Experimentation at the International Linear Collider

1. Experimentation at the International Linear Collider Felix Sefkow DESY Seminar on Particle and Astrophysics Uni Zürich, October 20, 2004

2. Outline • Physics case • Physics performance goals • Detector design considerations • Detector R&D Experimentation at the International Linear Collider

3. Anticipated discoveries • The history of particle physics is full of predicted discoveries: • Positron, neutrino, pions • Quarks, gluons • W, Z bosons • Charm, bottom • Most recent example: top • … Mostly made at hadron machines Zooming into the top mass Experimentation at the International Linear Collider

4. Complemented with precision • A success story to be continued: • e+e- colliders needed to investigate in detail the hadron machine discoveries • Charm physics at SPEAR • B physics at CESR and factories • Z (and W) boson properties at LEP Closing up to the Higgs Experimentation at the International Linear Collider

5. 21st century physics • Fundamental questions on matter, energy, space and time: • How do particles acquire mass? • Is there a Higgs boson? Where? • What is the origin of electroweak symmetry breaking? • Do the fundamental forces unify? • How does gravity tie in? • What is the universe made of? What is dark matter? Experimentation at the International Linear Collider

6. New physics around the corner • We expect the answers at the TeV scale • I.e. from the immediate generation of new colliders • For theoretical reasons: • SM w/o Higgs is inconsistent above ~ 1.3 TeV • Fine-tuning problem if nothing between mW and mPlanck • For experimental reasons • Electroweak precision data want Higgs below 200 GeV • Astrophysics wants a dark matter particle of few 100 GeV Experimentation at the International Linear Collider

7. The next steps • Therefore: New physics at the origin of electroweak symmetry breaking is expected to be discovered at the next (or even present) generation of hadron collider experiments • Whatever these discoveries will be… • Light Higgs • Heavy Higgs • New particles • No Higgs, no nothing • .. an e+e- collider with 0.5-1 TeV energy is needed to study it • Case has been worked out and well documented (e.g. TESLA TDR) • Independent of LHC findings, see e.g. answers to ITRP Experimentation at the International Linear Collider

8. The Linear Collider consensus • 200 GeV < √s < 500 GeV • Integrated luminosity ~ 500 fb-1 in 4 years • Upgrade to 1TeV • 2 interaction regions • Concurrent running with the LHC Experimentation at the International Linear Collider

9. If there is a light Higgs • Measure its profile • Quantum numbers • Couplings to fermions • Couplings to gauge bosons • Self coupling • Prove that the Higgs is the Higgs • Do Higgs precision physics • Deviations from SM, admixtures, SUSY Higgs e.g. spin Experimentation at the International Linear Collider

10. Z Z If there is a heavy (or no) Higgs • This is physics beyond the Standard Model • Something must be in the loops • Exploit precision potential of LC (tune energy, polarization, e option) • Really nothing overlooked at LHC? • Probe virtual effects • E.g. sensitivity of triple / quartic gauge couplings reaches far into the TeV range Experimentation at the International Linear Collider

11. If there are new states of matter • Example Supersymmetry • Precision measurements of SUSY particle masses and couplings • E.g. neutralino mass: δm/m ~ 10-3 allows extrapolation to GUT scale Gluino (LHC) (in mSUGRA model) Experimentation at the International Linear Collider

12. Or extra dimensions • Measure the number of extra space dimensions • Via single photon production Experimentation at the International Linear Collider

13. LHC LC synergy (anytime) • LHC  LC: Common interpretation: Example: absolute top Yukawa coupling from gg,qqttH (Hbb,WW) (@LHC) ( rate ~ (gt gb/W)2 ) and BR(H bb,WW) (@LC) (absolute measurement of gb/W ) Experimentation at the International Linear Collider

14. LHC LC synergy (simultanous) • LHC  LC: Common analysis • Example: predict χ04 mass from SUSY parameters as determined from lowest chargino and neutralino states at LC • Know where to look for the edge in the dilepton spectrum at LHC Experimentation at the International Linear Collider

15. LC Physics case • The case for an e+ e- collider with 500 GeV – 1 TeV energy rests on general grounds and is excellent in different scenarios • In particular, it holds independent of LHC findings • LHC and LC complement each other in an exciting fashion • Most fruitfully if run concurrently Experimentation at the International Linear Collider

16. The ILC • 2004: ITRP recommends that the LC be based on superconducting RF technology • ILCSC and ICFA endorse unanimously • GLC, NLC, TESLA merge into ILC • First workshop November at KEK • Goal: TDR in 2007 • Use existing designs! Experimentation at the International Linear Collider

