1. Sebastian Kuch University Erlangen-Nürnberg
Update on simulation for KM3NeT using ANTARES software
Sebastian Kuch
University Erlangen-Nürnberg
24-25 October
KM3NeT WP2 Meeting, CPPM

2. event generation genhen detector simulation km3
Simulation with ANTARES software
event generation genhen
109 muon-neutrinos, E-1.4-spectrum from 10 GeV to 107 GeV, up- and downgoing (4p)
detector simulation km3
No electronics simulation, hits with TTS and amplitude smearing, 40K-rate of 91 Hz/cm2 of photocathode area (corresponds to 40kHz for 10” PMT)
analysis
Calculate neutrino effective area for events with
more than 10 signal hits (=from muon track), after causality filter, no reconstruction
24-25 October
KM3NeT WP2 Meeting, CPPM

3. Multi-PMT cylinder storey
The cylinder storey alternative Photodetection layout
Use several small PMs instead of a few large ones !
For example 36 3“ PMs in 3 pressure resistant glass cylinders
Same photocathode area as 3 10“ PMs (ANTARES storey)
Advantages:
Higher Quantum efficiency (~35%)
Lower Transit Time Spread (0.5ns)
24-25 October
KM3NeT WP2 Meeting, CPPM

4. Comparison with ANTARES storeys
Place ANTARES storeys and cylinder storeys in cuboid grid with
distances of 62.5m (4840 storeys, 484 strings, height~600m, 1km3)
Run detector simulation and compare effective areas
24-25 October
KM3NeT WP2 Meeting, CPPM

5. Results for cylindrical storey
Effective area
(events with >10 signal hits selected, no reconstruction)
Gain in efficiency, especially at low energies
BUT WHY?
24-25 October
KM3NeT WP2 Meeting, CPPM

6. Simulation of cylinder storey with same QE as ANTARES
Effective area
(events with >10 signal hits selected, no reconstruction)
Gain in efficiency mostly because of higher Quantum Efficiency
24-25 October
KM3NeT WP2 Meeting, CPPM

7. Multi-PMT sphere storey
cylinder storey probably obsolete
New Idea from NIKHEF sphere storey
Place 42 3” PMTs in 17” Benthos sphere
1 sphere = 1 storey
24-25 October
KM3NeT WP2 Meeting, CPPM

8. Results for sphere storey
Effective area
(events with >10 signal hits selected, no reconstruction)
Effective area comparable to cylinder storey, better at low energies
24-25 October
KM3NeT WP2 Meeting, CPPM

9. ANTARES storey with 20“ PMs
Other direction Use larger PMs
Example: Hamamatsu 20” PM (R7250)
-Maximum Quantum efficiency ~20%
-TTS ~3.5 ns
Cuboid detector with
ANTARES storeys equipped with 20” PMs
Photocathode area times 4
Detector with same overall photocathode area has factor 4 less modules and therefore increased distances and/or no local coincidences. These effects mix and are difficult to discriminate
Gain of this concept depends on cost of 20” tube
24-25 October
KM3NeT WP2 Meeting, CPPM

10. Results for storeys with 20” PMs
Effective area
(events with >10 signal hits selected, no reconstruction)
If price of 20” tube is 4 times price of 10” there is nothing to be gained
Better below ~100 TeV
24-25 October
KM3NeT WP2 Meeting, CPPM

11. Ring Geometry
At E~1TeV muon range in water starts to exceed detector dimension (~1km)
Most muons enter from the outside
Optimize cross-section area instead of instrumented volume
Ring Geometry
Example:
-312 strings, 4992 (cylinder) storeys
-16 storeys/string (dstorey=42m), 1km3
24-25 October
KM3NeT WP2 Meeting, CPPM

12. Results for ring geometry
Effective area
(events with >10 signal hits selected, no reconstruction)
Less strings means less structures, less infrastructure and therefore less cost
Less strings, similar performance
24-25 October
KM3NeT WP2 Meeting, CPPM

13. Clusters of densely instrumented strings
Cluster Geometry
Spacing of storeys
energy threshold
Clusters of densely instrumented strings
Low energy events in clusters
High energy events hit several clusters
Example:
-8 clusters of 12 strings, 1km3
-52 storeys per string (dstorey=12m)
-4992 (cylinder) storeys
24-25 October
KM3NeT WP2 Meeting, CPPM

14. Results for cluster geometry
Effective area
(events with >10 signal hits selected, no reconstruction)
Less strings means less structures, less infrastructure and therefore less cost
Superior at lowest energies, worse above ~100 GeV
24-25 October
KM3NeT WP2 Meeting, CPPM

15. Influence of string/storey distance
storey spacing influences performance at different energies
Cluster detector
Systematic analysis of these effects
Variation of string and/or storey distances for cuboid
(with cylinder storeys)
Keep number of storeys equal (~cost neutral)
Volume will change obviously
(All concepts shown so far have 1km3 of instrumented volume)
24-25 October
KM3NeT WP2 Meeting, CPPM

16. Variation of storey distance
Effective area ratio
(relative to standard cuboid with cylinder storeys)
24-25 October
KM3NeT WP2 Meeting, CPPM

17. Variation of string distance
Effective area ratio
(relative to standard cuboid with cylinder storeys)
Performance above a few TeV can be increased by increasing the instrumented volume,
BUT at the cost of low energy efficiency
24-25 October
KM3NeT WP2 Meeting, CPPM

18. Summary
Multi-PMT modules with small PMs are a promising alternative, especially at lower energies, mostly due to higher QE
Ring geometry shows similar performance as homogeneous cuboid geometry, but requires less strings
Cluster geometry allows to increase efficiency below 100 GeV, but at the cost of a ~40% reduction above
Increase of string/storey distances increases performance above ~1 TeV (larger volume), but decreases performance below
24-25 October
KM3NeT WP2 Meeting, CPPM

19. Plans for the (near) future
Other concepts studied:
Detectors with more than 1 km3 of instrumented volume
Variations of ring- and cluster-geometry
Plans for the (near) future:
Get detailed specs for used instruments
Optimized selection of events (selection criteria)
ToDos:
Sensitivities to benchmark fluxes
Dedicated KM3NeT reconstruction algorithm
Energy reconstruction (Energy resolution!) ….
24-25 October
KM3NeT WP2 Meeting, CPPM