Recent History of Radio Searches for Ultra High Energy Neutrinos David Saltzberg University of California, Los Angeles SalSA meeting February 2, 2005 A tale of salt mines, particle accelerators and balloon flights---from the South Pole to the Moon, from the deep ocean to low-Earth orbit.

Summary UHE Models l Possible point of confusion:  Models give brightness  But, experiments measure intensity from P. Gorham

Quantifying Detection l [A  ]  t vs. energy (& background) for each neutrino flavor describes experiment ä  For example: [A  ] for a flat,black paddle=A£2   [V  ]=[A  ]£ L int accounting for neutrino cross section vs. energy ä(Discovery potential also depends on background) l Need many km 3 of material to detect > eV l Here I’ll give (my estimates of): äE thresh (approx.)  typical [V  ] and  t  Compare at the end with [A  ]  t for detection

km 3 and Beyond? Two Good Ideas by Gurgen Askaryan (I) (1962) UHE event will induce an e/  shower: In electron-gamma shower in matter, there will be ~20% more electrons than positrons. Compton scattering:  + e - (at rest)   + e - Positron annihilation: e + + e - (at rest)   +  lead e-e-

Two Good Ideas by Gurgen Askaryan (I) Excess charge moving faster than c/n in matter emit Cherenkov Radiation In dense material R Moliere ~ 10cm. <<R Moliere (optical case), random phases  P  N >>R Moliere (microwaves), coherent  P  N 2 Confirmed with Modern simulations + Maxwell’s equations: (Halzen, Zas, Stanev, Alvarez-Muniz, Seckel, Razzaque, Buniy, Ralston, McKay …) Each charge emits field |E|  e ikr and Power  |E tot | 2

The SLAC experiments 2000 & tons SiO 2 l Amplitude expected l 100% linearly polarized l Cherenkov angle SLAC FFTB

RICE Experiment l “Radio in Ice Experiment” l Dipoles ( MHz) on AMANDA South Pole l 200 x 200 x 200 meter array l E >~10 17 eV [V  ]» 10 km 3 -sr l Expected events in 5 years: ä~9 TD events ä2-7 GZK events ä~3 GRB/AGN events Candidate event I. Kravchenko, et al., ICRC-03, astro-ph/

South Pole Ice properties: RF propagation l Tried to measure attenuation from far hole in season l Refraction Made it difficult to transmit from a far hole to the RICE array l Radioglaciology proposal pending with NSF

South Pole Ice properties: RF attenuation l Deeper ice is, on average, even colder – So will have an even longer attenuation length

First results (1996) 12 hrs using single Parkes 64m dish in Australia. Limitted by R.F.I. T. Hankins et al., MNRAS 283, 1027 (1996) Using the Moon as a 200,000 km 3 target l Zheleznyk and Dagkesamanskii (1988) eV produces ~1000 Jy at 2GHz (1Jy = W/m 2 /Hz) l brightest quasars ~25 Jy at this frequency band l Moon as blackbody: ~200 Jy  no need to go to the moon  use radiotelescopes

Goldstone Lunar UHE Neutrino Search (GLUE) P. Gorham et al., PRL 93, (2004) Two antennas at JPL’s Goldstone, Calif. Tracking Station l limits on >10 20 eV ’s l regolith atten. len. ~20 m l ~123 hours livetime l [V  ] eff ~600 km 3 -sr l datataking complete Earlier experiment: 12 hrs using single Parkes 64m dish in Australia: T. Hankins et al., MNRAS 283, 1027 (1996)

A more detailed view of GLUE (since common to most radio detection)

FORTE satellite (Fast On-orbit Recording of Transient Events) l Main mission: synaptic lightning observation l Viewed Greenland ice with appropriate trigger ( ) ä1.9 MILLION km 3  38 days £ 6% l Can self-trigger on transient events in 22MHz band in VHF band (from 30 to 300 MHz) l Event characterization äpolarization äionospheric group delay and birefringence ätiming Log-periodic antennas N. Lehtinen et al., PRD 69, (2004)

Example Forte Event E thresh » eV [V  ] ~ 100,000 km 3 sr, but threshold extremely high.

>1 million cubic km! 60 days E >10 17 eV [V  ]~20,000 km 3 -sr ANITA 9-30 GZK events ~80 TD events P. Gorham, et al., NASA concept study report (2004)

ANITA Schedule l December: Anita-lite (completed) l Ongoing: payload construction l June 2005 Test run at Ft. Sumner, NM l June 2006 Final test at Palestine, TX l Dec 2006 First flight l Future seasons: 2 more flights

Anita-LITE l 18 day flight, Dec Jan. 04 l Piggyback on TIGER l Experience assembling the payload on the ice l Calibration studies included observation of ground pulse and Sun l Analysis of Anita-lite data äBackgrounds äTiming resolution äAngular resolution

Anita Lite Signal and Noise l Some on-board impulsive noise, will be removed for dedicated ANITA flight l No evidence for off-payload impulsive noise beyond McMurdo Station horizon

Anita Lite Resolutions Ground-to-payload pulse at ~250km from Williams’ Field Anita goal 300ps per antenna Anita-lite already 120 psec l Anita resolution on RF direction   » 0.5 ±   » 2 ± 375 MHz “tone burst”

SALSA: A possible salt detector l ~25km 3 in upper 3km of dome (75 km 3 water-equiv.)  >2£ denser than ice äeasier to deploy than S.Pole l Many competing effects make it not obvious which frequency is optimal: äattenuation, antenna effective height, Ch. emission formula, Ch. cone width, bandwidth, thermal noise äToy Monte Carlo used to study these events l As long as atten. length is smaller than dome, then optimum at longer wavelengths l Calorimetric; large V,  ; Cherenkov polarization usable for tracking l US likely TX or LA. Dutch investigating sites as well diapir action pushes out water

Salt Dome Detector Noise and attenuation length measurements l Estimated events/year  100 R X ==> 50/yr above eV from AGN ä1000 R X ==> 50/yr above eV from GZK or 5-10 GRB l RF environment protected by overburden. Noise level consistent with 300K. Hockley Dome measurements l Attenuation >250m (>500 m w.e.) (even at 750 MHz) l No evidence of birefringence or scattering P. Gorham et al., NIMA 490, 476 (2002)

Developing Ideas l Drone flights over deepest Antarctic Ice äuse the best ice: 4km deep äcloser  lower threshold äinstrument can be maintained l Europa orbiter

Comparison of Detector Discovery Potential: [A  ] £  t live