Auger and the ultra-high-energy cosmic rays:

(1)

Auger and the

ultra-high-energy cosmic rays:

Etienne Parizot

APC & Université Paris 7

results and perspective

The Pierre Auger Collaboration

(2)

Overview



Cosmic rays: context and history



The Pierre Auger Observatory and its first results

 Discovery of subatomic world



Cosmic ray phenomenology and observations

 Cosmic rays and high-energy physics

 Cosmic rays and astrophysics: main discoveries

 Ultra-high-energy cosmic rays

 The tree main observable: angular distribution, energy spectrum, mass composition



Perspective: astronomy, astrophysics, astroparticles

and high-energy physics!

(3)

I- Cosmic rays

and high-energy physics I- Cosmic rays

and high-energy physics



Discovery of the subatomic world



Discovery of cosmic rays



Birth of particle physics

(4)



Cathode rays (1879)

identified as electrons (Thomson, 1897)



X rays (Röntgen, 1895)

identified as photons by von Laue (1912)



Radioactivity of U (Becquerel, 1896)



3 types of radioactivity (Curie(s), Rutherford, Villard, 1898-1900)



1901: Wilson studies the discharge of electroscopes underground

road to cosmic rays

(5)

Cosmic ray physics

started one century ago

with this kind of instrument:

Charged electroscope Discharged electroscope

(6)

Anomalous ionising power…



1910: Theodore Wulf (Jesuit, amateur

physicist, who builds the best electroscopes) works on the top of Eiffel tower

ionisation larger than expected!



1911-1912:

Viktor Hess studies electroscope

discharge as a

function of altitude,

in a balloon

(7)

0 km 2 km 4 km 6 km 8 km 10 km

0 20 40 60 80

Intensité du rayonnement Synthèse des mesures

de Hess et de Kolhörster (1912 - 1914)

« The result of these observations seems to be explained in the easiest way by assuming that an extremely penetrating radiation enters the atmosphere from above » (V. Hess)

radiation intensity altitude

(1912-1914)

(8)

Unknown origin (still now!)



Thought to be high-energy photons by Millikan

calls this radiation “cosmic rays” in 1925



Identified as charged particles in 1928-1930

Bothe & Kohlörster (with Geiger counters, 1929)

Skobeltzyn (with cloud chambers with magnetic fields) Clay (latitude effect, 1928)

Compton et al. (latitude effect, 1930)



Primary particles inaccessible!

Make the most of secondaries…

(9)



Cloud chambers discovery of positrons (Anderson, 1932)



Light/matter reversibility

particle showers

discovery of muon (Neddermeyer &

Anderson, 1936)

(10)

A new science is born!



The list of discovered particles is long

 Positron  antimatter !

 Muon  Nature is not sparing!

 Pions : 

⁰

, 

⁺

, 

^-

 Kaons (K)

 Lambda ()

 Xi ()

 Sigma ()

« strange » particles

1932 1936 1947 1949 1949 1952

1953 (lifetime is much too long)



All this, thanks to cosmic rays…

…whose nature and origin are still unknown!

(11)

particle physics particle physics

astrophysics astrophysics Study of

cosmic rays Study of cosmic rays

1953

(12)

1953

Study of cosmic rays

particle physics

astrophysics

1912

astronomy

2007

particle physics

glorious timeline

Astroparticle physics

Cosmic ray physics

(13)

– II –

Cosmic rays and astrophysics – II – Cosmic rays and astrophysics



Long, rich and successful story



Major discoveries

 Non-thermal astronomy

 Central role of CRs in Galactic ecology

 Existence of CRs up to 10

²⁰

eV

 Proton astronomy is possible!

(14)

Non-thermal astronomy Non-thermal astronomy



Energetic particles are ubiquitous in the universe



Particle acceleration is a central problem

 Physics of powerful, high-energy sources

 Physics in “extreme conditions”

 Multi-scale problem + conditions very different from laboratory exp. (e.g. “collisionless shocks”)



Multi-wavelength astronomy: gives access to

high-energy processes ( “astroparticle physics”)

(15)

Cosmic Rays and Galactic Ecology Cosmic Rays and Galactic Ecology



Series of discoveries



Still very poorly understood!

 LiBeB nucleosynthesis

 One of the main components of the Galaxy (>1 eV/cm

³

)

 CRs control the ionization of the interstellar medium

+ heating + turbulent magnetic field + astro-chemistry!

+ price of wheat in England! + Stradivarius’s magic?



