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Three family models from the Heterotic string

Three family models from the Heterotic string. Stuart Raby. w/ R.J. Zhang and T. Kobayashi, Phys. Lett. B593, 262 (2004) & Nucl. Phys. B704, 3 (2005) . String Phenomenology 2005 Munich, Germany. June 13, 2005. Phenomenological Guidelines.

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Three family models from the Heterotic string

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  1. Three family models from the Heterotic string Stuart Raby w/ R.J. Zhang and T. Kobayashi, Phys. Lett. B593, 262 (2004) & Nucl. Phys. B704, 3 (2005) String Phenomenology 2005 Munich, Germany June 13, 2005

  2. Phenomenological Guidelines • Preserve gauge coupling unification • Low energy SUSY MZ << MG • Quarks and leptons in 16 of SO(10) • Higgs in 10 • Preserve GUT relations for 3rd family Yukawa • “Natural” See-Saw scale ~ MG • Use intuition from Orbifold GUTs

  3. E8 x E8 Heterotic string in 10D Compactify 6D on (T2)3 Then mod by Z6 = (Z3 x Z2) and Add Wilson lines

  4. First consider (T2)3/Z3 + W3 [Wilson line in SU3 torus] Massless modes From Untwisted sector + (G2 , SU3) twisted sector E6 GUT in 5D

  5. Then add Z2 orbifold + W2 [in long direction] P ( V2 ) P’ ( V2+ W2 ) E6 SO(10) SU(4)xSU(2)LxSU(2)R F3 = (4,2,1), F3c = (4c,1,2) , H = (1,2,2)

  6. E6 Orbifold GUT on M4 x S1/(Z2xZ’2)

  7. Exotics Two families sit on Z2 fixed points !! D4 family symmetry !!

  8. D4 family symmetry singlet doublet

  9. Z2 twisted sector Extra color triplets!!

  10. To summarize • 3rd family in bulk gauge-Yukawa unification • 1st and 2nd families on Z2 fixed points D4 family symmetry Higgs for PS symmetry breaking

  11. PS symmetry breaking F and D flat direction breaks PS to SM + gives mass to all SM non-singlets

  12. Gauge coupling unification ? 4D GUT 5D Orbifold GUT

  13. Gauge coupling unification ++ and -- modes are in overlap of and

  14. B.C.s Weak Strong

  15. Successes • Gauge coupling unification • 3rd generation and Higgs in bulk -> gauge-Yukawa unif. • D4 family symmetry : family hierarchy + suppress flavor violation

  16. D4 family symmetry

  17. So what’s the problem ? • Exotics ! • Extra color triplets ! • NO R parity !!! Solution ZN x Z2 orbifolds ??

  18. Few Exotics Fractional electric charge BUT Vector-like !! Mass at String scale Technical difficulty Not all exotics get mass

  19. R parity ?? R parity !! Technical difficulty T4 ( U3 T2 + T1T1 )

  20. R parity ?? R parity !! Technical difficulty T4 ( U3 T2 )

  21. Conclusions • New 3 family E6 orbifold GUT • 3rd generation -- gauge-Yukawa unif. • D4 family symmetry : family hierarchy + suppress flavor violation • Few vector-like exotics • Extra color triplets • NO R parity Possible solution in ZNxZ2 orbifold

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