Transcript Rezo Shanidze, Sebastian Kuch

Study of data filtering algorithms
for the KM3NeT neutrino telescope
R.Shanidze, B. Herold, Th. Seitz
ECAP, University of Erlangen
(for the KM3NeT consortium)
15 October 2009
Athens, Greece
Introduction
Neutrino, atmospheric-m and optical background rates
in the ANTARES telescope. (Mediterranean Sea, depth -2475 m)
• nm-event rate:
~ 0.1 mHz
• atmospheric m-rate(*):
~ Hz
• Optical background (40K, bioluminescence)
~ 60 kHz/PMT
PMTs (Strings x Storeys x PMT)
900 ( 12 x 25 x 3)
ANTARES solution(**):
- ‘ All data to shore concept’ g flexible software filters/triggers:
- External trigger (s): GCN/GRB ( SNEWS /Supernova )
- Standard triggers
- T2 / T3 triggers
Are these filtering / triggering schemes
40
- K trigger
applicable to KM3NeT telescope ?
(*) Integrated atm-m rate measured in ANTARES (preliminary):
F(h)=F0 x exp(-b(h-h0)), with F0 =1.72(+0.92-0.57) x10-3 m-2s-1, b=0.0019, ho=2000 m.
(*) ANTARS DAQ:
ANTARES Collaboration ( J.A. Aguilar et al., ) NIM A570(2007), 107 ( astro-ph/0610029 )
R. Shanidze, B. Herold, T. Seitz
VLVnT-09, Athens, 15 October, 2009.
Triggering “a la ANTARES”
Hit hierarchy:
a) L0.
PMT signal above defined threshold (0.3 p.e.)
b) L1
- at least 2 x L0 in the same story within Dtc
- ( 20 ns in ANTARES NT)
- PMT signal above threshold ( 5 p.e.)
The software filters/triggers are based on L1 hits.
“ standard triggers “ (*)
based one selection of (n x L1 hits) [x ( “causality”)]
ANTARES storey
T2/T3 Triggers (**)
•
1T2 ) 2 x L1 in adjacent storeys in t2=100 nsec
•
1T3 ) 2 xL1 in adjacent/next to adjacent storeys in t3=100/200 nsec
•
2T3 ) 2 x 1T3 clusters in the whole detector in a time window t =2.25 msec
(*) ANTARES-Soft-2005-005
(**) ANTARES-Soft-2008-009
R. Shanidze, B. Herold, T. Seitz
VLVnT-09, Athens, 15 October, 2009.
L1 Rates in ANTARES
L1 rates = L1(coincidences) + L1 (large p.e. signals)
L1 for coincidences (Dtc=20 ns) ≈ 600 Hz, for R0 = 70 kHz
( in addition ~20 Hz from single 40K decays )
Rate in a single PMT large hits in ANTARES ( from M. de Jong ):
a
A [ p.e. ]
R. Shanidze, B. Herold, T. Seitz
Rate [ kHz]
a) ANTARES PMT response ( in p.e.) from GRB trigger 61-334877
b) Corresponding rates R0~ 70 kHz, R2/3 ~ 6 kHz / 200 Hz
b
A [ p.e. ]
VLVnT-09, Athens, 15 October, 2009.
Contribution to
the large (> 1 p.e.)
amplitudes:
- K40
- atm. m
- PMT noise:
( auto-pulses,…)
ANTARES vs. KM3NeT
PMT
ANTARES
KM3NeT
OM
St.
DU
St.
PMTs
Dist(m)
Vol.
xPMT.
(DU)
(Tot.)
St./DU
(km3)
10”
3x1
25
12
300
900
14.5/70
0.01
8”
3x2
20
127
2540
15240
40/180
2.6
3”
1x31
20
300
6000
186000
30/130
3.1
Storey types in considered for KM3NeT:
ANTARES type, extended storey, MultiPMT storey
R. Shanidze, B. Herold, T. Seitz
VLVnT-09, Athens, 15 October, 2009.
