2. December 2005Valencia Workshop Very Forward Region Instrumentation Wolfgang Lohmann, DESY Basic functions: - Hermeticity to small polar angles - Fast and precise Luminosity measuremt - Shielding of the inner detectors -

November 2005LDC meeting 20mrad DID Shielding function 20mrad solenoid Due to the small bunch size  x ~100nm,  y ~5 nm and the large bunch charge, N x /bunch, beamstrahlung becomes important lots of e+e- pairs

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

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

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

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

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

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

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

15000 e + e - per BX 10 – 20 TeV (10 MGy per year) e + e - Pairs from Beamstrahlung are deflected into the BeamCal GeV Zero (or 2 mrad) crossing angle 20 mrad Crossing angle BeamCal Background in the BeamCal : (500 Gev, TDR) Zero or small X-angle: 30 TeV/BX 20 mrad X-angle: 60 TeV/BX Radiation hard sensors needed

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

Quantity Nominal Value Precision xx 553 nm4.8nm yy 5.0 nm0.1 nm zz 300  m11.5  m yy 02.0nm Beam Parameter Determination with BeamCal PRELIMINARY! 20 mrad crossing angle total energy first radial moment angular spread L/R, U/D F/B asymmetries Also simultaneous determination of several beam parameter is feasible, but: Correlations! Analysis in preparation Observables Fast Lumi estimate and feedback for beam steering

nominal setting (550 nm x 5 nm)  >100m IP L/R, U/D F/B asymmetries of energy in the angular tails Quantity Nominal Value Precision xx 553 nm4.2 nm zz 300  m7.5  m yy 00.2 nm Heavy gas ionisation Calorimeter and with PhotoCal Photons from Beamstrahlung

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

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

Sensor prototyping, Diamonds  ADC Diamond (+ PA) Scint.+PMT& signal gate 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 Pm1&2 Pads

Linearity Studies with High Intensities (PS fast beam extraction) 10 5 particles/10 ns Response to mip Diamond Sensor Performance Particle flux, N/cm 2 /10ns

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// desy.de/LC/FCAL We would be happy to welcome you to fight together!

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 Prototype tests mandatory Remark: The instrumentation of the forward region is relatively independent of the detector concept, Mechanics design just started, needs effort radiation hard sensors for the inner calorimeter – needs R&D no electronics concept so far