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Very Forward Region Instrumentation

Detailed overview of Wolfgang Lohmann's design functions and requirements for BeamCal and LumiCal, emphasizing precision, hermeticity, and shielding in forward region instrumentation.

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Very Forward Region Instrumentation

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  1. Very Forward Region Instrumentation Wolfgang Lohmann, DESY Basic functions: • Hermeticity to small polar angles • Fast and precise Luminosity measuremt • Shielding of the inner detectors- LDC meeting

  2. Shielding function 20mrad solenoid 20mrad DID • backscattering from pairs hitting the LumiCal edge LDC meeting

  3. Current design and Lumi measurement Head-on or small X-angle Gauge process: Bhabha Scattering Device: LumiCal 26 < q < 82 mrad BeamCal 300 cm VTX L* = 4m Beampipe FTD IP Accuracy (from Physics) O(<10-3)

  4. LumiCal LumiCal IP LumiCal Requirements on the Mechanical Design < 4 μm Requirements on Alignment and mechanical Precision (MC simulations, BHLUMI) Inner Radius of Cal.: < 4 μm Distance between Cals.: < 100 μm Radial beam position: < 0.6 mm < 0.6 mm

  5. Comparison head-on, 2, 20 mrad Radial beam shift: 400mm Centered around the outgoing beam Centered around the detector axis For a 20 mrad design LumiCal MUST be centered around the outgoing beam-pipe!

  6. Background in the LumiCal : (500 GeV, TDR) Zero or small X-angle: neglegible 20 mrad X-angle: 3-5 TeV Beamstrahlung pair background using serpentine field Number of Bhabha events as a function of the inner Radius of LumiCal 250 GeV Background from beamstrahlung

  7. Collaboration FCAL High precision design Head-on design Overlap region LumiCal rmin=8 cm rmax=28 cm BeamCal rmin=1.5 cm rmax=10 cm Beam hole ECFA2005 7

  8. Collaboration FCAL High precision design X- angle design (2 mrad) LumiCal rmin=13 cm rmax=28 cm (Reasonable Statistics) BeamCal rmin=2 cm rmax=16 cm Beam hole Larger hole for the beampipe  less Shielding for the inner detector ECFA2005 8

  9. Detectors are centered around the outgoing beam Collaboration FCAL High precision design X- angle design (step-2) BeamCal + 30o blind area (incoming beam) ECFA2005 9

  10. Technology Sensor carriers Si/W sandwich calorimeter, simulations at advanced level. No hardware devolepment up to now. Absorber carriers Mechanical frame: Decouple sensor support from absorber support structure

  11. BeamCal Zero (or 2 mrad) crossing angle • e+e-Pairs from Beamstrahlung are deflected into the BeamCal • 15000 e+e- per BX 10 – 20 TeV (10 MGy per year) • direct Photons for q < 200 mrad GeV 20 mrad Crossing angle Background in the BeamCal : (500 Gev, TDR) Zero or small X-angle: 30 TeV/BX 20 mrad X-angle: 60 TeV/BX

  12. Solutions for 20mrad X-angle Enlarge the radius of BeamCal DID, 20 mrad DID, large aperture (Ri(LumiCal) > 13cm) 20mrad AntiDID Anti-DID Field

  13. Detection of High Energy Electrons and Photons (Detector Hermeticity) √s = 500 GeV Single Electrons of 50, 100 and 250 GeV, detection efficiency as a function of R (‘high background region’) Detection efficiency as a function of the pad-size Red – high BG blue – low BG Message: Electrons can be detected!

  14. Beam Parameter Determination with BeamCal Observables total energy first radial moment thrust value angular spread L/R, U/D F/B asymmetries 20 mrad crossing angle Also simultaneous determination of several beam parameter is feasible, but: Correlations! Analysis in preparation PRELIMINARY!

  15. Technology for the BeamCal: • Radiation Hard • Fast • Compact W-Diamond sandwich sensor Space for electronics

  16. For a small crossing angle a pretty advanced design of the very forward region is worked out For 20 mrad crossing angle some studies are redone The forward calorimeters must be centered around the outgoing beampipe • -Complex mechanics • -interference with ECAL • -difficult background situation FE electronics – so far some ideas

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