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R.Shanidze, B. Herold, Th. Seitz ECAP, University of Erlangen

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.

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R.Shanidze, B. Herold, Th. Seitz ECAP, University of Erlangen

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  1. 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

  2. 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 - 40K trigger Are these filtering / triggering schemes 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.

  3. 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.

  4. 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) ANTARES PMT response ( in p.e.) from GRB trigger 61-334877 b) Corresponding rates R0~ 70 kHz, R2/3 ~ 6 kHz / 200 Hz • Contribution to • the large (> 1 p.e.) • amplitudes: • - K40 • - atm. m • - PMT noise: • ( auto-pulses,…) a b Rate [ kHz] A [ p.e. ] A [ p.e. ] R. Shanidze, B. Herold, T. Seitz VLVnT-09, Athens, 15 October, 2009.

  5. ANTARES vs. KM3NeT Storey types in considered for KM3NeT: ANTARES type, extended storey, MultiPMT storey R. Shanidze, B. Herold, T. Seitz VLVnT-09, Athens, 15 October, 2009.

  6. 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.

  7. 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) : • 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.

  8. 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.

  9. 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 KM3NeT: L1 rate: > R(L1) / ANTARES storeys: x 8.5 (20) ANTARES time: ~ x 5 ANTARES Max rate: ANTARE/5 ( ≈ 100 kHz) Accidental rates in ANTARES ( MC simulations/calculations) ANTARES-Phys-2006-008 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.

  10. 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) 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 A

  11. 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.

  12. 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.

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