L1 rates in with multi-PMT OM
Study of 40K rates in multi-PMT OMs:
( talk of B. Herold at this conference )
Optical rates 40K in multi-PMT:
studied with GEANT-4 simulations:
31 x 3” PMT ( QE as measured in Erlangen)
R0 in multi-PMT OM
~ 190 kHz ( ~ 6 kHz/PMT )
R. Shanidze, B. Herold, T. Seitz
VLVnT-09, Athens, 15 October, 2009.
K40 coincidences
Correlated rate ~ 1300 Hz :
 hits in the same PMT (1 PMT hit):
 hits in 2 or more PMTs (L1 hit):
14 %
86 % ( ~ 1120 Hz)
Accidental L1 rate
(10 ns window) :
• R0 = 6 kHz,
R(L1)=334 Hz
(calculations)
• K40 simulations:
~ 300 Hz
Calculations:
with
R. Shanidze, B. Herold, T. Seitz
VLVnT-09, Athens, 15 October, 2009.
L1 rates for the flexible tower storey
Calculations for L1:
- at lest 2 L0 hits from 6 PMTs on a storey in T=50 nsec window. (?)
( time window corresponds to 6m storey )
R(L1) rate per stores
as a function of R0.
for R0= 50/100
kHz,
R2(L1)=1.9 / 7.4 kH
Correlated L1 rate from
40K expected to be much
smaller
R. Shanidze, B. Herold, T. Seitz
VLVnT-09, Athens, 15 October, 2009.
Accidental L1 rates in ANTARES
Accidental rates for k(L1) hits
in the ANTARES telescope for
(tE = 2.2 msec, Rmax ≈ 500 kHz)
g Poisson statistics:
Rate(k)= Rmax(mk/k! •exp(-m) )
Maximum rate
Rmax = 1/tE ( ≈ 500 kHz )
with mean number L1:
m=R(L1)xNsto x tE
Accidental rates in ANTARES
( MC simulations/calculations)
ANTARES-Phys-2006-008
KM3NeT:
L1 rate: > R(L1) / ANTARES
storeys: x 8.5 (20) ANTARES
time:
~ x5
ANTARES
Max rate: ANTARE/5
( ≈ 100 kHz)
Significantly large number of L1 hits in the KM3NeT time
window (~ 10 msec) g additional strong suppression is necessary !
R. Shanidze, B. Herold, T. Seitz
VLVnT-09, Athens, 15 October, 2009.
Causality relation/filter
Causality relation (filter) :
Dt ij < ( dij / cn ) + 20 nsec
dij - distance between hits i and j
cn - speed of light in water
(n=1.35)
A
distance between OMs in the
multi-PMT/string configuration
(130m). Mean distance
between OM pairs:
d ≈ 1200 m
corresponds to:
t ≈ 5.4 ms
many L1 pairs will pass
causality filter.
d is small for the storeys
in the same DU.
adjacent storeys = T2
next to adjacent = T3
T2/T3 rates in ANTARES
T2(T3) is a pair or L1 with additional constraints:
- time interval 100(200) ns in ANTARES
- adjacent (next to adjacent) storeys
Advantage:

T2 / T3 rate
smaller the L1
• Number of
T2 pairs ≈ N storeys
Calculations for KM3NeT are coming soon
( will be included in VLVnT-09 proceedings )
R. Shanidze, B. Herold, T. Seitz
VLVnT-09, Athens, 15 October, 2009.
Summary and Outlook
•
Accidental L1 rate per storey is the main input in the filtering
algorithms and should be studied for all KM3NeT configurations.
• Standard causality filter, due to large distances between DUs are much
less effective for KM3NeT telescope.
• Filtering/triggering algorithms based on T2/T3 clusters are promising
approach for the high purity selection of neutruno and muon events.
•
Development of new, dedicated software filtering/triggering algorithms
seems to be necessary for the KM3NeT telescope.
R. Shanidze, B. Herold, T. Seitz
VLVnT-09, Athens, 15 October, 2009.