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Sensitivity to Z’ at CLIC & Polarization

Sensitivity to Z’ at CLIC & Polarization. Sabine Riemann (DESY) Meeting on Polarisation (A) 11 October 2011. Search reaches LHC,ILC,CLIC. from G.Giudice. Sensitivity to New Physics.

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Sensitivity to Z’ at CLIC & Polarization

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  1. Sensitivity to Z’ at CLIC& Polarization Sabine Riemann (DESY) Meeting on Polarisation (A) 11 October 2011

  2. Search reaches LHC,ILC,CLIC • from G.Giudice S. Riemann, CLIC Z’

  3. Sensitivity to New Physics g,Z’ f e+ f e- Fermion-Pair Production with long. Polarisation (s-channel) Four-fermion contact terms: effective parameterization of physics beyond the SM at ‘low’ energies, s ‹‹ L2  interference with SM • s, AFB, ALR, AFBLR sensitivity to helicity amplitudes and their modification Observables: s, AFB, ALR, AFBLR P+ = e+ pol P- = e- pol f e+ ? e- f S. Riemann, CLIC Z’

  4. Model-independent Z’ Search A. Leike, SR, Z.Phys. C75 (1997) 341 normalized Z’ coupling ee  ll (+lepton universality) Z’ obtained with stotfor Z’ obtained with AFB for Z’ obtained with ALR for S. Riemann, CLIC Z’

  5. Z’ model distinction at LC e+e-l+l- If no Z’ information from LHC (low couplings to quarks, high mass,…):  Z’ model distinction for mZ’ <4÷8√sLC Lint=1ab-1 (±0.2%) P-=0.8 (±0.5%) P+=0.6 (±0.5%) dsysl=0.2% dsysb=0.5% S. Riemann, CLIC Z’

  6. ee  g,Z,Z’  bb Z’ coupling to leptons from measurement of leptonic final states Good sensitivity with information using combination of all measurements A. Leike, SR, Z.Phys. C75 (1997) 341 S. Riemann, CLIC Z’

  7. Z’ model distinction at ILC e+e-l+l- e+e-bb Lint=1ab-1 (±0.2%) P-=0.8 (±0.5%) P+=0.6 (±0.5%) dsysl=0.2% dsysb=0.5% If no Z’ information from LHC distinction up to mZ’ ~4÷8√s S. Riemann, CLIC Z’

  8. Scaling of sensitivity to CI with polarization Scaling with polarization • Polarization of both beams increases luminosity • If polarization-dependent observables (ALR, ALRFB ) dominate sensitivity Improvement of sensitivity with positron polarization is not very large, but polarized beams are essential for model discrimination S. Riemann, CLIC Z’

  9. Sensitivity with polarized beams • Uncertainty of s, AFB, ALR, ALRFB • depends on uncertainty of pol measurement, in particular • DP should be ~0.5% or less to avoid dominating polarization error • DPeff decreases with e+ polarization • Problem: beamstrahlung  depolarization • CLIC beam sizes @ IP (hor./vert. in nm) > ILC beam sizes • Bailey et al., EPAC08-MOPP024 • depolarization-studies with GP and CAIN: C. Rimbault, LCWS08: • Lumi-weighted depol for ILC (500 GeV): DPlw ~ 0.23±0.01 % • Depol depends strongly on horizontal beam size variations: uncertainty of 10% on beamsize  uncertainty on depolarization is larger than 20% • Increasing depolarization with increasing CLIC energy • What is the uncertainty on depolarization at CLIC3TeV?? S. Riemann, CLIC Z’

  10. Summary & conclusion • Good sensitivity to Z’ beyond LHC search reach • Scaling of sensitivities is only very rough estimate, for high CLIC energies detailed studies necessary, in particular accuracy of polarization measurement • Polarization is essential to disentangle the Z’ model S. Riemann, CLIC Z’

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