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R.Shanidze, B. Herold, Th. Seitz ECAP, University of Erlangen (for the KM3NeT consortium) 15 October 2009 Athens, Greece Study of data filtering algorithms for the KM3NeT neutrino telescope

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Neutrino, atmospheric- and optical background rates in the ANTARES telescope. (Mediterranean Sea, depth -2475 m) -event rate: ~ 0.1 mHz atmospheric -rate(*): ~ Hz Optical background ( 40 K, bioluminescence) ~ 60 kHz/PMT PMTs (Strings x Storeys x PMT) 900 ( 12 x 25 x 3) Introduction ANTARES solution(**): - ‘ All data to shore concept’ flexible software filters/triggers: - External trigger (s): GCN/GRB ( SNEWS /Supernova ) - Standard triggers - T2 / T3 triggers - 40 K trigger (*) Integrated atm- rate measured in ANTARES (preliminary): (h)= 0 x exp(-b(h-h 0 )), with 0 =1.72(+0.92-0.57) x10 -3 m -2 s -1, b=0.0019, h o =2000 m. (*) ANTARS DAQ: ANTARES Collaboration ( J.A. Aguilar et al., ) NIM A570(2007), 107 ( astro-ph/0610029 ) Are these filtering / triggering schemes applicable to KM3NeT telescope ? R. Shanidze, B. Herold, T. Seitz VLVnT-09, Athens, 15 October, 2009.

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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 t c - ( 20 ns in ANTARES NT) - PMT signal above threshold ( 5 p.e.) T2/T3 Triggers (**) 1T2 ) 2 x L1 in adjacent storeys in t 2 =100 nsec 1T3 ) 2 xL1 in adjacent/next to adjacent storeys in t 3 =100/200 nsec 2T3 ) 2 x 1T3 clusters in the whole detector in a time window t =2.25 sec (*) ANTARES-Soft-2005-005 (**) ANTARES-Soft-2008-009 “ standard triggers “ (*) based one selection of (n x L1 hits) [x ( “causality”)] ANTARES storey The software filters/triggers are based on L1 hits. R. Shanidze, B. Herold, T. Seitz VLVnT-09, Athens, 15 October, 2009.

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Rate in a single PMT large hits in ANTARES ( from M. de Jong ): a) ANTARES PMT response ( in p.e.) from GRB trigger 61-334877 b) Corresponding rates R 0 ~ 70 kHz, R 2/3 ~ 6 kHz / 200 Hz Contribution to the large (> 1 p.e.) amplitudes: - K40 - atm. PMT noise: ( auto-pulses,…) L1 Rates in ANTARES A [ p.e. ] Rate [ kHz] a b L1 rates = L1(coincidences) + L1 (large p.e. signals) L1 for coincidences ( t c =20 ns) ≈ 600 Hz, for R 0 = 70 kHz ( in addition ~20 Hz from single 40 K decays ) R. Shanidze, B. Herold, T. Seitz VLVnT-09, Athens, 15 October, 2009.

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ANTARES vs. KM3NeT PMT OM xPMT. St. (DU) DU St. PMTs (Tot.) Dist(m) St./DU Vol. (km3) ANTARES 10”3 x 12512300 90014.5/70 0.01 KM3NeT 8”3 x 220127254015240 40/180 2.6 3”1x31203006000186000 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.

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L1 rates in with multi-PMT OM Study of 40 K rates in multi-PMT OMs: ( talk of B. Herold at this conference ) Optical rates 40 K in multi-PMT: studied with GEANT-4 simulations: 31 x 3” PMT ( QE as measured in Erlangen) R 0 in multi-PMT OM ~ 190 kHz ( ~ 6 kHz/PMT ) R. Shanidze, B. Herold, T. Seitz VLVnT-09, Athens, 15 October, 2009.

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K40 coincidences Correlated rate ~ 1300 Hz : hits in the same PMT (1 PMT hit): 14 % hits in 2 or more PMTs (L1 hit): 86 % ( ~ 1120 Hz) Accidental L1 rate (10 ns window) : R 0 = 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.

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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 ) Correlated L1 rate from 40 K expected to be much smaller R(L1) rate per stores as a function of R 0. for R 0 = 50/100 kHz, R 2 (L1)=1.9 / 7.4 kH R. Shanidze, B. Herold, T. Seitz VLVnT-09, Athens, 15 October, 2009.

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Accidental L1 rates in ANTARES Accidental rates in ANTARES ( MC simulations/calculations) ANTARES-Phys-2006-008 Accidental rates for k(L1) hits in the ANTARES telescope for (t E = 2.2 msec, R max ≈ 500 kHz) Poisson statistics: Rate(k)= R max (m k /k! exp(-m) ) Maximum rate R max = 1/t E ( ≈ 500 kHz ) with mean number L1: m=R(L1)xN sto x t E Significantly large number of L1 hits in the KM3NeT time window (~ 10 sec) additional strong suppression is necessary ! KM3NeT: L1 rate: > R(L1) / ANTARES storeys: x 8.5 (20) ANTARES time: ~ x 5 ANTARES Max rate: ANTARE/5 ( ≈ 100 kHz) R. Shanidze, B. Herold, T. Seitz VLVnT-09, Athens, 15 October, 2009.

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Causality relation/filter Causality relation (filter) : t ij < ( d ij / c n ) + 20 nsec d ij - distance between hits i and j c n - 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 s many L1 pairs will pass causality filter. d is small for the storeys in the same DU. adjacent storeys = T2 next to adjacent = T3

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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.

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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. Summary and Outlook R. Shanidze, B. Herold, T. Seitz VLVnT-09, Athens, 15 October, 2009.

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ANTARES T2/T3 triggers ANTARES-PHYS-2009-012. Performance of the 1T2 Trigger on Real Data / Escoffier, S This note deals with a comparison between the 3N and the 1T2 trigger logics applied on real data, in theEscoffier, S aim to study accidental background component included in the 1T2 trigger rate. [...] ANTARES-SOFT-2008-9 Performance of the T3 Triggers on MC Data / Escoffier, S In the present note we extend the earlier studies of T3 based triggers for the atmospheric neutrino flux (Bartol model), for the atmospheric muon flux (MUPAGE) and to some galactic neutrino fluxes estimated from − ray observations. [...] Escoffier, S ANTARES-SOFT-2007-016. Proposition for an alternative trigger based on the T3 cluster trigger / Carr, J ; Escoffier, S ; Zaborov, D This document describes a new trigger logic (2T3) based on coincidences of local clusters. [...]Carr, JEscoffier, SZaborov, D

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