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Experimental Aspects of Precision Luminosity Measurement

contributions from Forward Calorimetry Collaboration L.Suszycki AGH University of Science and Technology Cracow. Experimental Aspects of Precision Luminosity Measurement.

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Experimental Aspects of Precision Luminosity Measurement

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  1. contributions from Forward Calorimetry Collaboration L.Suszycki AGH University of Science and Technology Cracow Experimental Aspects of Precision Luminosity Measurement

  2. Forward Calorimetry CollaborationH. Abramowicz11, K. Afanaciev8, S. Denisov10, R. Dollan5, D. Drachenberg5, V. Drugakov8, I. Emeliantchik8, S. Erin10, R. Ingbir11, S. Kananov11, A. Kowal4, E. Kousnetsova5, R. Kwee5, W. Lange5, A. Levy11, W. Lohmann5, J. Lukasik4, M. Luz5, D. Miller7, I. Minashvili6, U. Nauenberg1, B. Pawlik4, N. Rusakovich6, A. Rybin10, N. Shumeiko8, A. Stahl5, L. Suszycki4, K. Suzdalev10, V. Vrba9, W. Wierba2, J. Zachorowski3, L. Zawiejski2, F. Zyazyulya81 University of Colorado, Boulder, USA, 2 Institute of Nuclear Physics, Cracow, Poland, 3 Jagellonian University, Cracow, Poland, 4 University of Science and Technology, Cracow, Poland, 5 DESY, Zeuthen, Germany, 6 Joint Institute of Nuclear Research (JINR), Dubna, Russia, 7 University College London, London, UK, 8 NC PHEP, Minsk, Belarus, 9 Institute of Physics of the Academy of Sciences of the Czech Republik, Praha, Czech Republik, 10 Institute of High Energy Physics, Protvino, Russia, 11 Tel-Aviv University, Tel-Aviv, Israel. L. Suszycki LCWS 04: Paris 19-23 April 2004 2

  3. TESLA TDR design (postponed) Low Angle Tagger (LAT) New mask design l*=4m Forward Calorimetry Layout LAT functionally is now LuminosityCalorimeter LumiCal • z = 305-325 cm • R= 8-28 cm • 26.2<<82 mrad • 0<<360 deg L. Suszycki LCWS 04: Paris 19-23 April 2004 3

  4. Luminosity measurement Based on Bhabha scattering e+e-  e+e-() At 250 GeV,  =5.5 nb, For L = 3.4 · 1034 cm-2s-1 rate R  180 Hz  `one minute` luminosity possible on-line Goal precision: L/L = 10-4 Can it be done? L. Suszycki LCWS 04: Paris 19-23 April 2004 4

  5. LumiCal Design Simulation Tungsten mask beam pipe • Si/W calorimeters on both sides of the IP • 16/64 concentric cylinders (in r) • 30 rings (in z) • 24/120 sectors (in ) • Detector simulation with Geant3.21 Two calorimeter structures considered: • Si pads • Si strips LCWS 04: Paris 19-23 April 2004 5

  6. Polar angle reconstruction • Polar angle reconstruction – good resolution, uniformity, no bias • Fiducial volume definition min is crucial: d/d ~1/3 , so tot(min, max) ~ min-2 , min = 26.2 mrad L/L = 2min/ min->min = 1.3 rad L. Suszycki LCWS 04: Paris 19-23 April 2004 6

  7. Angle reconstruction - Pad Design • „oscillations” around rec vs gen linear dependence due to detector granularity • resolution in is -dependent due to cylindrical geometry L. Suszycki LCWS 04: Paris 19-23 April 2004 7

  8.  Resolution as function of the number of cylinders (in r) and sectors (in φ) 24 sectors 48 sectors Angle reconstruction with simple energy weighting Both large bias and bad resolution ~0.2 – 0.3 mrad observed even using large numbers of cylinders/sectors LumiCal –  reconstruction A.Kowal (UST Cracow) L. Suszycki LCWS 04: Paris 19-23 April 2004 8

  9. Log. weight. E weight. Reconstruction Algorithm We explored two reconstruction algorithms: Energy weighting and logarythmic weghting Events Num. The log. weight fun. was designed to reduce steps in a granulated detector : 1. Selection of significant cells. 2. Log. smoothing. A Luminosity Detector for the Future Linear Collider HEP Tel Aviv University

