1 / 37

Electroweak Symmetry Breaking from the D4-D8-D8 System

Electroweak Symmetry Breaking from the D4-D8-D8 System. Joshua Erlich. College of William & Mary. w/ Chris Carone, Marc Sher, Jong Anly Tan. D8. D4. EWSB. D8. Budapest, June 25, 2007. Outline. Quick Technicolor Review The D4-D8-D8 system as a Technicolor model

olinda
Télécharger la présentation

Electroweak Symmetry Breaking from the D4-D8-D8 System

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Electroweak Symmetry Breaking from the D4-D8-D8 System Joshua Erlich College of William & Mary w/ Chris Carone, Marc Sher, Jong Anly Tan D8 D4 EWSB D8 Budapest, June 25, 2007

  2. Outline • Quick Technicolor Review • The D4-D8-D8 system as a Technicolor model • Precision Electroweak Constraints • Top-Down vs Bottom-Up AdS/QCD/Technicolor

  3. Your favorite strongly coupled theory (at least for the next 25 minutes) SU(N) gauge theory with Nf light Dirac fermions (QCD for short) A prototypical gauge theory featuring: Asymptotic Freedom Confinement Chiral Symmetry Breaking Electroweak Symmetry Breaking (when fermions are coupled to SU(2)W£ U(1)Y as in the SM)

  4. Invariant under separate SU(2) transformations on qL, qR Chiral Symmetry Breaking in QCD The up, down quarks are light compared to the QCD scale mu, md ~ few MeV m ~ 770 MeV

  5. J Jn Goldstones Chiral Symmetry Breaking in QCD Nonvanishing breaks chiral symmetry to diagonal subgroup (Isospin)

  6. QCD and Electroweak Symmetry Breaking Quarks are charged under electroweak symmetry, which in the quark sector is a gauged subgroup of the chiral symmetry £ U(1)B-L. qLqR+qRqL charged under SU(2)W£ U(1)Y , Invariant under U(1)EM Even in the absence of any other source of EWSB, nonvanishing hqLqR+qRqLi breaks EW to EM, gives small mass to W, Z bosons. But we need more EWSB -- lot’s more!

  7. Technicolor Weinberg,Susskind Assume a new asymptotically free gauge group factor GTC with NF techniquark flavors Gauge a SU(2) £ U(1) subgroup of the chiral symmetry (£U(1)B-L) Identify with electroweak gauge invariance The chiral condensate breaks the electroweak symmetry to U(1)EM The good: No fundamental scalars – no hierarchy problem The bad: Estimates of precision electroweak observables disagree with experiment ! walking TC may be better The ugly: No fermion masses ! Extended Technicolor

  8. A Minimal Technicolor Model Gauge group: GTC £ SU(2) £ U(1) SU(2) technifermion doublet PL=(p,m)L SU(2) technifermion singlets pR, mR Technifermion condensate (p p + m m) = 4 f 3 Breaks Electroweak Symmetry (No Standard Model fermion masses yet, doesn’t satisfy electroweak constraints…)

  9. The Basic Goals of AdS/QCD/Technicolor • To make predictions in strongly coupled theories like QCD or Technicolor, and compare with experiment • To cure problems in 4D models by modifying the strongly coupled theories in a controlled way

  10. The Technique Top-Down AdS/QCD • Engineer your favorite strongly coupled field theory (or a similar one) from a D-brane configuration • Use string theory to make quantitative predictions of observables in certain limits of the field theory

  11. Massless fluctuations of D4 branes describe non-supersymmetric SU(N) gauge theory QCD from strings Witten; Csaki,Ooguri,Oz,Terning; … Antiperiodic BC’s on fermions break SUSY  D4 U 0 1 2 3  5 6 7 8 U D4 x x x x x

  12. The U-tube Confinement, SB Adding massless chiral quarks Sakai,Sugimoto D8  D4 U D8 0 1 2 3 5 6 7 8 U D4 x x x x x D8 x x x x x x x x x Massless fluctuations of D4 branes describe non-supersymmetric SU(N) gauge theory Strings stretching from D4’s to D8’s are massless chiral quarks

  13. The D4-D8-D8 System Sakai,Sugimoto; Antonyan,Harvey,Jensen,Kutasov; Aharony,Sonnenschein,Yankielowicz D8 D4 D8 Confinement SB 0 1 2 3  5 6 7 8 U D4 x x x x x D8 x x x x x x x x x There is a one-parameter set of D8-brane configurations that minimize the D8-brane action.

