P. Gorham, SLAC SalSA workshop 1

Saltdome Shower Array: Simulations

Peter Gorham

University of Hawaii at Manoa

P. Gorham, SLAC SalSA workshop 2

salsaMC.c Simulation approach

2.5 km cube, 12 x 12 strings with 12 nodes each, spacing 225mCubic array, cartesian coordinates--fastest for prototyping, vector operations simplifiedUse earth density shell model, integrate along all neutrino tracksCharged & neutral current cross sections, three flavors, EM and hadronic treated separately, Alvarez et al LPM parameterization usedNo secondary brems or photonuclear interaction yetNo importance sampling--pure brute force monte-carlo integration of the volume and acceptance by counting ratio of detected interactions to total neutrino tracks startedInteractions 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

P. Gorham, SLAC SalSA workshop 3

Saltdome Shower Array (SalSA) concept

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Depth (km)

Halite (rock salt)• L(<1GHz) > 500 m w.e.• Depth to >10km• Diameter: 3-8 km• Veff ~ 100-200 km3 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 km3 water equivalent in top ~3km • ==>300-500 km3 sr possible

P. Gorham, SLAC SalSA workshop 4

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)

P. Gorham, SLAC SalSA workshop 5

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

P. Gorham, SLAC SalSA workshop 6

Basic array geometry simulated

A 2.5 km3 array with 225 m spacing, 122=144 strings, 123=1728 antenna nodes 12 antennas per node, dual polarization (6 dipoles, 6 slot-cylinders)~300 km3 sr at 1 EeVThreshold 1017 eV, few 100s antennas hit at 1 EeV, >1000 hits at 10 EeVRate: at least 10 events per year from rock-bottom minimal GZK predictions

P. Gorham, SLAC SalSA workshop 7

SalSA simulations: 1e18 eV event

Event near bottom of detector

Truncated bottom Cherenkov cone evident

Several dozen nodes hit cleanly (several hundred antennas)

P. Gorham, SLAC SalSA workshop 8

Event example, 1e19 eV shower

Event near top of detector

Truncated upper Cherenkov cone clearly evident

several hundred nodes and several thousand antennas hit

P. Gorham, SLAC SalSA workshop 9

Sensitivity to all GZK models

Includes all recent distinct estimates that are reasonably self-consistentAll-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 excludedMaximal models set parameters as high as possible consistent w/ data3 “minimal” models, all independent calculations

Engel et al 01Protheroe & Johnson 96Aramo et al 2004

P. Gorham, SLAC SalSA workshop 10

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