Ultra High Energy neutrinos detected from the orbit:

possibilities, limits and technical problems

Piero SpillantiniUniversity and INFN – Firenze (Italy)

9th Topical Seminar on Innovative Particle and Radiation Detectors – Siena, 23 May 2004

GeV|

TeV|

PeV|

EeV|

ZeV|

Direct detectionBalloons & Satellites

Indirect detection (EAS)

[arrays & florescence]

Ultra-High Energy CR[AUGER, TUS, EUSO,

KLYPVE?,OWL??]

Ultra High Energy cosmic rays

Extragalactic (gyro-radius)

Unknown acceleration mechanism:- cannot arrive from far away (CMB interaction)- no sources identified in 50-100 Mpc distance

Possible UP-DOWN generation: - e.g. topological defect decay

Attenuation length 100 Mpc

1 pc = 3.3 ly= 3.1 1016 m

a) Nucleons and nuclei?b) Electrons and photons?c) Neutrinos?

what particles? from where?

Protons: Interaction with CMB (2.7 K) photons p + +(1232) N Energy threshold: 5x1019 eV GZK (Greisen, Zatsepin, Kuzmin) cutoff Attenuation length 100 MpcNuclei: Fotodisintegration by CMB (2.7 K) photons Attenuation length 10 Mpc

Neutrons: decay Range 1 Mpc ( 1011)

a)

Electrons and photons: Pair production on CMB Compton scattering attenuation length 10 Mpc

b)

c) Neutrinos: attenuation length 40 Gpc

Comparison of the EECR Experiments

Experiment situation ‘effective’ area size (km2sr)

Fly’s Eye completed 400AGASA running 200HiRes running 500Auger/array under construction 7000 “ (Hybrid) “ “ 700

TUS in preparation* 6,000KLYPVE project 20,000EUSO approved phase A* 50,000OWL proposed 300,000

EAS

Fluorescence from space

1019 eV

The EUSO optics design consisting of two 2.5 m diameter plastic Fresnel lenses which focus light on a curved focal surface (right).

Pupil

ESA module

KLYPVE ??

OWL ???(two satellites)

TUS (on Satellite)

EUSO

Japan

ese m

odules

Russian sector

AUGER on ground

(Argentina site)

Basic EUSO Instrument Observational characteristics for the EECR/ telescope are:

Field of View ± 30° around NadirLens Diameter 2.5 mEntrance Pupil Diameter 2.0 mF/# < 1.25Operating wavelengths 300-400 nmAngular resolution (for event direction of arrival) ~ 1°Pixel diameter (and spot size) ~ 5 mmPixel size on ground ~ 0.8 0.8 km2

Number of pixel ~ 2.5 105

Track time sampling (Gate Time Unit) 833 ns (programmable)Operational Lifetime 3 years 

Top View

Earth

Multi-OWL Detector

R=6380km

30o

6680km

30o

 

Side View

3340km

1000 km

Protons coming from distances >20-50 Mpc interactwith the CMB (GKZ effect) producing pions, and finally

neutrinos (3 at each interaction).

Protons with E>1020eV interact several times beforedegrading under the GKZ cut-off

producing many e and neutrinos.

The energy of produced neutrinos is more than 1018eV

Cosmogenic neutrino component

This is the “less unprobable” neutrino componentexpected at the extreme energies.

It is not “model dependent”(i.e. it only depends from the proton source distribution)

No other neutrino sources will be considered, even if potentially much more abundant

(such “Top-Down” processes and models connected with GRB’s)

minMax

EUSO

The last more complete work is

“Ultra-High Energy Neutrino Fluxes and Their Constraints”

(Kalashek, Kuzmin, Semokov, Sigl)

[arXiv:hep-ph/0205050 v3 13 Dec 2002]

EUSO

How increase the number of neutrino events?

-Decrease the energy threshold (5 x 1019eV 1018eV)by improving the sensor efficiency (0.20 0.50)by improving the light collection (pupil 2m 6m)

(what implies reflective systems and modularity)

-Increase the target volume-by increasing the FOV (60° 140.8°)

(limited to 130º by attenuation by air and by distance) …….(light attenuation 0.5 for FOV 90°) ……………….

x 1.5 x 9

(x 30)(x 20) x 3

01000 1500 2000

30° 60° 65° 70°

HORIZON

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distance from Nadir (Km)1/2 FoV

Area of the calotta (10 Km )6 2

Are

a of

the

calo

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Are

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en b

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US

O

Atte

nuat

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fact

orattenuation due to geometry

attenuation due to atmosphere * TOTAL

attenuation

*Considered from the sea level

(EUSO)

500

45°

~minMax

EUSO

EUSO x 30

p + +(1232) N

e

cosmogenic neutrino events

0,001

0,01

0,1

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10

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0,1 1 10 100 1000 10000Energy (EeV)

Eve

nts/

year

cosmogenic neutrino 'e' flavor events (Max)

cosmogenic neutrino 'e' flavor events (min)

cosmogenic neutrino 3 flavor events (Max)

cosmogenic neutrino 3 flavor events (min)

Euso

Eusox 2.5

Eusox 2.5

Eusox 2.5

Max

min

Rejection > 10-4

golden Fluorescence only

Xmax

Select.Shape

Select.

