Special Topics in Nuclear and Particle Physics Astroparticle Physics Lecture 3 Cosmic Rays Sept. 15, 2015 Sun Kee Kim Seoul National University
High Energy Cosmic rays? >,? > ( )? > source & acceleration mechanism
: (98%), (2%) : 87%, 12%, : 1% :,
20km 까지증가 40km 까지감소 50km 이상일정 > 무엇인가외부로부터와서대기와의반응에의해증가한후대기에의해서흡수된다.
(2 ) 1 2. N + N π 's,k 's,! p + p,n + n,! hadronic shower, EM shower hadron, π + µ + +ν µ π µ +ν µ τ = 2.6 10 8 s (Electromagnetic shower), π 0 γγ τ = 8 10 17 s
(2 ) 1 π + µ + +ν µ τ = 2.6 10 8 s cτ = 7.8m 1 GeV: γ =1/0.14 ~ 7 γβcτ ~ 55m 100 GeV: γ =1/0.14 ~ 714 γβcτ ~ 5.5km 100 GeV 100 GeV µ + e + +ν e +ν µ τ = 2.2 10 6 s cτ = 660m 3 GeV: γ =3/0.1 ~ 30 γβcτ ~ 20km, 80% : 70 / m 2 /s/sr at 1 GeV 1/ cm 2 /min
(2 )
(2 ) / : 1 p + N p + N + kπ + kπ + + mπ 0 p + N n + N + kπ + (k +1)π + + mπ 0 N(π + ) N(π ) = 2k +1 2k = 1+ 1 2k k 2 N(π + ) N(π ) 1.25 N(µ + ) N(µ ) 1.27 PDG
Vertical flux measurement of muons
Muons at Surface
Stopping power Bethe-Bloch equation maximum energy transfer : : : ( ) minimum at βγ 3.5 minimum ionizing particle *equivalent thickness g/cm 2 g/cm 2 /ρ(g/cm 3 ) cm MeV/(g/cm 2 ) ρ(g/cm 3 ) MeV/cm
de dx & = $ % de dx #! " rad & + $ % de dx #! " coll Radiation length ( de / dx) rad = E / X 0 E = E 0 e x/x 0 σ rad 2 2 ( e / mc ) 2 ~ 300 m Critical energy E C ~ 0.56 cm
de dx & = $ % de dx #! " rad = be µ & + $ % de dx #! " = a coll
ν µ + N µ + N
Electromagnetic Shower Shower stops at E<Ec N( t) 2 E( t) E E( t max t 0 / 2 ) = E 0 t / t 2 max = E c t max N max E = ln E E 0 0 c / ln 2 / E c ~9.6 MeV for Pb ~100 MeV for air Radiation length
Electromagnetic Shower Longitudinal Shower profile ( EGS4 Simulation ) lateral spread à Moliere radius 90%(99%) contained in 1 (3.5)R M
Hadronic Shower Hadron interaction Interaction length λ I 17
Hadronic Shower
Hadronic Shower
Hadronic Shower ( ) 1030 g/cm 2 : ~ 27 X 0, ~12λ I x = X exp( h / H ) X=1030 g/cm 2, H = 6.5 km
(Balloon, Satelite) protons ~ 87%, He ~ 12% Li, Be, B produced by interaction - - 2
(<1 GeV/n).
