The EUSO Project

E.Plagnol - HENA June 2003 - 1

The EUSO Project

An overview of the Physics of EUSO

Detection of UHECR by fluorescence +Cerenkov The EUSO detector and the collaboration Acceptance,clouds and counting rates Horizontal showers and neutrinos Status and Summary


The Physics of Euso I : The GZK effect (Greisen-Zatsepin-Kuzmin)

The physics of Euso : Beyond the GZK effect (1020-1021 eV)Astronomy with UHECR and neutrinos


The Physics of Euso II

The contradictory (?) measurements of Agasa and Hires: is the GZK effect observed or not ?In reality :-A Hires (GZK) type spectrum would confirm a "classical" scenario,-An Agasa (Super-GZK) type spectrum would not close the debate.

A GZK spectrum• Hadronic nature of UHECR (protons)• Distribution of sources in the universe and

in the "GZK" neighbourhood (<50Mpc)• The measurement of the "GZK recovery"

The physics of the GZK recovery


The Physics of Euso III

The non observation of the GZK effect could open the way to a "new physics" :• Topological defects,• Super-massive particles,• Lorentz invariance.But a classical scenario could still be possible :• Strong magnetic fields (≈ 0.1µG et Fe, G.Sigl and M.Lemoine Astro-Ph/0209192v1)

Magnetic fields would create isolated regions (< 10 Mpc) : • No way in, no way out• Isotropy• Effects of caustics -> doublets.• A large statistics is necessary


The Physics of Euso IV

AUGER will resolve the Agasa-Hires enigma

Its counting rate (60 evts/an pour E > 1020eV (if E-2.7)) will limit its ability to study UHECR beyond 1020 eV.

Whatever the AUGER results show :

EUSO will be able to study the physics beyond GZK,

EUSO will either confront New Physics (Super-GZK) or the high field

physics (isotropy, correlations) with large statistics.


The detection of UHECR by Euso

Euso will detect UHECR fluorescence and Cerenkov from space (430 km) The atmosphere will act as a huge TPC : 200 000km2 and > 2.0 1012 tons The average transparency of the atmosphere is ~ 50% The interesting part of the signal is created above ~ 5 km where aerosols are rare.


The detection method


UHECR detection by Fluorescence and Cerenkov

An UHECR creates a particle front (velocity ~ c).A fraction (<1%) of the energy will be converted in fluorescence (N2) and Cerenkov photons. The space-time correlation of the detected photons allows a measurement of the

Energy (∆E ~ 30%), Direction (∆ ~ 1°) and nature (p-Fe) of the UHECR.


The EUSO detector : Who does what ?

Optics : USALight weight fresnel lenses

≈ 2m

Photo-détectors : Japan≈ 200 000 pixels

Mechanics : France - Italy

Electronics : France - ItalyAnalog - Digital

Ground Segment : Portugal

S.A. (LIDAR) : Suisse - Italy


Activities in France : LAPP, LPSC et APC/PCC

Analog ElectronicsFront End

Mechanical and thermalstudy of the focal surface

Simulations - ESAFAtmosphere

Lidar analysisCommunication

OutreachF.Vannucci


Japon

Italie-Alenia

USA

and elsewhere…

ESA

USA


Acceptances and Counting Rates

An "End to End" simulation of showers, detection and Trigger :

Showers : Corsika -> parametrisation GIL Photons production : Fluorescence (Kakimoto et al.) et Cerenkov

Transport in the atmosphere : Rayleigh, Mie, Ozone (LOWTRAN7) optics : Throughput and aberrations

Detector : Filters et quantum efficiencies Trigger : Threshold and persistency (Nthre, Npers)


Acceptances and Counting Rates

The abssolute threshold is fixed by ∆ et detection efficiency (~1019eV).The Trigger gives the evolution as a function of energy

The asymptotic efficiency will be influenced by the cloud coverage


Cloud effects

Cloud coverage will play an important role :• Hide part of the shower development (Smax),• Increase the Cerenkov reflection.

Cloud properties are obtained form the ISCCP database : Pixels of 280x280 km2 : Long., lat., 3hours : altitude, albedo, cloud fraction.


The effect of clouds

The presence of clouds reduces the efficiency ≈ 86% ≈ 53%


The counting rates for 3 years of observation (25% duty Cycle)

25% -> 3000 events for E > 1020eV for Super GZK … 250 for GZK

The asymptotic acceptance(>1020eV) de EUSO represents 10 times AUGER

Model dependentGZK recovery


Horizontal showers and Neutrinos

• The probability of observing a quasi- horizontal hadronic shower with its maximum below de 10 km is extremely weak.

• This probability is maximum for neutrinos.


Acceptance and limiting fluxes for neutrinos

The total acceptance of EUSO for neutrinos (interacting in the atmosphere) is ≈ 0.25 x 10 km2.sr

This corresponds to the observation of a J( E )*E2 ≈ 70 eV cm-2 sr-1 fluxFor horizontal (>85°) showers, the acceptance decreases by a factor ~ 15 (+ clouds)

The acceptance for neutrino is small, but if the fluxes are sufficient…, the observation of horizontal showers, below 10km, should sign the presence of neutrinos.

The interacting with the earth crust may have an acceptance x 10-100

Acceptance with identification


Status and Summary

International The ESA phase A will end in September 2003 ESA committees will then decide if EUSO goes into phase B…C,D… launch in 2009 ? NASA is committed to participate if ESA ok ! Switzerland (Neuchatel) and Germany (Max Planck, Munich) have joined the collaboration.

Physics• The physics of EUSO is "at the frontier" of new physics and of the study of UHECR

astronomy.

• After AUGER, EUSO will be able to study, with significant statistics, the physics of UHECR beyond 1020 eV : flux, correlations, GZK recovery,….

• High energy neutrino could be "at hand" if the fluxes are sufficient.

• The low energy threshold of EUSO will be lowered by a factor 2 ( ≈ 2-3 1019 eV).

• The EUSO detector is the first detector to observe UHECR from above. It will not be the last : USA and Japan are already studying new generations (x10 ?).

The observable mass seen by EUSO represents ≈ 2.0 1012 tonnes with good transparencyit is an opening for the future…

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The EUSO Project