1. F. Richard Feb 2003 A Z’ within the ‘Little Higgs’ Scenario The LHC/LC Study group meeting CERN

2. F. Richard Feb 2003 Introduction 2 examples of LHC/LC complementarity can be imagined:  Assume that a mass peak is observed at LHC in l + l - : which interpretation can be given (Extended groups, KK, Little Higgs…)  Assume that LHC finds a Higgs mass incompatible with LEP/Tevatron prediction  Can FLC solve the puzzle ?  Could this new input have an impact on LHC or Super-LHC ?  In this talk, I will illustrate these ideas within the ‘Little Higgs’ scenario

3. F. Richard Feb 2003 LEP1/SLD results  With LEP1/SLD leptonic asymmetries m H ~40 GeV  Same is true from W mass  Correlated effects through m t   ~2  significance (Tevatron can improve)  A b FB gives m H ~600 GeV 3  discrepancy  New physics (mixing with new heavy fermions) or experimental bias ? This result will be ignored  Speculative ideas for A LR and mW : G. Altarelli et al. SUSY V.A. Novikov New generation T. Takeuchi -N mixing + mH + U contrib  What about a Z’ ?

4. F. Richard Feb 2003

5. A Z’ Scenario  Extended GUT groups like E 6 or SO(10) predict Z’  /  or Z R W R  Several other motivations like R,  parameter, LR symmetry restoration…  TeV xtra-dimensions with KK excitations of Z/  (Antoniadis et al), String models  ‘Deconstruction’ (Arkani-Hamed et al)  A Z’ at 1 TeV + mixing allows for a heavy Higgs boson(Peskin and Wells)  Could explain an apparent light H at LEP1/SLD  With so many competing models it might be difficult to interpret a Z’ signal at LHC (LHC/LC Complementarity)

6. F. Richard Feb 2003 Deconstruction  Bottom up approach: cancel quad divergences  Top bottom approach More dimensions ~ more symmetries ->Theories with replicated symmetries which create the right low energy structure (reminiscent of QCD) ->Higgs is a pseudo-goldstone boson, with its mass stabilized without SUSY ->Perturbative theory which becomes strong at 4  f~10-100 TeV

7. F. Richard Feb 2003 Little Higgs  Phenomenology requires that there be extra gauge bosons, extra quarks, extra scalars  ‘Littlest Higgs’ the minimal version is used here (JL Hewett et al. C. Csaki et al.)  There are 3 parameters : 2 couplings Bh xg’(Q-I3) Zh ygI3 1 mass scale f  No mixing for x=1 but then interference operates at LEP2 Contribution to  finite at x=0  LEP/SLD ‘prefers’ f~5 TeV and low x with a 115 GeV Higgs

8. F. Richard Feb 2003

9. N. Arkani-Hamed et al hep-ph/0202089

10. F. Richard Feb 2003 mH=115 GeV

11. F. Richard Feb 2003  LEP/SLD prefers low x -> Bh heavy  FT problem with mH=115 GeV f=5 TeV f < 1 TeV (mH/200 GeV) 2  No problem with mH > 300 GeV 3 < f < 5 TeV at LEP/SLD  Very distinct behavior from other Z’ models (x fixed) or from SUSY (mH)  LEP/SLD cannot predict accurately masses mBh ~ f (0.1/x) mZh > 3 TeV  m  > 7 TeV m t’ > 9 TeV out of reach (weak contribution to LEP/SLD) Interpretation

12. F. Richard Feb 2003 mH=500 GeV

13. F. Richard Feb 2003 LEP/SLD + FT ForbiddenAllowed

14. F. Richard Feb 2003

16. Predictions from FLC  With m Bh ~f (0.1/x) -> Close to the LHC limit ~4 TeV  GigaZ would give adequate precision on Bh  M/M ~(M/7 TeV) 2  Interference at FLC can tell if Zh within LHC reach ~(M/6 TeV) 4 -> FLC can tell if these masses within the LHC range

17. F. Richard Feb 2003 Stephen Godfrey hep-ph/0201093

18. F. Richard Feb 2003 UED Scheme  LH with x -> 0 behaves like the Universal Extra Dimension model  In UED each particle has KK partner but Z KK not coupled to e+e- (no interference with Z)  Weak isospin violation measurable:  ~  (m top R) 2 (Appelquist et al.) -> mKK > 300 GeV with m H =115 GeV  If H at 500 GeV m KK ~ 200 GeV -> Accessible at TeVatron and FLC  GigaZ can predict mKK with good accuracy ~ (m KK /3 TeV) 2

19. F. Richard Feb 2003 K. Matchev (Arlington)

20. F. Richard Feb 2003

21. LH Scenario at LHC/FLC  ‘A Higgs with mH> 300 GeV has been seen at LHC and nothing else’ (Bh and Zh too heavy)  ‘LEP/SLD inconsistent with SM’  MSSM or standard Z’ cannot help  Within LH, GigaZ can predict the mass of Bh and tell if it can be reached at LHC with increased Luminosity  Synergy LHC-LC

22. F. Richard Feb 2003 UED Scenario  Scenario 1: ‘a light Higgs has been seen and nothing else’  No signal at FLC but GigaZ disagrees with SM (unclear with just LEP/SLD)  GigaZ can predict if KK observable at LHC  Synergy LHC-LC  Scenario 2: ‘a heavy Higgs has been seen and many indications of ‘SUSY’ particles’ Confusing/interesting situation  FLC should see these particles and give the correct interpretation  Complementarity LHC-LC

23. F. Richard Feb 2003 Conclusions  LEP/SLD data indicate that the gauge bosons predicted by the ‘Littlest Higgs’ model should be heavy  FT + LEP/SLD suggest that LH prefers a Higgs > 300 GeV  LHC will need full luminosity for direct observation of Bh  FLC can predict the mass of Bh and lower limits on Zh t’  masses  LEP/SLD data are also compatible with a heavy Higgs and UED  This scenario would result in a confused/exciting situation at LHC and would be ideal at FLC