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CBM ECAL development

CBM ECAL development. Yuri Kharlov IHEP, Protvino For IHEP-ITEP-INFN(Bologna) collaboration. Outline. Physics motivation Scintillator sampling calorimeters IHEP plastic scintillator facility R&D plans Simulations and data analysis. Physics with ECAL. Detection of photons and electrons

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CBM ECAL development

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  1. CBM ECAL development Yuri Kharlov IHEP, Protvino For IHEP-ITEP-INFN(Bologna) collaboration

  2. Outline • Physics motivation • Scintillator sampling calorimeters • IHEP plastic scintillator facility • R&D plans • Simulations and data analysis ECAL development /CBM collaboration meeting

  3. Physics with ECAL • Detection of photons and electrons • Reconstruction of mesons decaying in photons (0, , 0, etc). • e-tagging of open charm • -tagging of strange hyperons • Chiral symmetry restoration by precise measurement of short-lived mesons • EoS via collective effects (flow) • DCC detection via / fluctuations • Particle identification (photons, electrons, hadrons, nucleons) ECAL development /CBM collaboration meeting

  4. Flow • In HIC the high-density interaction zone is formed • Thermal pressure generates collective transverse expansion • Collective flow reflects time evolution of the pressure gradients and can provide information on EoS at the initial phase and during expansion • Collective flow may be one of the strongest probe for the degree of thermalization ECAL development /CBM collaboration meeting

  5. Photons as a probe for flow directed flow v1 in-plane out-of-plane elliptic flow v2 WA98: 0 flow Oct-2004 ECAL development /CBM collaboration meeting

  6. Charged-neutral particle fluctuations • Hot and dense matter formed in HIC may lead to a phase of restored chiral symmetry • After the system cools and expands, the normal QCD vacuum is returning where the chiral symmetry is spontaneously broken • Between these two marginal phases, a metastable state with desoriented chiral condansate may be formed • DCC can produce clusters of coherent pions in localized phase space domains • Formation of DCC can be associated with large EbyE fluctuations in the ratio of neutral to charged pions localized in pseudorapidity  and azimuth angle  ECAL development /CBM collaboration meeting

  7. Choice of e.m. calorimeter for CBM • There were 3 major types of solid-state calorimeters in the HEP history: • Cherenkov calorimeters (lead glass) (GAMS, E704, WA98, PHENIX) • Energy resolution is E/E=7-12%/E is limited by the final the Cherenkov threshold • Glass darkens in high radiation environment • Calorimeters made from inorganic scintillating crystals (PbWO4) (ALICE, ATLAS, CMS) • The best energy resolution E/E=2-5%/E • but they are expensive and degrade in high radiation environment • Scintillator sampling calorimeters from organic scintillators and heavy absorbers (PHENIX, DELPHI, HERA-B, LHCB) • So far typical energy resolution was E/E=8-15%/E • Recent R&D showed that E/E=2.5%/E is achievable (KOPIO) • Sampling calorimeters are relatively cheap and can be exposed to high radiation environment • Scintillator sampling e.m. calorimeter is the only choice for fixed-target heavy-ion experiment like CBM. ECAL development /CBM collaboration meeting

  8. Sampling calorimeters manufactures • Sampling calorimeters are just made of heavy absorber (Pb, W, U) and organic scintillators. • Heavy absorber can be produced in many metallurgic plants • Organic scintillators with properties satisfying ECAL needs can be produces by a very few number of manufacturer only at a competitive price: • Technoplast, Vladimir • IHEP, Protvino • Advantages to involve IHEP facilities for ECAL construction for CBM: • IHEP has a long history of electromagnetic and hadron calorimetry contributed to many of HEP-experiments, experience with design, component manufacturing, assembling, commissioning and operating the calorimeters • Well developed shop of molded scintillators and assembling of ECAL modules exists • Set of “know-how” to improve scintillator characteristics and light collection in the modules • Industry-like quality control exists • Rich experience with calorimeter read-out systems ECAL development /CBM collaboration meeting

