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30 Aprile 2007

Study of a Compensating Calorimeter for a e + e - Linear Collider at Very High Energy. 30 Aprile 2007. Vito Di Benedetto. ILC A future project for a e + e - Linear Collider. electron-positron collider; ILC's design consist of two facing linear accelerators, each 20 kilometers long;

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30 Aprile 2007

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  1. Study of a Compensating Calorimeter for a e+ e- Linear Collider at Very High Energy 30 Aprile 2007 Vito Di Benedetto

  2. ILCA future project for a e+ e- Linear Collider • electron-positron collider; • ILC's design consist of two facing linear accelerators, each 20 kilometers long; • c.m. energy 0.5 - 1 TeV; • ILC target luminosity: • 500 fb-1 in 4 years.

  3. Fourth Concept Detector (“4th”) • Basic conceptual design: 4 subsystems • Vertex Detector 20-micron pixels • Time Projection Chamber • Drift Chamber as alternative to overcome known limitations of the TPC technology • Double-readout calorimeters • Fibers hadronic calorimeter: scintillation/Čerenkov • Crystals EM calorimeter • Muon dual-solenoid spectrometer

  4. Requirements for ILC Detectors • Physics goal of ILC • Wide variety of processes • Energy range: Mz<ECM<1 TeV • Basic detectors requirements • Efficient identification and precise 4-momentum measurement of the particles • Extremely good jet energy resolution to separate W and Z • Efficient jet-flavor identification capability • Excellent charged-particle momentum resolution • Hermetic coverage to veto 2-photon background

  5. Calorimetry at ILC Most of the important physics processes to be studied in the ILC experiment have multi-jets in the final state Jet energy resolution is the key in the ILC physics The world-wide consensus of the performance goal for the jet energy resolution is:

  6. Problems in Hadron Calorimeters LESSONS FROM 25 YEARS OF R&D Energy resolution determined by fluctuations To improve hadronic calorimeter performance reduce/eliminate the (effects of) fluctuations that dominate the performance The most important fluctuation is in the em shower fraction, fem

  7. Solution: Dual Readout Calorimeter • Measurement of fem value event by event by comparing two different signals from scintillation light and Ĉerenkov light in the same device. Dual REAdout Module (DREAM) http://www.phys.ttu.edu/dream/ Back end of 2-meter deep module Physical channel structure Unit cell

  8. From DREAM to the 4th Concept HCAL • Cu + scintillating fibers • + Ĉerenkov fibers • ~1.5° aperture angle • ~ 10 intdepth • Fully projective geometry • Azimuth coverage • down to 3.8° • Barrel: 13924 cells • Endcaps: 3164 cells

  9. Simulation/Reconstruction Stepsinside ILCRoot Framework MC Simulation  Energy Deposits in Detector Digitization Detector response combined Pattern Recognition Recpoints Track Finding  Tracks Track Fitting  Track Parameters

  10. ILCRoot: summary of features • CERN architecture (based on Alice’s Aliroot) • Full support provided by Brun, Carminati, Ferrari, et al. • Uses ROOT as infrastructure • All ROOT tools are available (I/O, graphics, PROOF, data structure, etc) • Extremely large community of users/developers • Six MDC have proven robustness, reliability and portability • Single framework, from generation to reconstruction through simulation. Don’t forget analysis!!!

  11. Calibration • Energy of HCAL calibrated in 2 steps: • Calibrate with single 40 GeV e- • EC and ES • Calibrate with single 40 GeV  • C andS

  12. Once HCAL calibrated, calorimeter energy: Reconstructed energy

  13. HCAL Resolution Plots C EHCAL S 40 GeV e- C S EHCAL 40 GeV π-

  14. Reconstructed vs Beam Energy Visible energy fully measured Pions data all HCAL energy single recpart energy Total Energy c & s Independent on Energy Pattern Recognition

  15. Resolution for hadrons Total Energy Pions data all HCAL energy single recpart energy /ndf 1.351e-05/4 P0 0.3545± 0.01041 P1 0.001335±0.001704 Pattern Recognition /ndf 1.435e-05/4 P0 0.3803± 0.01072 P1 0.0002627±0.001756 Low statistics

  16. Particle Identification e • 40 GeV particles     e

  17. Jets Studies e+ e- -> q q (uds)

  18. The Jet Finder Algorithm • Look for the jet axis using a Durham algorithm • Charged tracks • Calorimeter cells • Calorimeter Clusters • Jet core • Open a cone increasingly bigger around the jet axis (< 60°) • Run a Durham j.f. on the cells of the calorimeter inside the cone • Jet outliers • Check leftover/isolated calo cluster/cells for match with a track from TPC+VXD • Add calorimetric or track momentum • Add low Pt tracks not reaching the calorimeter • Muons • Add tracks reconstructed in the MUD

  19. Total Energy Plots • No jet finder • Energy calibration with no material in front

  20. Energy Resolution • Single jet (jet finding included) • Total visible Energy (no jet finding)

  21. Physics Studies e+e- -> ZoHo -> cc

  22. Jet Finder Performance • Angular resolution < 2° • Energy resolution = 4 GeV

  23. Jet-Jet Mass Plot

  24. The 4th Concept has chosen a Calorimeter with Dual Readout The technology has been tested at a test beam, but never in a real experiment Performance of Calorimeter is expected to be extremely good: σE/E = 38%/√E (single particles) σE/E = 39%/√E (jets) An ECAL design with Dual Readout crystal technology is under way Conclusions

  25. Hadronic Calorimeter Cells Bottom view of single cell Bottom cell size: ~4.8 × 4.8 cm2 Top cell size: ~ 8.8 × 8.8 cm2 Prospective view of clipped cell Cell length: 150 cm Number of fibers inside each cell: 1980 equally subdivided between Scintillating and Cerenkov Fiber stepping ~2 mm

  26. Simulation (1)‏ Light production in the fibers simulated through 2 separate steps: Energy deposition (hits) in active materials calculated by the tracking algorithm of the MC Conversion of the energy into the number of S and C photons by specific routins taking account several factors: energy of the particle, angle between the particle and the fiber, etc. Poisson uncertaintity introduced in the number of photon produced

  27. Simulation (2)‏ • Response function of the electronics not yet simulated (digits)‏ • Random noise generated to test the ability of reconstruction algorithm to reject such spurious “hits”

  28. Reconstruction • Clusterization ( pattern recognition) • cluster = collection of nearby “digits” • Build Clusters from cells distant no more than two towers away • Unfold overlapping clusters through a Minuit fit to cluster shape • Reconstructed energy E adding separately ES and EC of all the cells belonging to the reconstructed cluster

  29. e+e- -> ZoHo -> cc • Pandora-Pythia (Ecm=350 GeV, MH=140 GeV) + Fluka • No MUD (use MC truth) • Cut recoil mass 20 GeV around Zo mass • Maximize j.f. efficiency through yt cut (ff=97%)

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