Calorimetry in Astrophysics

1. Calorimetry in Astrophysics • Direct measurements of particles/photons in space • Use of the atmosphere and rocks for calorimetric type measurements • Technical issues for these kind of efforts • The effects of resolution • Calibration of large-scale calorimeter techniques • (This discussion is about existing or completed experiments) • Simon Swordy - University of Chicago (s-swordy@uchicago.edu)

2. Things not really included: Silicon bolometers for microwave background (MSAM/TopHat) X-ray quantum calorimetry (XQC Wisconsin/NASA GSFC)

3. tmax ~ 2 DirectMeasurements tmax ~ 3.5 IndirectMeasurements tmax ~ 5

4. All-photon spectrum of extragalatic light (from Ressell and Turner via Steve Ritz) DirectMeasurements IndirectMeasurements

5. Calorimetry in Space EGRET/CGRO: gamma-ray telescope. NaI calorimeter, 76x76cm2 8r.l. deep. Energy resolution ~9% near 1GeV The mother of all space-based calorimeters (so far!): SOKOL on Kosmos-1543 in late 1970s-early 80s. ~5 had , 2000kg Measurements of CRs above 2TeV.

6. Thin Calorimetry used for direct investigations of cosmic rays at high energy Results on measurements of P, He (see astro/ph 0202159) JACEE/Runjob emulsion/x-ray film stacks

7. Advanced Thin Ionization Calorimeter (ATIC) Track around Antartica Winter 2000/2001 Balloon launch Dec 28th 2000

8. Calorimeter - BGO ~ 50 x 50 cm2 x 22 r.l. (1.2) 10 layers of 2.5 x 2.5 x 25cm BGO Crystals Uses ASICs from ACE mission with dynode feeds for dynamic range

9. Single event at ~ 2 TeV Data under analysis Events above 100 GeV depth profile Total energy deposit spectrum

10. Electron/Proton discrimination - key cosmic ray measurement Width of shower in 2nd layer near 100GeV. Solid-electrons, Dashed-protons (Left hand side - simulations, Right hand side - beam test)

11. Effects of energy resolution Effects of energy resolution on measured spectra Finite resolution, constant with energy in E/E Relative energy resolution improves with increasing energy Energy resolution develops a high energy `tail’ at high energies For cosmic rays measured flux at some energy is larger than the actual flux by approximately 2 x E/E

12. Atmospheric Calorimetry Atmosphere is ~ 1000 g/cm2 (vertical) ~11, 27 r.l. • Detection techniques for air-showers: • Detection of particles at ground level • Detection of cherenkov light from shower • Detection of air fluorescence from shower • Nascent radio emission measurements

13. Atmospheric depth of shower maximum (from Joe Fowler, Chicago PhD 2000)

14. Flucutations in shower development are large • (1 PeV showers) • Fluctuations in first interaction point • Fluctuations in inelasticity in first interaction

15. Ground array - Chicago Air Shower Array (Dugway, Utah) km2 sized site

16. Single event in CASA(electrons at ground level) and BLANCA (Cerenkov light) Electron lateral distribution Cerenkov lateral distribution At this site MIA also measures muon content - using buried counters

17. Also, DICE - Cerenkov imaging experiment at this site Cerenkov imaging is used extensively in detecting gamma showers - Whipple 10m telescope

18. Sky noise Imaging technique Gamma ray Local muon

19. 108 solar mass black hole at the lunch table, redshift ~0.03. Observations with Whipple telescope

20. Air Fluorescence The magic of air flourescence - isotropic light which is proportional to the number of electrons at all depths (!) The downside - it’s not that bright and is affected by atmospheric absorption N2* -> N2 + h is in competition with N2* + N2 -> 2N2 The excited state is collisionally quenched. As dE/dx per unit length goes up with higher atmospheric pressure the efficiency of light production decreases linearly with pressure => a fast electron produces the same amount of light per unit pathlength at all altitudes

21. The HiRes experiment in Dugway, Utah. Also the site of the Fly’s Eye experiment

22. Example of a HiRes event at 2x1019eV

23. Event at 3x1020 eV longitudinal development seen with Fly’s Eye (ApJ 1995)

24. Highest Energy Cosmic Ray Events

25. Detection of radio emission • The oppositely charged particles in air showers separate due to the geomagnetic field. This produces a time varying dipole -> radiation. This has been seen in the radio region but it is extremely difficult to get a consistent result here. • The Askaryan effect - which predicts an relative negative component of a shower in normal material should produce microwaves from dense material. This has been observed recently at SLAC (Saltzberg, Gorham et al. PRLett. 2001, 86) • This has been suggested by the same authors as a way to look for neutrino showers originating in the lunar regolith using 2 widely spaced microwave antennae

26. More stuff on Rocks and Ice: AMANDA uses strings of phototubes to look for cerenkov light produce by upward moving muons and showers in the Antartic ice (from

27. Upward-going muon events in AMANDA (from Miocinovic)

28. Yet more rocks……..

29. Calorimetry plays a key role in modern particle astrophysics • Direct measurements need to understand fluctuations to make accurate measurements • Indirect techniques need absolute calibrations and accurate simulations. • Plans exist for large space-borne calorimeters with thousands of channels (ACCESS), A huge air-shower ground and fluorescence array in Argentina and North America (Auger) and far larger detectors than AMANDA aimed at neutrinos (Icecube, ANTARES, NESTOR …). Also arrays of high energy gamma-ray cerenkov imaging detectors are to be built (VERITAS, HESS, MAGIC, CANGAROO, ……)