Instrumentation of the Very Forward Region of a Linear Collider Detector

1. Instrumentation of the Very Forward Region of a Linear Collider Detector Wolfgang Lohmann, DESY Snowmass Workshop

2. Used by H. Yamamoto 0.5 0.4 113mrad 0.3 Inst. Mask BeamCal W 0.2 300 cm QD0 W 0.1 Pair-LuMon 46mrad VTX 0 LowZ Mask BeamPipe L* = 4m Exit radius 2cm @ 3.5m -0.1 W W -0.2 ECAL Support Tube -0.3 FTD IP -0.4 HCAL YOKE LumiCal 5 Tesla -0.5 4 0 0.5 1 1.5 2 2.5 3 3.5 Simulation studies on several designs SiD Forward Masking, Calorimetry & Tracking,20 mrad crossing angle Design for 0-2 mrad crossing angle (FCAL design)

3. Functions of the very Forward Detectors BeamCal 300 cm VTX L* = 4m FTD IP LumiCal • Detection of electrons and photons at small polar angles- important for searches (see talk by Philip&Vladimir • Measurement of the Luminosity with precision O(<10-3) using Bhabha scattering (see talk by Halina) • Shielding of the inner Detectors • Fast Beam Diagnostics LumiCal: 26 < q < 82 mrad BeamCal: 4 < q < 28 mrad PhotoCal: 100 < q < 400 mrad PhotoCal downstram

4. Measurement of the Luminosity (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 (rough Estimate) Inner Radius of Cal.: < 1-4 μm Distance between Cals.: < 60 μm Radial beam position: < 0.7 mm < 0.7 mm

6. Concept for the Mechanical Frame Decouple sensor frame from absorber frame Sensor carriers Absorber carriers

7. 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

8. X- angle background Beamstrahlung pair background using serpentine field Number of Bhabha events as a function of the inner Radius of LumiCal 250 GeV Christian Grah, DESY-Zuethen Background from beamstrahlung

9. Fast Beam Diagnostics (BeamCal and PhotoCal) e+ e- • e+e-Pairs from Beamstrahlung are deflected into the BeamCal Zero crossing angle • 15000 e+e- per BX 10 – 20 TeV (10 MGy per year) • direct Photons for q < 200 mrad GeV 20 mrad Crossing angle

10. Beam Parameter Determination with BeamCal Observables total energy first radial moment thrust value angular spread L/R, U/D F/B asymmetries √s = 500 GeV Head-on or 2 mrad

11. 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!

12. 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

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

14. Detection of High Energy Electrons and Photons √s = 500 GeV Single Electrons of 50, 100 and 250 GeV, detection efficiency as a function of R (‘high background region’) (talk by V. Drugakov and P. Bambade) Detection efficiency as a function of the pad-size (Talk by A. Elagin) Red – high BG blue – low BG Message: Electrons can be detected!

15. Detection of High Energy Electrons and Photons Efficiency to identify energetic electrons and photons (E > 200 GeV) Realistic beam simulation √s = 500 GeV Includes seismic motions, Delay of Beam Feedback System, Lumi Optimisation etc. (G. White) Fake rate

16. 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 !)

17. 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

18. Diamond Sensor Performance Linearity Studies with High Intensities (PS fast beam extraction) 105 particles/10 ns Response to mip

19. Univ. of Colorado, Boulder, AGH Univ., INP & Jagiell. Univ. Cracow, JINR, Dubna, NCPHEP, Minsk, FZU, Prague, IHEP, Protvino, TAU, Tel Aviv, DESY, Zeuthen Workshop on the Instrumentation of the Very Forward Region of the ILC Detector Tel Aviv, Sept. 15.-20. 2005. http//alzt.tau.ac.il/~fcal/

20. 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 • Mechanics design work ongoing • calorimeters in the very forward region deliver very valuable information about beam parameters • High energy electron detection down to small polar angles is feasible with compact and fine segmented calorimeters; easier for small crossing angle • Studies with sensors started- needs more effort • Prototype tests mandatory Remarks • The instrumentation of the forward region is relatively independent of the detector concept,

21. Backup Slides

22. Shower LEAKAGE in old (TDR) and new LumiCal design Shower in LumiCal (new design) Shower in LAT (TDR design)

23. Diamond performance as function of the absorbed dose Linearity of a heavy gas calorimeter (IHEP testbeam)

24. Comparison 500 GeV - 1TeV Comparison Sampling Heavy Crystal Comparison Sampling Heavy Crystal

26. Depositions on the calorimter frontface