Auger: a New Window into Ultra High Energy Cosmic Rays Antoine - - PDF document

Les Houches 2002

School and Workshop on Neutrino Particle Astrophysics

Les Houches, France 21/01-01/02 2002.

Auger: a New Window into Ultra High Energy Cosmic Rays

Antoine Letessier-Selvon, LPNHE, IN2P3-CNRS, University of Paris VI & VII.

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Contents

• I

UHECR Problematics

• II

EAS characteristics and detection technics.

• III Auger.
• IV

Photon and Neutrino detection.

References :

• M. Nagano and A. A. Watson, Observation and implication of the

ultrahigh-energy cosmic rays, Review of Modern Physics, Vol 72, No 3 (2000) 689.

• X. Bertou, M. Boratav and ALS, Physics of Extremely High Energy Cosmic

Rays, International Journal of Modern Physics A., Vol 15, No 15 (2000) 2181.

P .Bhattacharjee and G.Sigl, Origin and Propagation of Extremely High Energy Cosmic Rays, Physics Report Vol. 327 (2000) 109.

• V. Berezinsky, P

.Blasi, A.Vilenkin, Signatures of Topological Defects, Physical Review D58 (1998).

Auger Design Report, http://www.auger.org/admin/DesignReport.

S.Yoshida and H.Dai, The Extremely High Energy Cosmic Rays, J.Phys. G24 (1998) 905.

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Ultra High Energy Cosmic Rays

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Taille

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Observed spectrum (characteristics)

10

17

10

18

10

19

10

20

10

21

10

22

10

• 1

10

• 2

10

• 3

dF dE

2

E [Arbitrary Unit]

dE dF

E

• 3.0

1 100 10

dE dF

E

• 2.7

CR I CR II CR III Knee ENERGY [eV]

10 10 10

16 15 14

Cutoff?

dE dF

E

• 3.2

Flattening Expected Curve for Extragalactic Origins Dip 2nd Knee

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Above 10

eV

Production mechanisms? How to obtain such a high energy ?

Primary nature (Composition) ?

Sources distribution ? Where do they come from and how do they reach us ?

Where does the spectrum ends ? The very existence of cosmic rays above 10

want to solve. Orders of magnitude ( at 10

10 Joule

2g of lead out of a hunt gun (350 km/h).

detection surface

1000km

10

¡1% muons (1GeV)

10-100Mpc i.e. between 10

Universe (10 Gpc)

World record: E = 3

100 km/h, 100 millions times a LHC beam)

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Transport

Nucleons: GZK cut-off from pion photo-production on the CMB.

and

Proton energy as a function

• f source distance.

After 100Mpc the final energy falls below

Mean energy loss length of protons as recently calcu- lated with a Monte Carlo [Stanev et al].

A comparision with other cal- culations.

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Consequences on observed spectra :

10

17

10

18

10

19

10

20

10

21

10

22

10

• 3

10

• 1

10

• 2

0.016 0.032 0.1

ENERGY [eV]

1.0 0.5 0.004 0.008 0.057

dF dEE

[Arbitrary Unit]

3

1 10

Observed spectra as a function of observed distance from the source (in units of z). The injection spectra is a power law :

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Photons : EM cascades. (Pair production)

Threshold on CMB :

Targets : CMB photons, infra-red (IR) and, at very high energy, radio (URB). NB: IR and URB are not very well known.

10 12 14 16 18 20 22 24

• 3
• 2
• 1

1 2 3 4 5 photon+IR photon+CMBR photon+radio proton pair proton photopion Iron red shift limit

neutrinos at the sources.

photo-production.

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Magnetic Fields. 1) Affects the development of EM cascades. Dominant above :

At threshold (dependent upon the URB density) the loss is about

10

2) Bends and delay charged particles :

Left : Bottom :0.5 kpc trajectory in the Galactic disk or (equivalently) 1 Mpc in inter-galactic space. Top : 30 Mpc trajectory in a random field of 1 Mpc coherence length. Right : Time delays computed in the same conditions.

