Optimization of tower design R. Coniglione, C. Distefano and P. Sapienza Istituto Nazionale di Fisica Nucleare- Laboratori Nazionali del Sud First estimates of sensitivity to point-like sources for different detector lay-out based on tower structures (ONE project) R. Coniglione, Paris 23-24 February ‘09

Sensitivity calculation The sensitivity is calculated following the Feldman and Cousins method. We minimize the average flux limit: optimizing the following three parameters: L -> likelihood of reconstructed track Nfit -> number of hits before the last fit (very rough energy estimator) Rbin ->search cone radius. R. Coniglione, Paris 23-24 February ‘09

Codes & simulation inputs Code -> ANTARES codes with Aart strategy modified by LNS Water -> Labs: ANTARES normalized at 60m or NEMO Lscat : ANTARES codes Opt. bkg -> 60 kHz distributed on ± 1 ms window Trigger -> (local coincidence) OR (high amplitude hit p.e.>2.5p.e.) Point source -> d = -60° a = -1.8, -2.0, -2.2 atmospheric -> from 102 to 108 GeV and 4p - Bartol flux m atmospheric -> NO R. Coniglione, Paris 23-24 February ‘09

Parameters to be optimized Detector lay-out Geometry parameters Number of structures -> 91 towers - hexagon Number of storeys/structure -> 20 Bar length ->10m PMT -> 10” 35%QE – Genova fit1 acceptance Number of PMT/floor -> 6 (2 at bar edges down-horizontally looking) +2 at the center of the bar down-looking at 45° Parameters to be optimized Distance between floors -> 30m or 40m Distance between towers -> 130m, 150m and 180m Number of PMT/floor -> 4 or 6 PMT quantum efficiency -> 23% or 35% R. Coniglione, Paris 23-24 February ‘09

… as a function of the distance between floors Sensitivity (GeV s-1 cm-2) to a point like source - 1 year Spectral index Distance between towers Bar length Distance between floors Number of floors -1.8 -2.0 -2.2 150 _ 20 40 10* 2.8 10-10 2.85 10-9 2.5 10-8 150 _ 20 30 10* 3.3 10-10 3.3 10-9 2.8 10-8 *Absorption length ANTARES normalized at 60 m -1.8 -2.2 Same number of PMT & structures  ~15% better sensitivity for 40m floor distance R. Coniglione, Paris 23-24 February ‘09

Source spectrum Source a = -2 Source a = -2.2 Source a = -1.8 Expected n in an angular bin of 1° around a source with d=-60° in one year x 0.2 Number of expected n / year Source a = -2 Source a = -2.2 Source a = -1.8 Atmospheric n source normalized at E-2 dN/dE = 10-7 cm-2 GeV s-1 R. Coniglione, Paris 23-24 February ‘09

… as a function of the distance between floors Neutrino effective areas Distance between towers Bar length Distance between floors Number of floors quality cuts applied(~0.1°@30TeV) 150_204010(cut L=-5.8) 150_203010(cut L=-5.5) 150_204010 Ratio 150_203010 *Absorption length ANTARES normalized at 60 m Same number of PMT & structures R. Coniglione, Paris 23-24 February ‘09

… as a function of the distance between towers Bar length Distance between floors Number of floors Neutrino effective areas quality cuts applied(~0.1°@30TeV)  130_20 40 10 (cut L=-5.8)  150_20 40 10 (cut L=-5.8)  180_20 40 10 (cut L=-5.2) Ratio with respect to 130_204010 ratio Same number of PMT & structures *Absorption length NEMO log10 En (GeV) R. Coniglione, Paris 23-24 February ‘09

… as a function of the distance between towers Sensitivity (GeV s-1 cm-2) to a point like source - 1 year Spectral index Distance between towers Bar length Distance between floors Number of floors -1.8 -2.0 -2.2 130 _ 20 40 10* 3.1 10-10 3.1 10-9 2.6 10-8 150 _ 20 40 10* 2.8 10-10 2.8 10-9 2.4 10-8 180 _ 20 40 10* 2.7 10-10 2.5 10-8 *Absorption length NEMO 150m better than 130m (~10%) Very little differences in sensitivity between 150-180m R. Coniglione, Paris 23-24 February ‘09

