1. Aspen 4/28/05Physics at the End of the Galactic Cosmic Ray Spectrum - “Below the Knee” Working Group “Below the Knee” Working Group Report - Day 3 Binns, Hörandel, Mitchell, Moskalenko, Müller, Streitmatter, Takita, Vacchi, Yodh, et al. Issues directly bearing on measurements to knee energies: 1.Combined spectral measurement approaching 10 15 eV Calorimeter at high mountain altitude measures surviving protons TRD balloon instrument measures heavy composition 2.L/M measurements - Propagation B/C to highest possible energy to determine energy dependent pathlength. TRD on balloon or in space 3.High Energy electrons above ~1 TeV Identify local sources Local diffusion coefficient to high energy Calorimeters or synchrotron X-ray detectors Note: Should not abandon high precision space instrument too quickly. Years invested in study. TRD/Calorimeter (ACCESS) could achieve listed goals.

2. Aspen 4/28/05Physics at the End of the Galactic Cosmic Ray Spectrum - “Below the Knee” Working Group Technical Issues: How realistic are proposed techniques? - 1 High mountain altitude, large-area proton calorimeter: –Measures unaccompanied (uninteracted primary) protons –Area required ~100 m 2 (depends on run time) –To veto showers, requires large “carpet” of veto counters and/or Cherenkov telescope with extremely large FOV. Even non-interacting events will have accompanying electrons Cherenkov telescope would limit efficiency by requiring night operation –Absolute flux (not slope) requires ~3% p/air cross-sections for 15% accuracy. How well can instrument itself measure cross-sections using inclined measurements? Mainly issue of statistics. May drive area/run time. –What fraction of interacting events mimic non-interacting primaries?

3. Aspen 4/28/05Physics at the End of the Galactic Cosmic Ray Spectrum - “Below the Knee” Working Group Technical Issues: How realistic are proposed techniques? - 2 Large-area TRD balloon instrument –Measures  to ~10 5 for ~Z≥5. –Easily calibrated in electron beam. –Area required to reach 10 15 eV in 10 LDB flights ~30 m 2 Weight? Launch logistics –10 LDB flights may require 15-20 years. –What is energy limit of B/C ratio measurement due to atmospheric secondaries? Atmosphere above balloon comparable to galactic grammage traversed at ~1 TeV (check) –Event by event energy resolution? TRD space instrument –Limitation to B/C only B statistics and energy resolution

4. Aspen 4/28/05Physics at the End of the Galactic Cosmic Ray Spectrum - “Below the Knee” Working Group Techniques - High Energy Electrons Measurements must extend well beyond ~1 TeV. Need ~1.5m 2 sr yr exposure. Calorimeters: –PAMELA to fly October 2005 Si/W imaging calorimeter with self-trigger mode - 600 cm 2 sr. Measurements to ~2 TeV –Other calorimeters - e.g. Japanese proposal for JEM flight. Synchrotron radiation in magnetic field of Earth –Detect fan of hard X-radiation –Does not need to directly detect incident electron - large collecting power –CREST (Cosmic Ray Electron Synchrotron Telescope) Balloon instrument. Full instrument ~4m 2 measures >2 TeV in single ULDB flight. –AMS?

5. Aspen 4/28/05Physics at the End of the Galactic Cosmic Ray Spectrum - “Below the Knee” Working Group Complementary Measurements Precision proton and elemental spectra from magnetic- rigidity spectrometers (BESS-TeV, AMS?). –Provide precise reference up to about 1 TeV. Air Cherenkov measurements down to ~10 14 eV. –Primary pulse gives charge, shower gives energy –May be able to connect to highest energy direct measurements. Positrons and antiprotons. –Secondaries from protons probe propagation –Antiprotons propagate over great distances (small cross-section) Trace average proton spectrum In combination with measured (local) proton spectrum can indicate local fluctuations Simultaneous measurement by magnet spectrometers (e.g. BESS/BESS-Polar, HEAT, CAPRICE, IMAX, PAMELA, AMS?) –No existing techniques to measure antiprotons above ~50 GeV

6. Aspen 4/28/05Physics at the End of the Galactic Cosmic Ray Spectrum - “Below the Knee” Working Group “Classical” Cosmic Ray Measurements Very important for understanding of knee even if measured at lower energy –Indicate sources –Probe propagation –Important clues to stellar environments in which CR originate Radioactive isotopes –Confinement time –Time to acceleration –Matter distribution in path Secondary/primary ratios - pathlength distribution Ultra-heavies - probe source, e.g. sample of OB association material/WR stars Others already mentioned (e +, p-bar, element spectra)