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Production or Acceleration

Or how to achieve

10

Acceleration (Bottom-Up) “Classic”

• Supernova remnants (SNR). Not energetic enough
• Radio Galaxies (powerful ones!). Ok but rather far away
• Young neutron stars. Hard to escape, loss at the source
• GRB. Cosmological distribution

Sources far away (

GZK cut off Sources nearby (

visible.

Decay (Top-Down) “Exotic” Massive particles or TD are the source of CR (no acceleration)

• Topological defects collapses, intersections or interactions

(strings, Monopoles, super-conducting strings, vortons...)

Fluxes, constraints from CMB isotropy, EGRET measurements of diffuse gamma rays and

• Massive (M

10

cryptons).

DK (

100Mpc) and flux (@10

Cosmological distribution or DM like? Solve Acceleration, power and invisibility,

and

are dominant at the source.

Mixed : e.g. Kaluza-Klein

interactions (Physics (just) beyond SM)

• [Nussinov and Shrok (1999), Sigl (2000)] :

• [Kachelrie

and Pl¨ umacher (2000)] :

(

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Hillas-plot

(100 EeV) (1 ZeV)

Neutron star White dwarf SNR Crab max AGN

Protons

Colliding galaxies

(candidate sites for E=100 EeV and E=1 ZeV)

GRB Virgo Galactic disk halo Clusters RG lobes

E ~ ZBL

1 au 1 pc 1 kpc 1 Mpc

• 9
• 3

3 9 15

3 6 9 12 15 18 21 x log(Magnetic field, gauss) log(size, km)

Fe (100 EeV) Protons

x

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Some Top-down predictions

Kalashev, Kuzmin and Semikoz [1999].

• 5
• 4
• 3
• 2
• 1

1 2 3 4 10 12 14 16 18 20 22 log10(j(E)E2) (eV cm-2 s-1 sr-1) log10(E/eV)

γ e p n νe νµ

,

and

. (

• 6
• 5
• 4
• 3
• 2
• 1

1 2 3 10 12 14 16 18 20 22 24 log10(j(E)E2) (eV cm-2 s-1 sr-1) log10(E/eV)

γ e p n νe νµ

,

and

. (

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Gamma Ray Burst :

Expanding fireball model : [Waxman] Engine?

Distribution : very likely cosmological (after glow). High luminosity (energy output)

Time delays: cosmological distribution

a few local events. At most 1 every 50 years within 100 Mpc. 2 UHECR events (AGASA and FE) within 26 months and with

too large for a single source

EGMF

1e+22 1e+23 1e+24 1e+25 1e+26 1e+17 1e+18 1e+19 1e+20 1e+21 J(E) x E3 (m-2 sr-1 s-1 eV2) Energy (eV)

UHECR fluxes from GRB [Scully and Stecker 2000]. 3 redshift dependence of the GRB density:

• Solid strong (

• Dashed same as star formation rate (

• Dotted no redshift dependence

The GZK cut-off is always visible.

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Extended Air Showers

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EAS phenomenology

EAS:(Extensive Air Shower) Particle cascade due to the interaction of a cosmic ray in the upper atmosphere. Hadronic primaries (nucleon/nucleus) : At each step the hadronic energy (

30%

. At ground level 90% of the energy (outside the core) is electromagnetic and the remaining 10 % are carried by muons and neutrinos.

[Fig 2.1]

In the EM cascade the low energy particles number is proportional to the total shower energy, i.e. to the primary energy.

where

level (

). The muon number however does not increase linearly with the primary

• energy. Muons come from the pion decays whose energy increase faster

(

) than their number (

). With a Monte Carlo:

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Atmospheric developments

Schematic development of an atmospheric shower. Three components are depicted (case of an hadronic primary). Hadronic cascade (leading nucleon) close to the axis (100m), EM cascade (

component extend a few km from the axis. [Fig 2.1]

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Superposition principle : a nucleus

is equivalent to A protons thus :

Then a

energy. “light” primaries The muons component is small, but more important, the depth of interaction varies from one light particle to the other (proton,photon/neutrino). The measurements of the muons and EM density ration (