Role in Earth climate, species evolution, health…

 CRs regulate star formation

(16)

Existence of very high energies!



Up to a few 10

²⁰

eV (at least!)



Very large rigidity  source pointing?

 Tens of Joules!

 Lorentz factor of 10

¹¹



Challenge for acceleration theories

yes, eventually!

1 s  3500 yr

Sun/Earth distance  1.5 m

 with LHC magnetic field,

required radius = 6010

⁶

km (Sun/Mercury distance) acceleration time = 815 years

 with ILC electric field, required radius = 1.510

⁹

km (Saturn)

(17)

– III –

Measurement of high-energy CRs – III –

Measurement of high-energy CRs



Cosmic ray-induced atmospheric showers



Two complementary observational techniques



The Pierre Auger Observatory and its hybrid concept

(18)

(19)

(20)

1 part/m

²

/year

1 /km

²

/century!

1 part/m

²

/s

ankle

knee

non thermal

Limit for

satellites

(21)



Some confusion at high E…

[CR flux] x E

(22)

[CR flux] x E

GZK

ankle

Second knee?

knee



Essentially due to uncertainties in the energy scale

(23)

Particle cascades and “showers”

One

very energetic particle

Many

less energetic particles

 same thing in the Earth atmosphere!

(24)

“Extensive Air Showers”

• Induced by cosmic rays in the atmosphere

(25)

EM & hadronic “sub-showers”

• elecromagnetic and hadronic subshowers p + p



e

⁺

e

^-

π

⁰

π

^±

µ

^±

π

⁰

 e

⁺

e

^-

π

^±



µ

^±

π

^±

“hadronic” “EM”

(26)

Shower development

• High-energy hadronic interactions

 extrapolation of hadronic models

important source of uncertainty!

grammage (g/cm

²

)

• yet unexplored physics

 ≥ 300 TeV in p-p center-of-mass frame

• “Forward cross sections” important!

• Implications for high-energy physics

(27)

QuickTime™ et un décompresseur TIFF (LZW) sont requis pour visionner cette image.

• comparison of observables with MC simulations

Density of shower particles

Fluorescence photons from astmosphere

 lateral distribution

 longitudinal

shower development (sensible to EM sub-shower)

(sensible to EM and hadronic sub-showers)

QuickTime™ et un décompresseur TIFF (LZW) sont requis pour visionner cette image.

(28)

Composition-sensitive observables Composition-sensitive observables



Depth of shower maximum development: X

_max

low E high E high E

low A high A

atmospheric depth (g/cm

²

)



Stochastic process fluctuations ^large

small

fluctuations

(29)

+ fluctuations in X smaller for heavier nuclei

Expectations from different hadronic models

(30)

Composition-sensitive observables Composition-sensitive observables



Parameters of the shower front



NB: dependence on CR arrival direction

 Radius of curvature  “time delays” in particle arrival times

 Thickness of the front  “rise time” of the measured signals



Relative weight of hadronic subshower

 “number of muons”  F _µ (Fe)/F _µ (p) ~ 1.27 (Sibill 2.1) ~ 1.39 (QGSJet 2)

 Zenith angle of the shower  atmospheric depth

 attenuation of EM subshower only

(31)

¡ Bienvenida en la tierra cósmica !

(32)

The Pierre Auger Observatory

Southern site Northern site



Participating Countries



Argentina



Australia



Brazil



Czech Republic



France (+ Vietnam)



Germany



Italy



Mexico (+ Bolivia)



Netherlands



Poland



Slovenia



Spain



United Kingdom



USA

50 Institutions, 400 Scientists

3 000 km

²

20 000 km

²

(33)

38° South, Argentina, Mendoza, Malargue 1.4 km altitude, 850

g/cm ²

Argentina Australia

Bolivia

^*

Brasil Czech Republic

France Germany

Italy Poland Mexico Slovenia

Spain United Kingdom

USA Vietnam

^*

The Pierre Auger Observatory

(34)

9th July 2007

1438 deployed 1400 filled

1364 taking data

AIM: 1600 tanks

(35)

QuickTime™ and a

TIFF (Uncompressed) decompressor are needed to see this picture.

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(37)

(Cherenkov water tank)

PMT

Plastic tank 12 m³ of clean water

Solar pannel Comms antenna

GPS antenna

battery

Diffusive white “liner”

(38)

(39)

(40)

Completed!

(41)

Central Laser Facility (laser optically linked

Year around balloon borne atmospheric measurements.

Drum for uniform illumination of each fluorescence camera – part of end to end calibration .