Cosmic ray energy spectrum 1 GeV 10 15 ev power law
Measurement of cosmic ray energy spectrum E.S.Seo(2014)
Direct measurement of primary cosmic ray 1,, ) Calorimeter : sampling EM component ATIC, CREAM, Fermi-LAT Spectrometer : sign of charge, momenta AMS, PAMELA,
BESS Spectrometer with a Superconducting magnet(1t) TOF ODC MAGNET JET/IDC
BESS
ATIC Thin calorimeter, balloon borne experiment
CREAM Thin calorimeter, balloon & ISS de/dx : Silicon charge detector of CREAM for cosmic ray measurment
de/dx : Silicon charge detector of CREAM for cosmic ray measurment de / dx z 2
Indirect measurement of primary cosmic ray - Extensive air shower 1 air shower Particle counting : Ground Detector Array scintillators, water cherenkov detectors Air fluorescence : Telescope Hybrid : Telescope + ground detector array * :,
Extensive Air Shower Air shower ( E 0 >100 TeV ) shower core : number of muons above 1GeV at ground level * Ne : total number of charged particles number of muons/m 2 at distance r from the shower core
Air shower simulation Extensive Air Shower Watson (2002)
Extensive Air Shower Composition : Shower maximum depth λ I ~ 80 g/cm 2 for proton ~ 15 g/cm 2 for Fe Shower maximum depth 1. Watson (2002)
Air Shower Measurement Air fluorescence detectors samples longitudinal shower profile Ground arrays sample the shower front
Cosmic Ray Experiments for UHECRs Past Volcano Ranch, USA à Scintillators Haverah Park, UK à Water Cerernkov SUGAR, Austrailia à Scintillators Fly s Eye, USA à Fluorescence Future Telescope Array Auger North à Fluorescence + Scintillator Present Yakutsk, Russia à Scintillators, atmospheric cerenkov Agasa, Japan à Scintillators, Muon detectors HiRes, USA à Fluorescence Auger-South, USA à Fluorescence à Water Cerenkov Telescope Array à Fluorescence à Scintillator array
Air Shower Measurement Ground detector array by Ground detector array 1% : 100% duty cycle ~O(m 2 ) Plastic scintillator Water Cherenkov detector
AGASA ~100 km 2
AGASA
Air Shower Measurement by Fluorescence telescope Air fluorescence detectors duty cycle ~10% Fly s eye (or HiRes)
Pierre Auger Observatory 3000 km 2 Hybrid : ground detector array(water Cherenkov) + fluorescent detector 27 FD at 5 station FD : 440 PMTs
Auger-South 12,000 liter x 1600 1.5 km Lateral density distribution Fitted Electromagnetic Shower
Telescope Array (TA) 730 km 2 Hybrid : ground detector array(scintillator) + fluorescent detector 3m 2 Scint. x 507 1.3 km
Telescope Array (TA) 730 km 2 Hybrid : ground detector array(scintillator) + fluorescent detector
Greisen-Zatsepin-Kuzmin (GZK) Cutoff (Cosmic Microwave Background). Cosmic microwave background (CMB) ρ γ 400 / cm 3 T γ = 2.725K E γ E γ = kt = 8.617 10 5 ev/k 2.725K=2.35 10 4 ev 6 10 4 ev Photoproduction γ + p (Δ + ) p + π 0 n + π +
p p = (E p,p p ) p γ = (E γ = p γ,p γ ) p p + p γ = (E p + p γ,p p + p γ ) (p p + p γ ) 2 = (E p + p γ ) 2 (p p + p γ ) 2 = E 2 2 2 2 p + p γ + 2Ep p γ p p pγ 2p p p γ = m 2 p + 2E p p γ 2p p p γ = m 2 p + 2E p E γ (1 cosθ) = m 2 p + 4E p E γ p p = (E p = m p,0) p π 0 = (E π 0 = m π 0,0) p p + p π 0 = (m p + m π 0,0), (p p + p π 0 ) 2 = m 2 p + m 2 π 0 + 2m p m π 0 m 2 p + 4E p E γ = m 2 p + m 2 π 0 + 2m p m π 0 E p = m 2 + 2m π 0 p m π 0 4E γ = m 0 (2m π p + m π 0 ) 4E γ E γ 6 10 4 ev E p 10 20 ev
10 20 ev UHECR on the atmosphere or on a detector S = ( p 1 + 2 p p p ) CM energy 1 2 2 2 2E 1 m N 450 TeV 2 10 20 ev 10 9 ev Two orders of magnitude higher than LHC!!
Radio Emission from Cosmic Ray Air Shower Geo-synchrotron radiation of electrons in the shower Radio-wave below 100 MHz Discovered in 1965 by Jelly et al.(nature 205, 327) Difficulties in radio measurement/interpretation of data Shifted to Ground arrays/fluorescence tecniques Digital data processing technology Renaissance?
LOPES A LOFAR Prototype Station LOPES at KASCADE-Grande Detection and imaging of atmospheric radio flashes from cosmic ray air shower, LOPES collaboration, Falcke et al, 2005, Nature, May 19
LOFAR LOFAR : Radio telescope array for 10-210MHz with >100 km baseline, www.lofar.org ADetecting cosmic rays with the LOFAR radio telescope A&A 560, A98(2013)