1. Calculation of detector characteristics for KM3NeT
storey properties
fluxes and rates
sources
18 / 11 / 2008
Christopher Lindsay Naumann - Geometry studies for KM3NeT

2. Mean photocathode surface (revision)
can calculate “mean photocathode surface” for a single storey from
properties of PMTs (size, angular acceptance)
positioning and number of OMs
βtilt
θphot α
dpmt φ θμ z
“ANT”
“MULTI”
-mean surface for light: response to plane wave
-mean surfaces for muons: integration over all light emission directions
“NEMO4”
18 / 11 / 2008
Christopher Lindsay Naumann - Geometry studies for KM3NeT

3. Mean surfaces for all storey types (without QE)
photocathode surface [cm2]
mean photocathode surface as function of light direction (plane wave)
ANT MULTI NEMO-4 NEMO-6
…and as function of muon direction (theta)
light
photocathode surface [cm2]
ANT MULTI NEMO-4 NEMO-6
gives a measure for the acceptance for up- and downgoing muon events.
have to scale with quantum + collection efficiency
muon
18 / 11 / 2008
Christopher Lindsay Naumann - Geometry studies for KM3NeT

4. Effective detection range
Photocathode surface also defines range in which a muon can be detected (absorption, dilution)
-> “effective detection range” Rdet(Eμ,θμ) for a muon of energy Eμ, dir. θμ
Pdet>50%
Rdet
-> defines an active “pixel size” around each storey at a certain p.e. threshold (e.g. 2 p.e. for “L1”)
Pdet<50%
 simple toy Monte-Carlo study:
generate “tracks” (straight lines)
count number of Rdet spheres hit
apply “trigger” criterion (e.g. 5L1)
-> “trigger efficiency”
-> effective areas (μ and )
2 p.e. range [m]
ex.: ANT storey
log10Eμ [TeV]
18 / 11 / 2008
Christopher Lindsay Naumann - Geometry studies for KM3NeT

5. 2 p.e. response of the detector to a 10 TeV track
“muon” track
“touched” (triggered) storeys (at least 2 p.e. with P>50%)
Geometry only ! No timing info !
18 / 11 / 2008
Christopher Lindsay Naumann - Geometry studies for KM3NeT

6. Comparison with existing results
Comparison with results from existing Monte-Carlo:
Tower Design 4-OM
points: existing MC
curves: this work
very good agreement with detailed Monte-Carlo (NEMO group + S. Kuch)
Tower Design 6-OM
A [m2]
data: Coniglione et al, Paris 10/08
A [m2]
CUBOID geometry, thesis S. Kuch
log10E [TeV]
also: qualitative results (influence of string or storey distance, etc) reproduced.
Simple tool but works well (at least for guidance / qualitative results)
and much faster than full physics Monte-Carlo !
18 / 11 / 2008
Christopher Lindsay Naumann - Geometry studies for KM3NeT

7. Comparison of KM3NeT architectures
string and tower architectures, normalised to 1km3 inst. volume
String Design (“SD”)
Δ lines = 95m
Δ storeys = 25m
20 storeys per string
256 strings (1km3)
Tower Design (“TD”)
Δ towers = 140m
Δ storeys = 40m
18 storeys per tower
100 towers (1km3)
ANT-type storeys:
15360 OMs
4-OM bars (TD-4): 7200 OMs
MULTI-PMT storeys:
5120 OMs ×31 PMTs
6-OM bars (TD-6): OMs ? ?
KM3NeT
18 / 11 / 2008
Christopher Lindsay Naumann - Geometry studies for KM3NeT

8. Comparison: neutrino effective areas (2π up-going)
normalised to same volume:
here SD more sensitive (higher OM density)
TD-6 better than TD-4 at low E
SD-ant SD-multi TD-4 TD-6
effective area per photocathode area:
at high energies, TD-4 best (fewest OMs), worst at low energies
SD-ant SD-multi TD-4 TD-6
no reconstruction-> “single-tower” advantage of the TD not included !
18 / 11 / 2008
Christopher Lindsay Naumann - Geometry studies for KM3NeT

9. Expected source rates - examples
use the 1km3 designs with expected fluxes for HESS sources (see talk later…)
angular resolution 0.1°, energy res. ΔlogE=0.5, 5 years
DET
S(B)>5TeV nσ
P(3 σ)
Ecut
SD-ant
3.1 (8.2)
1.1
12%
160TeV
TD-4
1.9 (4.1)
0.9
13%
126TeV
TD-6
2.4 (6.1)
1.0
10%
RXJ1713 (SNR)
probability for 3 sigma in 5 years
optimum energy cut
DET
S(B)>5TeV nσ
P(3 σ)
Ecut
SD-ant
5.1 (3.3)
2.8
47%
10 TeV
TD-4
3.4 (1.7)
2.6
48%
5 TeV
TD-6
4.2 (2.5)
2.7
45%
8 TeV
Vela-X (PWN)
18 / 11 / 2008
Christopher Lindsay Naumann - Geometry studies for KM3NeT

10. Conclusions and Outlook
Mean storey surface gives relative sensitivity to up- and downgoing tracks
Detection range calculation allows fast estimate of detector properties -> toy model Monte-Carlo
Effective areas and systematic effects in good agreement with existing work
-> extrapolate to different total volume / PK surface, quantum efficiency, absorption length, PMT size…
-> can generate approximate effective areas for event rate calculations
Thank you !
18 / 11 / 2008
Christopher Lindsay Naumann - Geometry studies for KM3NeT

11. Backup slides
18 / 11 / 2008
Christopher Lindsay Naumann - Geometry studies for KM3NeT

12. optical modules with ANTARES-type 10” PMT (curved photocathode)
Storey types studied
ANTARES-type storey:
optical modules with ANTARES-type 10” PMT (curved photocathode)
3 optical modules per storey, tilted downward by 45° (or variable)
Multi-PMT storey:
31 x 3” PMT distributed in sphere
flat angular response
single, downward looking OM per storey
NEMO-type storey:
10” PMT (as for ANTARES)
4 optical modules per storey: 2 x horizontal, 2 x vertical down
18 / 11 / 2008
Christopher Lindsay Naumann - Geometry studies for KM3NeT

13. Average photocathode area for neutrinos and muons
weighted by expected quantum efficiencies:
ANT/NEMO: 32%
MULTI-PMT: 42%
mean photocathode area per storey integrated over all muon directions (isotropic flux)
up to now, have ignored quantum efficiency !
down up
38%
75%
51%
=> NEMO surfaces per storey largest… but uses 4 OMs !
18 / 11 / 2008
Christopher Lindsay Naumann - Geometry studies for KM3NeT

14. Qualitative results, example: line distance in string architecture
detection probability
string architecture (100 string grid, 25m storey distances) with ANT storeys
String distances:
85m, 100m, 150m, 200m, (50m) 1 .8
50m .6 .4
200m .2
As expected, improvement for larger dS at higher energies; break point slightly below 10 TeV
In good agreement with results from NESSY and Sebastian Kuch -1 1 2 3
log10Eμ [TeV]
Aeffμ [km2]
200m 5
85m 1
0.5
0.1
0.05
0.01
log10Eμ [TeV] -1 1 2 3
18 / 11 / 2008
Christopher Lindsay Naumann - Geometry studies for KM3NeT