H (km) 400 400

Total FoV (o) 60 90

Radius on ground (km) 235 413

Area on ground (103km2) 173 536

Pixel on ground (km * km) 0.8 x 0.8 1.6 x 1.6 pixel on detector (cm) 0.6 2.0

“ “ with corrector 1.2

Area/pixel (n. of pixels) 270k 238k

Pupil diameter (m) 2.0 2.0 5.0 7.5 10.0

Photo detection efficiency 20% 50% 50% 50% 50%

E threshold (EeV) 50 20 5.5 3.2 2.3

Proton events/year,

GKZ + uniform source distrib. 1200 8000 300k 900k 1800k

with Ep >100 EeV) 100 100 310 310 310

Neutrino events per year ( min) 0.6 1.5 18 30 42

Neutrino events per year ( Max) 12 18 108 120 138

EUSO like Multi-mirror

2 5 10 m

20 5 2.2 EeV

(Threshold for: h=400km and light detection efficiency 50%)

deploymentd

single mirrorfield of view

total field of view

triggerdata handlingtelemetry

sensors

Design of a mirror optics, based on the Schmidt camera principle, with FOV up to 25°

• Entrance pupil MUST be in the mirror centre of curvature• Mirror is then larger than EPD (depending on FOV)• Light shield is anyway necessary for stray light reduction• The correcting plate greatly improves performances• F/# investigated as low as 0.6• Detector diameter smaller than any other proposed solution• Weight saving solution (both for optics and detector)• Obscuration acceptable for FOV up to 25°• Vignetting almost constant for all FOV

• Low sensitivity to misalignment (except decenter) • Optical system design scalable to any dimension

A proposed 5 m EPD mirror system

correcting plate and/or filter

mirrorlight shield

focal plane

FEATURES

light shield mirrorcorrecting plate and/or filter

focal plane

INOA

Design of a mirror optics, based on the Schmidt camera principle, with FOV up to 25°

FEATURES

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Aspherical mirror + Schmidt corrector

Spherical mirror + Schmidt correctoroptimized at marginal field angles

Spherical mirror + Schmidt corrector

Spherical mirror with ± 15° FOV

Spherical mirror with ± 25° FOV

Resolution of 5 m EDP reflecting systemINOA

Possible deployment techniques• Self deployment (like most antennas)• Assembling by robots on the Shuttle• Assembling by robotic arms on the ISS

After assembling on ISS, the system could remain as external payload, as EUSO

ORSeveral systems could be assembled this way then moved to a different orbit as free flyers

(space factory concept)

In orbit mirror deploymentINOA

The proposed mirror diameter requires in orbit deployment or assemblingMaximum diameter possible with current launchers is 3mAngular tollerance are not so stringent, 0.1º (0.001º mechanically possible)

A mirror system is a consistent solution for post-EUSO The construction is possible with existing technologies The system can be scaled up, to get:

higher signal lower threshold energyhigher orbit increased observed area

Some further optimization is possible Many items still to be investigated:

tolerances thermal behaviorsupporting mechanicsdetectorscosts...

Conclusions INOA

Schematic example of the EUSO focal surface assembly showing how the individual macrocells could be mounted to approximate the curve focal surface of the optics. The shape of the focal surface shown in the figure does not correspond to the “real geometry” but it is meant to give an overall artistic vision of the assembly philosophy.

Each macrocell consists of 6x6 Photomuliplier Tube assemblies, associated light guides and electronics and is a modular unit.

Fig. 3.5 - Each PMT is a commercially

available 8x8 anode device; here it is shown with a possible light guide used to match the active area to the focal surface.

Configuration 3 with the Main Telescope (MT) and the Auxiliary Telescopes (AT).

cosmogenic neutrino events

0,001

0,01

0,1

1

10

100

0,1 1 10 100 1000 10000

Energy (EeV)

Eve

nts/

year

cosmogenicneutrino events(Max)

cosmogenicneutrino events(min)

Euso

Eusox 2.5

Eusox 2.5

Eusox 2.5

Eusox 2.5

Max

min

integral of detected events

0,001

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10

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Energy (EeV)

even

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ear

proton ev. [flux as E (̂-2.7)]

proton ev. [flux as E (̂-3)]

neutrino events (Max)

neutrino events (min)

proton ev (GZK cutoff)

Euso

Eusox 2.5

Eusox 2.5

Eusox 2.5

Eusox 2.5

Max

min

min

cosmogenic neutrino events / proton events

0,000001

0,00001

0,0001

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Energy (EeV)

even

t rat

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neutrino(Max)/proton

neutrino(min)/proton

Euso

Eusox 2.5

Eusox 2.5

Eusox 2.5

Eusox 2.5

Max

min

integral of detected events

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0,1 1 10 100 1000 10000Energy (EeV)

even

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proton ev. [flux as E (̂-2.7)]

proton ev. [flux as E (̂-3)]

neutrino events (Max)

neutrino events (min)

proton ev (GZK cutoff)

Euso

Eusox 2.5

Eusox 2.5

Eusox 2.5

Maxmin

H (km) 400 400

Total FoV (o) 60 90

Radius on ground (km) 235 413

Area on ground (103km2) 173 536

Pixel on ground (km * km) 0.8 x 0.8 1.6 x 1.6 pixel on detector (cm) 0.6 2.0

“ “ with corrector 1.2

Area/pixel (n. of pixels) 270k 238k

Pupil diameter (m) 2.0 2.0 4.0 6.0 10.0

Photo detection efficiency 20% 50% 50% 50% 50%

E threshold (EeV) 50 20 5 2.2 0.8

Proton events/year,

GKZ + uniform source distrib. 1200 8000 270k 1800k 15000k

with Ep >100 EeV) 100 100 310 310 310

Neutrino events per year ( min) 0.2 0.5 7 14 31

Neutrino events per year ( Max) 4 6 37 46 56

EUSO like Multi-mirror

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FIELD ANGLE

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SObscuration of the focal plane

FOV 40°

FOV 50°

FOV 60°

F/#

Vignetting of a lens systemStill the Leica Noctilux-M 50 F / 1.0

Transmission of wide field, low F/#, lens systems is low at edge field

signal at marginal field angles may be under threshold !