* Astronomy

Members Login
Username 
 
Password 
    Remember Me  
Home -> Astronomy News -> Physics News -> SO(10) SUSY GUTs
Post Info TOPIC: SO(10) SUSY GUTs
Blobrana


L

Posts: 131433
Date:
RE: SO(10) SUSY GUTs
Permalink  
 

Title: The Early Universe with High-Scale Supersymmetry
Author: Sibo Zheng

The large tensor-to-scalar ratio reported by BICEP2 collaboration may lead to distinctive phenomenology of high-energy scale. Assuming the same origin of SUSY breaking between inflation and MSSM, we show model independent features in such high-scale SUSY. The simplest hybrid inflation, together with a new linear term for inflaton field which is induced by large gravitino mass, is excluded by BICEP2 data. For superpartner masses far above electroweak scale we estimate the reheating temperature TR after inflation. We find that TR might be beneath the value required by thermal leptogenesis if inflaton decays to its products perturbatively, but above it if non-perturbatively instead. Due to kinematically blocking effect the gravitino overproduction can be also evaded in high-scale SUSY.

Read more (518kb, PDF)



__________________
Blobrana


L

Posts: 131433
Date:
Permalink  
 

Title: Leptogenesis and Neutrino Masses in an Inflationary SUSY Pati-Salam Model
Authors: C. Pallis, N. Toumbas

We implement the mechanism of non-thermal leptogenesis in the framework of an inflationary model based on a supersymmetric (SUSY) Pati-Salam Grand Unified Theory (GUT). In particular, we show that inflation is driven by a quartic potential associated with the Higgs fields involved in the spontaneous GUT symmetry breaking, in the presence of a non-minimal coupling of the inflaton field to gravity. The inflationary model relies on renormalisable superpotential terms and does not lead to overproduction of magnetic monopoles. It is largely independent of one-loop radiative corrections, and it can be consistent with current observational data on the inflationary observables, with the GUT symmetry breaking scale assuming its SUSY value. Non-thermal leptogenesis is realised by the out-of-equilibrium decay of the two lightest right-handed (RH) neutrinos, which are produced by the inflaton decay. Confronting our scenario with the current observational data on light neutrinos, the GUT prediction for the heaviest Dirac neutrino mass, the baryon asymmetry of the universe and the gravitino limit on the reheating temperature, we constrain the masses of the RH neutrinos in the range (10^10-10^15) GeV and the Dirac neutrino masses of the two first generations to values between 0.1 and 20 GeV.

Read more (81kb, PDF)



__________________
Blobrana


L

Posts: 131433
Date:
SUSY
Permalink  
 

Title: Single-Scale Natural SUSY
Authors: Lisa Randall, Matthew Reece

We consider the prospects for natural SUSY models consistent with current data. Recent constraints make the standard paradigm unnatural so we consider what could be a minimal extension consistent with what we now know. The most promising such scenarios extend the MSSM with new tree-level Higgs interactions that can lift its mass to at least 125 GeV and also allow for flavour-dependent soft terms so that the third generation squarks are lighter than current bounds on the first and second generation squarks. We argue that a common feature of almost all such models is the need for a new scale near 10 TeV, such as a scale of Higgsing or confinement of a new gauge group. We consider the question whether such a model can naturally derive from a single mass scale associated with supersymmetry breaking. Most such models simply postulate new scales, leaving their proximity to the scale of MSSM soft terms a mystery. This coincidence problem may be thought of as a mild tuning, analogous to the usual mu problem. We find that a single mass scale origin is challenging, but suggest that a more natural origin for such a new dynamical scale is the gravitino mass, m_{3/2}, in theories where the MSSM soft terms are a loop factor below m_{3/2}. As an example, we build a variant of the NMSSM where the singlet S is composite, and the strong dynamics leading to compositeness is triggered by masses of order m_{3/2} for some fields. All the interesting low-energy mass scales, including linear terms for S playing a key role in EWSB, arise dynamically from the single scale m_{3/2}. However, numerical coefficients from RG effects and wavefunction factors in an extra dimension complicate the otherwise simple story.

Read more (274kb, PDF)



__________________
Blobrana


L

Posts: 131433
Date:
SU(3)^5
Permalink  
 

Title: Naturally large Yukawa hierarchies
Authors: Enrico Nardi

The spontaneous breaking of the SU(3)^5 quark/lepton flavor symmetry by means of three multiplets of scalar 'Yukawa fields' admits vacua with one O(1) and two vanishing vacuum expectation values (vevs) for each multiplet. If the number of generations is equal to three, and only in this case, the vanishing vevs are lifted to exponentially suppressed entries by the inclusion of symmetry invariant logarithmic terms. A strong hierarchy for the Yukawa couplings and a quark mixing matrix that approaches a diagonal form are obtained in a natural way from O(1) parameters. This scenario provides a concrete realization of the minimal flavor violation hypothesis.

