1. New Physics effect on Higgs boson pair production processes at LHC and ILC Daisuke Harada (KEK, Graduate University for Advanced Studies) in collaboration with E. Asakawa (Meiji-Gakuin), S. Kanemura (U-Toyama), Y. Okada (KEK), K. Tsumura (ICTP) arXiv:0809.0094 [hep-ph] Phys. Lett. B 672 (2009) 354-360; arXiv:0902.2458 [hep-ph]; Papers in preparation KEKPH2010, February. 19. 2010

2. 2 My talk plan Ⅰ.Ⅰ. Ⅱ.Ⅱ. Ⅲ.Ⅲ. Introduction Double Higgs production process Ⅳ.Ⅳ. New physics effect on hhh coupling THDM, Scalar LQ and chiral 4 th generation

3. 3 Introduction Ⅰ.Ⅰ. The Higgs sector is the last unknown part of the Standard Model. After the discovery of Higgs boson, it is important to measure the Higgs self-coupling. The standard model for elementary particles is very successful in describing high energy phenomena up to O(100) GeV. The SM has several problems. If the SM is an effective theory up to Planck scale, Higgs mass is O(100) GeV comes from large fine-tuning cancellation between its bare mass and quadratic radiative corrections. This problem is known as Hierarchy problem. This fine tuning problem suggests that new physics beyond the SM should be appear at TeV scale. Test for the Higgs potential Search for New Physics effect We study the impacts of new physics effects on the hhh measurement at LHC and ILC.

4. 4 Measurement of hhh coupling Measurement at collider experiment LHC (SLHC) ILC Photon Collider (PLC) We focus on these processes. ILC

5. 5 THDM, Scalar LQ and 4 th generation Ⅱ.Ⅱ. We focus on the following models; 1. two Higgs doublet model (THDM), 2. scalar leptoquark (LQ) model, 3. chiral 4 th generation model.

6. 6 Two Higgs Doublet Model Higgs potential Higgs doublets CP-evenCP-oddCharged bosons

7. 7 SM-like limit Lightest Higgs has the same tree-level coupling as the SM Higgs boson and the other Higgs bosons do not couple to gauge bosons. We consider following parameters Non-decoupling limit We assume that the masses of the extra Higgs bosons degenerate. rho parameter constrain In the THDM, extra Higgs boson loop correction is known as non-decoupling effect.

8. 8 Scalar LQ model In addition to the SM, we introduce the scalar LQ. Higgs potential LQ-lepton-quark interaction LQ Lepton Quark with charge +1/3 with charge +4/3 Scalar LQ Lower bounds of masses HERA Tevatoron for

9. 9 Chiral 4 th generation model Yukawa coupling In addition to the SM, we introduce the chiral 4 th generation quark and Lower bounds of masses For simplicity, we assume that masses of the chiral 4 th generation quark are degenerate and 4 th generation quark do not mix with the SM quarks. G. Kribs, T. Plehn, M. Spanowsky and T. Tait S parameter

10. 10 New Physics effect on hhh Non-decoupling effect term appear in 1-loop correction loop effect ~ -10% Effective hhh coupling In the SM, top loop correction is known as non-decoupling effect. counter term Ⅲ.Ⅲ. Higgs potential In the SM, tree level hhh (hhhh) coupling is given by

11. 11 New Physics effect on hhh coupling S. Kanemura, Y. Okada, E. Senaha, C. P. Yuan non-decouplingdecoupling Effective hhh coupling term appear in 1-loop correction We set M=0. receive their masses from the VEV. heavier Higgs boson loop effect ~ 100%non-decoupling

12. 12 New Physics effect on hhh coupling Effective hhh coupling Chiral 4 th generation Scalar LQ Chiral 4 th generationFor We set M=0.

13. 13 Double Higgs production process Ⅳ.Ⅳ. We studied the impacts of the new physics effect on the hhh coupling and double Higgs boson production process in THDM, scalar LQ and chiral 4 th generation model. LHC (SLHC) ILC PLC

14. 14 ILC

15. 15 New Physics effect on Zhh process Effective hhh coupling “new particle / top” loop effect

16. 16 New Physics effect on Zhh process For THDM Scalar LQ Chiral 4 th generation This process at the ILC with a center of mass energy of 500 GeV is very useful to distinguish whether the new particle is boson or fermion. The cross section becomes large (small) If new particle is boson (fermion). SM THDM SM LQ SM 4th

17. 17 PLC

18. 18 pole box “New particle / top” loop effect W boson and top loop diagrams Effective hhh coupling New Physics effect on process

19. 19 Additional one-loop diagrams 4 th generation Scalar LQ / THDM with SM-like limit

20. 20 Sub Cross Section in THDM THDM SM THDM SM Cross section is enhanced by the effect of Threshold enhancement of top pair production Threshold enhancement of charged Higgs pair production

21. 21 Full Cross Section in THDM Initial laser beam mean helicityInitial electron helicity We use following values The full cross section is given from the sub cross section by convoluting the photon luminosity spectrum.

22. 22 Sub/Full Cross Section in LQ and 4 th generation Scalar LQwith charge +1/3 sub full SM LQ SM 4th For Chiral 4 th generation

23. 23 LHC

24. 24 Additional one-loop diagrams pole top loop diagrams box 4 th generation Scalar LQ

25. 25 Sub/Full Cross Section in THDM and LQ For sub full SM LQ THDM SM THDM LQ SM

26. 26 Sub/Full Cross Section in 4 th generation For Sub cross sectionFull cross section SM 4th SM 4th

27. 27 Summary We calculated double Higgs production process in THDM with SM-like limit, scalar LQ and chiral 4th generation model. The cross section can be largely changed from the SM. additional contribution of new particle loop Effective 1-loop hhh vertex enhanced by the non-decoupling effect The cross section strongly depend on each new physics model. THDMScalar LQ 4 th generation ILC PLC LHC For hhh coupling with charge +1/3 ILC, PLC, LHC PLC, LHC

28. 28 Backup Slide

29. 29 hhh measurement at the LHC U. Baur, T. Plehn, D. Rainwater At the LHC, vanishing Higgs self-coupling is excluded. At the SLHC, Higgs self-coupling can be determined with an accuracy of 20-30 %.

30. 30 hhh measurement at the ILC ACFA Higgs Working Group 2002 At the 1 st ILC, Higgs self-coupling can be determined with an accuracy of 20-30 %. 1 st ILC

31. 31 hhh measurement at the PLC E.Asakawa, D. Harada, S. Kanemura, Y. Okada, K. Tsumura at TILC 08 Photon linear collider (Eee < 500GeV) is useful to measure the HHH coupling for mH = 150-200.

32. 32 Photon Linear Collider Compton backscattering Electron beam energy wavelength laser electron bunch Interaction point conversion point

33. 33 Vacuum instability in the 4 th generation There are two ways to avoid the vacuum instability problem in 4 th generation model. 1. SM4 + THDM 2. SM4 In this case, SM Higgs boson mass should be heavy. We can avoid the vacuum instability by Extra Higgs boson.

34. 34 Radiative correction to hhh coupling In the SM, the effective potential is given by

35. 35 Sub/Full Cross Section in scalar LQ Scalar LQwith charge +4/3 For sub full SM LQ

36. 36 Appendix effectiveand vertices come from dimension-6 operator

37. 37 Appendix (a)(b) (c) (d)