The Twin Higgs. with Zackaria Chacko and Hock-Seng Goh hep-ph/

Transcription

1 with Zackaria Chacko and Hock-Seng Goh hep-ph/

2 Naturalness and LHC LHC is going to be exciting from the start (first 10 fb -1 ). t L +? = Natural SMt R NP

3 Naturalness and LHC LHC is going to be exciting from the start (first 10 fb -1 ). t L +? = Natural SMt R NP { NP is related to the SM top by a symmetry. NP is around a TeV. Colored NP at a TeV! Will be produced abundantly at LHC!

4 Singlet New Physics Not necessarily! what do we really need to cancel the SM loop? t L t R + t

5 Singlet New Physics Not necessarily! what do we really need to cancel the SM loop? t L t R + t vertices

6 Singlet New Physics Not necessarily! what do we really need to cancel the SM loop? t L t R + t # of d.o.f. vertices

7 Singlet New Physics Not necessarily! what do we really need to cancel the SM loop? t L t R + t # of d.o.f. vertices t does not have to be colored! Not produced at LHC... :-(

8 Outline Motivation. The mechanism. A model. Phenomenology, Cosmology.

9 Motivation The LEP Paradox

10 LEP Paradox (Barbieri, Strumia) SM Higgs seems to be light. Paradox!? No new physics up to Λ 5 10 TeV

11 A Hint? Something is protecting the Higgs. We are not seeing any sign of new physics This would be explained automatically if the new physics that is protecting the Higgs is all in SM singlets. Is this possible? (yes)

12 The Mechanism A new mechanism for the Higgs as a Goldstone

13 Higgs as a Goldstone The Higgs mass is protected if it is a PNGB. An old idea Kaplan-Georgi Recently, Little Higgs (collective symm. breaking). - A new realization of the Higgs as a pseudo. Discrete symmetry Global symmetry

14 A Toy Example A global SU(4) symmetry w/ one fundamental V (H) = m 2 H 2 + λ H 4 H 2 = M 2 2λ f 2 SU(4) SU(3) 7 Goldstones

15 SU(2) A SU(2) B Gauge a subgroup SU(2) A SU(2) B our SM twin SM In some basis, H transforms as ) H = ( HA H B 6 eaten. 1 Goldstone left. SU(2) A SU(2) B breaks global SU(4).

16 Radiative Corrections At 1-loop: V =

17 Radiative Corrections At 1-loop: V = 9g2 A Λ2 64π 2 H A H A

18 Radiative Corrections At 1-loop: V = 9g2 A Λ2 64π 2 H A H A + 9g2 B Λ2 64π 2 H B H B

19 Radiative Corrections At 1-loop: V = 9g2 A Λ2 64π 2 H A H A + 9g2 B Λ2 64π 2 H B H B Impose a twin symmetry: A B Z 2 g A =g B V = 9g2 Λ 2 ( ) 64π 2 H A H A + H B H B SU(4) invariant! Does not give a Goldstone mass.

20 Twin Mechanism (Global Symmetry) + (Discrete Symmetry) Quadratic terms are globally symmetric. No quadratic divergences. Quartic terms can violate global symmetry. Goldstone mass only log divergent.

21 The Model Mirror Symmetric Twin Higgs For a Left-Right implementation, see next talk.

22 SM A SM B Z 2 Double all of the SM. Impose. In particular L y t H A t A t A + y t H B t B t B Z 2 : quadratic divergence has the form cλ 2 ( H A 2 + H B 2) A B SU(4) invariant. A A + A A

23 SU(4) breaking Radiative corrections induce t A, t B V = κ ( H A 4 + H B 4) with κ y4 t 16π 2 log Λ f Goldstone mass is m h y2 t. 4π f Need f GeV. Alternative: see Thomas` talk, after the break e.g. assume m 5 10 TeV + strong coupling. Can look at EFT below Λ m.

24 Soft Breaking The potential as is gives v A = v B f 2 But then Λ 4πf is too low. Add V soft = µ 2 H A 2 a mild cancelation needed to get EW scale

25 Phenomenology and Cosmology All new physics is SM singlets

26 LHC Signals A standard model higgs.

27 LHC Signals A standard model higgs. If we are luck we can measure- Higgs decay to invisibles, BR O(v 2 /f 2 ). Modification of ZZh, W W h, tth, h 3,... also of O(v/f). (correlations).

28 LHC Signals A standard model higgs. If we are luck we can measure- Higgs decay to invisibles, BR O(v 2 /f 2 ). Modification of ZZh, W W h, tth, h 3,... also of O(v/f). (correlations). If we are really lucky (work in progress): Twin hadrons decay back to SM with displaced vertices. A Hidden Valley signal (Strassler and Zurek).

29 Cosmology Twin baryons could be dark matter. Light twin matter is dangerous during BBN. Small Z 2 breaking in light yukawa sector. Make twin matter Heavier than a few GeV. (Barbieri, Gregiore, Hall) More entropy production in our QCD transition? Late inflation? LHC implications are drastic enough to overshadow these issues.

30 Conclusions mechanism is a very simple to get a pseduo-goldstone Higgs. Can be implemented in mirror symmetry. A natural model with pure singlet new physics up to 5-10 TeV, explaining the `LEP paradox. Naturalness doesn't guarantee an easy LHC signal. Seeing BSM physics may be a challenge.

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