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Physics at a Future Linear Collider

Physics at a Future Linear Collider. Tobias Haas, DESY-F1 DIS04/WG E7 16 April, 2004. This Talk. Collider: Linear Collider Basics Rates and Backgrounds Polarisation Additional Collider Options Detector Considerations VXD, Tracking and Calorimetry Physics Higgs Supersymmetry

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Physics at a Future Linear Collider

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  1. Physics at a Future Linear Collider Tobias Haas, DESY-F1 DIS04/WG E7 16 April, 2004

  2. This Talk • Collider: • Linear Collider Basics • Rates and Backgrounds • Polarisation • Additional Collider Options • Detector Considerations • VXD, Tracking and Calorimetry • Physics • Higgs • Supersymmetry • Precision parameter determinations • Summary and conclusions Tobias Haas: Physics at a Future Linear Collider

  3. Acknowledgments • Material used here is based on work done for • TESLA TDR • US and Japanese LC studies • ECFA/DESY study • Ongoing ECFA LC study • In particular, I have used material from • K. Desch, E. Gross, H. Nowak, D. Miller, P. Grannis, G. Moortgat-Pick Tobias Haas: Physics at a Future Linear Collider

  4. Linear Collider Basics • LEP gave ~ 1 fb-1 /expt. in 11 years, with 107 Z0 LEP1 • At √s = 500 GeV one needs 500 fb-1 to get: • ~ 30,000 Zh120 • ~ 50,000 h120νν • 106 W+ W- • At √s = 1000 GeV one needs 1000 fb-1 to get: • ~ 6,000 HA (300GeV) • ~ 3,000 h500νν • ~ 2,000 WWνν (if no Higgs) • Need lots of luminosity to scan multiple thresholds, vary polarisation, go to γγ, e-γ, e-e- Tobias Haas: Physics at a Future Linear Collider

  5. Linear Collider Basics New problems, including: A decade of R&D at SLAC, DESY and KEK has given: Wakefields “Accelerator” Emittance growth ~ x100: More bunches with more charge. Disruption “Experiment” Beamstrahlung Pair production ~ 1/100 reduction in σy to 5 nm: Lower emittance, demagnify more Tobias Haas: Physics at a Future Linear Collider

  6. Linear Collider Basics 1010 electrons/bunch, with  ~ 106 dimensions ~ nanometers Big E and B fields • Disruption: • e+e- beams focus each other inward (L enhanced), then fly apart after collision: • e-e- defocus immediately (L reduced). • Beamstrahlung: • Synchrotron radiation in the field of the opposing bunch gives a smeared spectrum • Pair Production: • Incoming beam particles scatter from the beamstrahlung photons: Tobias Haas: Physics at a Future Linear Collider

  7. Rates and Backgrounds NLC bunch structure different but average flux the same • Much gentler than LHC: • Record everything and sort out offline: trigger-less Hard virtual photons from beam particles make h.e.  collisions. Cross section is dominated by resolved photon-photon (0.02/bx, c.f. 20/bx @ LHC) HERA input important for rate calculations. Tobias Haas: Physics at a Future Linear Collider

  8. Polarisation SLC has shown that e- can be polarised to ~80%; hope for more in 10 years. e- • Much harder: • Have to make polarised ’s, then pair produce e+e- • Needs e- with >160 GeV, so use incoming beam: • TESLA e+ source: If acceptances are restricted, should be possible to get ~50% e+ polarization, maybe more with reduced L. e+ • Uses: • Turn off SM bg processes (Anything that couples to W±) • Measure polarisation dependence of signal, e. g. asymmetries like ALR . • Sensitivity to CP. Tobias Haas: Physics at a Future Linear Collider

  9. Additional Collider Options Easiest: Add a second e- gun at the e+ end. Especially useful if SUSY sector complicated. (Needed for  and e) e-e- Use Compton backscattering of near-visible laser light: 2nd IR Right choice of e- and laser polarisations gives “monochromatic” peak with ~80% of full energy and ~50% of Lee .  e Include bypass in linac to get good L at MZ and 2MW; Polarisation is important; Hope for L = 5·1033. GigaZ Tobias Haas: Physics at a Future Linear Collider

