1. TA-EUSO: First simulation study and status
Kenji Shinozaki (RIKEN)
JEM-EUSO Simulation Meeting, SASKE, Kosice
2011-Nov-3

2. Outline Site and concept overview Optics design, performance and goals
Simulation
Expected signal intensity
Expected event rate
Status & plan
Summary

3. Black Rock Mesa
TA-EUSO will be allocated at Black Rock Mesa FD Station
Electron Light Source at 100m
Most nearby SD is at ~3.5 km
Central Laser Facility ~21km

5. Optics design (baseline on proposal)
Spot size ~ 6mm (RMS) corresponding off axis
2PDM (~8°x8° FOV) will be mounted on FS

6. Field of view
TA-FD station consiting of 12 telescope (ca. 10m2) triggers all event within TA-EUSO FOV
Fake trigger rate ~2—3 Hz per station
From TA Collaboration
FD-triggger can be offered upon their approval of written agreement
Further detailed data (eg. shower-detector-plane, reconstruction) is subject to their discussion

7. Goals Establishing functionality of PDM tested in field
2PDMs will be mount on FS
Cross calibration with TA-FD
Night sky
Electron Light Source (corres. ~1016eV shower)
Cetral Laser Facility
Air shower photons
Physics (using very best events)
Higher resolution measurement especially lateral distribution at shower axis
Concept plot
ELS
CLF
EAS
#. of photoelectron (TA-FD)
TA-EUSO
TA-FD
~X max
TA-SD
#. of photoelectron (TA-EUSO)
~ground
Core distance [m]
Log(#. of electrons; arbitrary)

8. Shower image (time-integrated) approaching shower (1)
Arrival direction
ZA=45, AZ=25
Landing at 10km
Landing at 3km
Landing at 3km
Landing at 1km
10^18 eV ZA=45 degrees shower
NKG-like lateral spread assumed hereafter (fluorescence only)
Optics spot-size not included herein

9. Shower image (time-integrated) approaching shower (2)
Arrival direction
ZA=45, AZ=0
Landing at 10km
Landing at 3km
Landing at 3km
Landing at 1km

10. Shower image (time-integrated) (overhead) receding shower
Landing at 10km
Landing at 3km
Landing at 3km
Landing at 1km

11. Snapshot of shower (GTU-by-GTU)

12. Signal intensity estimation
Contours for signal intensity from EAS (E0=10^18eV, Xmax=700 g/cm2 assumed) in unit of photoelectron per gate time unit (2.5 microsec)
Npe = (Ne x FY x R x A x e x cT )/4pL2
Ne: No. of EAS electron at point of interest at distance L
FY: Fluorescence yield (~4 photon/m)
R: Transmittance by Rayleigh scat.
A: Lens aperture (=1m^2)
e: Efficiency (throughput x filter transmittance x QE = 10%; assumed)
T: gate time (2.5 microsec corres. 750m)
Point of interest
Site of telescope (H~1400 m asl) L

16. Estimation of number of events (E>1018eV)
Optimised elevation of FOV is ~30° where ~ 100pe/GTU expected from 10km distant shower
TA-FD covers 3—33° elevation that allows direct cross calibration
Assuming TA spectrum (ICRC)
CLASS-II event (>100pe) ~100 events / year (R~10km)
CLASS-I event (>400pe) ~10 events / year (R<~3km) taking into account duty cycle ~ 10%

17. Best event scenario:
Shower arriving behind FD site and landing in SD area
Hybrid data (if available) provide shower geomery
TA-EUSO observes at closer distance to resolve spatial electron distribution

18. Status & plan
ICRC supports us in FY2011 for site survey that is planned in early 2012 along with a few Telescope Array Collaborators
Kakenhi (Grant-In-Aid for Scientific Research) funds proposal submitted for 72 PMTs, travel expenses for construction and operation for FY2012—2015
Construction complete with 1 PDM is expected in Summer to Autumn 2012 to start commissioning
Actual operation starts FY2013 in proposal with the fabrication of 2nd PDM in parallel
It is proposed to reallocate TA-EUSO telescope to Pierre Auger Observatory after the planned project in Utah.

19. Summary
TA-EUSO Kakenhi proposal submitted and local discussion with TA Collaborators actively started
First simulations show that the current design is sufficient for test PDMs and to cross-calibrate with TA-FD using TA calibration facilities
Key simulation work
For ESA viewpoint, the study of lateral distribution very near shower core and the method of retrieval from observed data are needed in the time of actual operation
Implementation in ESAF is also desired
Optics parameters
Interface to eg. CORISKA or other 3D shower simulation code including lateral distribution on the shower axis
Interface to TA analysis code highly desired (if approved by TA)

20. Snapshot of shower (GTU=6)
EAS near maximum

21. Snapshot of shower (GTU=9)

22. Snapshot of shower (GTU=12)

23. Snapshot of shower (GTU=13)

24. Snapshot of shower (GTU=14)

25. Snapshot of shower (GTU=15)

26. Snapshot of shower (inputted showers)
Landing at 10km
Landing at 10km
Landing at 3km
Landing at 3km
Landing at 3km
Landing at 3km
Landing at 1km
Landing at 1km
For nearby showers, more PDMs needed
Distant showers hardly distinguishable, while trigger is given by TA.