17. Timeline AcceleratorDetector • 2005 CDR Concept study, costing, R&D • 2007 TDR CDRs • 2008 site selection; proposals form Global Lab • 2009 TDRs • 2015 start commissioning Tied together Basic design choices Experimentation at the International Linear Collider

18. ZHH Precision physics • Discoveries and precision measurements • rare processes • often statistics limited • final states with heavy bosons W, Z, H • need to reconstruct their hadronic decay modes, multi-jet events • Excellent track resolution • Flavor tagging 500 events Experimentation at the International Linear Collider

19. Vertexing and Tracking • Vertex detector • Charm tagging (!): H  cc • Multi-jet combinatorics • Need 5 m  10 m / p • Main tracker • Higgs recoil • Slepton decay momentum endpoint • Need to be 10x better than LEP TPCs Experimentation at the International Linear Collider

20. Gaseous or Silicon? + easy pattern recognition + low material budget + robust and fast + no endplates, no HV Experimentation at the International Linear Collider

21. Jet energy resolution • Challenge: separate W and Z in their hadronic mode • Dijet masses in WW, ZZ events: LC design goal LEP-like detector Experimentation at the International Linear Collider

22. W, Z separation • Imagine – there is no Higgs: WW scattering violates unitarity at ~ 1.2 TeV, or new forces show up • irreducible background: ZZ • probe quartic gauge couplings up to EWSB scale of ~3 TeV Dilution factor vs cut: integrated luminosity equivalent Experimentation at the International Linear Collider

23. The Higgs boson total width • gives access to all couplings • for low MH from σ (WW fusion) • and BR (H → WW*) • worth 20% precision, 40% lumi, again 5 s/B in ZH → ZWW → 4jets ℓν 2 jet resol. Experimentation at the International Linear Collider

24. The Higgs potential • Is the Higgs the Higgs? • Check λ = M2H/2v2 6 jets Experimentation at the International Linear Collider

25. Triple Higgs signal • few tens of events • reconstruct observable from 3 dijet masses • impossible with a LEP-like detector Nev (1ab-1) s/√B 5 sigma Experimentation at the International Linear Collider

26. Other requirements • directional resolution • photon impact parameter (need e.g. few cm @ 20 GeV) • hermeticity • suppress two photon background to SUSY events • lepton identification • timing decay of a longlived neutralino Experimentation at the International Linear Collider

27. Time resolution • background pile-up from γγ→ hadrons can be a problem at the LC • ~ 1 event every 2 - 4 BX • on average 6 GeV per event in main calorimeter: • example: Higgs mass signal in WW fusion re-optimize cuts and window for each case preliminary • capability to time-stamp detector signals does affect physics performance Experimentation at the International Linear Collider

28. Physics performance goals • The excellent precision physics potential of an electron positron linear collider has to be matched by an unprecedented detector performance • The W vs. Z boson mass separation dictates a jet energy resolution of 30% / √E - twice as good as achieved in LEP detectors • Some key physics topics are exclusively accessible with such an advanced detector Experimentation at the International Linear Collider

29. Particle Flow Algorithms • Best jet energy resolution with minimum calorimetry • tracking detectors to measure energy of charged particles (65% of the typical jet energy) • EM calorimeter for photons (25%) • EM and HAD calorimeter for neutral hadrons (10%) Experimentation at the International Linear Collider

30. Contributions to s(Ejet) • With anticipated resolutions: Ideally realistically (courtesy D.Karlen) Experimentation at the International Linear Collider

31. The PFLOW paradigm • The confusion term dominates • Each particle should be reconstructed and measured separately • For the jet energy measurement spatial resolution / particle separation power is more important than energy resolution Experimentation at the International Linear Collider

32. Imaging calorimetry red: track based green: calorimeter based ZHHg qqbbbb Experimentation at the International Linear Collider

33. Calorimeter concept • large radius and length • to separate the particles • large magnetic field • to sweep out charged tracks • “no” material in front • stay inside coil • small Moliere radius • to minimize shower overlap • small granularity • to separate overlapping showers • figure of merit: B R2calo / (r2M+r2cell) Experimentation at the International Linear Collider

34. e+e–→ WW @ √s = 800 GeV 14% of events have > 50 GeV (32% for SD) Energy sum of close photons (GeV) Photon hadron separation • for smaller Rcalo can “buy” separation power with B, but… • magnetic field limited by mechanical stability : B2Rcoil < ~ 60 T2m • photons closer than rM to ch. hadron are difficult to reconstruct Eγ/ E SD TDR push rM and photon reconstruction to the limit rM (SD: R=1.27 m, here with 6T, TESLA TDR: R=1.68m, B=4T) (JC Brient) Experimentation at the International Linear Collider