  10. Detector Considerations • Vertexing: • Flavour tagging with high purity and efficiency • Tracking: • Momentum resolution to measure recoil masses • Calorimetry: • Good segmentation and excellent EM energy resolution Tobias Haas: Physics at a Future Linear Collider

  11. VXD for Heavy Flavour Identification • Flavour couplings of Higgs are basic to test SUSY scenarios: Many have different +2/3 vs. -1/3 couplings. b vs. c best hope. • 5 layers with 800 Mio pixels. Innermost layer at 1.5 cm • 0.03% X0/layer Tobias Haas: Physics at a Future Linear Collider

  12. Overall Tracking Higgs dictates: Whatever its decays, if coupled to Z0 (and light enough), will see its recoil against Z0→ e+e- or μ+μ- . Need momentum resolution: Tesla TDR Tesla TDR • TESLA TDR: • Silicon tracking inside a big TPC, B = 4T; • Good dE/dx; Tobias Haas: Physics at a Future Linear Collider

  13. Calorimetry/Energy Flow • In e+e- → VVνν: • Separate WW→ 4 jets from ZZ→ 4 jets • EWSB has to appear if nowhere else • In e+e- → tt → bbWW → 6 jets • Measure all the interesting features! Tobias Haas: Physics at a Future Linear Collider

  14. Summary of Assumptions • Machine: • √s = 500 … 1000 GeV • L= 2 … 3 x 1034 cm-2s-1 → several 100 fb-1/year • Polarisation: P(e-)  80%, P(e+)  60% • Detector: • Hermetic (H→ invisible) • Excellent EM calorimeter ( H→  ) • Excellent momentum resolution (ZH→ l+l-X, recoil mass) • Small beamspot (500x5 nm), small beampipe radius and VXD allow b/c separation and τ-ID Tobias Haas: Physics at a Future Linear Collider

  15. Higgs Physics ECFA/DESY Higgs LC working group, M. Battaglia, K. Desch, A. Djouadi, E. Gross, B. Kniehl, et al. • Several 104Higgs bosons produced / year for “light” Higgs; • Detection with high efficiency; • Nearly background free. Tobias Haas: Physics at a Future Linear Collider

  16. LC is a Higgs Analyzer • Measure Higgs properties: • Production rate, • Mass, • Lifetime, • Spin and parity. • Higgs Branching Fractions: • Matter couplings (ghff) • Gauge bosons (ghZZ) • Establish the Higgs Mechanism as EWSB by measuring the Higgs coupling to itself (λ) Tobias Haas: Physics at a Future Linear Collider

  17. Cross Section: HZ, Hνν Higgs Strahlung: Recoil mass ine+e-→ μ+μ-X WW-Fusion: Missing mass ine+e-→ ννbb N. Meyer, K. Desch (2000) • ΔσHνν 3 – 8 % P. Garcia-Abia, W. Lohmann (2000) • Very low bg; • Model independent; • ΔσZH  3% • μ+μ-, e+e- combined Tobias Haas: Physics at a Future Linear Collider

  18. ee → HZ → bbqq Use 5C fit to signal on top of bg ΔmH = 40 … 70 MeV Higgs Mass mH < 130 GeV mH > 2 mZ mH (GeV) • ee → HZ → ZZZ , ZWW • H → ZZ, WW with hadronic decay, so no missing energy • Use 4C kin fit • ΔmH 400 MeV (0.2%) • ΔΓH 800 MeV (25%) Tobias Haas: Physics at a Future Linear Collider

  19. For √s~mH+mZ (Threshold) For J=0 σ~β J=1 σ~β3 J=2 σ~β5 Threshold scan with 20 fb-1/pt P: Angular Distribution: Spin and Parity Tobias Haas: Physics at a Future Linear Collider

  20. Battaglia, Borissov, Richard (1999) Higgs Branching Fractions • Disentangle bb, cc and gg using simultaneous fit to lifetime-sensitive variables: 500 fb-1 Tobias Haas: Physics at a Future Linear Collider

