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

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1 Instrumentation of the Very Forward Region of a Linear Collider Detector Wolfgang Lohmann, DESY August 2005 Snowmass Workshop

2 Used by H. Yamamoto Simulation studies on several designs Design for 0-2 mrad crossing angle (FCAL design) 0.5 SiD Forward Masking, Calorimetry & Tracking, 20 mrad crossing angle VTX IP 300 cm FTD L* = 4m LumiCal BeamCal Tesla Inst. Mask Beam Pipe 46mrad E C A L HC AL YOK E Q D W W Pair- LuMon LowZ Mask Support Tube W W 113mrad Exit radius 3.5m

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

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

5 Requirements on the Mechanical Design IP LumiCal 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 - (γ ) Simulation: Bhwide(Bhabha)+CIRCE(Beamstrahlung)+beamspread Event selection: acceptance, energy balance, azimuthal and angular symmetry. < X >= X W i W σ ( θ )( rad i ) i E W i = max{0,[ const( Ebeam ) + ln( E i T )]} mean _( θ rec θ gen )( rad 0.13e-3 rad 0.11e-3 rad Constant value ) value of the constant 4 layers 10 rings 30 layers 15 rings 15 layers 20 rings 11 layers 10 rings More in the talks by Halina Abramowicz

8 X- angle background Number of Bhabha events as a function of the inner Radius of LumiCal Beamstrahlung pair background using serpentine field 6.E Nmber of Bhabha evets per year 5.E+09 4.E+09 3.E+09 2.E+09 1.E+09 Events per year Background (GeV) 250 GeV Background (GeV) 0.E R min (cm) Background from beamstrahlung 0 Christian Grah, DESY-Zuethen

9 Fast Beam Diagnostics (BeamCal and PhotoCal) e + e - e + e - Pairs from Beamstrahlung are deflected into the BeamCal e + e - per BX TeV (10 MGy per year) direct Photons for θ < 200 µrad Zero crossing angle 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 Quantity Nominal Value Precision σx 553 nm 1.2 nm σy 5.0 nm 0.1 nm σz 300 µm 4.3 µm y nm 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 Quantity Nominal Value Precision σx 553 nm 4.8nm σy 5.0 nm 0.1 nm σz 300 µm 11.5 µm y 0 2.0nm 20 mrad crossing angle Also simultaneous determination of several beam parameter is feasible, but: Correlations! Analysis in preparation PRELIMINARY!

12 and with PhotoCal Photons from Beamstrahlung IP >100m Heavy gas ionisation Calorimeter L/R, U/D F/B asymmetries of energy in the angular tails Quantity Nominal Value Precision σx 553 nm 4.2 nm σz 300 µm 7.5 µm y nm nominal setting (550 nm x 5 nm)

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

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) Message: Electrons can be detected! Red high BG blue low BG

15 Detection of High Energy Electrons and Photons Realistic beam simulation s = 500 GeV Efficiency to identify energetic electrons and photons (E > 200 GeV) mean energy in particular cell (high BG near BP) Emean, GeV Erms, GeV real beams ideal beams Includes seismic bunch # motions, Delay of Beam energy RMS in particular Feedback cell (high System, BG near Lumi BP) Optimisation etc. (G. White) real beams ideal beams bunch # Fake rate

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

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

18 Diamond Sensor Performance Response to mip Linearity Studies with High Intensities (PS fast beam extraction) 10 5 particles/10 ns Diamond response [ADC ch] Relative Intensity [a.u.]

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 http//alzt.tau.ac.il/~fcal/

20 The instrumentation of the forward region is relatively independent of the detector concept, 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

21 Backup Slides

22 Shower LEAKAGE in old (TDR) and new LumiCal design FTD LAT 83.1 mrad Vertexdetector IP 27.5 mrad 3000 mm 55.5 mrad 297 mm Tungsten shield Quadrupole Graphite LCAL Inner Mask Shower in LAT (TDR design) Shower in LumiCal (new design)

23 Diamond performance as function of the absorbed dose Linearity of a heavy gas calorimeter (IHEP testbeam) Mean, ADC ch FAP21 FAP22 FAP23 e - ] 6 Number of Ionization Electrons [ E/P = 2000 V/(cm atm) Dose, Gy Beam Energy [GeV]

24 Efficiency [%] Efficiency [%] Comparison Sampling Heavy Crystal 60 Comparison 500 GeV - 1TeV GeV e Sampling GeV e - Comparison, s = 500 GeVSampling Heavy Crystal 400 GeV e, - s = 1 TeV Crystal Radius [cm] Radius [cm]

25 e + out e - out Z e - in B = 4T B = 4T e + in X

26 Depositions on the calorimter frontface

27 Headon 20mrad BeamPar MPI resolution MPI resolution σx σx σy σy σz σz off x off y w y N σx (ave) σx (diff) σy (ave) σy (diff) σz (ave) σz (diff) Beam offset x Beam offset y Vertical waist shift N per Bunch (ave) N per Bunch (diff)