P ierre Colin Dmitry Naumov Patrick Nedelec

XXXXeme Rencontres de Moriond Pierre COLIN March 2005

Pierre ColinDmitry NaumovPatrick Nedelec

RECONSTRUCTION OF EXTENSIVE AIR SHOWERS

FROM SPACE

• Stand alone method using only EAS induced light.• General algorithms for any space project.

( EUSO, OWL, TUS, KLYPVE… )


Purpose: Reconstruct initial UHECR parameters

Energy (spectrum)

Direction (UHECR sources map)Particle type (proton, iron, neutrino, gamma, etc.)

Physics hopes

?


Angles (Zenithal θ and Azimuthal φ)Altitude of shower maximum: HmaxDepth of shower maximum: XmaxTotal energy released E

Shower parameters

Hmax

Xmax

UHECR :

Direction

Particle type

Energy

E


UHECR

Detection from space

Extensive air shower

Air fluorescence (isotropic)

Space telescope

Cerenkov light(directional)

Ground scattering

Cloud

EUSO simulation

Fluorescence Cerenkov echo

SIGNAL = f(t)


Data fit

fit: 2 Gaussians: Fluorescence + Cerenkov

+ constant: Background noise • Monte Carlo data

- Global fit Fluorescence Cerenkov Background

Available information: for every GTU (Time Unit ~2.5 µs) Number of detected photons: Ni


ReconstructionReconstruction

Get angles (θ,φ)

Get Hmax

Get Xmax

Get E

Monte Carlo Data

Signal analysis (Trigger conditions): 3 samples of events

Fluorescence events

Cerenkov events

Golden events

(Fluo+Cer)Reconstruction

Get angles (θ,φ)

Get Hmax

Get Xmax

Get E

TWO METHODS

Key parameterGolden eventFluorescence

event

Need Cerenkov echo

Only signal shape


Hmax reconstruction : Cerenkov method

For golden events :

We use Cerenkov echo

: Time between Cerenkov and fluorescence maximum

(Classical method)

Disadvantage: We need to know Hcer to reconstruct Hmax

: Relief, Cloud altitude (Lidar?)

max

2

cos 2 1

H c c R

c R n

AAAAAAAAAAAAAAAAAAAAAAAAAAAA

x

y

z

EUSO

α

ΔH

Cerenkov echo

Fluorescence

R

maxn

AAAAAAAAAAAAAA

ΔH = Hmax - Hcer

ΔH Hmax = ΔH + Hcer


Hmax reconstruction : Cerenkov method

Method not efficient for large angle (horizontal EAS)

Test of the method: no cloud events (Hcer = 0 )

Reconstructed Hmax vs Simulated Hmax Relative Erreur

Error<10% for <60°


(Brand new method)For Fluorescence event:

Hmax reconstruction : Shape methodF

luor

esce

nce

Yie

ld (

ph/m

)

We use only Fluo signal

NeL Y N

L= EAS track length

= # emitted photon

Ne = # charged particles in EAS

Y = Fluorescence Light Yield

Y: smooth variation with altitude

In one GTU i: Li = LGTU csteNi η·Y·Ne·LGTU = # detected ph/GTU

Ni is quite independent of the altitude: Ni

NeNmax (η·Y)max·Nemax

·LGTU

Transmission η has also a smooth variation with altitude


Total shower lenght: L = LGTU = xtot / (h)

Ntot = Ni η·Y·< Ne>·L η·Y·<Ne>· xtot / (h)

Xtot = L·(h)

L20=100 km

Hmax reconstruction : Shape method

L5 = 15 km

5 km 20 km

For horizontal showers:

00

1 avec 8

( )

h

HtotN e H km

h

Ntot varies dramatically with altitude:



Approximation:<η·Y·Ne> = (η·Y)max ·< Ne>< (h) > = (Hmax)

Generalization for all angles :

(Hmax) Hmax

maxmax

max( )e GTU

tot e tot

N N LH

N N x

Nmax/Ntot (Hmax)

Thanks to η & Y smooth variation with altitude

Varies like ln(E)



Good Method to reconstruct large angle EAS !

Reconstructed vs Simulated Hmax Relative Erreur

Test of the method:

Error<10% for >60°


Simulated Simulated

Direction reconstruction :

There is relationship between (i

x,iy) and (θ,φ) angle of EAS.

Rec

onst

ruct

Assuming infinite pixel resolution

Rec

onst

ruct

Θ

Available information: for every GTUPhoton incident angles: i

x, iy

Direction:

σ ~ 2°


Xmax reconstruction

(reconstructed Xmax – simulated Xmax) (Θ) in g/cm2

Hmax by Cerenkov echo Hmax by shape method

σ<5% for <50° σ ~ 10 %

Golden events fluorescence events


Energy reconstruction

m a x

m a x m a x4 et

N Y N L

m a xG I L m o d e l : 1 , 4 5 G e Ve

EN

E reconstructed by shape method (fluorescence)

for 1020 eV protonσ = 22%


Shape method good for UHE neutrinos!

protons

neutrinos

Neutrinos create mainly horizontal EAS without Cerenkov echo.


Conclusion

We can reconstruct any EAS : 0° to 90° or more ! This first trial is very promising.

We have developed two complementary methods to reconstruct EAS from space using UV light signal.

using Cerenkov echo• Efficient for “vertical” showers (<60°)• Need complementary information (echo altitude) using only signal shape• Efficient for “horizontal” showers (>60°)• UHE Neutrino astronomy from space is possible


BONUS SLIDE


Simulated data

Available information: for every GTU(Time Unit ~2.5 µs)

Photon incident angles: i

x, iyNumber of detected photons: Ni

x

y

z

Space telescope

αx

αy


Hmax

ix, i

y EUSO simulation


If we add pixel resolution:

EUSO event on focal plan (M36)

Error : more from detector than from method

EUSO simulation


Iron proton

SLAST simulation of Xmax(g/cm2)

Xmax reconstruction

Xmax change with RCUE type:

Xmax = f(E/A)(E/A is energy by nucleon)

Xmax for Golden events Xmax for fluorescence events

Test with 10 000 protons and 10 000 iron nuclei



m a x

m a x m a x4 et

N Y N L

m a xG I L m o d e l : 1 , 4 5 G e Ve

EN

Y : Fluorescence yield (ph/m) Kakimoto Model

η : Atmosphere transmission Lowtran Model

ε : Detector efficiency

ΔΩ : Detector solid angle


UHECR

Air scattering

Detection from space


Air fluorescence (isotropic)

Space telescope

Cloud

Cerenkov light(directional)

Ground scattering

EUSO simulation

SIGNAL = f(t)

P ierre Colin Dmitry Naumov Patrick Nedelec

Documents

Transcript of P ierre Colin Dmitry Naumov Patrick Nedelec