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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 2018

(2)

First 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 2018

(3)

First 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 2018

(4)

Why 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

(5)

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)

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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

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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

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Pierre Auger

(9)
(10)

John Linsley

(11)

Gamma Ray Bursts

(12)

Gamma Ray Bursts

Active Galactic Nuclei

Supernovae

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Gamma Ray Bursts

Active Galactic Nuclei

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Gamma Ray Bursts Colliding galaxies

(15)

Gamma Ray BurstsGamma Ray Bursts

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Gamma Ray Bursts

Blazars

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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

4

km/s

(18)

Acceleration mechanism: concept Acceleration mechanism: concept

Particles go back and forth across a shock wave (Supernovae shocks) Net energy gain

front speed : V ~ 10

4

km/s

(19)

No acceleration acceleration deceleration

In all cases unchanged velocity in the racket frame

In all cases unchanged velocity in the racket frame

Acceleration mechanisms

Acceleration mechanisms

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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

(21)

Particles gain energy on crossing a shock front from upstream to downstream and back again (Supernovae shocks) typical shock: Vs ~ 10

4

km/s

1° order Fermi acceleration

Diffusive shock acceleration Diffusive shock acceleration

T

(22)

Energy spectrum Energy spectrum

power-law spectrum

power-law spectrum

Energy 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

-2-2

T

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Inside the engine of an astrophysical Inside the engine of an astrophysical

source….

source….

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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

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Gravitational waves!

(26)

26

Particles with energy up to 10

20

eV

(i.e. factor 100-1000 higher than at CERN) Propagation features depend on inner nature Multi-messenger astronomy

across the

universe...

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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

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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

19.5

eV

The Review of Particle Physics (2018) M. Tanabashi et al.(Particle Data Group), Phys. Rev. D 98, 030001 (2018).

http://pdg.lbl.gov/

(29)

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 CR

Confinement 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

(30)

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

(31)

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

-4

eV -> Protons ~ 10

20

eV efficiently absorbed

T

(32)

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

19

eV

p e e

p

CMB

0

    

p

p

CMB

T

(33)

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

2

Attenuation length smaller but at higher energies

T

(34)

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

(35)

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

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What cosmic rays do when they enter the

terrestrial atmosphere?

Let’s see tomorrow

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