1 / 20

Lecture 1: Introduction

Lecture 1: Introduction. Cosmic-ray spectrum and measurements. Spectrometers ( D A = 1 resolution, good E resolution). Air showers. Calorimeters (less good resolution) + TRACER. Air-shower arrays on the ground to overcome low flux. Don’t see primaries directly.

roberthickey
Télécharger la présentation

Lecture 1: Introduction

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Lecture 1: Introduction Cosmic-ray spectrum and measurements PS638 T. Gaisser

  2. Spectrometers (DA = 1 resolution, good E resolution) Air showers Calorimeters (less good resolution) + TRACER Air-shower arrays on the ground to overcome low flux. Don’t see primaries directly. Primary spectrum Knee Ankle Current questions PS638 T. Gaisser

  3. Spectral Energy Distribution (linear plot shows most E < 100 GeV) (4p/c) Ef(E) = local differential CR energy density Energetics of cosmic rays • Total local energy density: • (4p/c) ∫ Ef(E) dE ~ 10-12 erg/cm3 ~ B2 / 8p • Power needed: (4p/c) ∫ Ef(E) /tesc(E) dE galactic tesc ~ 107 E-0.6 yrs Power ~ 10-26 erg/cm3s • Supernova power: 1051 erg per SN ~3 SN per century in disk ~ 10-25 erg/cm3s • SN model of galactic CR Power spectrum from shock acceleration, propagation PS638 T. Gaisser

  4. Solar flare shock acceleration Coronal mass ejection 09 Mar 2000 PS638 T. Gaisser

  5. SOHO/ LASCO CME of 06-Nov 1997 PS638 T. Gaisser

  6. Particle with E1 u1 ~ 4/3 V Forward shock Contact discontinuity, V Shocked ISM SN ejecta u1 ~ 4/3 V E2 = x E1 Supernova blast wave acceleration Unshocked ISM Supernova progenitor SNR expands into ISM with velocity V~ 104 km/s. Drives forward shock at 4/3 V TSN ~ 1000 yrs before slowdown Emax ~ Z x 100 TeV PS638 T. Gaisser

  7. Composition PS638 T. Gaisser

  8. Four ways to plot spectra • Particles per GeV / nucleon • for propagation/fragmentation in gas • Particles per GV / nucleon • for propagation/acceleration in magnetic fields • Nucleons per GeV / nucleon • for production of secondaries in the atmosphere • Particles per GeV / nucleus • for air shower experiments PS638 T. Gaisser

  9. Two kinds of measurements Hodoscope: e.g. EAS Inclusive: e.g. muon flux PS638 T. Gaisser

  10. Two kinds of measurement at accelerators • Spectrometer measures inclusive cross section • for example, the HARP experiment • 4π detector • Goal is to detect all particles produced in an interaction • for example, a collider detector like Atlas PS638 T. Gaisser

  11. Definition of energy spectrum • Number of particles per m2 sr s • i.e. Rate per unit area per solid angle • Differential: dN / d ln(E) = E x dN / dE • Preferable to dN / dE for power-law spectrum • δE / E ~ constant, so binning of data is logarithmic • Integral: N(>E) per m2 sr s • If dN / d ln(E) ~ K (E)-gthen • dN / d ln(E) = g x N(>E) PS638 T. Gaisser

  12. Acceptance • Detector acceptance = area x solid angle • Example: • 2 parallel planes of area A1, A2 • Separation d >> sqrt (A1) and d >> sqrt(A2) • Approx acceptance = A1 x A2 / d2 • In general • A x Ω = ∫∫dx1dy1 x ∫ dφ∫ sin(θ) dθ • For each point inside A1 constraints on the solid angle integral depend on (x1,y1) and require the vector in the (θ,φ) direction to pass inside A2 • Evaluate integral by Monte Carlo PS638 T. Gaisser

  13. CAPRICE spectrometer AΩ ~ 0.3 m2 x 0.3 m2 / 10 m2 ~ 0.01 m2 sr CAPRICE 1998 PS638 T. Gaisser

  14. BESS spectrometer AΩ ~ 0.085 m2 sr PS638 T. Gaisser

  15. Magnetic spectrometer • Momentum measurement • Gyroradius: rL = Pc / (zeB) ≡ R / B • Rigidity: R = Pc / ze (units = GV) • Measure z with dE / dX in scintillator ~ z2 • P = A x pN; pN = momentum / nucleon • Example: 100 GeV/c proton in B = 104 Gauss • rL = 333 m • Maximum Detectable Momentum (MDM) • δp ~ eB┴ δt from Lorentz force equation; δt ~ L / c • δx / L ~ δp / p ~ eB┴L / (pc)  (pc)max ~ eB┴L2 / δxmin • Example: for B┴L2 = 0.8 Tm2, (pc)max~ 240 GeV for protons in a detector with 1 mm spatial resolution PS638 T. Gaisser

  16. Time of Flight (TOF) • Two scintillators separated by L • β = L / (cΔt) • δβ = -(L/cΔt) x (δt/Δt) = β x (δt/Δt) • δβ / β ~ δt / Δt • Need sub-nanosecond time resolution to measure velocity of a relativistic particle over a scale of 1 m PS638 T. Gaisser

  17. Cherenkov radiation Cherenkov angle: cos(θc) = 1 / (βn) Threshold: β > 1 / n Intensity: ~ z2 x sin2(θc) = z2 x [1 – 1 / (βn)2] • Uses: • Threshold detector, e.g. separate e+ from p • Use gas or other material with small n ~ 1.003 • Measure energy near threshold • Use plastic or clear material with n ~ 1.5 PS638 T. Gaisser

  18. TRACER uses transition radiation PS638 T. Gaisser

  19. Compilation from RPP Note TRACER measurements in 3 energy ranges PS638 T. Gaisser

  20. Balloon-borne calorimeters • RUNJOB emulsion chamber • Russian-Japanese collaboration • Detector material interleaved • with sheets of photographic emulsion • Primary ID (pink) • Interaction in Target (yellow) • Secondaries separate (blue) • Photons make cascades in • calorimeter (violet) • Calibrate at accelerator • Important for overlap with EAS PS638 T. Gaisser

More Related