) gives a lot of information on the primary type. N.B : Detector response for the same shower varies depending on the detector sensitivity to muons. Simplified development model Let

be the interaction length in Air and

which particles only decay or dE/dx. Then :

• The particle number at a given depth

grow like

(where

• The secondaries mean energy is

• As

• one gets:

et

where

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Experimental Techniques To be measured: 1 Primary direction

shower axis 2 Primary energy 3 Primary composition (mass) [1] Primary direction : A) With a surface detector : use the lateral distribution 1) Take at least 3 stations hit (3 times and 3 energies) and estimate the shower plane normal. 2) Suppose a symmetry around the shower axis and given a reference lateral profile get the shower impact point on ground. 3) Re-estimate the shower axis taking into account the shower plane curvature 4) Loop on 1, 2 and 3 (3 times is usually enough) to obtain the shower geometrical parameters.

B) With a fluorescencei detector : use the longitudinal profile. In this case

is in the plane defined by the hit photo tubes and the eye’s center. The lateral profile is not used and can be studied for ground array reconstructions. The axis position within the plane is given by the PM times. To obtain a good precision on the shower ground impact a second detector is needed (stereo mode) or a ground detector (hybrid mode).

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[2] Primary energy : A) With a surface detector

• Extrapolation/interpolation of the measured densities

• ptimal distance. (proportionality with

• Õ×ÖÙØÛÚ is compared to Monte Carlo predictions (adapted to the

specific detector, e.g. scintillators or ˇ Cerenkov)

• this estimate depends weakly on

1) The physics of the first interactions. 2) The primary type.

Resolution is about 20% (15% from 1 and 2, and 15% from statistical fluctuations) B) With a fluorescence detector

• ã❄ä➅å

• Ü

where

is the electromagnetic energy which represents 90% of the primary energy.

• Resolution of 5% for hadronic showers and 10% for photons.

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[3]Primary Mass (Composition) : A) With a surface detector 1)

). Reminder : Superposition model

• ✁

: a)

Fewer stage before reaching

b)

Less EM energy. This result is common to all interaction models (realistic ones!) 2) Rise time

B) With a fluorescence detector

• ✙➳ý✛✚✢✜

position B) In Hybrid mode : With a reference point (e.g. 1000m from the core) and a reference energy

and

For a given primary these observables are correlated (via the shower developments speed) giving distinct curves according to the primary type. There are unknowns in the primary interaction models (in-elasticity, cross section, multiplicity). Fluorescence detector allows to study the longitudinal profiles and thus to constraint those unknown parameters.

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Auger

Large detection surface. 6000

Uniform sky coverage. Two sites, Argentina being installed, one foreseen in Utah, USA.

Combined detector. Use two detection techniquess for cross calibrations, hybrid

• peration.

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Performances

Duty Cycle : 100 % Array, 10% Fluorescence

Efficiency :

% above 10

Resolutions: * Energie (array) :

(10

(10

* Energie (hybrid) :

(10

(10

* Angle (array) :

(10

(10

* Angle (hybrid) :

(10

* Statistiques :

10

* Identification:

• statistical for

• shower by shower ID for neutrino and gamma.

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Hybrid operation mode :

A n g l e Shower detector plane " F l y ' s e y e " w i t h a c t i v e p h o t o t u b e s I m p a c t p o i n t C e r e n k o v t a n k s

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Situation

Objectives in 2001

40 Cherenkov tanks

2 fluorescence cameras (2x30

Done:

40 tank deployed (position and water)

30 equiped with electronics almost all runing.