  21. σ(HHZ) is very small: < 0.1 fb Signature: 4 b-tagged jets + Z Unfold coupling from total cross section Need very high lumi: (1000 fb-1 @ 500 GeV) Higgs Selfcoupling and Higgs Potential Tobias Haas: Physics at a Future Linear Collider

  22. Summary on Higgs • The LC will do an excellent job on profiling the Higgs: • Determine JPC unambiguously, • Accurate mass and width, • Measure the branching fractions for all dominant decays; distinguish SM from SUSY Higgs; verify the coupling to mass, • Measure the Higgs self couplings; determine the potential. Tobias Haas: Physics at a Future Linear Collider

  23. Aim: Precise mass and cross section measurements of all kinematically accessible sparticles: Explore SUSY breaking mechanism, Unification at High Energy? Supersymmetry Tobias Haas: Physics at a Future Linear Collider

  24. Tobias Haas: Physics at a Future Linear Collider

  25. SUSY Scenarios and Examples Only scenario with squarks in reach of LC500 Tobias Haas: Physics at a Future Linear Collider

  26. mSUGRA Scenario SPS5 Tobias Haas: Physics at a Future Linear Collider

  27. Example 1: Light stop • If mstop< 250 GeV, may not be detected at LHC • Assumptions: • mstop= 180 GeV • cosθt = 0.57 • Δm < mW • topology: • 2c jets + Emiss • 2b jets + Emiss Tobias Haas: Physics at a Future Linear Collider

  28. Example 1: Light stop • Procedure: • Use 9 event variables (Evis,N0 jets, thrust, N0 clusters, E║miss, E┴miss, jets, acoplanarity, M(jets)) • Charm tag (ZVTOP) • Feed into NN or Iterative Discriminant analysis • Polarization! Tobias Haas: Physics at a Future Linear Collider

  29. Topology: 2 acoplanar muons + Emiss Require good muon detection efficiency of the detector Small backgrounds: SM: 2f, 2γ, 4f processes SUSY: like χ20χ1+ Use the “Endpoint” method Example II: Scalar Muons Tobias Haas: Physics at a Future Linear Collider

  30. Example II: Scalar Muons • smuons decay isotropically: • decay spectrum is flat except for radiation effects: • Relate the two kinematic endpoints to the masses of smuon and neutralino • ΔM=200MeV E1 E2 Tobias Haas: Physics at a Future Linear Collider

  31. Example III: Threshold Scans • Good choice if mass range already known (e. g. top, or something found at LHC) • Precision: • Limited by the beam spread (1%) • Statistics • Remember “beamstrahlung”, ISR and FSR • Gives also info about the nature of a sparticle: • σ ~ β3 (Boson) • σ ~ β (Fermion) Tobias Haas: Physics at a Future Linear Collider

  32. Threshold Scan: top • is the classic • is very clean • Fit mt from the excitation curve • 10 fb-1/point • δ(mt) ~ 100 MeV αS mt Tobias Haas: Physics at a Future Linear Collider

  33. Σ(lumi)=100 fb-1 10 fb-1/point a few months of running δ(mμ) < 100 MeV Threshold Scan: smuon ~ Tobias Haas: Physics at a Future Linear Collider

  34. Threshold Scan: neutralino • Same procedure • δ(mμ) ~ 50MeV • possibly also squarks if light enough! ~ Tobias Haas: Physics at a Future Linear Collider

  35. Mass Accuracy Tobias Haas: Physics at a Future Linear Collider

  36. From the physical observables Reconstruct the mass parameters at the EW scale according to Evolve the parameters to high scale through the RGE’s e. g. mSUGRA gives a very different pattern than GMSB What is the Mechanism of SUSY Breaking?Extrapolate to High Energies! mSUGRA GMSB Tobias Haas: Physics at a Future Linear Collider

  37. Summary and Conclusions • An e+e- collider with 500 … 1000 GeV has a very rich program or new physics • It is an essential complement to the LHC • Precise exploration of Higgs boson properties • Establish essential elements of the Higgs mechanism • Very precise measurement of SUSY parameters • Extrapolate to the GUT scale • Studies are being performed at a very detailed level all around the world • The next ECFA LC workshop is next week in Paris • I hope we will manage to start building it within the foreseeable future. Tobias Haas: Physics at a Future Linear Collider

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