Cosmic rays:
Cosmic rays:
a walk across the Universe a walk across the Universe
Lorenzo Perrone Lorenzo Perrone
Dipartimento di Matematica e Fisica Dipartimento di Matematica e Fisica Universit
Università à del Salento e INFN Lecce del Salento e INFN Lecce
Using particle physics to understand and image the Earth
ISAPP
Ferrara 2-12 July 2018First day:
History, nature, sources and propagation of Cosmic Rays Composition and energy spectrum
Second day:
Observation and overview of detection techniques
The case of ultra-high energy cosmic rays: focus on the Pierre Auger Observatory Second day:
Observation and overview of detection techniques
The case of ultra-high energy cosmic rays: focus on the Pierre Auger Observatory
OUTLOOK
Reading code:
slides marked with a red and bold T have technical content
Using particle physics to understand and image the Earth
ISAPP
Ferrara 2-12 July 2018First day:
History, nature, sources and propagation of Cosmic Rays Composition and energy spectrum
Second day:
Observation and overview of detection techniques
The case of ultra-high energy cosmic rays: focus on the Pierre Auger Observatory Second day:
Observation and overview of detection techniques
The case of ultra-high energy cosmic rays: focus on the Pierre Auger Observatory
OUTLOOK
Reading code:
slides marked with a red and bold T have technical content
Using particle physics to understand and image the Earth
ISAPP
Ferrara 2-12 July 2018Why studying cosmic rays Why studying cosmic rays
Cosmic rays are “natural”
abundance: ~ 300 particles/s/m2 20% of natural radioactivity
Multi-messenger astronomy → access to astrophysical sources
Study of fundamental interactions up to energies well beyond man-made
accelerators nowadays available
Long record of pioneering discoveries → insight into new physics is in their DNA
1896- 1903:
1896- 1903: Discovery of natural radioactivity (H. Bequerel) and first Discovery of natural radioactivity (H. Bequerel) and first measurements (E. Rutherford)
measurements (E. Rutherford) 1910:
1910: T. Wulf goes on top of the Eiffel tower and measures the T. Wulf goes on top of the Eiffel tower and measures the
concentration of radioactivity at high altitude (using an electroscope) concentration of radioactivity at high altitude (using an electroscope)
Smaller flux than at ground level Smaller flux than at ground level BUT….
BUT….Not as small as predicted Not as small as predicted First puzzle…..
First puzzle…..
Historical restrospective Historical restrospective
Wulf Electroscope (1909)
+
+ +
At the same time D. Pacini were performing similar measurements in deep water in
front of Livorno (Italy)
6am August 7, 1912 Aussig, Austria
Victor F. Hess: the 1912 flight (5350 m) Victor F. Hess: the 1912 flight (5350 m)
Cosmic rays come from outer space Cosmic rays come from outer space
Nobel prize in 1936
for the discovery of Cosmic Rays
1930:
1930: B. RossiB. Rossi predicts a east-west asymmetry if they were charged particles predicts a east-west asymmetry if they were charged particles due to the geomagnetic field. Later (1934)
due to the geomagnetic field. Later (1934) he observs a time coincidence at large he observs a time coincidence at large distance, first hints of extensive air showers
distance, first hints of extensive air showers
What are they? Radiation or particles?
What are they? Radiation or particles?
1932:
1932: Millikan vs Compton. Millikan vs Compton.
Photons or charged particles?
Photons or charged particles?
D. Skobeltsyn: picture of cosmic ray event in cloud chamber with B-field
The beginning of particle physics!
1932:
1932: Carl Anderson, positron (antimatter) discovery in CR
1937:
1937: Neddermeyer and Anderson, muon discovery 1940’s:
1940’s: several discoveries, pions and strange particles
Pierre Auger
John Linsley
Gamma Ray Bursts
Gamma Ray Bursts
Active Galactic Nuclei
Supernovae
Gamma Ray Bursts
Active Galactic Nuclei
Gamma Ray Bursts Colliding galaxies
Gamma Ray BurstsGamma Ray Bursts
Gamma Ray Bursts
Blazars
Acceleration mechanism: concept Acceleration mechanism: concept
Concept
Particles go back and forth across a shock wave (Supernovae shocks) Net energy gain
front speed : V ~ 10
4km/s
Acceleration mechanism: concept Acceleration mechanism: concept
Particles go back and forth across a shock wave (Supernovae shocks) Net energy gain
front speed : V ~ 10
4km/s
No acceleration acceleration deceleration
In all cases unchanged velocity in the racket frame
In all cases unchanged velocity in the racket frameAcceleration mechanisms
Acceleration mechanisms
lab frame cloud frame
Energy conservation
energy gain
Fermi acceleration Fermi acceleration
2° order acceleration (not much effective) Particles accelerated by interaction with a moving magnetized cloud
Cosmic Rays and Particle Physics T. Gaisser
Cambrige University Press (1990)
T
Particles gain energy on crossing a shock front from upstream to downstream and back again (Supernovae shocks) typical shock: Vs ~ 10
4km/s
1° order Fermi acceleration
Diffusive shock acceleration Diffusive shock acceleration
T
Energy spectrum Energy spectrum
power-law spectrum
power-law spectrumEnergy after k encounters
Probability of remaining within the acceleration region
Particles accelerated up to energies larger than E
~ 1 ~ 1 integral spectrum integral spectrum
→ → differential spectrum dN/dE ~ E differential spectrum dN/dE ~ E
-2-2T
Inside the engine of an astrophysical Inside the engine of an astrophysical
source….
source….