2 cam´ eras

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Milestones in 2001

01/03/2001 First telescope building completed

12/03/2001 Communication LSX/Pm, Internet communication

14/03/2001 Monitoring at CDAS

26/04/2001 40th tank deployed

04/05/2001 Second Fd building site survey

24/05/2001 First FD light

23/07/2001 First 2-fold coincidence SD

12/08/2001 First 4-fold coincidende SD (

19/08/2001 First 5-fold coincidence SD (

28/10/2001 Office building inauguration

29/10/2001 First laser hybrid trigger

09/12/2001 First hybrid event

02/01/2002 Start of second FD building

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Sun 9 Dec. 02:56:45 2001, first hybrid event Sun 9 Dec. 05:37:25 2001, second hybrid event

SD Data

First hybrid, SD tank HURON Second hybrid, SD tank HUARA

FD Events

First hybrid, FD Los Leones bay 4 Second hybrid, FD Los Leones bay 5

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A shower event from January :

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A horizontal event :

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A Golden Hybrid event :

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Photons and Neutrinos detection

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Motivations

Primary and dominate at the source (TDs, Relic). By products of pion photo-production (GZK

Undeflected by magnetic field. Unaffected by energy losses (

Good signature/probe of standard and new physics If max

Auger

by numbers :

= 50 E

MFP

300 E

km (

10

Attenuation length at 1 EeV: 300 km bremsstrahlung, 30 km with pair production, 18 km downto 6 km if high

Remember :

Auger

40x60 km Shower size

15 km

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Photons

1] Electromagnetic Effects at Ultra High Energy LPM

Suppression of E.M. processes above a characteristic

product.

Geomagnetic Conversions

The probability of conversion depends on :

Therefore

is large in the Earth field for

above

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Photons Life of a Photon

B

Preshower EM component below ELPM

No specific shower signature !

Interaction withB above EL

Young shower correlated with B direction ! γ

Slowly developing shower

e e+ e

− ~10 km

3

40 km

deep showers (large

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Photons

2] Discriminating Variables

Fluorescence profile

Ground observable (e.g. 1/R)

Best statistical significance given by Ground array

Even a small (less than 10%) fraction of the total flux can be identified

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Neutrinos

Horizontal Showers

2 atm 36 atm 1 atm

Earth

Thickness depending on zenith angle

shower front after 1 atm. after 3 atm.

Protons Neutrinos

Shower aspect at various depths

Horizontal showers (above 70

between protons and neutrino

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Neutrinos

Background rejection Studies from ground signal of

various injection altitude. altitude = 2 km ”Neutrino like” Altitude = 3 km

200 500 400 600 1000 200 500 400 600 1000 200 500 400 600 1000 200 500 400 600 1000 distance to axis(m)

time (ns)

altitude = 20 km ”Protons like” Altitude = 100 km Cosmic background

1 per day Rejection power lager than

OK

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Neutrinos

Atmospheric Showers Acceptance (water km

GZK TD & SMRP AGN BLL GRB

1 event/10 years/decade in Auger

no signal unless speculative models

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Neutrinos

Underground Interaction (

τ

ν c.c. interaction in earth

AUGER

Andes desintegration τ

Atmospheric Shower

incident

90 91 92 93 94 95

• 2
• 1

1 2 theta Log[E18]

• 6
• 3

Maximum sensitivity:

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Neutrinos

Some

showers

W E

km 4000 m

Examples of 10

(

more upgoing

than downgoing from Andes.) at

at

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Neutrinos

Multi Bangs

incident neutrino

m

decay atmospheric

α α

c.c. interaction tau decay

91 92 93 94 95 96 .05 .1 .15 .2 .25 .3 .35

Detection probability (% ) (degrees) θ quadruple bang triple bang double bang single bang total

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Neutrinos

A summary of Auger expected performances

GZK GRB TD AGN-1 AGN-2

ν ν e and sensitivity µ τ ν sensitivity 2

• 2
• 1
• 1

τ ν limit (E )

• 2

1 0.1 10 10

2

10

4 3

10

0.1 1 10

2 3

10 10

Neutrino energy (EeV) E f(E) (EeV .km .y .sr ) Hatched area represents two extreem DIS energy loss models. Flux divided by two (full mixing hypothesys

Dotted line speculative. Dahsed line probable. Solid line certain. Limit is 90% C.L after 5 years. Expected number of events after 5 years. E-loss AGN-1 TD GRB GZK AGN-2 BS+PP 135.0 11.5 2.5 8.5 14.5 BS+PP+DIS-high 50.0 4.0 1.0 3.0 5.5

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