  14. QCD bound state masses and interactions • Probe brane limit: Assume Nf¿N(Karch,Katz) • Determine shape of D8-brane by minimizing D8-brane action in D4-brane background • Fluctuations of the D8-brane describe bound states of quarks; D8-brane action determines their masses, decay constants, form factors, couplings, …

  15. The U-tube D4 brane geometry period:

  16. Stationary Solution: Probe brane limit D8-brane action

  17. Probe brane limit Induced metric on D8-brane:

  18. Vector mesons on the D8-branes SU(Nf) gauge fields live on the D8-branes – identify 4D modes with vector mesons

  19. Vector mesons on the D8-branes Solve equations of motion for modes of the vector field Symmetric modes are identified with vector resonances Antisymmetric modes are identified with axial vector resonances In this setup, vector and axial vector masses alternate Axial Vector Vector

  20. Holographic Technicolor Hirn,Sanz; Piai; Agashe,Csaki,Grojean,Reece; Hong,Yee,… Technicolor is like QCD. AdS/QCD makes nonperturbative predictions in theories like QCD. Simple idea: Use AdS/QCD to define and make predictions in Technicolor-like Models of EWSB

  21. Gauging the EW symmetry on the D8 branes Decompose the D8-brane gauge fields in modes Turn on non-vanishing solution at boundaries (zero modes) These solutions correspond to sources for the electroweak currents Decay constants are read off of couplings between sources and resonances

  22. Precision Electroweak Constraints Particle Data Group

  23. Oblique Parameters Peskin & Takeuchi Oblique corrections describe influence of new physics on vacuum polarization corrections to electroweak observables -- Parametrized by three quantities that can be calculated from matrix elements of products of electroweak currents: S,T,U The S parameter in QCD-like technicolor theories is estimated to be too large to be consistent with precision electroweak measurements

  24. Constraints on S,T PDG

  25. The SS S Parameter – first few contributions

  26. The S Parameter – sum over all modes g2N=4, N=4 Factor of 10 too big

  27. Other phenomenology This model doesn’t satisfy electroweak constraints, but what else could be predicted in the model? Can also predict meson couplings, form factors. Technibaryons appear as skyrmions.

  28. Can the model be saved? The lightest resonances contributed negatively to S. Can we truncate the model consistently at some scale before S becomes too positive?

  29. For small enough box, naively S decreases, but the electroweak sector becomes strongly coupled at the TeV scale so it is hard to calculate First thought Raise the confinement scale with respect to the chiral symmetry breaking scale: Put the D8 branes in a box (but this isn’t string theory anymore!)

  30. Second thought Deconstruct the extra dimension: Replace gauge fields in extra dimension by a finite tower of massive resonances Resulting theory is reminiscent of little Higgs models, analysis should be similar.

  31. Geometry: AdS5 between z=0 and z=zm SU(2) £ SU(2) AdS5 z=0 z=zm Bottom-Up Approach JE,Katz,Son,Stephanov; Da Rold,Pomarol; Brodsky,De Teramond; Hirn,Sanz;… Forget about the details of the stringy construction. Build in details of your favorite model, and calculate strong interaction observables by analogy with stringy constructions.

  32. Top-Down vs Bottom-Up • Bottom-Up • Not sure how well model describes 4D field theory • Desired properties of field theory built in • Easier to satisfy electroweak constraints • Top-Down • Field theory described is well understood • Calculable models predict new states • Difficult to satisfy electroweak constraints

  33. Final Thoughts • The D4-D8-D8 system provides a predictive model of EWSB. • 2. Standard Model fermions, masses must be included to make the model complete. • 3. Related models may satisfy electroweak and FCNC constraints: walking technicolor models from D-branes? • How does the 2 UV boundary paradigm affect 5D models of EWSB? • The AdS/CFT correspondence can be used with metric on D8-brane to calculate current correlators, agrees with effective theory on D8-branes: is this a hint as to why AdS/CFT works?

  34. Final Thoughts • The D4-D8-D8 system provides a predictive model of EWSB. • 2. Standard Model fermions, masses must be included to make the model complete. • 3. Related models may satisfy electroweak and FCNC constraints: walking technicolor models from D-branes? • How does the 2 UV boundary paradigm affect 5D models of EWSB? • The AdS/CFT correspondence can be used with metric on D8-brane to calculate current correlators, agrees with effective theory on D8-branes: is this a hint as to why AdS/CFT works?

  35. Final Thoughts • The D4-D8-D8 system provides a predictive model of EWSB. • 2. Standard Model fermions, masses must be included to make the model complete. • 3. Related models may satisfy electroweak and FCNC constraints: walking technicolor models from D-branes? • How does the 2 UV boundary paradigm affect 5D models of EWSB? • The AdS/CFT correspondence can be used with metric on D8-brane to calculate current correlators, agrees with effective theory on D8-branes: is this a hint as to why AdS/CFT works?

  36. Final Thoughts • The D4-D8-D8 system provides a predictive model of EWSB. • 2. Standard Model fermions, masses must be included to make the model complete. • 3. Related models may satisfy electroweak and FCNC constraints: walking technicolor models from D-branes? • How does the 2 UV boundary paradigm affect 5D models of EWSB? • The AdS/CFT correspondence can be used with metric on D8-brane to calculate current correlators, agrees with effective theory on D8-branes: is this a hint as to why AdS/CFT works?

  37. Final Thoughts • The D4-D8-D8 system provides a predictive model of EWSB. • 2. Standard Model fermions, masses must be included to make the model complete. • 3. Related models may satisfy electroweak and FCNC constraints: walking technicolor models from D-branes? • How does the 2 UV boundary paradigm affect 5D models of EWSB? • The AdS/CFT correspondence can be used with metric on D8-brane to calculate current correlators, agrees with effective theory on D8-branes: is this a hint as to why AdS/CFT works?

More Related