  10. Logarithmic Constant 400 GeV After selecting: We explored a more systematic approach. The first step is finding the best constant to use under two criteria: 1. Best resolution. 2. Minimum bias. Constant value Constant value A Luminosity Detector for the Future Linear Collider HEP Tel Aviv University

  11. Energy dependent constant The goal is to find a global weight function. Is the log. weight really a constant ? Constant value A Luminosity Detector for the Future Linear Collider HEP Tel Aviv University

  12. Angular resolution Results using ‘pure electron’ simulation Can we maintain same detector properties using a more ‘real’ MC ? Beam Energy (GeV) A Luminosity Detector for the Future Linear Collider HEP Tel Aviv University

  13. Azimuthal resolution Events Num. E weight. Log. weight. A Luminosity Detector for the Future Linear Collider HEP Tel Aviv University

  14. B.Pawlik (INP-PAN, Cracow) LumiCal – Stripped design • 30 tungsten rings • every second ring has either 120 radial or 64 concentric Si strips • 2960 readout channels • but necessary sectioning of Si sensors will give factor of ~3 - 4 L. Suszycki LCWS 04: Paris 19-23 April 2004 14

  15. B.Pawlik (INP-PAN, Cracow) Stripped LumiCal reconstruction results • Accuracy in -reconstruction is ~50rad • Energy measurement with accuracy of 5 GeV (E~0.31√E) • low segmentation level seems to be sufficient (~3000 readout channels) LCWS 04: Paris 19-23 April 2004 15

  16. B.Pawlik (INP-PAS, Cracow) Stripped LumiCal -Bhabha eventsReconstruction : energy 7GeV (0.44√E)Angle ~0.09 mrad ACOLINEARITY ~1MRAD Egen - Erec θgen – θrec(mrad) θL – θR (mrad) L. Suszycki LCWS 04: Paris 19-23 April 2004 16

  17. Detector mechanics • Calorimeter assembling -perfect homogenity, - stable • Calorimeter positioning(rmin =8 cm), rmin = 4 m,z = 0.2mm Challenging for mechanics and thermal stability!rmin = 1m x T for steel support ( factor 1/3 for W support) • Monitoring of calorimeter shift and/or deformation due to:- temperature- ageing- ground motionLaser method for on-line control is being developed L. Suszycki LCWS 04: Paris 19-23 April 2004 17

  18. J.Zachorowski (UJ), W.Wierba (INP-PAN) Cracow Laser monitoring of the LumiCal detector displacement(very preliminary) Requirements on alignment: Inner Radius of LumiCal < 4 μm Axial LumiCal position < 60 μm reconstruction of He-Ne laser spot on CCD camera possible resolution of ~1m if the center of the light spot is determined with accuracy better than 0.1 pixel LCWS 04: Paris 19-23 April 2004 18

  19. slope 0.127pixel/mm To be done: Small-pixel BW camera, Manually controlled sensitivity, Semiconductor laser, Piezoelectric movement of camera, Independent measurement of displacement, Multiframe statistics. Laser scan of x and y positions

  20. Monitoring of the beam parameters Generator level Bhabha simulation (A.Stahl, Desy-Zeuthen) yieldspermissible beam deviations:beam offset r= 650 mIP longitudinal offset z= 150 mbeam tilt  = 0.2 mrad Beam Calorimeter (BeamCal) foreseen for fast beam diagnostics may help L. Suszycki LCWS 04: Paris 19-23 April 2004 20

  21. Conclusions • High precision luminosity measurement involves numerous experimental and technical problems • First MC results indicate ways of the future work • Angle reconstruction must be done very carefully minimizing the bias • Special system for monitoring the detector possible moves and/or deformations has to be built • Limited space for detector makes mechanics and electronics still more difficult • Optimized design of LumiCal is strongly dependent on choice of the LC option L. Suszycki LCWS 04: Paris 19-23 April 2004 21

  22. Thank you The end

  23. Cell Size 1.3cm*2cm> 1.3cm*6cm< ~1 Radiation length ~1 Radius Moliere Detector Design 15 cylinders * 24 sectors * 30 rings = 10800 cells 8 cm 0.31 cm Silicon 28 cm 0.34 cm Tungsten R L 6.10 m A Luminosity Detector for the Future Linear Collider HEP Tel Aviv University

  24. R. Ingbir (TAU) • resolution # of cylinders LumiCal pad–design optimization • # of active rings around the shower maximum • logarithmic weighting in angle reconstruction • () ~ 70 rad feasible L. Suszycki LCWS 04: Paris 19-23 April 2004 24

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