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

2. 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; c.m. energy 0.5 - 1 TeV; ILC target luminosity: 500 fb -1 in 4 years.

3. Fourth Concept Detector (“4 th ”) 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: M z <E CM <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 The most important fluctuation is in the em shower fraction, f em 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

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

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

9. Simulation/Reconstruction Steps inside 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 - E C and E S Calibrate with single 40 GeV    C and  S

12. Reconstructed energy Once HCAL calibrated, calorimeter energy:

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

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

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

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

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 P t 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 Total visible Energy (no jet finding) Single jet (jet finding included)

21. Physics Studies e + e - -> Z o H o -> cc

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

23. Jet-Jet Mass Plot

24. Conclusions 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: σ E /E = 38%/√E (single particles) σ E /E = 39%/√E (jets) An ECAL design with Dual Readout crystal technology is under way

28. Bottom view of single cell Bottom cell size: ~4.8 × 4.8 cm 2 Top cell size: ~ 8.8 × 8.8 cm 2 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 Hadronic Calorimeter Cells Hadronic Calorimeter Cells

30. Simulation (1)‏ Light production in the fibers simulated through 2 separate steps: 1. Energy deposition (hits) in active materials calculated by the tracking algorithm of the MC 2. 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

31. 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”

32. 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 E S and E C of all the cells belonging to the reconstructed cluster

33. e + e - -> Z o H o -> cc Pandora-Pythia (E cm =350 GeV, M H =140 GeV) + Fluka No MUD (use MC truth) Cut recoil mass 20 GeV around Z o mass Maximize j.f. efficiency through y t cut (  ff =97%)