1 / 40

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.

domani
Download Presentation

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

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related