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APP-VII Introduction to Astro -Particle Physics

This introduction to astro-particle physics explores the concept of building a km3 detector in the sea for high-energy neutrino astronomy, using sea water as a target/detector. It covers topics such as muon range, Cherenkov light detection, transparency of water, energy loss processes, muon timing accuracy, neutrino interactions, and more.

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APP-VII Introduction to Astro -Particle Physics

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  1. APP-VIIIntroduction to Astro-Particle Physics Maarten de Jong

  2. High-energy neutrino astronomy ‘How to build a km3 detector in the sea…’

  3. 1960 Markov’s idea: Use sea water as target/detector nm+ N→ m+ X • Range of muon • Detect Cherenkov light • Transparency of water

  4. e+ e- muon energy loss Bremsstrahlung Ionisation Bremsstrahlung (+…) dE/dx [MeVg-1cm2] stochastic processes Ionisation 200 MeV/m (1g/cm3) ~constant critical Energy Energy [GeV]

  5. muon range Bremsstrahlung + … E(x) x average range

  6. muon range in water Bremsstrahlung + … range [km] Ionisation Energy [GeV]

  7. muon range in water (II) muon km detector neutrino interaction effective volume ≥ instrumented volume

  8. 1 2 3 4 5 Huygens principle → Cherenkov effect wavefront muon muon 1 2 3 4 5 Threshold effect index of refraction visible light

  9. Cherenkov angle wavefront Dtc/n muon Dtcb

  10. Energy threshold velocity Energy

  11. Cherenkov light yield charge of particle number of photons unit track length unit wavelength index of refraction velocity of particle

  12. Energy loss Ionisation

  13. Arrival time of light t d muon l s t0

  14. Arrival time of light (II) minimum

  15. Arrival time of light (III) dispersion t → Light scattering muon timing accuracy ~ns

  16. photon detection QE(l) photo-multiplier tube (PMT) A ~50 cm e W pressure resistant glass sphere

  17. d muon dx

  18. Absorption of light in sea water Smith & Baker Measurements absorption length [m] ultra violet wavelength [nm] red

  19. Light absorption (II) absorption length QE, absorption, etc.

  20. Neutrino interactions

  21. reminder ~ MeV Sun Kamiokande (solar) neutrino telescope

  22. reminder (II) u > GeV d u W nucleon quark-gluon sub-structure Deep Inelastic Scattering

  23. kinematics xPn nucleon Pn struck quark elastic scattering on a quark

  24. quark xPn W ‘brick wall’ -xPn Energy-momentum conservation x ≡ momentum fraction of nucleon carried by struck quark Lorentz invariant Björken

  25. u d u u d u u d u nucleon structure smallQ2 QCD evolution largeQ2 q(x) very largeQ2 ⅓ 0 1 x ‘wavelength of microscope’

  26. reminder Weak interaction left-handed • fermions → h = –1 • anti-fermions → h = +1

  27. cross sections quark = fermion q q xPn

  28. cross section very largeQ2 cross section [cm2] Left handedness of weak interaction Energy [GeV]

  29. nucleon at rest = detector frame

  30. detector frame Physics Kinematics

  31. median nm scattering angle nota bene: Numerical calculation increases increases angle [deg] decreases decreases Energy [GeV] Measure direction of muon→ neutrino telescope

  32. Antares neutrino telescope

  33. ~200 persons • 6 countries • ~40 km off the coast near Toulon 12 lines ~2.5 km 500 m 250 Atm. ~200x200 m2 25 storeys / line

  34. 12 x 25 = 300 detection units Optical beacon timing calibration 10” PMT photon detection Electronics readout titanium frame mechanical support Hydrophone acoustic positioning ~1 m

  35. Muon detection ‘causality’

  36. reminder(same observer, 2 events) line element causally connected causally disconnected

  37. reminder (II) time like separations light like separations space like separations

  38. hit 3 x hit 1 hit 2 same event, ≥2 observers hit ≡ detected photon at position and time causally connected hit (1,3) and (2,3) are causally related, but not hit (1,2)

  39. Accidental coincidences ‘background’

  40. count rate time window number of sources number of coincidences Total rate Probability

  41. directional information muon z1 z2 ~km R

  42. directional information (II) ¶ ¶ ¶() local coincidences (and large pulses)

  43. multi-directional trigger Field of View =

  44. multi-directional trigger (II) effective volume [m3] majority (other) multi-directional 10log(En)

  45. coincidences between PMTs 40K  40Ca + e- 1g 40K  40Ca + e-  2g number of coincidences e- Dt [ns]

  46. coincidences between floors data Monte Carlo muons muon direction Rate [Hz] Dt [ns]

  47. coincidences between floors (II) muons Rate [Hz] N1 N2 < N1 depth [m] stopping (atmospheric) muons

  48. d l t0 dx = 20 cm dt = 1 ns dq = 0.2 deg. Reconstruction principle t medium properties

  49. Neutrino effective area ‘very small’ ? zenith angle: integrated 0-30 degrees 30-60 degrees 60-90 degrees Area [m2] 10log(E/GeV)

  50. Neutrino propagation trough Earth neutrino absorption probability Energy [GeV]

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