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Instrumentation of the Forward Region of the TESLA Detector

Instrumentation of the Forward Region of the TESLA Detector. International Europhysics Conference on High Energy Physics Aachen, July 19th 2003. TESLA. T eV E nergy S uperconducting L inear A ccelerator. Main Parameters Energy: 90 to 800+ GeV

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Instrumentation of the Forward Region of the TESLA Detector

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  1. Instrumentation of the Forward Region of the TESLA Detector International Europhysics Conference on High Energy Physics Aachen, July 19th 2003

  2. TESLA TeV Energy Superconducting Linear Accelerator • Main Parameters • Energy: 90 to 800+ GeV • Luminosity (500GeV): 3.4 x 1034 cm-2 s-1 • Beam size (500 GeV): 553 x 5 nm • Physics Potential • Precision measurements and searches in: • Higgs physics • Supersymmetry • EW precision tests (GigaZ) • QCD and top thysics • yet unimagined physics Karsten Büßer, EPS-HEP Conference Aachen

  3. The TESLA Detector • Detector Concept • Precision vertex detector • Large gas filled central tracking detector • Highly segmented calorimeters • 4T magnetic field, tracking detectors and calorimeters inside the coil Karsten Büßer, EPS-HEP Conference Aachen

  4. Beam Induced Backgrounds Main background source for the detector are beamstrahlung pairs Karsten Büßer, EPS-HEP Conference Aachen

  5. GEANT3simulation of 10 pair particles Tasks for the Forward Region • Shielding of the tracking detectors against backscattered beamstrahlung background • Provide instrumentation for: • Precision luminosity measurement • Hermeticity: • Extension of the energy flow measurement down to small angles • Beam diagnostics Karsten Büßer, EPS-HEP Conference Aachen

  6. TESLA Forward Calorimeters • Instrumented tungsten mask • Two calorimeters: • LAT • Low Angle Tagger • 27.5 – 83.1 mrad • actual task :„Luminosity Calorimeter“ • LCAL • Luminosity Calorimeter • 4.6 – 30 mrad • actual task: „Beam Calorimeter“ Karsten Büßer, EPS-HEP Conference Aachen

  7. Luminosity Measurement Physics Requirements:ΔL/L≈ 0.02% (GigaZ) Process: e+ e-→ e+ e- elastic Bhabha Scattering e+ e-→ e+ e-γ radiative Bhabha Scattering Statistics: for L= 3.4 x 1034 cm-2 s-1 rate R ≈ 170 Hz Systematics: • from detector acceptance: since σtot(Θmin,Θmax) ~ Θmin-2 – Θmax-2 ≈ Θmin-2 then ΔL/L= 2ΔΘmin/Θmin with Θmin= 27.5 mrad, ΔL/L= 10-4ΔΘmin= 1.4 µrad (!) • from theory: At LEP achieved: 5.0 x 10-4 Karsten Büßer, EPS-HEP Conference Aachen

  8. Low Angle Tagger Geometry (as defined in the TESLA TDR) • 14 cylinders in Θ • 24 sectors in Φ • 40 rings in z • 13440 cells in MC studies • Conical Setup • r: 4 – 12 cm • (not affected by • beamstrahlung pairs) • z: 140 – 200 cm • Silicon/Tungsten sandwich • 40 X0 The LAT serves as a shield ! Karsten Büßer, EPS-HEP Conference Aachen

  9. Energy Response Energy Resolution LAT Performance GEANT3 simulation studies show the response to high energetic electrons Karsten Büßer, EPS-HEP Conference Aachen

  10. LAT Performance Energy Response and Resolution Angular Resolution Red: Cut on desposited energy (>2.5 GeV) Karsten Büßer, EPS-HEP Conference Aachen

  11. LAT Outlook • New TESLA beam optics are under development which would allow to move the quads out of the detector (increasing l* from 3m to ≤5m). • Mask and calorimeters would move • Flat LAT seems possible • Simulation studies for a flat LAT are under way → angular resolutions down to 1.4 µrad are still challenging! • Alignment tolerances for detectors are stringent: • Δz < 60 µm • Δr < 0.75 µm • Alignment monitor system probably needed TESLA-TDR l*=3m Design study l*=4.1m Karsten Büßer, EPS-HEP Conference Aachen

  12. The LCAL Technology options under study: • Diamond -Tungsten Sandwich, rm~ 1cm • Crystal PbWO4, rm~ 2cm 30 layers, 30 X0 Karsten Büßer, EPS-HEP Conference Aachen

  13. LCAL and Pair Background Deposited Energy, Diamond/W Pairs from Beamstrahlung per bunch crossing (BX) Produced: #: ~130000, Etot: ~360 TeV on each LCAL: #: ~15000, Etot: ~20 TeV Dose: ≤ 10 MGy/y Karsten Büßer, EPS-HEP Conference Aachen

  14. LCAL as Beam Monitor nominal beam • Number of produced pairs is a measure of the luminosity • Deposited energy on the LCAL is input for the TESLA fast feedback system • rΦ energy distribution on the LCAL is an indicator for beam misalignments tilted beam: x‘=3.5 mrad Karsten Büßer, EPS-HEP Conference Aachen

  15. LCAL as Physics Device One 250 GeV electron and pair background from one BX Generated Background added Reconstructed Karsten Büßer, EPS-HEP Conference Aachen

  16. Reconstruction Simple algorithm: • subtract average (10 BX) background • search for cells with signal > 3σ of background fluctuation • require longitudinal chain of signal cells 4.6 mrad 30 mrad Karsten Büßer, EPS-HEP Conference Aachen

  17. Energy Resolution of the LCAL Energy resolution is dominated by the background Karsten Büßer, EPS-HEP Conference Aachen

  18. Fake Rates 500 BX Karsten Büßer, EPS-HEP Conference Aachen

  19. Conclusion • LAT • Luminosity measurment with 0.02% accuracy will be challenging • LCAL • Several technologies are under study • Detection of high energetic electrons is possible with high efficiency below 10 mrad • Energy resolution is dominated by background subtraction • Need to look into more clever algorithms • OUTLOOK • TESLA interaction region might change (increasing l*) • Redesign of the forward region, impact on calorimeters ? • R&D has started Test stand for Si and Diamond sensors in Zeuthen Karsten Büßer, EPS-HEP Conference Aachen

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