Required effective volume for various thresholds E thr (eV)V eff for 1 evt/yr (km 3 we) 10 17 6 10 18 8 10 19 33 10 20 very large
Scattering Depending on salt grain size, scatt ~ 0.15-1.4 km IceCube photons are described well by random-walk diffusion of particles But the acoustic waves are large-wavelength and bipolar -> interference? Prompt pulse width is ~10 -5 s, but the scattered signal is spread over ~10 -1 s The absorbed signal is gone. Is the scattered signal useful? For now, consider only prompt signal
Acoustic pulse simulation Adaptation of code written with Nikolai Lehtinen for the SAUND experiment Following Learned’s 1979 prescription, use a Green’s function method: integrate over the cascade energy deposition Use hadronic shower parametrization (including LPM effect) from Alvarez-Muniz & Zas, 1998 Input: X 0, E crit, R Moliere, v sound, C p, Output: pressure vs. time at arbitrary position with respect to cascade (assuming no scattering or absorption) Afterwards apply exponential attenuation factor using a given scattering length (here, 1.4 km)
Pancake detection contours Receivers within the contour for each energy would trigger. Attenuated with scatt = 1.4 km 17.51818.51919.5 20 Log(E/eV)
Array geometry considerations For reconstruction, require 3 strings hit Set string spacing ~ pancake radius, receiver spacing on each string ~ pancake thickness This minimizes number of holes drilled and cable length Most sensitive to vertical down-going events (horizontal pancakes); sensitivity slowly rolls off away from vertical
A possible array 4 strings, 1 km separation 200 receivers/string, 10 m separation Fiducial cylinder R = 1.5 km, H = 2 km, V = 14 km 3
MC: Sensitivity at 1 EeV 1700/10 4 events triggered on ≥ 3 strings, i.e. V eff = 5 km 3 we
Conclusions If pure enough, some domes may have scatt ~ 1 km and abs > 10 3 km Need to measure impurities (layered and/or random shale, clay, …?), grain size, scatt, and abs Need to measure the noise environment Inside the purest salt domes, sound may travel farther than indicated by current measurements. Coincident radio/acoustic neutrino detection would be superior to either (uncalibrated!) method alone.