Impact of Polarization at the Z-Pole: Physics Case Summary

1. Z-factory: lumi and polarization updates • Physics Case ‘short summary • Impact of polarization at the Z-pole ‘parameter play’ G. Moortgat-Pick

2. Physics Case: Z-pole data • Why do we need such data a.s.a.p.? • E.g. discrepancy between ALR(l) and AFB(b) • SLD: best single measurement, based on 5x105 Z’s • world average: sin2θeff=0.23153±0.00016 (central value, errors added in quadrature) • most sensitive observables: mW, sin2θeff,(g-2)μ,… We do need it already now ….. ←in b’s G. Moortgat-Pick

3. Electroweak precision data G. Moortgat-Pick

4. Relevance for ‘Higgs’ • Higgs prediction but also powerful consistency test! (see later) G. Moortgat-Pick

5. mW vs. central value sin2θeff → Consistent with SM and SUSY G. Moortgat-Pick

6. mW vs. SLD-value sin2θeff → not consistent with the SM G. Moortgat-Pick

7. mW vs. LEP -value sin2θeff → not consistent with neither SM nor SUSY G. Moortgat-Pick

8. Relevance for SUSY/New Physics Today: Δswq=1.6x10-4 ~1x10-4 G. Moortgat-Pick

9. mt vs. central value sin2θeff G. Moortgat-Pick

10. mt vs. SLD -value sin2θeff G. Moortgat-Pick

11. mt vs. LEP -value sin2θeff • And please remember: sin2θsensitive to SUSY also in worst case scenarios (‘LHC sees nothing’) ! G. Moortgat-Pick

12. What’s about other models? Z’@GigaZ? • Z-Z’ mixing effects: impact of heavy new gauge bosons at GigaZ → extends even LHC region in some models! G. Moortgat-Pick

13. mtop= 173.3 +- 1.1 GeV • Further uncertainties: G. Moortgat-Pick

14. Which accuracy should be envisaged? • δsin2θ ≤ 1 x 10-4 would be reasonable now (i.e. before ILC run) ! Conservative approach: • accept only luminosities that yield δsin2θ≤5x10-5 • assume ΔP/P=0.5% (SLD achieved: 0.25%) • Assume 500 days of running • Which polarization is needed? Two cases: • Both P(e-)=P(e+) (‘RR’) • P(e-)=90%, P(e+)= variable (‘LR’) G. Moortgat-Pick

15. What’s the role of polarization? • Statistical uncertainty of ALR • If only polarized electrons:Δ ALR given by polarimeter uncertainty → depends on ΔσL, ΔσR, ΔP/P → main uncertainty at LC from ΔP/P~ 0.5 %→ 0. 25%... • If both beams are polarized: Blondel scheme →uncertainty depends on ΔσLL, ΔσLR, ΔσRL, ΔσRR not on ΔP/P ! →Some running in LL and RR required, about 10-20% of the time G. Moortgat-Pick

16. Lumi requirements (up to 1x1033) • P(e-)=90% • P(e-)=P(e+) • Boundary (δsin2θ< 5x10-5) not achievable without P(e+)! • (At GigaZ: several 1033 needed to get 9.5x10-5 with P(e-) only) G. Moortgat-Pick

17. Lumi requirements (up to 2x1032) • P(e-)=90% • P(e-)=P(e+) • Remark: ‘kinks’ no physics, just my ‘quantized’ step approach… G. Moortgat-Pick

18. Lumi requirements (up to 7x1031) • P(e-)=90% • P(e-)=P(e+) • ‘Minimum’ polarization: ~P(e-)=P(e+)=25% (‘RR’) • ~ P(e+)=20% (‘LR’) G. Moortgat-Pick

19. Further needs…. • Stable energy: since ΔALR / Δ√s ~ 0.2% / GeV • Energy spread should be controlled to ~MeV • Well understood and stable polarization (‘spin tracking’) • helicity flipping (if not: only alternative Blondel scheme applicable, loss of factor 2 in precision ) • Beamstrahlung has to be known to ~few % G. Moortgat-Pick

20. Conclusions • Promising potential to achieve: δsin2θ <1x10-4 • Please remember: all results shown here were for δsin2θ <5x10-5 ! (factor 2 safety limit!) • ‘Minimum P(e+)’~25% (for very moderate lumi) • But P(e+) is mandatory! • Paper on ‘Z-pole’ in queue • was originally triggered by ‘physics use of ILC Z-pole calibration data’ • Polarization session at ECFA workshop: • Scheduled ‘polarization needs at Z-pole’ G. Moortgat-Pick