Read more  (21kb, PDF)



__________________
Blobrana


L

Posts: 131433
Date:
Electroweak Symmetry Breaking
Permalink  
 

Title: Dark Matter and Electroweak Symmetry Breaking from SO(10)
Authors: Kristjan Kannike

We consider a minimal model of GUT scalar dark matter (DM) stabilised by the discrete gauge matter parity P_{X} that arises from breaking of SO(10). The dark sector comprises the complex singlet S and the inert doublet H_{2}. GUT scale parameters are evaluated to the electroweak scale via Renormalisation Group Equations (RGEs). Experimental and theoretical constraints limit the DM mass to the 80 GeV to 2 TeV range. The EW symmetry breaking is radiative and can occur via RGE running and 1-loop matching corrections from integrating out DM. Because the next-to-lightest scalar is almost degenerate with DM, it gives a background free displaced decay vertex at the LHC.

Read more (1336kb, PDF)

__________________
Blobrana


L

Posts: 131433
Date:
Leptogenesis
Permalink  
 

Title: Examining leptogenesis with lepton flavour violation and the dark matter abundance
Authors: Steve Blanchet, Danny Marfatia, Azar Mustafayev

Within a supersymmetric (SUSY) type-I seesaw framework with flavour-blind universal boundary conditions, we study the consequences of requiring that the observed baryon asymmetry of the Universe be explained by either thermal or non-thermal leptogenesis. In the former case, we find that the parameter space is very constrained. In the bulk and stop-coannihilation regions of mSUGRA parameter space (that are consistent with the measured dark matter abundance), lepton flavour-violating (LFV) processes are accessible at MEG and future experiments. However, the very high reheat temperature of the Universe needed after inflation (of about 10¹² GeV) leads to a severe gravitino problem, which disfavours either thermal leptogenesis or neutralino dark matter. Non-thermal leptogenesis in the preheating phase from SUSY flat directions relaxes the gravitino problem by lowering the required reheat temperature. The baryon asymmetry can then be explained while preserving neutralino dark matter, and for the bulk or stop-coannihilation regions LFV processes should be observed in current or future experiments.

Read more (772kb, PDF)

__________________
Blobrana


L

Posts: 131433
Date:
RE: SO(10) SUSY GUTs
Permalink  
 

As damp squibs go, it was quite a spectacular one. Amid great pomp and ceremony - not to mention dark offstage rumblings that the end of the world was nigh - the Large Hadron Collider (LHC), the world's mightiest particle smasher, fired up in September last year. Nine days later a short circuit and a catastrophic leak of liquid helium ignominiously shut the machine down.
Now for take two. Any day now, if all goes to plan, proton beams will start racing all the way round the ring deep beneath CERN, the LHC's home on the outskirts of Geneva, Switzerland.

Read more

__________________
Blobrana


L

Posts: 131433
Date:
Permalink  
 

Title: SO(10) SUSY GUTs, the gravitino problem, non-thermal leptogenesis and axino dark matter
Authors: Howard Baer, Heaya Summy
(Version v2)

Simple SUSY GUT models based on the gauge group SO(10) require t-b-\tau Yukawa coupling unification, in addition to gauge coupling and matter unification. The Yukawa coupling unification places strong constraints on the expected superparticle mass spectrum, with scalar masses ~ 10 TeV while gaugino masses are quite light. A problem generic to all supergravity models comes from overproduction of gravitinos in the early universe: if gravitinos are unstable, then their late decays may destroy the predictions of Big Bang nucleosynthesis. We present a Yukawa-unified SO(10) SUSY GUT scenario which avoids the gravitino problem, gives rise to the correct matter-antimatter asymmetry via non-thermal leptogenesis, and is consistent with the WMAP-measured abundance of cold dark matter due to the presence of an axino LSP. To maintain a consistent cosmology for Yukawa-unified SUSY models, we require a re-heat temperature T_R ~ 10^6-10^7 GeV, an axino mass around ~ 0.1-10 MeV, and a PQ breaking scale f_a ~ 10^{12} GeV.

Read more (18kb, PDF)

__________________
Blobrana


L

Posts: 131433
Date:
Permalink  
 

Title: SO(10) SUSY GUTs, the gravitino problem, non-thermal leptogenesis and axino dark matter
Authors: Howard Baer, Heaya Summy

Simple SUSY GUT models based on the gauge group SO(10) require t-b-\tau Yukawa coupling unification, in addition to gauge coupling and matter unification. The Yukawa coupling unification places strong constraints on the expected superparticle mass spectrum, with scalar masses ~ 10 TeV while gaugino masses are quite light. A problem generic to all supergravity models comes from overproduction of gravitinos in the early universe: if gravitinos are unstable, then their late decays may destroy the predictions of Big Bang nucleosynthesis. We present a Yukawa-unified SO(10) SUSY GUT scenario which avoids the gravitino problem, gives rise to the correct matter-antimatter asymmetry via non-thermal leptogenesis, and is consistent with the WMAP-measured abundance of cold dark matter due to the presence of an axino LSP. To maintain a consistent cosmology for Yukawa-unified SUSY models, we require a re-heat temperature T_R ~ 10^6-10^7 GeV, an axino mass around  ~ 0.1-10 MeV, and a PQ breaking scale f_a ~ 10^{12} GeV.

Read more (18kb, PDF)

__________________
Page 1 of 1  sorted by
 
Quick Reply

Please log in to post quick replies.
Home -> Astronomy News -> Physics News -> SO(10) SUSY GUTs


Create your own FREE Forum
Report Abuse 		Powered by ActiveBoard