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Exploiting spin effects to unravel the structure of NP at a future LC

Exploiting spin effects to unravel the structure of NP at a future LC. ‘Big’ HEP questions Physics case for polarized beams Requirements to a Linear Collider Requirements to a Z-factory Summary. Gudrid Moortgat -Pick Hamburg University. ‘Big’ questions …and possible answers.

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Exploiting spin effects to unravel the structure of NP at a future LC

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  1. Exploiting spin effects to unravel the structure of NP at a future LC • ‘Big’ HEP questions • Physics case for polarized beams • Requirements to a Linear Collider • Requirements to a Z-factory • Summary GudridMoortgat-Pick Hamburg University SPIN2010, Jülich, 28.9.10 GudridMoortgat-Pick

  2. ‘Big’ questions …and possible answers • Shortcomings of the Standard Model • Establish electroweak symmetry breaking LC • Hierarchy problem? • Unification of all interactions? • Embedding of gravity in field theory? • Baryon asymmetry in Universe? • Content of dark matter • Neutrino mixing and masses • Why is new physics expected at TeVscale? • Protect hierarchy between mweak and mplanck • Dark matter consistent with sub-TeV scale WIMPs Higgs mass with respect to large quantum corrections: SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  3. ‘Big’ questions …and possible answers • Shortcomings of the Standard Model • Establish electroweak symmetry breaking LC • Hierarchy problem? LHC, LC • Unification of all interactions? LC • Embedding of gravity in field th? cosmo,LHC, LC • Baryon asymmetry in Universe? v-, cosmo, LHC, LC • Content of dark matter?v-, cosmo, LHC, LC • Neutrino mixing and masses v-, cosmo-exp. SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  4. ‘Big’ questions …and possible answers • Shortcomings of the Standard Model • Establish electroweak symmetry breaking LC • Hierarchy problem? LHC, LC • Unification of all interactions? LC • Embedding of gravity in field theory? cosmo,LHC, LC • Baryon asymmetry in Universe? v-, cosmo, LHC, LC • Content of dark matterv-, cosmo, LHC, LC • Neutrino mixing and masses v-, cosmo-exp. • Goal of a Linear Collider? • observe, determine and precisely reveal the structure of the underlying physics model ! SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  5. Required features at LHC & ILC LC, today only LHC, LC: CP e.g. LC, partially LHC SPIN2010, Jülich, 28.9.10 GudridMoortgat-Pick

  6. Characteristics of pp collider composite particles collide E(CM) < 2 E(beam) strong interaction in initial state `no' polarization applicable LHC: √s = 14TeV, used ŝ = x1x2s few TeV small fraction of events analyzed multiple triggers superposition with spectator jets Large potential for direct discovery and of the e +e-(γe, γ γ) collider Pointlike particles collide Known E(CM) = 2 E(beam) well defined initial state polarized initial e- and e+ beams ILC: √s = 500 GeV -- 1 TeV, tunable most events in detector analyzed no triggers required clean +fully reconstructable events Large potential for discovery also via high precision Why a linear collider? SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  7. The unique advantage of e+e- • Their clean signatures allow precision measurements • Sensitive to the theory at quantum level (i.e. contributions of virtual particles, ‘higher orders’)! • Such measurements allow predictions for effects of still undiscovered particles, but whose properties are defined by theory. Enables powerful discoveries and/or consistency checks and the determination of the underlying structure! t SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  8. Requirements for such`precision frontier’ ICFA Parameter Group for a future LC: SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  9. Why are polarized beams required? • Please remember: excellent e- polarization ~78% at SLC: • led to best measurement of sin2θ=0.23098±0.00026 on basis of L~1030 cm-2s-1 • Compare with results from unpolarized beams at LEP: • sin2θ=0.23221±0.00029 but with L~1031cm-2s-1 See importance and more details later when discussing ‘Z-factory’ • Comprehensive list of physics examples with polarized beams at a LC: GMP et al., Physics Rept., hep-ph/0507011 • Only few examples here, has to be weighted wrt LHC expectations! SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  10. Beam polarization at HEP colliders SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  11. Beams polarization at linear colliders • Polarized e- beams: • strained photocathode technologies (SLC, etc. ) • see talks at PESP@Bonn, W. Hillert • expected for the LC P(e-)~80-90% • Polarized e+ beams: e+ polarization is an absolute novelty! • Expected at ILC P(e+) ~ 60% • in RDR baseline already ~30% achievable • see talks by A. Schaelicke, K. Laihem • Measurement via Compton polarimetry: ΔP/P<0.25% exp. • see talks by M. Beckmann, D. Kaefer SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  12. Short overview: e+ sources at ILC -200m e+ yield and polarization depends on beam energy and undulator length SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  13. Short overview: e+ sources at ILC s -200m • in general: demanding challenges for the e+ source! e+ yield and polarization depends on beam energy and undulator length SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  14. Physics: pol.cross sections in general Polarized cross sections can be subdivided in: σRR, σLL, σRL, σLR are contributions with fully polarized L, R beams. In case of a vector particle only (LR) and (RL) configurations contribute: SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  15. Effective polarization • Effective polarization: SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  16. Relation between Peffand ALR • How are Peffand ALR related? • That means: • With pure error propagation (and errors uncorrelated), one obtains: • With SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  17. Gain in accuracy due to P(e+) SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  18. P(e±) sensitive to interaction structure Definition: Helicityλ=s * p/|p| ‘projection of spin’ Chirality= handedness is equal to helicity only of m=0! • Annihilation channel: SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  19. Complete fixing of initial state via P(e+) • Scattering channel: direct access to chirality of final state ! from SM processes SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  20. Something ‘new’ detected at early LHC • Supersymmetry-like signals • New physics model with high predictive power • ‘light’ SUSY consis- tent with precision fits • Extra gauge bosons and/or large extra dimensions • High precision in indirect searches allow model distinction and couplings determination SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  21. Verify SUSY properties at ILC in t-channel SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  22. Slepton `chiral’ quantum numbers SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  23. Models with extra dimensions • String theory: 10 or 11 dimensions of space-time • Extra dimensions ‘compactified’, too small to be detected so far: To a tightrope walker, the tightrope is one-dimensional: he can only move forward or backward But to an ant, the rope has an extra dimension: the ant can travel around the rope as well ! SPIN2010, Jülich, 28.9.10 GudridMoortgat-Pick