Hadronic or electromagnetic?
Hadronic or electromagnetic?
Inverse-compton (IC) Syncrotron (S)
Synchrotron Self-Compton (SSC) High-energy photons produced by electromagnetic processes
S SSC
Photon Spectra of Mkn 501 (Konopelko et al. 2003, ApJ, 597, 851).
High-energy photons and neutrinos produced by hadronic and electr. processes. Astrophysical neutrinos, if observed, would be privileged messengers of cosmic sources
Gamma-ray astronomy
Gamma-ray and
neutrino astronomy
Gravitational waves!
26
Particles with energy up to 10
20eV
(i.e. factor 100-1000 higher than at CERN) Propagation features depend on inner nature Multi-messenger astronomy
across the
universe...
Most of Li, Be, B produced by spallation of CNO
[Sc, T, Cr by by spallation of Fe]
The more reactions the higher their abundances
Memory of the propagation
Elemental composition at GeV energy
Elemental composition at GeV energy
At ~ GeV energies
~ 79% protons
~ 15% He nuclei
~ 5% heavier nuclei
~ 1% free electrons
~ 10-5 10-4 antiprotons
- most likely extragalactic
energy >~ 1018 eV
- galactic origin
energy <~ 1016-17 eV
- isotropic ?
Anisotropy is still an open point
- composition changes with energies
still mixed at 10
19.5eV
The Review of Particle Physics (2018) M. Tanabashi et al.(Particle Data Group), Phys. Rev. D 98, 030001 (2018).
http://pdg.lbl.gov/
200-300 pc
20 kpc
Cosmic Rays Propagation through the Milky Way Cosmic Rays Propagation through the Milky Way
Magnetic fields drive the path of CR
Magnetic fields drive the path of CRConfinement depends on energy and rigidity
High-energy and low Z particles likely escape the galaxy for energy larger than 3 1015 eV knee region
knee region
Intergalactic magnetic field <~10-9 Gauss
Z
CRs spend 20 million years in our Galaxy constant flux of CRs requires an injection power of ~2 1041 erg/s 3 supernovae/century may provide this power
pp FeFe
300pc
Magnetic deflection reduced at the highest energies:
ASTRONOMY with charged Cosmic-Rays
Propagation at the highest energies Propagation at the highest energies
Proton, 1020 eV, less than 1 degree deflection along 1kpc (1 Mpc ) with B ~ 10-6 (10-9) Gauss
Gyroradius exceeds the size of our Galaxy
Particles with energies above few EeV (1 EeV = 1018 eV)
are most likely of extragalactic origin
Propagation of high-energy protons Propagation of high-energy protons
Threshold for pair-production
Threshold for photo-pion
Energy Attenuation length
pair-production
photo-pion interaction
length
CMB~ 6 10
-4eV -> Protons ~ 10
20eV efficiently absorbed
T
Flux Suppression (GZK cut-off)
Flux Suppression (GZK cut-off)Protons at E >10
Protons at E >102020 eV within 100 Mpc
eV within 100 Mpc
Propagation of protons: implications Propagation of protons: implications
E
thr~ 5x10
19eV
p e e
p
CMB
0
p
p
CMBT
Propagation of high-energy nuclei Propagation of high-energy nuclei
Attenuation length for iron nuclei
pair-production (CMB, IR)
photo-disintegration (CMB,IR) Giant Dipole Resonance
Energy shared among nucleons, higher energy threshold for individual processes
Inelasticity decreases as 1/A, cross sections increases as Z
2Attenuation length smaller but at higher energies
T
Propagation of high-energy photons Propagation of high-energy photons
interaction and attenuation length for photons
pair-production (CMB)
interaction lengths attenuation lengths
CMB CMB+RB
Threshold for pair-production
100 EeV photons interact within few tens of Mpc
Electron/positrons initiate an electromagnetic shower
T
The energy spectrum of high energy cosmic rays
1 particle cm-2s-1
1 particle m-2y-1
1 particle km-2century-1
Direct measurement:
Direct measurement:
satellites (AMS), satellites (AMS), balloons (CREAM) balloons (CREAM)
Ground array Ground array ~ km~ km22 Kascade-Grande, Icetop Kascade-Grande, Icetop High-altitude ground array,
High-altitude ground array,
~0.01 km
~0.01 km22 ARGO-YBJ, ARGO-YBJ, Tibet ASg
Tibet ASg
Ground/Hybrid array Ground/Hybrid array Auger
Auger 3000 km3000 km22 TA
TA 700 km700 km22
courtesy of R. Engel
“knee”
“ankle”
Above LHC energy