Karsten Büßer Instrumentation of the Forward Region of the TESLA Detector International Europhysics Conference on High Energy Physics Aachen, July 19th 2003

19/07/20032Karsten Büßer, EPS-HEP Conference Aachen TESLA TeV Energy Superconducting Linear Accelerator Main Parameters Energy: 90 to 800+ GeV Luminosity (500GeV): 3.4 x cm -2 s -1 Beam size (500 GeV): 553 x 5 nm Physics Potential Precision measurements and searches in: Higgs physics Supersymmetry EW precision tests (GigaZ) QCD and top thysics yet unimagined physics

19/07/20033Karsten Büßer, EPS-HEP Conference Aachen The TESLA Detector Detector Concept Precision vertex detector Large gas filled central tracking detector Highly segmented calorimeters 4T magnetic field, tracking detectors and calorimeters inside the coil

19/07/20034Karsten Büßer, EPS-HEP Conference Aachen Beam Induced Backgrounds Main background source for the detector are beamstrahlung pairs

19/07/20035Karsten Büßer, EPS-HEP Conference Aachen Shielding of the tracking detectors against backscattered beamstrahlung background Provide instrumentation for: Precision luminosity measurement Hermeticity: → Extension of the energy flow measurement down to small angles Beam diagnostics Tasks for the Forward Region GEANT3 simulation of 10 pair particles

19/07/20036Karsten Büßer, EPS-HEP Conference Aachen Instrumented tungsten mask Two calorimeters: LAT Low Angle Tagger 27.5 – 83.1 mrad actual task :„Luminosity Calorimeter“ LCAL Luminosity Calorimeter 4.6 – 30 mrad actual task: „Beam Calorimeter“ TESLA Forward Calorimeters

19/07/20037Karsten Büßer, EPS-HEP Conference Aachen Physics Requirements: Δ L / L ≈ 0.02% (GigaZ) Process:e + e - → e + e - elastic Bhabha Scattering e + e - → e + e - γradiative Bhabha Scattering Statistics: for L = 3.4 x cm -2 s -1 rate R ≈ 170 Hz Systematics: from detector acceptance: since σ tot (Θ min,Θ max ) ~ Θ min -2 – Θ max -2 ≈ Θ min -2 then Δ L / L = 2ΔΘ min /Θ min with Θ min = 27.5 mrad, Δ L / L =  ΔΘ min = 1.4 µrad (!) from theory: At LEP achieved: 5.0 x Luminosity Measurement

19/07/20038Karsten Büßer, EPS-HEP Conference Aachen Geometry (as defined in the TESLA TDR) 14 cylinders in Θ 24 sectors in Φ 40 rings in z cells in MC studies Conical Setup r: 4 – 12 cm (not affected by beamstrahlung pairs) z: 140 – 200 cm Silicon/Tungsten sandwich 40 X 0 Low Angle Tagger The LAT serves as a shield !

19/07/20039Karsten Büßer, EPS-HEP Conference Aachen Energy ResponseEnergy Resolution LAT Performance GEANT3 simulation studies show the response to high energetic electrons

19/07/200310Karsten Büßer, EPS-HEP Conference Aachen Energy Response and ResolutionAngular Resolution Red: Cut on desposited energy (>2.5 GeV) LAT Performance

19/07/200311Karsten Büßer, EPS-HEP Conference Aachen LAT Outlook New TESLA beam optics are under development which would allow to move the quads out of the detector (increasing l * from 3m to ≤5m). Mask and calorimeters would move Flat LAT seems possible Simulation studies for a flat LAT are under way → angular resolutions down to 1.4 µrad are still challenging! Alignment tolerances for detectors are stringent: Δz < 60 µm Δr < 0.75 µm Alignment monitor system probably needed TESLA-TDR l*=3m Design study l*=4.1m

19/07/200312Karsten Büßer, EPS-HEP Conference Aachen Technology options under study: Diamond -Tungsten Sandwich, r m ~ 1cm Crystal PbWO 4, r m ~ 2cm 30 layers, 30 X 0 The LCAL

19/07/200313Karsten Büßer, EPS-HEP Conference Aachen Pairs from Beamstrahlung per bunch crossing (BX) Produced: #: ~130000, E tot : ~360 TeV on each LCAL: #: ~15000, E tot : ~20 TeV Deposited Energy, Diamond/W LCAL and Pair Background Dose: ≤ 10 MGy/y

19/07/200314Karsten Büßer, EPS-HEP Conference Aachen LCAL as Beam Monitor Number of produced pairs is a measure of the luminosity Deposited energy on the LCAL is input for the TESLA fast feedback system rΦ energy distribution on the LCAL is an indicator for beam misalignments nominal beam tilted beam: x‘=3.5 mrad

19/07/200315Karsten Büßer, EPS-HEP Conference Aachen One 250 GeV electron and pair background from one BX GeneratedBackground addedReconstructed LCAL as Physics Device

19/07/200316Karsten Büßer, EPS-HEP Conference Aachen Simple algorithm: subtract average (10 BX) background search for cells with signal > 3σ of background fluctuation require longitudinal chain of signal cells 4.6 mrad 30 mrad Reconstruction

19/07/200317Karsten Büßer, EPS-HEP Conference Aachen Energy Resolution of the LCAL Energy resolution is dominated by the background

19/07/200318Karsten Büßer, EPS-HEP Conference Aachen 500 BX Fake Rates

19/07/200319Karsten Büßer, EPS-HEP Conference Aachen Conclusion LAT Luminosity measurment with 0.02% accuracy will be challenging LCAL Several technologies are under study Detection of high energetic electrons is possible with high efficiency below 10 mrad Energy resolution is dominated by background subtraction Need to look into more clever algorithms OUTLOOK TESLA interaction region might change (increasing l*) → Redesign of the forward region, impact on calorimeters ? R&D has started Test stand for Si and Diamond sensors in Zeuthen