  24. Searches for extra dimensions SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  25. Extra dimensions Distinction between SM and different models of extra dimensions • Detect and determine new kind of physics even in the multi-TeV range • Transversely-polarized beams require P(e-) and P(e+) ! SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  26. Polarimetry requirements • SLC experience: measured ΔP/P=0.5% • Compton scattered e- measured in magnetic spectrometer • Goal at ILC: measure ΔP/P≤0.25% • Dedicated Compton polarimeters and Cherenkov detectors • Use upstream and downstream polarimeters • Machine feedback and access to luminosity-weighted polarization • Use also annihilation data: `average polarization’ • Longterm absolute calibration scale, up to ΔP/P=0.1% SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  27. Compton polarimetry at ILC • Upstream polarimeter: use chicane system • Can measure individual e± bunches • Prototype Cherenkov detector tested at ELSA! • Downstream polarimeter: crossing angle required • Lumi-weighted polarization (via w/o collision) • Spin-tracking simulations required SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  28. Expected depolarization effects • In general: two effects cause depolarization • Largest Effects during beam-beam interaction • Spin precession (T-BMT) and spin-flip (ST) effects • Have been compared for ILC and CLIC: • Theoretical updates due to strong field environment • See also talk by A. Hartin • Spin treatment in DR, spin rotators, BDS under work • See also talks by D. Barber SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  29. EW precision measurements@Z-factory • GigaZ option at the ILC: • high-lumi running on Z-pole/WW • 109 Z in 50-100 days of running • Needs machine changes (e.g. bypass in the current outline) • Dedicated Z-factory: • fraction of GigaZ • but strong physics case given already now! • Both facilities need polarized e- and e+ beams • Use of Blondel scheme required to get ΔP/P≤0.1% • Measurement of e.g. sin2θW with unprecedented precision achievable! SPIN2010, Jülich, 28.9.10 GudridMoortgat-Pick

  30. Why electroweak precision data? SPIN2010, Jülich, 28.9.10 GudridMoortgat-Pick

  31. Relevance of ew data today • Most sensitive observables: mW, sin2θeff,(g-2)μ,… • Large discrepancy between ALR(l) and AFB(b) • world average: sin2θeff=0.23153±0.00016 (central value, errors added in quadrature →brute force) • Impact of this measurement ? ←in b’s SPIN2010, Jülich, 28.9.10 GudridMoortgat-Pick

  32. Measuring the ew mixing angle • Measuring the AFB , ALR can be interpreted as measuring sin2θW • LEP result: sin2θW=0.23221±0.00029 • SLC result: sin2θW=0.23098±0.00026 • Discrepancy between AFB and ALR -> impact on Higgs tests ! SPIN2010, Jülich, 28.9.10 GudridMoortgat-Pick

  33. mW vs. central value sin2θeff → Consistent with SM and SUSY SPIN2010, Jülich, 28.9.10 GudridMoortgat-Pick

  34. mW vs. SLD-value sin2θeff → not consistent with the SM SPIN2010, Jülich, 28.9.10 GudridMoortgat-Pick

  35. mW vs. LEP -value sin2θeff → not consistent with neither SM nor SUSY SPIN2010, Jülich, 28.9.10 GudridMoortgat-Pick

  36. 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 SPIN2010, Jülich, 28.9.10 GudridMoortgat-Pick

  37. Blondel scheme for GigaZ / Z-factory — • Measurement of sin2θ in e+e-→Z→f f : • With Blondel Scheme at ILC: • (80%,60%) : Δsin2θ= 1.3x10-5 • but Δmtop= 0.1 GeV required! • With Blondel Scheme at a Z-factory: • and still Δmtop~1 GeV (i.e. before ILC run): Δsin2θ= 1x10-4 useful! • but polarized beams required, i.e. P(e+)≥ 20% ! SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  38. Summary • Polarized e- and e+ beams to optimize LC physics potential • Not only powerful for ‘chirality’ and couplings of new particles! • Physics potential of either GigaZ or Z-factory a.s.a.p. • Δsin2θ <1x10-4 seems reasonable now! • Special care of machine design needed to exploit polarization • High lumi source designs, spin rotators, precise spin tracking • Precise Compton polarimetry (up- and downstream) …. But polarization is these efforts worth ! … • Further news on polarization at a LC • Webpages: www.ippp.dur.ac.uk/LCsources • Further spin effects under work, e.g. CP at LHC, LC, ….. SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  39. Relevance in worst case scenarios • Hints for new physics in worst case scenarios: • Only Higgs @LHC • No hints for SUSY • Deviations at Zpole • Hints for SUSY • Discrepancy SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

  40. mtop= 173.3 +- 1.1 GeV • Further important input quantities: mass of top • δsin2θ ~ 1 x 10-4 would be reasonable now (i.e. before ILC run) ! LHC ILC SPIN2010, Jülich, 28.9.10 Gudrid Moortgat-Pick

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