Lidar at each Fluorescence building

(42)

(43)

E = 5.3 10

¹⁹

eV

E = 4.8 10

¹⁹

eV E = 4.9 10

¹⁹

eV

stereo events

E

_em

calculated by fitting a

GH profile and integrating

(44)

(improvements expected soon…)

source systematic uncertainty Fluorescence yield

P, T and humidity effects Calibration

Atmosphere Reconstruction Invisible energy

14%

7%

9.5%

4%

10%

4%

Total: 22%

(45)

20 May 2007 E ~ 10

¹⁹

eV

(46)

Time, t

Χ°

R

_p

km

(47)

CERN, 11 December 2007 — Particle Physics Seminar: Auger results on UHECRs — E. Parizot (APC / Univ. Paris 7)

No.4

Theta = 59.9 [degree]

E = 86 [EeV]



SD energy estimator: interpolated signal in a tank at 1000 meters and 38°

(48)

(49)

Cross-calibration of detectors

FD energy SD energy

estimator

(50)

Cross-calibration of detectors

Fractional dispersion of FD/SD energy estimates

Very good

estimator !

(51)

IV- Phenomenology of high-energy Cosmic Rays and Auger results IV- Phenomenology of high-energy

Cosmic Rays and Auger results



Energy spectrum: differential flux



Angular spectrum: arrival directions



Mass spectrum: composition

(52)

The GZK effect



Greisen (1966) + Zatsepin & Kuz’min (1966)



Energy losses through e

⁺

/e

^-

pair and pions production!



Threshold : E

_

 2 m

e

c

²

in the proton rest frame

 p

e

⁺

e

^-

Proton rest frame

p  p

“Cosmic frame”

E

_

> 1 MeV



Threshold : E

_

 m

_

c

²

in the proton rest frame E

_

> 160 MeV

(53)

10^-6 10^-5 0,0001

0,001 0,01 0,1 1

10⁶ 10⁷ 10⁸ 10⁹ 10¹⁰

σκ

(mbarn)

E (eneV)

roductiondeions

roductiondeairese⁺/e^-

[cross section] x [inelasticity]

(54)

10 100 1000 10⁴

19 19,5 20 20,5 21

λ

^att

(Mc)

lo(E)(eV)

rotonattenuationlenth(inCMB)

Attenuation length – horizons

1000 Mpc

100 Mpc

10 Mpc 10

¹⁹

eV 10

²⁰

eV

10

²¹

eV

(55)

Evolution of the CR energy

(56)

10^-12 10^-11

10¹⁷ 10¹⁸ 10¹⁹ 10²⁰ 10²¹

Flux

E×

a

Enerie(eneV) z=0.01,i.e.D ∼60Mc

"Propagated" spectrum

accumulation

Source spectrum:

E

^-2.3

up to infinity...

GZK cutoff

(57)

10^-12 10^-11

10¹⁷ 10¹⁸ 10¹⁹ 10²⁰ 10²¹

Flux

E×

a

Enerie(eneV)

z=0.01 z=0.1

D 60Mc≈ D 530Mc≈

accumulation

pions prod.

pair prod.

accumulation

GZK cutoff

(58)

0,1 1 10

0,1 1 10 100 1000

Φ (E) × E

2.3

(eV

2

m

-2

s

-1

sr

-1

)

Enerie(eV)

ectreroaé

(sourceuniqueauredshiftz _s)

z_s=0.01 z_s=0.1

z_s=0.3

z_s=0.5 z_s=0.65

z_s=1

(59)

10²³ 10²⁴ 10²⁵ 10²⁶

10¹⁷ 10¹⁸ 10¹⁹ 10²⁰ 10²¹

AGASA

Stereo Fly's Eye Akeno 1 km2

distribution uniforme de sources de z=0.001 à z=1

(spectre source en E^-2.5)

Φ (E) ×

³

E

(eV

2

m

-2

s

-1

sr

-1

)

Uniform source distribution

GZK cutoff

(60)

calib. uncert. 10%

FD syst. unc. 22%

5165 km

²

sr yr ~ 0.8 full Auger year

(61)

Slope = -2.62 ± 0.03

calib. uncert. 10%

FD syst. unc. 22%

5165 km

²

sr yr ~ 0.8 full Auger year

(62)

5165 km

²

sr yr ~ 0.8 full Auger year

Exp. Obs.

