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New Physics search via WW-fusion at the ILC

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. Introduction.

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New Physics search via WW-fusion at the ILC

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  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. 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. Gaemews et.al. Z.Phys.C1:259,1979 Hagiwara et.al. Nucl.Phys.B282:253,1987 Hagiwara et.al. NPB496,66,1996 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 Koji TSUMURA

  3. 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) Koji TSUMURA

  4. 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 Koji TSUMURA

  5. Dimension-six operators • 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 3rd generation quarks. • Bottom quark operators are strongly constrained by Z→bb. Koji TSUMURA

  6. 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. 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 Hikasa et. al. PRD58, 114003 (1998) Gounaris et. al. PRD52, 451 (1995) has no linear contribution. Koji TSUMURA

  7. 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, WLWL, ZLZL, hZL and t anti-t), then we obtained Koji TSUMURA

  8. 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 ) Koji TSUMURA

  9. WW-fusion @ ILCKanemura Nomura Tsumura PRD 74, 076007 (2006) • Solid , dotted • The non-SM (t1,Dt) effect can be significant under the unitarity bounds. • 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 ? SM SM Koji TSUMURA

  10. 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. Koji TSUMURA

  11. WW-fusion in the SM Effect of top-Yukawa LL polarized WW is dominant. Other polarization sets Koji TSUMURA

  12. WW-fusion with Ot1 Enhanced by the effect of effective top-Yukawa Higgs width become wide Not changed !! Koji TSUMURA

  13. WW-fusion with ODt Enhanced by the effect of effective top-Yukawa Energy dependence differ from t1 Enhancement from the t-channel process Direct effect of Dt Koji TSUMURA

  14. WW-fusion with Ot3 little enhancement through t-channel Strongly modified vector int. in right-handed vector current Koji TSUMURA

  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 Koji TSUMURA

  16. WW-fusion @ ILCKanemura 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 Koji TSUMURA

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