  9. Role of IHEP in calorimetry • Scintillator sampling calorimetry in IHEP: • 1985: invention of the molding technology • 1988: first “shashlyk” R&D with INR • 1992: PHENIX ECAL (BNL, RHIC) • 1993-1995: HERA-B ECAL (DESY, with ITEP) • 1994: DELPHI STIC (CERN, LEP) • 2000: COMPASS HCAL (CERN, SpS) • 2001: ATLAS HCAL (CERN, LHC) • 2004: LHCb HCAL (CERN, LHC) • 2000-200?: KOPIO (BNL, AGS) ECAL development /CBM collaboration meeting

  10. Plastic scintillator facility in IHEPhttp://www1.ihep.su/ihep/ihepsc/index.html • The research and development program of plastic  scintillators started in IHEP morethan 20 years ago. The works were concentreted in the following directions: • the production of polysterene scintillators using the process of styrene polymerization in blocks; • the extrusion of bulk-polymerized scintillators from blocks; • the production of molded scintillators by the injection molded technique. • Scintillators manufactured be methods 1 and 2 were tested and used in domestic experiments at IHEP as well as some experiments abroad • With the help of method 3, large volumes of scintillators for several experiments in IHEP(~3 tons) and for hadron calorimeters Hcal1 and Hcal2 of experiment in COMPASS (~2 tons) were manufactured. • During the last decade the demand on molded scintillators for various projects (PHENIX, HERA-B, ATLAS, LHC-b) have inceased up to several tens of tons per year. • Production time scale: 15 tons of scintillators (>750,000 plates) for KOPIOcould be manufactures in 1.5 years. ECAL development /CBM collaboration meeting

  11. Plastic scintillator facility in IHEP Injected mold machime in automatic processing of the tiles. Injected mold scintillator production facility 3x3 module for KOPIO Plates for KOPIO ECAL development /CBM collaboration meeting

  12. Calorimeter readout • Readout systems (photo-multipliers and high-voltage system) were provided by IHEP for PHENIX (16 000 channels), HERA-B (6000 channels); LHCb (6500 ECAL+1800 HCAL channels); • ECAL needs photodetectors with low rate effect. R&D on photo-multipliers with stability 1% at I=20mA takes place. ECAL development /CBM collaboration meeting

  13. E.M. calorimeter in PHENIX [NIM A 499: 521-536, 2003] R&D: 1994 Typical sampling lead-scintillator calorimeter of 15,552 channels 66 sampling layers (4 mm Sci + 1.5 mm Pb) Total radiation length: 18 X0 Total nuclear interaction length: 0.85 I Transverse cell size 5.55.537.5 cm3 DE/E=2.1  8.1%/E(GeV) x=1.55 mm  5.7 mm/E(GeV) for normal incidence Time resolution = 100 ps for e.m. showers and 270 ps for hadronic showers 36 fibers of WLS-doped polystyrene penetrate the modules Modules are assembled into 6x6-array supermodules ECAL development /CBM collaboration meeting

  14. E.M. calorimeter STIC in DEPLHI [NIM A 425 (1999) 106] Small angle Tile Calorimeter for luminosity monitoring 47 Pb(3mm)-Sci(3mm) layers 2 Si strip detectors inserted after 7 and 13 sampling layers to measure shower development 1600 WLS fibers (0.79 fiber/cm2) DE/E=3% at 45 GeV Df=1.5 Dr=0.3-1 mm ECAL development /CBM collaboration meeting

  15. E.M. calorimeter in KOPIO First prototype for KOPIO (INR, Troitsk): 240  (0.35 mm lead + 1.5 mm scint.) Energy resolution 4%E(GeV). (for 1 GeV/c positron) Contributions to the energy resolution: E865 E923 KOPIO prototype To achieve the energy resolution of 3%E(GeV) the sampling, photo-statistics and light collection uniformity have to be improved Test beam results and the simulation model is described in [NIM A 531 (2004) 476] Economy: adequate performance for ~1/10 cost of crystals ECAL development /CBM collaboration meeting

