Acoustic vs radio vs optical detection of neutrino-induced cascades in ice and water Relevant papers by PBP: 1. Mechanisms of attenuation of acoustic waves in Antarctic ice. NIM A325, 346 (1993). 2. Comparison of optical, radio, and acoustical detectors for UHE neutrinos. Astropart. Phys. 5, 43 (1996). 3. Implications of optical properties of ocean, lake, and ice for UHE neutrino detection. Appl. Optics 36, 1965 (1997). 4. Limits on contribution of cosmic nuclearites to galactic dark matter. Phys. Rev. D 38, 3813 (1988).

I  E02 I  E0 I I  E02

Veff per PMT for optical detection of cascade For Rmax >> a, eff, use 3D random walk of scattering photons with absorption, and integrate over time. N =108 E0(TeV) Cherenkov photons give rise to fluence at r : F(r) = 3N exp(- r/p)/16πreff photons m-2 where propagation length p  (aeff/3)1/2 Define Rmax such that F(Rmax)  APMT  = 1 photon Then Veff = 4πRmax3/3 for a single PMT

Integrate over Cherenkov spectrum, PMT efficiency, and p

Scattering in AMANDA ice

Veff for coherent radio emission RICE array S/N = 6 no LPM Ideal antenna; S/N = 1 RICE array; includes LPM

Coherent Cherenkov radio emission (predicted by G Coherent Cherenkov radio emission (predicted by G. Askaryan (1962); observed by Saltzberg et al., PRL 86, 2802 (2001)) Compton scattering knocks electrons into the cascade; positrons annihilate  ~20% excess negatively charged cylinder, which emits coherently like a giant nucleus, Z2, for wavelength >> cascade size Pradio  E02/X02 at Cherenkov angle 56º ± 2.4º Veff  E03 for r < atten

Attenuation of radio and microwaves in ice new measurement (Kansas) nimag  (/4π) a a = 0.24 km a = 2.5 km wavelength [µm] 500 MHz

Latest RICE data: the front-runner!

proposed for future: GLUE (radio from Moon) AMANDA limit (prelim.) Waxman-Bahcall limit

Acoustic pressure pulse is hydrothermal; propagates as thin disc with thickness h Veff = π Rmax2 h; pick Rmax such that S/N = 1 (h ≈ 10 m) Attenuation in ice is due to: Scattering at crystal boundaries (a = grain size) scatt = 8.6 km (0.2 cm/a)3 (20 kHz/f)4 and Absorption is due to molecular reorientation For ice, abs = 4 km at -55ºC; 1 km at -45ºC; 0.13 km at -28ºC

Solid curves are for random orientations of c-axes; dashed curves are for c-axes aligned within 20º of vertical. Numbers refer to grain size in cm. Ice at -55ºC scattering absorption

Sound absorption in seawater at 4ºC (chem. reaction rate is fn of T and P) 10 1 water + MgSO4 + B(OH)3 0.1 Absorption, dB/km 10-2 water+MgSO4 10-3 pure water 10-4 Frequency [Hz]

Emission pattern for a 10 PeV cascade is roughly disc-like at radial distance ~3 km (Butkevich et al.) 45 m R [m] 2µPa 40 µPa 2.9 km Z [m]

Amplitude of initial peak in pulse from proton burst after subtraction of 4.0ºC data curve is proportional to thermal expansivity of water

Signal in hydrophone at Lake Baikal (inverted due to electronics). S Signal in hydrophone at Lake Baikal (inverted due to electronics). S. Mikheyev: “There exists 1.4  excess of some acoustic signals in time window ±0.5 ms within 40 m of EAS core. Too small to claim anything, but too large to stop searching.”

Acoustic noise at 600 m in Lake Baikal (N. Budnev et al. ) Acoustic noise at 600 m in Lake Baikal (N. Budnev et al.). Possible signal from particle cascade. Rarefaction precedes compression, as expected for Twater < 4ºC time

Sensitivity to neutrino-induced em cascades Method. Emin to Emax (eV) Sensitivity to neutrino-induced em cascades Method Emin to Emax (eV) E2dN/dE (GeV cm-2 s-1 sr-1) AMANDA 1e13 - 1e15 ~10-7 (preliminary) RICE (radio) 3e17 - 1e21 10-6 - 3x10-7 ANITA (radio) 1e18 - 3e20 could reach 3x10-8 in 100 hr flight moon (radio) 1e19 - 1e22 ≤ 2x10-4 Baikal(acous.) ? possible signals, but … AUTEC(acous.) >1e20? TBD So far, no positive detection. Which technique will score first?

Peak frequency of thermoelastic pulse would be Dave Waters asks: Could hydrophones in ocean detect nuclearites (fragments of quark-star collisions) that might comprise Galactic dark matter? Look for source ~1 nm diameter passing through entire ocean at speed  ≈ 10-3. Problems: Peak frequency of thermoelastic pulse would be >1 GHz. How much is radiated at f < 1 kHz? 2. I did searches that supposedly ruled out nuclearite masses from 10-18 to 102 g.

would violate Galactic Fluxes above this line would violate Galactic dark matter limits Herrin and Teplitz events mica mica

Herrin and Teplitz (1996) studied >106 USGS seismic data and found 2 epilinear signals consistent with ton-mass nuclearites passing through Earth. Here is the trajectory of one of them.

Thermal noise = (4πkT f2f /vL2)1/2

a be