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Advanced Instrumentation Design for LumiCal at 500 GeV

Explore the innovative design of LumiCal for LHC detectors, focusing on hermeticity, luminosity measurement precision, and shielding functions. Detailed insights on technology, simulations, and performance factors are examined to enhance beam parameter determination and efficiency.

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Advanced Instrumentation Design for LumiCal at 500 GeV

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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- Valencia Workshop

  2. Shielding function Due to the small bunch size sx~100nm, sy~5 nm and the large bunch charge, N x 1010/bunch, beamstrahlung becomes important 20mrad solenoid lots of e+e- pairs LDC meeting 20mrad DID

  3. Current design Head-on or small X-angle Bhabha Scattering LumiCal 26 < q < 82 mrad BeamCal 4 < q < 28 mrad 300 cm VTX Beampipe FTD IP PhotoCal downstream (100 < q < 400 mrad L* = 4m

  4. Precise Luminosity Measurement, LumiCal Two Fermion Cross Sections at High Energy, Physics Case: Giga-Z , e+e- W+W- Gauge Process: e+e- e+e- (g) Goal: <10-3 Precision • Technology: Si-W Sandwich Calorimeter Optimisation of Shape and Segmentation, Key Requirements on the Design • MC Simulations

  5. Requirements on the Mechanical Design LumiCal IP LumiCal < 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

  6. 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

  7. 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!

  8. Performance Simulations for e+e- e+e-(g) 0.13e-3 rad 0.11e-3 rad 30 layers 15 rings value of the constant Simulation: Bhwide(Bhabha)+CIRCE(Beamstrahlung)+beamspread Event selection: acceptance, energy balance, azimuthal and angular symmetry. Constant value 4 layers 11 layers 15 layers 10 rings 10 rings 20 rings • More in the talks by Halina Abramowicz

  9. background Background in the LumiCal : (500 GeV, TDR) Zero or small X-angle: negligible 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

  10. 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) • Radiation hard sensors needed 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

  11. 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!

  12. Beam Parameter Determination with BeamCal Fast Lumi estimate and feedback for beam steering Observables total energy first radial moment 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!

  13. and with PhotoCal IP >100m Photons from Beamstrahlung Heavy gas ionisation Calorimeter nominal setting (550 nm x 5 nm) L/R, U/D F/B asymmetries of energy in the angular tails

  14. Technologies for the BeamCal: • Radiation Hard • Fast • Compact Heavy crystals W-Diamond sandwich sensor Space for electronics

  15. Sensor prototyping, Crystals Light Yield from direct coupling Compared with GEANT4 Simulation, good agreement and using a fibre ~ 15 % Similar results for lead glass Crystals (Cerenkov light !)

  16. Sensor prototyping, Diamonds Scint.+PMT& Diamond (+ PA) gate signal ADC Pads Pm1&2 May,August/2004 test beams CERN PS Hadron beam – 3,5 GeV 2 operation modes: Slow extraction ~105-106 / s fast extraction ~105-107 / ~10ns (Wide range intensities) Diamond samples (CVD): - Freiburg - GPI (Moscow) - Element6

  17. Diamond Sensor Performance Linearity Studies with High Intensities (PS fast beam extraction) 105 particles/10 ns Response to mip Particle flux, N/cm2/10ns

  18. Univ. of Colorado, Boulder, AGH Univ., INP & Jagiell. Univ. Cracow, JINR, Dubna, NCPHEP, Minsk, FZU, Prague, IHEP, Protvino, TAU, Tel Aviv, DESY, Zeuthen look to our web-page: http//www.zeuthen-desy.de/LC/FCAL We would be happy to welcome you to fight together!

  19. Summary • Many (and promising) results in simulations/design studies • Concept for a Luminometer for small crossing angle is advanced, 20 mrad needs a different design – work to be done • compact and fine segmented calorimeters necessary, needs R&D • radiation hard sensors for the inner calorimeter – needs R&D • Mechanics design just started, needs effort • no electronics concept so far • Prototype tests mandatory Remark: • The instrumentation of the forward region is relatively independent of the detector concept,

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