>10

^19.6

eV 132 ± 9 51

> 10

²⁰

eV 30 ± 2.5 2

calib. uncert. 10%

FD syst. unc. 22%

Slope = -2.62 ± 0.03

significance = 6s

(63)

60° ≤ q ≤ 80°

inclined events:

29% of the nominal data set

1510 km

²

sr yr

(> AGASA)

(64)

Energy spectrum facts Energy spectrum facts

There is an ankle

How to interpret it?

Galactic/Extragalactic transition?

Spectral feature from pair-production energy losses of pure-proton UHECRs?

analyse composition!

or

There is a “cut-off”

How to interpret it?

GZK effect?

Limit of the acceleration process?

analyse arrival directions!

or

(65)



If one can identify cosmic-ray sources, one can

infer their distances and check the energy evolution of the horizon scale

Confirmation of GZK effect Confirmation of GZK effect



Can we identify source?

probably soon!

(66)

Auger anisotropy results Auger anisotropy results



Angular resolution of ~1°: good enough!



No large-scale signal (dipole) at any energy above 1 EeV



No significant excess emission from Galactic center



No signal from BL-Lacs as possibly seen by HiRes

e.g. a < 0.7% for 1 EeV ≤ E ≤ 3 EeV

none of the previous reports have been confirmed…

(67)

Main Auger result



Highest energy cosmic rays have an anisotropic distribution!



First evidence that proton

astronomy is possible indeed!



Correlation with the most nearby AGNs in the 12

^th

Véron-Cetty/Véron catalogue



Opening of a new era:

QuickTime™ and a

 Study of particle acceleration in high-energy astrophysical sources

 Multi-messenger study of sources

 High-energy physics!

(68)

Auger main anisotropy result Auger main anisotropy result

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Position of the 27 highest energy events on an equal exposure map

(69)

Position of the 27 highest energy events on an equal exposure map

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décompresseur TIFF (LZW)

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Galactic and supergalactic planes

Auger main anisotropy result

(70)

QuickTime™ and a TIFF (Uncompressed) decompressor

are needed to see this picture.

Auger main anisotropy result

(71)

QuickTime™ and a TIFF (Uncompressed) decompressor

are needed to see this picture.

Dq ≤ 3.1°

Dq ≤ 3.1° z ≤ 0.018 z ≤ 0.018 (D ≤ 75 Mpc) (D ≤ 75 Mpc)

E ≥ 56 EeV E ≥ 56 EeV

Auger main anisotropy result

(72)

QuickTime™ and a

The energy above which the correlation is most significant corresponds to an energy where the CR flux drops… (supporting the GZK interpretation)

Auger main anisotropy result

(73)

Significance of the anisotropy result



Véron-Cetty / Véron, 12th Edition, 2006

“This catalogue should not be used for any statistical analysis as it is not complete in any sense, except that it is, we hope, a complete survey of the literature.”

Not an “AGN correlation” result!

(74)

Significance of the anisotropy result

Not an “AGN correlation” result!



1st step: search between HECR arrival directions and various source catalogues (hard to estimate how many, how intensively, etc.)



A very large “raw significance” was found with the 12

^th

VCV catalogue of AGNs

Did not seem to be fluctuation

Auger collaboration set up a prescription for future data



Even after taking into account generous penalty factors for a posteriori searches and scanning of parameter space

(data from 2004/01/01 to 2006/05/26)

12 out of 15 events above “56 EeV” are closer than 3.1°

from an AGN in 12

^th

VCV with z ≤ 0.018 (D ≤ 75 Mpc)



Most significant a posteriori “correlation signal”:

3.2 expected

from isotropic

distribution

(75)

Significance of the anisotropy result

Not an “AGN correlation” result!



2nd step: predefine a region in the sky where there seems to be an excess of CR flux, and see if the next highest energy cosmic rays come from this region



Independent data set



prescribed parameters



unambiguous significance (Confidence Level)



Result: 99% CL that the excess we had seen in the original data set was not a random fluctuation from an otherwise isotropic cosmic ray distribution

“CR distribution is anisotropic at the highest energies!”

Largely corroborated by other analyses, independent of any source catalogue (papers to appear very soon!)

21% chance from isotropic distribution

8 “correlating

events” out of 13

(2.7 expected)

(76)

Astrophysical implications?



Not clear yet! (very low statistics to check against any model, whether naive or sophisticated)



NB: no claim from Auger!

YES



Can UHECRs come from AGNs?



Do UHECRs have to come from AGNs?

But we knew that before!

NO!

See further analysis of the observed “correlation” and

analyses with other catalogues, to appear very soon…

(77)

Centaurus A, Virgo, Fornax, etc.

