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P. Gorham, SLAC SalSA workshop1 Saltdome Shower Array: Simulations Peter Gorham University of Hawaii at Manoa

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P. Gorham, SLAC SalSA workshop2 salsaMC.c Simulation approach 2.5 km cube, 12 x 12 strings with 12 nodes each, spacing 225m Cubic array, cartesian coordinates--fastest for prototyping, vector operations simplified Use earth density shell model, integrate along all neutrino tracks Charged & neutral current cross sections, three flavors, EM and hadronic treated separately, Alvarez et al LPM parameterization used No secondary brems or photonuclear interaction yet No importance sampling--pure brute force monte-carlo integration of the volume and acceptance by counting ratio of detected interactions to total neutrino tracks started Interactions must hit 5/8 antennas on node, and 5 nodes (thus 25 total antennas at 2.8 sigma each) --this is a conservative requirement to ensure tracks can be reconstructed

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P. Gorham, SLAC SalSA workshop3 Saltdome Shower Array (SalSA) concept 1 2 3 4 5 6 7 Depth (km) Halite (rock salt) L ( 500 m w.e. Depth to >10km Diameter: 3-8 km V eff ~ 100-200 km 3 w.e. No known background >2 steradians possible Antenna array Qeshm Island, Hormuz strait, Iran, 7km diameter Isacksen salt dome, Elf Ringnes Island, Canada 8 by 5km Salt domes: found throughout the world typical: 50-100 km 3 water equivalent in top ~3km ==>300-500 km 3 sr possible

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P. Gorham, SLAC SalSA workshop4 Strawman array scale compared to salt dome Strawman array (2.5km cube, 12 x 12 strings, 12 nodes per string--8 shown) easily fits into Humble dome (for example)

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P. Gorham, SLAC SalSA workshop5 Choice of antenna spacing La = 250m (solid), 900, (dash-dot) 250m assumed in sims 225m spacing used gives threshold of ~50-100PeV with good detector efficiency 2.8 sigma in 5/12 antennas in “node” trigger gives negligible thermal noise

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P. Gorham, SLAC SalSA workshop6 Basic array geometry simulated A 2.5 km 3 array with 225 m spacing, 12 2 =144 strings, 12 3 =1728 antenna nodes 12 antennas per node, dual polarization (6 dipoles, 6 slot-cylinders) ~300 km 3 sr at 1 EeV Threshold 10 17 eV, few 100s antennas hit at 1 EeV, >1000 hits at 10 EeV Rate: at least 10 events per year from rock-bottom minimal GZK predictions

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P. Gorham, SLAC SalSA workshop7 SalSA simulations: 1e18 eV event Event near bottom of detector Truncated bottom Cherenkov cone evident Several dozen nodes hit cleanly (several hundred antennas)

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P. Gorham, SLAC SalSA workshop8 Event example, 1e19 eV shower Event near top of detector Truncated upper Cherenkov cone clearly evident several hundred nodes and several thousand antennas hit

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P. Gorham, SLAC SalSA workshop9 Sensitivity to all GZK models Includes all recent distinct estimates that are reasonably self-consistent All-Iron UHECR model (Ave et al 2004) included as rock- bottom (but is not really consistent with UHECR data) None of the models shown are yet excluded Maximal models set parameters as high as possible consistent w/ data 3 “minimal” models, all independent calculations Engel et al 01 Protheroe & Johnson 96 Aramo et al 2004

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P. Gorham, SLAC SalSA workshop10 Existing Neutrino Limits and Potential Future Sensitivity RICE limits for 3500 hours livetime GLUE limits ~120 hours livetime ANITA sensitivity, 3 flights: 8 to 30 GZK neutrinos IceCube & Auger estimates (based on Saltzberg 2004 Nobel symposium paper) ~3-10 events for IceCube, 0.5-3 for Auger SalSA sensitivity, 3 yrs live 40-150 GZK neutrino events from conservative models

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