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Collider Signatures of Warped Extra Dimension

Delve into the flavor structure of warped extra-dimensional models, systematic exploration of the framework, and collider signals such as top quark flavor violations in the context of Warped Extra Dimensions (WED). Discover the implications of WED for the International Linear Collider (ILC) and the forward-backward asymmetry in e+e- collisions leading to potential new physics discoveries. Explore the possibility of CP violation and top-quark electric dipole moments in WED scenarios. Uncover the challenges and exciting prospects of studying WED through experimental signals at the LHC and the ILC.

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Collider Signatures of Warped Extra Dimension

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  1. Collider Signatures of Warped Extra Dimension Amarjit Soni HET, BNL (soni@bnl.gov) DPF06, Honolulu A. Soni

  2. Outline • Introuction & Motivation: WED basics • Enhanced tcZ • Prospects @ LHC • e+ e- ->t c: clean & unique signal @ the ILC • FB asymmetry & enhanced RH couplings characteristic of WED • top quark edm • CP problem of WED • enhanced nedm • Summary & Outlook DPF06, Honolulu A. Soni

  3. Flavor structure of warped extra dimensional models(Agashe,Perez&Soni) • Systematic exploration of underlying framework, hepph/0408134->PRD’05 • B-factory signals for a WED,hepph/0406101->PRL’04 • Collider Signals of top quark flavor violations, hepph/0606293 DPF06, Honolulu A. Soni

  4. RS-WED: Brief introduction DPF06, Honolulu A. Soni

  5. Regarding HP • Due to warping there is exponential hierarchy between te cutof scales of the theory @ the 2 ends of the extra dim. • Thus ΛEWSB is protected due to a low cutoff near the TeV brane while the high scale of gravity is generated at the other end, the Planck brane DPF06, Honolulu A. Soni

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  13. For now appreciable uncertainties accompany WED predictions DPF06, Honolulu A. Soni

  14. t -> c Z Effective Lagrangian from WED DPF06, Honolulu A. Soni

  15. Experimental signals @ the LHC At the LHC expect 108 top pairs so should be accessible. Specifically with 100 fb-1 ,upper limit on BR(t->cZ)~10-5 is feasible (ATLAS) With enough statistics angular analysis would also be very informative. WED predicts predominantly RH couplings. DPF06, Honolulu A. Soni

  16. t -> c γ,G At the LHC expected sensitivity for these is BR(t->c γ,G) ~ 10-5 , -4 so not promising DPF06, Honolulu A. Soni

  17. Comparison with the SM • In SM & in 2HDM BR (t -> c V) with V= γ , G, Z computed long ago (Eilam, Hewett, A.S, PRD’91) In the SM 1-loop graph is extremely GIM suppressed as {(mb , ms , md )2 / mt2 ) ->0 } DPF06, Honolulu A. Soni

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  19. Implications of WED for the ILC • e+ e- -> t c : A unique, clean & spectacular signal for WED is possible. The importance of this reaction for searching fcnc was 1st stressed in Atwood, Reina & A.S, PRD’96. Extensively studied since then, See e.g. Bar-Shalom & Wudka, PRD’99 (eff. Lag); J.A.Aguilar-Saavedra,PLB’01 (Exptal aspects TESLA vs LHC); Han & Hewett, PRD’99 (eff. Lag) Cao,Xiong & Yang, NPB’03 (SUSY) Yue,Wang,Di & Yang,PLB’05 (littlest Higgs); Arhrib & Hou, JHEP’06 (4th family)……. DPF06, Honolulu A. Soni

  20. e+ e- -> t c @ the ILC Rtc is around 2X10-5 for Ecm~200GeV and increases to ~ 2X10-4 at higher energies DPF06, Honolulu A. Soni

  21. Forward-Backward Asymmetry ine+ e- -> t c, a key prediction of WED For unpolarized beams: AFB is ~7% @ low energies and increases with energy to ~11%; higher with pol. beams. A distinctive feature of WED is that it predicts AFB positive due to dominance of RH coupling. DPF06, Honolulu A. Soni

  22. e+ e- -> t c: Some notable features • fcnc searches with b s (or in general q q’ , light flavors)…At ILC these are extremely difficult to detect due to the overwhelming background from b b (q q) X (mis) tagging efficiency…. • CONTRAST this with tc….Here fcnc reaction can be studied simply extremely efficiently by staying at cm energies of about 200-335GeV. Then t t is NOT possible. • Thus physics of crucial importance is possible with a LOW ENERGY OPTION for the ILC • At such energies, due to its huge mass, Et is significantly more than Ecm/2 …. • The opposite side is an effectively massless “charm” jet carrying energy appreciably less than Ecm/2 • AND IT MUST NOT CONTAIN A b-jet. So lots of handles. • Recall also top decays are very efficient analyzers of its polarization.. which can be a very helpful diagnostic of the underlying dynamix. DPF06, Honolulu A. Soni

  23. More on e+ e- -> t c @ the ILC DPF06, Honolulu A. Soni

  24. Prospects for CP violation • In general, in RS1 scenarios, the mixing coeffs. e.g. (UR)23 are complex ; therefore should expect new CP-odd phase(s) • For exploring these, the beam polarization at ILC should prove very useful • Recall expect e- (80%) and e+ (60%) polarization • Top decay to b W and charm jet so FS has several momenta allowing construction of TN odd observables which can be used for extracting info on new CP-odd phase(s) associated with WED DPF06, Honolulu A. Soni

  25. Possibilty of top-quark edm with WED • In RS direct KK-exchanges can endow CP-odd phase(s) to flavor-daigonal processes. • This can lead to top-quark edm: At the ILC with the parameters mentioned, using e+ e - -> t (b W+) t(b W-) edm form-factors >~ 10-20 e-cm seem accessible. {See Atwood, Bar-Shalom,Eilam,+AS, PR’01} DPF06, Honolulu A. Soni

  26. ‘CP-Problem’ in WED scenarios In WED (as in many other BSM scenarios), nedm is expected to be close to current exptal bounds (~10-26 e-cm) & >> SM (<10-30 e-cm) Moral: While we definitely should move enthusiastically towards an ILC, it would be short-sighted to short-change nedm expts. DPF06, Honolulu A. Soni

  27. Summary & Outlook • RS-WED scenarios offer a fascinating resolution to the Planck-weak hierarchy and also amielorate the flavor puzzle of the SM • Generically tcz coupling esp. RH ones are significantly enhanced • Br(t->cZ) ~ 10-5 enormously enhanced over the SM…LHC with its O(108) top pairs should be able to study this including the top polarization which has specific RH dominance prediction in WED • At the ILC, WED leads to the possibility of a spectacular signature via significantly enhanced e+ e--> t c • Also predicts FB asymmery >7% as necessitated by the dominance of RH couplings in WED • Especially gratifying that this crucially important FC physics with its clean signature is accessible with the low energy option of the ILC. • WED can endow t-quark with very large electric dipole moment of O(10-19 ) e-cm, which may be measurable at the ILC • RS-WED has a CP ‘problem’ in that nedm may be significantly enhanced and close to current exptal bounds • It is extremely important that we vigorously hunt for signals of WED at the high energy frontiers of LHC & ILC and also in the low energy experiments in search for nedm. DPF06, Honolulu A. Soni

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