35. Tungsten vs. iron • elm./had separation: keep X0 / λI small X0 = 1.8cm, λI=17cm X0 = 0.35cm, λI=9.6cm • Moliere Radius for W: rM = 0.9cm • effectively a factor ( 1 + Gap / 2.5mm ) more • technology challenge: thin readout gap Iron Tungsten (images courtesy H.Videau) Experimentation at the International Linear Collider

36. Silicon cost and area Curves of constant cost • optimize together with tracking system: # layers, radius and length • PFLOW emphasizes size over sampling 50 20 layers TESLA TDR cost/area ($/cm²) Length of the ECAL barrel 10 25 layers 30 layers DATA from H.F-W. Sadrozinski, UC-Santa Cruz SiD detector 2 $/cm² Internal radius of the ECAL Blank wafer price 6'' (JCB) 1 ~3000 m2 needed Experimentation at the International Linear Collider

37. ECAL optimization • overall detector geometry • thin sampling layer technology • photon reconstruction / separation Follow also other lines of development: • don’t completely forget energy resolution! • lead or tungsten scintillator calorimeters (Asia, Colorado) • hybrid silicon and scintillator sampling (Italy, Kansas) Experimentation at the International Linear Collider

38. Huge Detector concepts • Sizes • :5T 4T 3T • Si Tracker Gasous Tracker (+Si?) Gasous Tracker • SiW ECAL SiW or Hybrid ECAL Hybrid or Scint ECAL Experimentation at the International Linear Collider

39. Hybrid ECAL (Italy) • at Frascati • and CERN LCcal collaboration S.Miscetti Experimentation at the International Linear Collider

40. Joint European /Asian tests • 6 GeV electrons (slide from Tohru Takeshita) Experimentation at the International Linear Collider

41. Hadron calorimeter concepts • The HCAL should be imaging, too • Tungsten would be best, but chose iron for cost reasons Readout options: • Digital: radically imaging; counting hits with gas or scintillator • Analogue: classical scintillator – but pushing the granularity • semi-digital: scint. with small # of thresholds (2 bit ADC) Experimentation at the International Linear Collider

42. Number of cells hit Energy (GEV) Analog vs. digital • Digital: pad size 1cm asymptotic value • suppress Landau fluctuations: at low E superior to analogue • need ideas for high E, e.g. multiple thresholds (semi-digital) (V.Zutshi) Experimentation at the International Linear Collider

43. RPC analog Scint. digital Gas vs. scintillator • width of shower pattern appears larger in scintillator • will be recovered using amplitude or density information (L.Xia) Experimentation at the International Linear Collider

44. Gas HCAL optimization • RPC: comparison avalanche vs. streamer mode • pad multiplicity and energy resolution Geant 3 m= 2 1.4 • Alternative: GEM foils • R&D issues for both: • large area detectors, reliability • low cost electronics concept 1 (V.Ammosov) Experimentation at the International Linear Collider

45. Scintillator granularity • new photodetectors allow individual readout of small tiles Si Photo-Multiplier • optimize granularity for shower separation (A.Raspareza) Experimentation at the International Linear Collider

46. HCAL optimization For the scintillator option • granularity vs. amplitude for position and energy • optimize the new photodetectors • and study alternatives (APD, … ) • calibration and monitoring • nonlinear systems • pattern recognition software • (De-) tails are important: • confront high granularity HCALs with hadron beam stack for different HCAL options Experimentation at the International Linear Collider

47. Required sensitivity • 10’000 particles, compare Geant 3 (histo) vs. Geant 4 (points) (study by D.Ward) 1 GeV p+ longitud. (ECAL+HCAL) 50 GeV p+ Scintillator RPC transverse in HCAL 5 GeV p+ • differences vary with energy, particle type, detector material,… Experimentation at the International Linear Collider

48. Model dependence • There are no data to which this could have been tuned… Experimentation at the International Linear Collider

49. International effort • Linear collider detector R&D is partially organized in (open) proto-collaborations, e.g. CALICE: 164 Physicists, 28 Institutes, 9 Countries: 3 Regions • CALICE prepares beam test series in 2005-06 • ECAL and HCAL together, different options • electron and hadron beams, start end 2004 at DESY Experimentation at the International Linear Collider

50. Detector / Calorimeter concept • The linear collider physics represents a formidable challenge for calorimeters, • met by a world-wide R&D effort, internationally coordinated • An interesting test beam period is ahead of us, to sharpen our views on imaging calorimetry and particle flow algorithms, • to further push for overall optimized detector concepts Experimentation at the International Linear Collider