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Calorimetry and Cherenkov Radiation

Explore the development of hadron cascades, EM showers, and Cherenkov radiation in calorimeters, with a focus on particle energy composition and resolution improvement techniques.

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Calorimetry and Cherenkov Radiation

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  1. RICH200720 Oct 2007 Trieste Hadron cascades Aldo PENZO (INFN-Trieste) Calorimetry and Cherenkov Radiation EM showers Cherenkov radiation red =e±/γ,green = μ±,blue = hadrons

  2. p g po p- p+ e+ e- EM showersvsHadron cascades Hadron cascades develop 2 components (hard and EM) evolving with different scales: -po → ggis ”one-way” process -po production stops when the energy available drops below pion production threshold Hadron cascades copiously produce po ‘s, which generate ggpairs, originating EM showers EM showers contain essentially e± and g’s

  3. lI X0, λI [cm] X0 Z Development of hadron cascades Fluctuations due to po production 2 scales for hadronic cascade development: -lI for strong interactions -Xo for EM interactions

  4. Protons 80 60 80 40 EM Shower Particles 60 20 Non-EM Charged Particles Fraction of Cascade Energy (%) 40 0 1 10 100 Pions 20 Bind Energy + Nucl. Fragm. 0 1 10 100 Primary Energy (GeV) Hadron Cascade Composition • EM energy ~ 50% • Visible non-EM energy (dE/dX) ~ 25% • Invisible non-EM energy (nuclear breakup) ~25% • Invisible escape energy (neutrinos) ~ 1% (Ranft ´72, Baroncelli ´74, Gabriel ´76) Barion number conservation implies EM fraction lower in proton - induced showers than in pion - induced ones

  5. 10 GeV electrons (< 4 MeV) Neutron yields (< 1 MeV) (> 20 MeV) Predominance of SOFT particles In Lead ~ 40% energy deposited by e± with E < 1 MeV Non-EM components in Lead: - Ionizing particles ~ 56% ~ 70% protons ~100 MeV (spallation) - Neutrons ~ 10% (37 neutrons/GeV) (Evaporation neutrons ~3 MeV) - Invisible 34%

  6. e/h = 1 / Hadronic vs EM response Not all hadrons’ energy is “visible”: • Lost nuclear binding energy • neutrino energy • Slow neutrons, … Hadron calorimeters usually are, to various degrees, non – compensating:

  7. “Compensation” virtues High precision hadron calorimeters should have equal response to electromagnetic and strongly interacting particles (compensation condition e/h =1) in showers generated by incoming hadrons, in order to achieve: • linear response in energy to hadrons, • gaussian energy distribution for mono-energetic hadrons, • relative energy resolution (dE/E), improving as sqrt(1/E). This is of prime relevance for the measurement of jets, involving various particles of different energies, with a substantial fraction of neutral pions… However: not always virtue really pays… Any benefits with non-compensating calorimeters?

  8. qC b > 1/n Cherenkov Calorimeters Radiator nqC Tkin(MeV) e±pp • Lead glass 1.67 53o • Water 1.33 41o • Quartz 1.45 45o 0.2 190 400 • PbWO4 2.2 63o cos qC = 1/(bn)

  9. “Non-Compensation” Benefits In Cherenkov calorimeters, with e/h »1, only EM showers, (mainly low energy e±) contribute: • Shower profiles thinner (rM), • Better containment, • Lower background As rad-hard materials for the active parts of calorimeters, quartz fibers are 1st choice: • ZDC for Heavy Ions experiments at SPS, RHIC, LHC,… • Large rapidity detectors at LHC (HF) • Polarimeters e±: Compton back-scattering SLC, HERA, ILC

  10. Quartz Fibers qT • QF with fluorine-doped silica cladding (QQF) can stand ~20 Grads, with ≤ 10% light loss; • MIP particle produces about 200 Cherenkov photons in 1 cm quartz (~ 500eV); • same MIP particle deposits about 4.5 MeV by ionization qT ~ 20o qC

  11. Quartz Fibers for Calorimetry • DRDCP54 (1994) - Development of quartz fiber calorimetry (A. Contin, P. Gorodetzky, R. DeSalvo et al.) Directional properties of Cherenkov light in fibers 45o