(78)

Centaurus A, Virgo, Fornax, etc.

QuickTime™ and a

Galactic plane: catalogue even more

incomplete + larger deflections expected

(79)

Auger results on CR composition Auger results on CR composition



If ultra-high-energy nuclei exist, they can be photo-dissociated on their way from their sources by interaction with the CMB



NB: even if no UHE nuclei reach the Earth, the

phenomenology of extragalactic CRs depends on the

presence or not of nuclei at the source

(80)

10

³

10

⁴

10

⁵

10

¹⁸

10

¹⁹

10

²⁰

UHECR flux (arb. units)

source spectrum: E

^-2.6

protons only

E

max

(p) = 3 10

¹⁹

eV

E

max

(p) = 3 10

²⁰

eV N(≥10

¹⁹

eV) = 866

Examples of "propagated" spectra

(81)

0,1 1 10

17 17,5 18 18,5 19 19,5 20 20,5

Φ(E) ×

3E (10

24 eV

2m

-2s

-1sr

-1)

log10 E (eV) mixed composition

(uniform source distribution) Q(E) ~ E^{- 2.3}

HiRes 1 (mono) HiRes 2 (mono)

inferred Galactic component

Mixed composition (Allard et al.)

Source spectrum in E ^-2.3

Ankle = gal./extragal. transition

0,1 1 10

17 17,5 18 18,5 19 19,5 20 20,5

Φ(E) ×

3E (10

24 eV

2m

-2s

-1sr

-1)

log10 E (eV) protons only

(uniform source distribution) Q(E) ~ E^{- 2.6}

HiRes 1 (mono) HiRes 2 (mono)

inferred Galactic components with cut

with low E cut

Pure protons (cf. Berezinsky et al.)

Source spectrum in E ^-2.6

Ankle = "pair production dip"

(82)

+ fluctuations in X

_max

smaller for heavier nuclei

Expectations from different hadronic models

(83)

measured over 2 decades in E

+ fluctuations in X to be exploited

(84)

Problems with high-energy physics?

+ fluctuations in X

_max

to be exploited

At variance with other results?

Implications for

high-energy physics

+ muon excess!

(85)

111 69 25 12 426

326 Large number of events allows good control

Comparison with previous studies

(86)

Photon limit



Photon-induced showers look very different

Showers at E = 10

¹⁹

eV, θ = 0º :



Top-down models predict abundant fluxes of UHE photons

SHDM models: decay of super- heavy dark matter accumulated in Galactic halo

TD models: supermassive particle

decay from topological defect

interaction or annihilation

(87)



Larger X

max

: photon showers delayed by > 200 g/cm

²

at 10

¹⁹

eV

≠ SD observables: smaller rise time of the signals

LPM effect

(88)

QuickTime™ and a

astro-ph/0712.1147

(89)

astro-ph/0712.1147

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Top-down models are

essentially excluded!

(90)

composition E spectrum directions

matches astrophysical expactations

Implications for

gal./extragal. transition?

Unity with the CR science and sources at low E?

Maes HECR studies even richer!

some nuclei, no photons

ankle + GZK cutoff

Excellent news!

40 years-old prediction!

 nearby sources

 « proton astronomy »!

+ isolated sources!

+ high-energy physics study of showers (muons, hadronic models, energy scale)

cf. knee + LHC !

anisotropic sky

Most important result since 100 years!

 “cosmic-ray astronomy” is possible

(it just began!)

 cosmic rays integrated

into the scientific corpus

of astrophysics

(91)

Cosmic rays, year zero!



Historical opening of a non-photonic astronomy!



All this starts today!



Eventually: identification and study of individual sources



Many questions



sources, CR origin, acceleration mechanisms, behaviour of energetic sources in the universe, link with low-energy CRs and galactic ecology



Necessary to increase collecting power at the highest energies

Auger Nord (Lamar, Colorado) (sources are there: let’s go and get them!)



study of high-energy physics

(92)

Final word

1

2



Individual sources



GZK cutoff not so meaningful/important



Measuring the overall spectrum is the past!



Individual source spectra are astrophysically rich!

Individual cut-offs, distance, low-E depletion, EGMF structure…



GZK horizons and high-energy physics



Correlation of high-energy CRs with nearby sources:

another way to detect the GZK effect!



+ direct shower studies…



Constraints on the experimental energy scales!



Challenging shower physics!  LHC most awaited…

(93)

Merci !

(94)

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