recordsLinked to original sources

arXiv2006

D-brane Standard Model variants and Split Supersymmetry: Unification and fermion mass predictions

We study D-brane inspired models with U(3) x U(2) x U(1)^N gauge symmetry in the context of split supersymmetry. We consider configurations with one, two and three (N=1,2,3) abelian branes and derive all hypercharge embeddings which imply a realistic particle content. Then, we analyze the implications of split supersymmetry on the magnitude of the string scale, the gauge coupling evolution, the third family fermion mass relations and the gaugino masses. We consider gauge coupling relations which may arise in parallel as well as intersecting brane scenarios and classify the various models according to their predictions for the magnitude of the string scale and the low energy implications. In the parallel brane scenario where the U(1) branes are superposed to U(2) or U(3) brane stacks, varying the split susy scale in a wide range, we find three distinct cases of models predicting a high, intermediate and low string scale, M_S ~ 10^{16} GeV, M_S ~ 10^7 GeV and M_S ~ 10^4 GeV respectively. We further find that in the intermediate string scale model the low energy ratio m_b / m_τis compatible with b-τYukawa unification at the string scale. Furthermore, we perform a similar analysis for arbitrary abelian gauge coupling relations at M_S corresponding to possible intersecting brane models. We find cases which predict a string scale of the order M_S \ge 10^{14} GeV that accommodate a right-handed neutrino mass of the same order so that a see-saw type light left-handed neutrino component is obtained in the sub-eV range as required by experimental and cosmological data. Finally, a short discussion is devoted for the gaugino masses and the life-time of the gluino.

hep-ph↗

arXiv2006

Unification and fermion mass relations in low string scale D-brane models

In this talk, gauge coupling evolution is analyzed in D-brane inspired models with two Higgs doublets and a U(3)xU(2)xU(1)^N gauge symmetry. In particular, we focus on D-brane configurations with two or three abelian factors. We find that the correct hypercharge assignment of the Standard Model particles is reproduced for six viable models distinguished by different brane configurations. We also investigate the bottom tau quark mass relation and find that the correct low energy m_b / m_τratio is obtained for equal b-τYukawa couplings at a string scale around 10^3 TeV.

hep-ph↗

arXiv2005

Gauge coupling and fermion mass relations in low string scale brane models

We analyze the gauge coupling evolution in brane inspired models with $U(3) \times U(2) \times U(1)^N$ symmetry at the string scale. We restrict to the case of brane configurations with two and three abelian factors (N=2,3) and where only one Higgs doublet is coupled to down quarks and leptons and only one to the up quarks. We find that the correct hypercharge assignment of the Standard Model particles is reproduced for six viable models distinguished by different brane configurations. We investigate the third generation fermion mass relations and find that the correct low energy $m_b/m_τ$ ratio can be obtained for $b-τ$ Yukawa coupling equality at a string scale as low as $M_S \sim 10^3$ TeV.

hep-ph↗

arXiv2003

On Nonstandard Vacuua in Minimal Supergravity Models

The plethora of scalar fields participating in the formulation of a softly broken supersymmetric theory can threat the stability of the standard vacuum. The generic situation is twofold. Directions in scalar field space may exist along which the potential becomes unbounded from below or local minima deeper than the standard one are likely to appear where charge and/or color symmetries are broken. An investigation of these matters requires a thorough study of the tree level effective potential as well as its radiative corrections. However, the presence of many different mass scales in such a generic supersymmetric theory needs an appropriate renormalization improved treatment. Combining the decoupling theorem with a conveniently chosen renormalization scale for each field configuration, the well known multimass scale problem is circumvented. In this context, the ordinary universal soft-parameters case of the minimal supersymmetric model as well as a non-universal case of a brane world minimal supergravity model are examined closely for unphysical vacuua.

hep-ph↗

arXiv1999

An efficient renormalization group improved implementation of the MSSM effective potential

In the context of MSSM, a novel improving procedure based on the renormalization group equation is applied to the effective potential in the Higgs sector. We focus on the one-loop radiative corrections computed in Landau gauge by using the mass independent renormalization scheme $\bar{DR}$. Thanks to the decoupling theorem, the well-known multimass scale problem is circumvented by switching to a new effective field theory every time a new particle threshold is encountered. We find that, for any field configuration, there is a convenient renormalization scale $\tilde{Q}^*$ at which the loop expansion respects the perturbation series hierarchy and the theory retains the vital property of stability.

hep-ph↗