1 / 29

L.Suszycki †‡

Instrumentation of the very forward region of the TESLA detector – summary of the Workshop on Forward Calorimetry and Luminosity Measurement, Zeuthen, 13-14 November 2002. L.Suszycki †‡ Faculty of Physics and Nuclear Techniques, University of Mining and Metallurgy,Cracow, Poland

platt
Download Presentation

L.Suszycki †‡

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Instrumentation of the very forward region of the TESLA detector – summary of the Workshop on Forward Calorimetry and Luminosity Measurement, Zeuthen, 13-14 November2002 L.Suszycki†‡ Faculty of Physics and Nuclear Techniques, University of Mining and Metallurgy,Cracow, Poland ECFA DESY Linear Collider Workshop Prague, 15th-18th November 2002 †For the LCAL group: K. Afanaciev, V. Drugakov, G. Klämke, E. Kousnetzova, W. Lohmann, A. Stahl, M. Ternick ‡For the LAT group:H. Abramowicz, A. Eskreys, S. Kananov, D. Kisielewska, A. Kowal, A. Levy, L. Suszycki, W.Wierba

  2. Very forward region of TESLA Two calorimeters: • LCAL – Luminosity CALorimeter covering angles 5 – 27.5 mrad, actually it is“Beam Calorimeter” • LAT – Low Angle Tagger covering angles 27.5 – 83.1 mrad, actually it is“Luminosity Calorimeter” L.Suszycki: Instrumentation...

  3. Tasks for the very forward region detectors • Precision luminosity measurement • Beam diagnostics • Detection and measurement of electrons and photons at small angles • Extension of the energy flow measurement down to small angles • Shielding of the tracking detectors against backscattered beamstrahlung L.Suszycki: Instrumentation...

  4. Beamstrahlung • Energy deposition via e+e- pairs ~20 TeV/bunch cr.One year of runs makes a dose ~10 Mgy/year in LCAL a need of radiation hard sensors • Radial distribution up to ~4 - 5cm  LAT should be save • Azimuthal anizotropy caused by magnetic field L.Suszycki: Instrumentation...

  5. LCAL design • Shape • Two technology options: • crystal PbWO4 – Moliere radius ~2 cmLSO crystals considered • diamond-tungsten sandwich - Moliere radius ~1 cmSegment size ~half of RM • Readout via optical fibres L.Suszycki: Instrumentation...

  6. LCAL segmentation R-z projection x-y projection 30 layers = 30 radiation lengths 12 rings L.Suszycki: Instrumentation...

  7. Half barrel of the diamond-tungsten sandwich calorimeter LCAL calorimeter L.Suszycki: Instrumentation...

  8. L.Suszycki: Instrumentation...

  9. Background in LCAL Example of a 250 GeV electron event1. Generated 2. Background added 3. Reconstructed L.Suszycki: Instrumentation...

  10. Detection of particles in LCAL Simple algorithm to find electron or gamma: • search for cells with signal > 3 sigma of background • require longitudinal chain of such cells Efficiency and energy resolution depend on number of ADC bits  10 bits sufficient L.Suszycki: Instrumentation...

  11. Energy measurement in LCAL Energy resolution as functions of : R Energy L.Suszycki: Instrumentation...

  12. Angular resolution of LCAL Energy dependence R dependence L.Suszycki: Instrumentation...

  13. Fake events in LCAL • High energetic particles in background • Beamstrahlung fluctuationsElectron energy spectrum generated (tail >20 GeV only is shown) ...and reconstructed L.Suszycki: Instrumentation...

  14. Beam diagnostics in LCAL Measurement of x and z ExerciseInput:x = 600 nm, z = 250 mResult:x = 597 nm, z = 241 mMore about: see A.Stahl talk at this workshop L.Suszycki: Instrumentation...

  15. 14 `cylinders` in R24 `sectors` in 40 `rings` in z13440 cells assumed for MC studies Conical setup R: 4 to 12 cmz: 140 to 200 cm Silicon-tungsten sandwich 40 X0 deep LAT geometry L.Suszycki: Instrumentation...

  16. Elastic e+e-  e+e- radiative e+e-  e+e-  Example of elastic Bhabha event  (scale ratio 8:1!) Born approximation d/d ~ -3 tot(27.5, 83.1mrad)5nb Bhabha scattering L.Suszycki: Instrumentation...

  17. Luminosity measurement • R = L ·obs , where obs =theor  acceptance • For L = 3.4 · 1034 cm-2s-1 rate R  170 Hz  `one minute` luminosity possible on-line • Systematic errors:1. from detector acceptance • Since tot(min, max) ~ min-2 - max-2  min-2 • then L/L = 2min/ min = 2rmin / rmin • With rmin  5 cm, L/L = 10-4 needs rmin = 2.5 m • Challenging for mechanics and thermal stability!Use of interferometry to monitor position and shape? • 2. from theoryAt LEP energy theor. error achieved 5. 10-4.At TESLA may be harder L.Suszycki: Instrumentation...

  18. L.Suszycki: Instrumentation...

  19. Luminosity measurement (cont`d) • Luminosity spectrum due to • ISR • Beamstrahlung • Beam energy spread • can be measured through acolinearity of Bhabha events - • - resolution better than 0.1 mrad necessary • Background and corrections • Beamstrahlung • Synchrotron radiation • Beam-gas bremsstrahlung • Thermal photons from the rest gas • Beam size effect • So far no estimations done... L.Suszycki: Instrumentation...

  20. LAT shower example Only photons (blue) and electrons (red) over 5 MeV are displayed L.Suszycki: Instrumentation...

  21. LAT calorimetryShowers well contained within ~ 30 radiation lengths: L.Suszycki: Instrumentation...

  22. LAT – showers...Two examples of hits generated by 250 GeV electrons:Upper plots show all hits, lower plots show the shower coresStrong scattering may affect energy measurement L.Suszycki: Instrumentation...

  23. LAT energy response and resolution L.Suszycki: Instrumentation...

  24. Much poorer performance in the first bin (first cylinder)  the effect increasing with energy LAT angular uniformityEnergy response Energy resolution L.Suszycki: Instrumentation...

  25. rec calculated using a simple energy weighting Accuracy not satisfactory Background not incorporated More sophisticated algorithm must be used for Bhabha measurement LAT angular resolution L.Suszycki: Instrumentation...

  26. LAT fiducial volume Remark: LAT size is 27.5 to 83.1 mrad L.Suszycki: Instrumentation...

  27. LAT fiducial volume (cont`d).Energy deposit as a function of polar angle All events cut Edep > 2.5 GeV L.Suszycki: Instrumentation...

  28. LAT performance improvedEnergy cut Edep > 2.5GeV applied Energy response and resolution Angular resolution L.Suszycki: Instrumentation...

  29. Summary and outlook LCAL • Advanced studies of the several technologies • Detection of hard electrons and gammas with high efficiency feasible • Fake events due to beamstrahlung fluctuations may be a problem • Beam diagnostics looks promising • R&D started LAT • First MC studies done • Problems with energy resolution and angular resolution • Shape and segmentation is still an open questionflat LAT “ l=5m” option is very recommended:1. Makes mechanical design more realistic2. Improves resolution • Single module for tests will be prepared soon The LCAL+LAT proposal will be recommended by the PRC, so let`s look forward in this adventure! L.Suszycki: Instrumentation...

More Related