1. New Physics search via WW-fusion at the ILC Koji TSUMURA (Osaka Univ. → KEK after April ) in collaboration with S. Kanemura & K. Matsuda KEK Theory Meeting on Particle Physics Phenomenology 2007 Mar. 1-3

2. KEK-PH 07 Mar. 1-3Koji TSUMURA2/15 Introduction 4-fermi interaction has been tested in collision & decays. ee -> WW has been well examined @ LEP by using helicity analysis. For Higgs boson & heavy fermions, we would like to study vector boson fusion (WW-fusion) process. –Higgs boson strongly couples to heavy particles. Kanemura, Nomura, Tsumura, PRD74:076007,2006 Larios et.al. hep-ph/9709316 Asakawa, Hagiwara, Eur.Phys.J.C31:351,2003 Grzadkowski et.al. JHEP 0511:029,2005 Cho, Hagiwara et.al. PRD73:054002,2006 Gaemews et.al. Z.Phys.C1:259,1979 Hagiwara et.al. Nucl.Phys.B282:253,1987 Hagiwara et.al. NPB496,66,1996

3. KEK-PH 07 Mar. 1-3Koji TSUMURA3/15 New Physics search via top-Higgs interaction –For lighter Higgs boson (SUSY like scenario) ee -> ttH associate production –For heavier or intermediate Higgs boson masses If theory has (relatively) heavy Higgs, WW-fusion can be an useful probe. (Effective theory approach, extra Higgs, Little Higgs, Extra-D, Top Color, etc.) T. Han, et. al. PRD61, 015006 (2000)

4. KEK-PH 07 Mar. 1-3Koji TSUMURA4/15 Effective theory approach –Below the new physics scale, the non-SM int. is characterized by higher dimension operators. –The coupling strength can be calculated in each model. –ex. MSSM Feng, Li, Maalampi PRD69,115007 –ex. Extra Higgs

5. KEK-PH 07 Mar. 1-3Koji TSUMURA5/15 –Complete set of gauge invariant dim.6 ops. Has been discussed. Buchmuller et. al in NPB268, 621 (1986) 4-fermi operators Scalar only (6 scalar, 4 scalar + 2 derivative) Scalar & vector operators 2-fermi operators (Yukawa + 2 scalar) 2-fermi operators (Yukawa + 2 derivative [2 vector] ) … so many operators !! –We introduce these dim.6 ops. for 3 rd generation quarks. Bottom quark operators are strongly constrained by Z→bb. Dimension-six operators

6. KEK-PH 07 Mar. 1-3Koji TSUMURA6/15 Experimental limits –Direct search No experimental bound for. There are no stringent bounds for by vector boson exchange processes at LEP and Tevatron. ex. for –Precision data can give oblique corrections. Hikasa et. al. PRD58, 114003 (1998) Gounaris et. al. PRD52, 451 (1995) has no linear contribution. Ot1 : no experimental bound Ot3 : weaker bound from oblique correction ODt : smaller ⊿ ρ compare to t2, tWΦ, tBΦ In this talk, we concentrate on three dim.6 operators Ot1: direct correction for top-Yukawa ODt: correction for top-Yukawa including derivatives Ot3: right-handed vector interaction

7. KEK-PH 07 Mar. 1-3Koji TSUMURA7/15 Unitarity bounds –Tree level unitarity for dim.6 ops. Has been discussed. Gounaris et. al. in Z. Phys. C76, 333 (1997). Imposing unitarity @ Considering 2-body scattering channels (hh, W L W L, Z L Z L, hZ L and t anti-t), then we obtained

8. KEK-PH 07 Mar. 1-3Koji TSUMURA8/15 Effects of dimension-six coupling –Effective top-Yukawa –Decay width for Higgs boson Kanemura Nomura Tsumura PRD74, 076007 (2006) For, non-SM effect (only ) can be observed in the top-pair production. For lighter Higgs mass, loop induced decays can be enhanced. For, we can not reach non-SM effect. (main )

9. KEK-PH 07 Mar. 1-3Koji TSUMURA9/15 –Solid, dotted –The non-SM (t1,Dt) effect can be significant under the unitarity bounds. WW-fusion @ ILC Kanemura Nomura Tsumura PRD 74, 076007 (2006) SM The non-SM (t1,Dt) effect can be significant under the unitarity bounds. How to extract more information ? Smaller dim.6 coupling ? Smaller Higgs mass ? Much operators ? Separate each operator ?

10. KEK-PH 07 Mar. 1-3Koji TSUMURA10/15 Helicity amplitude for WW-fusion –Amplitudes are calculated which respect to W- boson helicity and t-quark spin. To obtain further information, we consider top- quark spin correlations. By using W-boson helicity, each amp. can be checked by BRS sym. In this talk, we concentrate on the WW-fusion sub-process.

11. KEK-PH 07 Mar. 1-3Koji TSUMURA11/15 WW-fusion in the SM LL polarized WW is dominant. Effect of top-Yukawa Other polarization sets

12. KEK-PH 07 Mar. 1-3Koji TSUMURA12/15 WW-fusion with Ot1 Higgs width become wide Not changed !! Enhanced by the effect of effective top-Yukawa

13. KEK-PH 07 Mar. 1-3Koji TSUMURA13/15 WW-fusion with ODt Enhanced by the effect of effective top-Yukawa Enhancement from the t-channel process Direct effect of Dt Energy dependence differ from t1

14. KEK-PH 07 Mar. 1-3Koji TSUMURA14/15 WW-fusion with Ot3 little enhancement through t-channel Strongly modified vector int. in right-handed vector current

15. KEK-PH 07 Mar. 1-3Koji TSUMURA15/15 Summary –New Physics effect can be seen in WW-fusion. –dim.6 operators can be distinguished by using helicity method (top-spin correlation) We concentrate on the WW-fusion sub-process. We should calculate spin correlation for the full- process. We should estimate detectable size of dim.6 coupling. –Issues Smaller values of dim.6 coupling. (not only t1,Dt,t3 but also t2, tWΦ,tBΦ) Lighter Higgs

16. KEK-PH 07 Mar. 1-3Koji TSUMURA16/15 WW-fusion @ ILC Kanemura Nomura Tsumura PRD 74, 076007 (2006) –Dotted curves are calculated by using the package CalcHEP. The EWA results agree with those of CalcHEP in about 20-30 % error for heavier Higgs boson. SM