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Calorimetry in High-Energy Elementary-Particle Physics. J.A.Crittenden, Cornell University. 1/27. Part II: Calorimeter Technologies.
Typology: Lecture notes
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Joint Dutch Belgian German Graduate School Calorimetry in High-Energy Elementary-Particle Physics
Joint Dutch Belgian German Graduate School Calorimetry in High-Energy Elementary-Particle Physics
LR(cm) LR(cm)
All shower particles lose energy only via interactions with the absorber, which is also the active material, so e / mip = 1
Joint Dutch Belgian German Graduate School Calorimetry in High-Energy Elementary-Particle Physics
Each crystal 5 cm square by 30 cm (16 L
) long Silicon photodiode readout
Joint Dutch Belgian German Graduate School Calorimetry in High-Energy Elementary-Particle Physics
CsI: QWG3 Topical School. B Heltsley, LEPP. Beijing, Oct 2004
Joint Dutch Belgian German Graduate School Calorimetry in High-Energy Elementary-Particle Physics
4
76000 Lead tungstate crystals
Joint Dutch Belgian German Graduate School Calorimetry in High-Energy Elementary-Particle Physics
Automated quality control Light yield Light transmission Radiation hardness 12 th^ International Conference on Calorimetry in High-Energy Physics Chicago, Illinois, 6-9 June 2006
Joint Dutch Belgian German Graduate School Calorimetry in High-Energy Elementary-Particle Physics
Joint Dutch Belgian German Graduate School Calorimetry in High-Energy Elementary-Particle Physics
Energy resolution scales with the inverse square root of the sampling fraction. ZEUS (U): f em = 4% Compensation can be achieved in lead, but since it produces fewer neutrons than uranium, f em must be reduced and so the resolution suffers. In this case, the thickness of the absorber was doubled and the thickness of the scintillator halved.
Joint Dutch Belgian German Graduate School Calorimetry in High-Energy Elementary-Particle Physics
EM
H Purely hadronic component π^0 component
Signal fluctuations are not gaussian Fluctuations in EM part affect overall resolution Signal is not proportional to E Ratio of signal for electrons and hadrons depends on energy Relative resolution does not scale with E -1/
Joint Dutch Belgian German Graduate School Calorimetry in High-Energy Elementary-Particle Physics
Intrinsic e/h S π / S e S π Intrinsic e/h The signal from pions approaches that for electrons as the em fraction of the shower increases with energy. The linearity of the signal from pions is poor for the same reason.
Joint Dutch Belgian German Graduate School Calorimetry in High-Energy Elementary-Particle Physics
At low energy (E<5 GeV), hadrons lose more of their energy via ionization than via shower formation and nuclear interactions. As a result, even compensating calorimeters exhibit nonlinearity at low energy. Since an essential characteristic of a compensating calorimeter is a lower sampling fraction for e and h than for mips, the sampling fraction decreases with hadron energy. ZEUS, 1990
Joint Dutch Belgian German Graduate School Calorimetry in High-Energy Elementary-Particle Physics
em I. Absorb the e+e- pairs from low energy photons in the passive material. If one uses a high-Z material, not only are more low-energy photons produced, they are also preferentially absorbed in the high-Z material (photo-effect), AND the e+e- they produce can't get out of it. For example, for 511 keV photons, f/f
=0.27 in uranium and 0.83 in steel. In this manner, the overall f
can be reduce 30-40%. II. Wrap the passive material in a material of lower Z. The thickness can be tuned to absorb photoelectrons and reduce their contribution. ZEUS used 0.3 mm stainless steel cladding to reduce f
by 10%. (ref:Wigmans)
Joint Dutch Belgian German Graduate School Calorimetry in High-Energy Elementary-Particle Physics
Joint Dutch Belgian German Graduate School Calorimetry in High-Energy Elementary-Particle Physics
3.2 mm U + 2.6 mm Sci f e = f h = 4% f mip = 7% MIP sampling fraction U: 1.09 MeV/(g/cm 2 ) x 18.65 g/cm 3 = 20.3 MeV/cm Sci: 1.95 MeV/(g/cm 2 ) x 1.0 g/cm 3 = 1.95 MeV/cm
