Optimization studies of a tower based km3 detector R. Coniglione, C. Distefano and P. Sapienza Istituto Nazionale di Fisica Nucleare- Laboratori Nazionali del Sud First estimates of sensitivity to point-like source for different detector lay-out based on tower structures Preliminary results R. Coniglione, KM3NeT-WP2, Paris 10-11 December ‘08

Codes & simulation inputs Code -> ANTARES codes with Aart strategy modified by LNS Water -> ANTARES absorbtion length normalized at 60m and scattering length used in ANTARES codes PMT -> 10” PMT with 35% of QE – angular acceptance Genova fit1 (the old one) Bkg -> 60 kHz distributed on ± 1 ms window (correspond to 40kHz for a standard PMT quantum efficiency) Trigger-> (local coincidence) OR (high amplitude hit p.e.>2.5p.e.) Point source -> d = -60° a = -1.8, -2.0, -2.2 (normalized to a flux of E-2 dN/dE = 10-7 cm-2 GeV sr-1) n atmospheric -> from 102 to 108 GeV and 4p - Bartol flux m atmospheric -> NO sensitivity -> 90% confidence level (Feldman and Cousins method) R. Coniglione, KM3NeT-WP2, Paris 10-11 December ‘08

Parameters to be optimized Detector lay-out Parameter fixed Number of structures -> 91 towers Number&type of PMT -> 10920 PMTs of 10” 35%QE Number of PMT/floor -> 6 (2 at bar edges down-horizontally looking) +2 at the center of the bar down-looking at 45° Number of storeys/structure -> 20 Parameters to be optimized Distance between structures -> 130m 150m and 180m Distance between floors -> 30m and 40m Bar length -> 8m and 10 m All the detectors have the same cost R. Coniglione, KM3NeT-WP2, Paris 10-11 December ‘08

The first two comparisons Detector lay-out The first two comparisons The more “dense” geometry compared with the less “dense” geometry -> different instrumented volume Structure distance (m) Storey distance Bar length Volume (km3) 130_203008 130 30 8 Hexagon L0.65 H  0.57 V= 0.62 150_204010 150 40 10 Hexagon L0.75 H  0.76 V= 1.11 R. Coniglione, KM3NeT-WP2, Paris 10-11 December ‘08

Effective neutrino areas Distance between towers Bar length Distance between floors Number of floors No quality cuts applied 130_203008 150_204010 150_204010 Ratio 130_203008 quality cuts applied(~0.1°@30TeV) R. Coniglione, KM3NeT-WP2, Paris 10-11 December ‘08

Point source sensitivity Distance between towers Bar length Distance between floors Number of floors dN/dE E-2 source d=-60° 130_203008 150_204010 R. Coniglione, KM3NeT-WP2, Paris 10-11 December ‘08

Sensitivity dN/dE E-2.2 source d=-60° 130_203008 150_204010 ratio Distance between towers Bar length Distance between floors Number of floors dNn/dEn ((E-2.2/GeV) cm-2 s-1) 130_203008 150_204010 ratio R. Coniglione, KM3NeT-WP2, Paris 10-11 December ‘08

Sensitivity dN/dE E-1.8 source 130_203008 150_204010 ratio Distance between towers Bar length Distance between floors Number of floors dN/dE E-1.8 source dNn/dEn ((E-1.8/GeV) cm-2 s-1) 130_203008 150_204010 ratio R. Coniglione, KM3NeT-WP2, Paris 10-11 December ‘08

Different distances between towers but … same tower structures Detector lay-out Different distances between towers but … same tower structures Structure distance (m) Storey distance Bar length Volume (km3) 130_204010 130 40 10 Hexagon L0.65 H  0.76 V=0.84 150_204010 150 Hexagon L0.75 H  0.76 V= 1.11 180_204010 180 Hexagon L0.9 H  0.76 V= 1.6 R. Coniglione, KM3NeT-WP2, Paris 10-11 December ‘08

Effective neutrino areas Distance between towers Bar length Distance between floors Number of floors No quality cuts applied 130_204010 150_204010 180_204010 quality cuts applied(~0.1°@30TeV) 150(180)_204010 130_204010 Ratio R. Coniglione, KM3NeT-WP2, Paris 10-11 December ‘08

Point source sensitivity Distance between towers Bar length Distance between floors Number of floors dN/dE E-2 source d=-60 130_204010 150_204010 180_204010 dNn/dEn ((E-2/GeV) cm-2 s-1) ratio R. Coniglione, KM3NeT-WP2, Paris 10-11 December ‘08

Point source sensitivity Distance between towers Bar length Distance between floors Number of floors dN/dE E-2.2 source d=-60 130_204010 150_204010 180_204010 dNn/dEn ((E-2.2/GeV) cm-2 s-1) ratio R. Coniglione, KM3NeT-WP2, Paris 10-11 December ‘08

Point source sensitivity Distance between towers Bar length Distance between floors Number of floors dN/dE E-1.8 source 130_204010 150_204010 180_204010 dNn/dEn ((E-1.8/GeV) cm-2 s-1) ratio R. Coniglione, KM3NeT-WP2, Paris 10-11 December ‘08

Source spectrum dependence Expected n in an angular bin of 1° around a source with d=-60° in one year 150(180)_204010 130_204010 Ratio 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 = 10-9 cm-2 GeV sr-1) R. Coniglione, KM3NeT-WP2, Paris 10-11 December ‘08

Sensitivity & cuts Sensitivity to a point like source a=-2 - 1 year L nfit RBIN Sensitivity (GeV sr-1 cm-2) 130_203008 -5.7 36 0.4 3.38 10-9 130_204010 -5.4 26 2.79 10-9 150_204010 -6.1 2.88 10-9 150_203010 33 3.28 10-9 R. Coniglione, KM3NeT-WP2, Paris 10-11 December ‘08

Study of sensitivity for dark matter and diffuse neutrino flux How to continue… Effect of the number of PMTs in the bar (4 vs 6) Effect of the number of floors in the structure (20 vs 16) Effect of the atmospheric muons Study of sensitivity for dark matter and diffuse neutrino flux R. Coniglione, KM3NeT-WP2, Paris 10-11 December ‘08