  12. Quasi-isotropy of soft shower particles R. Wigmans – Frascati Calorimetry Conf., June 1996

  13. Sharper shower profiles L.R. Sulak – Frascati Calorimetry Conf., June 1996

  14. CMS HF Calorimeter 2003 Test Beam 25 ns Intrinsically very fast Fast time response Y. Onel, Chicago Calorimetry Conf. , June 2006

  15. CMS – HF Quartz Fiber Calorimeter ~ 1000 km quartz fibers 1 HF weights ~ 250 tons ~2000 PMT readout (magn. field ~ 0 )

  16. HF Cross-section and front view

  17. p/e values for SPACAL and HF

  18. Energy resolution of HF c - Noise, etc • Electromagnetic energy resolution is dominated by photoelectron statistics and can be expressed in the customary form. The stochastic term a= 198% and the constant term b= 9%. • Hadronic energy resolution is largely determined by the fluctuations in the neutral pion production in showers, and when it is expressed as in the EM case, a = 280% and b = 11%. b - Constant term (calibration, nonlinearity) a – Statistical fluctuations

  19. Challenge…. Improving the energy resolution? Mockett 1983 SLAC Summer Institute … A technique is needed that is sensitive to the relative fraction of EM energy and hadronic energy deposited by the shower. This could be done hypothetically if the energies were sampled by two media: one which was sensitive to the beta equals one electrons and another which was sensitive to both the electrons and other charged particles. For example one sampler could be lucite which is sensitive only to the fast particles, while the other sampler could be scintillator. • See also Erik Ramberg et al. , Dave Winn et al. , … ….and DREAM… (R. Wigmans et al.)

  20. DREAM 4 I L C Main theme:multiple measurements of every shower to suppress fluctuations • Spatial changes in density of local energy deposit • Fluctuations in EM fraction of total shower energy • Binding energy losses in nuclear break-up fine spatial sampling with SciFi every 2mm clear fibers measuring only EM component of shower via Cherenkov light from electrons (Eth = 0.2 MeV) measure MeV neutron component of shower. Like SPACAL Like HF Triple Readout DREAM =SPACAL + HF

  21. DREAM [DualREAdoutModule] prototype is 1.5 ton heavy (S, Q fibers 0.8 mm f ) Cell [basic element of detector] 2m long extruded copper rod, [4 mm x 4 mm]; 2.5mm hole contains 7 fibers:3 scintillator & 4 quartz(or acrylic plastic). DREAM 4 I L C In total, 5580 copper rods (1130Kg) and 90 km optical fibers. Composition (volume) Cu: S : Q : air = 69.3 : 9.4 :12.6 : 8.7 (%) Effective Rad. length (X0)=20.1mm;Moliere radius(rM)=20.35mm Nuclear Inter. length ( lint )=200mm;10 lint depth Cu. Filling fraction = 31.7%; Sampling fraction = 2.1%

  22. Tower : readout unit Hexagonal shape with 270 cells (Fig. b); Readout 2 types of fibers to PMTs (PMT: Hamamatsu R580) (Fig. a) DREAM • Detector: 3 groups of towers (Fig. b) center(1), inner(6) & outer(12) rings; • Signals of 19 towers routed to 38 PMT 4 I L C Fig. a: fiber bundles for read-out PMT; 38 bundles of fibers Fig b : front face of detector with rear end illuminated: shows 3 rings of honey-comb hexagonal structure..

  23. DREAM calibrated with 40 GeV e- into center of each tower, recover linear hadronic response up to 300 GeV for p- and “jets” DREAM 4 I L C

  24. New issues and options • (Light-Emitting) Active Media Study Xstals, Cerenkov radiators, neutron sensitive scintillators • (Photon-Sensing) Detectors Develop SiPM (popular objective… … need good technology partners) • (Time-Domain) Signal Processing Fast Pulse Shape digitizer

  25. Differentiating Cherenkov and Scintillation light in PBWO4

  26. Angular dependence and L-R asymmetry

  27. Studies with pions Preliminary results

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