… as a function of distance between towers considerations for high energy neutrino detection En>100 TeV High energy effective neutrino areas No quality cuts applied En>100 TeV Distance between towers Bar length Distancebetween floors Number of floors Aeff (m2) 130_204010 150_204010 180_204010 cos(qn)=[-0.5,0.5] & En>100 TeV cos(qn) Aeff (m2) 130_204010 368 150_204010 425 180_204010 483 R. Coniglione, Paris 23-24 February ‘09

… as a function of the number of PMT/floor Neutrino effective areas Distance between towers Bar length Distance between floors Number of floors quality cuts applied(~0.1°@30TeV) 150_204010  4 PMT/floor(cut L=-5.8)  6 PMT/floor(cut L=-5.8) 6 PMT/floor Ratio 4 PMT/floor ratio *Absorption length NEMO 6PMT/floor -> 10920 PMTs 4 PMT/floor -> 7280 PMTs R. Coniglione, Paris 23-24 February ‘09

… as a function of the number of PMT/floor Sensitivity (GeV s-1 cm-2) to a point like source - 1 year Spectral index Distance between towers Bar length Distance between floors Number of floors -1.8 -2. -2.2 150_204010* 4 PMT/floor 2.9 10-10 2.9 10-9 2.5 10-8 6 PMT/floor 2.8 10-10 2.8 10-9 2.35 10-8  Little differences in sensitivity 6 PMT/floor 10” 35% QE 4 PMT/floor 10” 35% QE or R. Coniglione, Paris 23-24 February ‘09

… as a function of PMT quantum efficiency Neutrino effective areas 13x13 towers 18floors* Quality cuts applied (~0.1°@30TeV)  max 45% /max 23%  max 35% /max 23% QE max 23%  QE max 35%  QE max 45% ▬ ref det with QE 33% *See R. Coniglione VLVnT08 R. Coniglione, Paris 23-24 February ‘09

… as a function of PMT quantum efficiency Sensitivity (GeV s-1 cm-2) to a point like source - 1 year Distance between towers Bar length Distance between floors Number of floors Spectral index -1.8 -2.0 -2.2 180 _ 20 40 10* 35% QE (60kHz) 2.8 10-10 3.0 10-9 2.6 10-8 180_20 40 10* 23% QE (40kHz) 3.0 10-10 3.2 10-9 3.0 10-8 Better sensitivity for 35%QE …but which is the effect of background? R. Coniglione, Paris 23-24 February ‘09

… effect of the optical background Sensitivity to point like source a=-2 - 1 year 60kHz 45 kHz 0.1 kHz 180_204010 4PMT/floor 3.0 10-9 (L=-6.2, Nfit=20, Rbin=0.5) 2.8 10-9 (L=-9.8, Nfit=22, 2.4 10-9 (L=-9.8, Nfit=20, R. Coniglione, Paris 23-24 February ‘09

… one more “exercise” Sensitivity No cuts on Nfit but on En Sensitivity to point like source a=-2 - 1 year Sensitivity (GeV cm-2 s-1) 3.0 10-9 (L=-6.2, Nfit=20, Rbin=0.5) 2.8 10-9 (L=-6.1, log10(Ev)=3.5, Geometry 180_204010 with 4PMT/floor No cuts on Nfit but on En R. Coniglione, Paris 23-24 February ‘09

cost/benefit analysis needed Summary Same detector components Floor distance 30m-40m->better sensitivity (~15%)for 40m Distance between towers 130m-150m-180m -> slightly better sensitivity at 150m and higher effective areas at high energy Different number of PMTs or QE PMTs 6/4 PMT/floor ->higher effective areas at low energy but (< 10%) better sensitivity QE 23% or 35% -> higher effective areas at low energy for 35% QE – sligthly better sensitivity (< 10%) filtering procedure for background hits rejection to be improved cost/benefit analysis needed R. Coniglione, Paris 23-24 February ‘09

Summary THE END R. Coniglione, Paris 23-24 February ‘09