  16. KOPIO: 3%/E [CALOR 2004, Perugia, Italy, March 29-April 2, 2004] ECAL development /CBM collaboration meeting

  17. KOPIO: Calorimeter module • The design innovations: • New scintillator tile(BASF143E + 1.8%pTP + 0.04%POPOP produced by IHEP) with improved optical transparency and improved surface quality. The light yield is now ~ 60 photons per 1 MeV of incident photon energy. Nonuniformity of light response across the module is <2.3% for a point-like light source, and < 0.5% if averaged over the photon shower.. • New mechanical designof a module has four special "LEGO type" locks for scintillator’s tiles. These locks fix the position of the scintillator tiles with the 300-m gaps, providing a sufficient room for the 275 m lead tiles without optical contact between lead and scintillator. The new mechanical structure permits removing of 600 paper tiles between scintillator and lead, reduces the diameter of fiber’s hole to 1.3 mm, and removes the compressing steel tape. The effective radiation length X0 was decreased from 3.9 cm to 3.4 cm. The hole/crack and other insensitive areas were reduced from 2.5 % up to 1.6 %. The module’s mechanical properties such as dimensional tolerances and constructive stiffness were significantly improved. • New photodetector Avalanche Photo Diode (630-70-74-510 produced by Advanced Photonix Inc.) with high quantum efficiency (~93%), good photo cathode uniformity (nonuniformity  3%) and good short- and long-term stability. A typical APD gain is 200, an excess noise factor is ~ 2.4. The effective light yield of a module became ~24 photoelectrons per 1 MeV of the incident photon energy resulting in negligible photo statistic contribution to the energy resolution of the calorimeter. ECAL development /CBM collaboration meeting

  18. KOPIO: light yield in scintillator Light yield variation over tile’s samples ECAL development /CBM collaboration meeting

  19. KOPIO: light collection in the tile Tile (face view) ECAL development /CBM collaboration meeting

  20. KOPIO: energy resolution Energy resolution for 220-370 MeV photons: ECAL development /CBM collaboration meeting

  21. KOPIO: time resolution Time difference in two modules was measured ECAL development /CBM collaboration meeting

  22. KOPIO: photon detection inefficiency Simple estimate of Inefficiency (due to holes): Effect of holes is negligible if incident angle > 5 mrad ECAL development /CBM collaboration meeting

  23. CBM ECAL module ECAL development /CBM collaboration meeting

  24. Choice of sampling • High energy resolution is achieved with very fine sampling, hPb0 • Scintillator thickness hSc cannot be very thin to provide lateral uniformity • Smaller fraction hPb/hSc results in larger Moliere radius  larger cell and worse position resolution ECAL development /CBM collaboration meeting

  25. Particle identification • PID in ECAL based on: • Shower shape • Pre-shower • TOF • Charge track matching • Good identification of photons, electrons, charged and neutral hadrons, (anti)nucleons. • (GEANT3 simulation for PHOS, ALICE)  e- anti-n p- ECAL development /CBM collaboration meeting

  26. p0 spectrum and background subtraction (Pb-Pb at 5.5 ATeV) ECAL development /CBM collaboration meeting

  27. R&D plans 2005 • Determine the smallest possible thickness of the Sci tile with light collection uniformity better than 3% • Assemble a prototype of 55 or 66 cells with RM=3.5-4.0 cm and 20X0-long. Study possibility to use Pb and W as an absorber. • Run a beam test with this prototype in IHEP at e- and - beams at 7-23 GeV/c. Measure E/E, x, t, response uniformity vs x, shower shape. ECAL development /CBM collaboration meeting

  28. Simulations plans in 2005-2006 • Further ECAL development within the cbmroot framework • Optimize the overall geometry and the cell sizes in all ECAL areas • Physics signal simulations (0, , , strange hyperons) • Develop response functions to reproduce test beam results • Reconstruction algorithm • Particle identification • Full simulations of signal and background • Pre-shower simulations ECAL development /CBM collaboration meeting

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