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The Higgs Reduction Mechanism in Free Fermionic Models. Elisa Manno (with A. Faraggi and C.Timirgaziu) Eur. Phys. J. C (2007) University of Liverpool UKBSM Workshop, 29-30 March 2007. Outline. Motivations Free Fermionic Models (FFM) Yukawa selection mechanism

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the higgs reduction mechanism in free fermionic models
The Higgs Reduction Mechanism in Free Fermionic Models

Elisa Manno (with A. Faraggi and C.Timirgaziu)

Eur. Phys. J. C (2007)

University of Liverpool

UKBSM Workshop, 29-30 March 2007

outline
Outline
  • Motivations
  • Free Fermionic Models (FFM)
  • Yukawa selection mechanism
  • Higgs doublet-triplet splitting
  • Model with reduced Higgs spectrum
  • Conclusions
motivations
Motivations

In the free fermionic formulation we have realistic models

  • Existence of 3 chiral generations
  • Observable gauge group : SU(3)xSU(2)xU(1)n
  • N=1 Supersymmetry
  • Standard SO(10) embedding for the weak hypercharge
  • Stability of the proton

Heterotic string vacua with solely MSSM states are derived.

the free fermionic models
The Free Fermionic Models
  • Field content (light-cone gauge)

{ 12 1,..6 y1,..6 1,..6  y1,..6 1,..61,..5 1,2,3 1,..8}

left sector (susy)right sector

  • A model is constructed by specifying

the phases picked up by the WS fermions

along non-contractible loops

f → e –i(f)π f

  • The phases are consistent with modular invariance
slide5
The phases are given in terms of basis vectors

b = { (12 ),  (1),  (2),..}

  • For a given basis B = {b1,..bn}

the Hilbert space = mi bi , mi = 1,..Nbi -1

is obtained by acting on the vacuum with bosonic

and fermionic operators

  • The physical spectrum is obtained by applying the GSO projections
  • If B = {1,S,b1,b2,b3} + opportune choice of , , 

b.c. basis vectors we have 4D models with N=1 Susy

+ 3 chiral generations, one from each bi, i=1,2,3.

yukawa selection mechanism
Yukawa selection mechanism

The Yukawa selection mechanism is given

by the vector responsible of the breaking

SO(10) → SU(5) x U(1)

The b.c. basis vectors in  fix the Yukawa couplings

Quh , LNh

Qdh , Leh

Each sector bi gives rise to an up-like or down-like cubic level Yukawa coupl.

i= |  L- R| =0,1

down-quark type

Yukawa coupl.up-quark type

Yukawa coupl.

higgs doublet triplet splitting
Higgs doublet-triplet splitting

The NS sector gives 3 multiplets of Higgs

states in the 10 of SO(10) each of them

associated with one of the twisted sectors bi.

Higgs electroweak doublets hi, hi i,i+1(4,5)*i

Higgs colour tripletsDi, Di i,i+1(4,5)*i

The doublet-triplet splitting mechanism results from the b. c. in  which break

SO(10) → SO(6) x SO(4)

i=| L–R| = 0,1

hi projected outhi remains in the spectrum

slide8
We look for models such that…
  • No Higgs triplets ; one Higgs doublet

 3() = 1

  • Up-quark type Yukawa couplingsselected

3() = 1

  • No chiral fractionally charged exotics
model with reduced higgs spectrum
Model with reduced Higgs spectrum

SO(10) breaking Hidden gauge group breaking

b1 sector b2 sector b3 sector

model with reduced higgs spectrum1

Project out the untwisted vectorial repr.

 = 1

(up-quark type Yukawa coupling is selected)

Model with reduced Higgs spectrum

keep h1keep D2keep h3

conclusions
Conclusions
  • Free Fermionic Models produce some of the most realistic stringmodelsto date.

The presence of 3 pairs of Higgs doublets is generally reduced by the analysis of supersymmetric flat directions.

  • An alternative option for the reduction of the Higgs states is given by an opportune choice of free fermion boundary conditions at the string scale.
  • The previous mechanism also provides a reduction of the moduli space.
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