LUNASKA UHE Neutrino Flux Limits - From Parkes Onwards The Lunar Cherenkov Technique – From Parkes Onwards R. Protheroe R. Crocker C. James D. Jones R. McFadden J. Alvarez-Muniz R. Ekers P. Roberts C. Phillips S. Tingay R. Bhat T. Stanev LUNASKA “Lunar UHE Neutrino Astrophysics with the Square Kilometre Array” The LUNAKSA Collaboration

LUNASKA The Lunar Cherenkov Technique: From Parkes Onwards 2 Outline Part 1: Simulation results from Parkes –The Parkes Lunar Cherenkov experiment –Simulation results on directional sensitivity –Directional dependence of current limits Part 2: UHE Particle Astronomy –Resolution of arrival direction –Spectral information –The Square Kilometre Array (SKA)

LUNASKA The Lunar Cherenkov Technique: From Parkes Onwards 3 The Parkes Lunar Cherenkov Experiment Overview –Hankins et al 1996 –1 st use of the Lunar Cherenkov technique –Used Parkes 64m antenna –No aperture/limits calculated Observations –Jan 18th-19 th 1995 –10.5 hours on-line –Only 2 hours at the limb Signal Detection –1.425 GHz RCP & LCP data –500 MHz bandwidth recorded –Trigger from 2x100 MHz sub-bands –RFI discrimination: ionospheric delay

LUNASKA The Lunar Cherenkov Technique: From Parkes Onwards 4 Parkes – Aperture and Limit Parkes UHE Neutrino Isotropic Flux Limit: –Instantaneous aperture comparable to GLUE, Kalyazin –Short observation time = weak constraints –Since surpassed by other experiments –What can we learn? C. W. James et al., 2007 APERTURELIMIT

LUNASKA The Lunar Cherenkov Technique: From Parkes Onwards 5 Directional Aperture Definition Effective isotropic aperture (km^2-sr) usually quoted But is calculated from: where is the directional aperture to neutrinos at coordinates (relative to the Moon) Origin of Directional Dependence Lunar shadowing Cherenkov geometry Refraction and surface roughness Beam pointing Beam centre

LUNASKA The Lunar Cherenkov Technique: From Parkes Onwards 6 Parkes Directional Aperture Directional Aperture for –Centred 15 0 from the Moon –FWHM ~ in, 30 0 in –Significant lunar ‘shadow’ Peak Sensitivity to a Point Source Define Directionality: Peak sensitivity (km 2 ) Effective aperture (km 2 sr) Total solid angle (sr) –For Parkes Limb-Pointing, d=28 –Sensitivity will be highly directional –Observation Times Matter!

LUNASKA The Lunar Cherenkov Technique: From Parkes Onwards 7 Parkes Directional Sensitivity Sensitivity to 10 ZeV neutrinos of the Parkes experiment Directional sensitivity in celestial coordinates:

LUNASKA The Lunar Cherenkov Technique: From Parkes Onwards 8 GLUE GLUE Sensitivity Goldstone Lunar UHE Neutrino Experiment 120 hr over 3 yrs Approx. times from Williams (2004) Approximate combined sensitivity to 10 ZeV neutrinos of the Parkes and GLUE experiments (Dates from Kalyazin unavailable) APPROXIMATE!

LUNASKA The Lunar Cherenkov Technique: From Parkes Onwards 9 ANITA-lite ANITA-Lite Sensitivity Concentrated in (Barwick et al 2004) Uniform coverage assumed in this region Missing: ANITA Kalyazin Auger Hi-Res … Other et al Approximate combined sensitivity to 10 ZeV neutrinos of the Parkes, GLUE, and ANITA-Lite APPROXIMATE! (note log scale)

LUNASKA The Lunar Cherenkov Technique: From Parkes Onwards 10 Part 1 Summary: From Parkes Parkes Limit Aperture comparable to other lunar Cherenkov experiments Isotropic limits now obsolete Potentially strong point-source limit Directional Sensitivity Apertures are highly directional Current limits are anisotropic Scope for targeted observations of suspected sources Complimentary experimental sensitivities

LUNASKA The Lunar Cherenkov Technique: From Parkes Onwards 11 Part 2: Onwards Currently: –UHE neutrinos have not be discovered –Lunar Cherenkov pulses unobserved –Current aim: remedy this! Ultimate Aim: Perform UHE particle astronomy –Energy Resolution –Arrival Direction –Particle Type (CR or Neutrino) How can this be achieved?

LUNASKA The Lunar Cherenkov Technique: From Parkes Onwards 12 Resolution of Arrival Direction Worst Case Reconstruction –Assumes no signal spectral information –Use inverse likelihood of detection –This is the directional sensitivity CONCLUDE:Use information on signal origin to reconstruct arrival direction. Moon Unresolved Sensitivity annular Moon ‘shadow’ < 5 0 Very broad sensitivity! Moon Resolved Restricts signal origin Sensitivity narrows

LUNASKA The Lunar Cherenkov Technique: From Parkes Onwards 13 Apparent Signal Origin –The apparent signal exit position from lunar surface –Will be resolved using radio-arrays –Can be used to constrain the arrival direction –Simulated using a -fn antenna beam Results: –Good resolution in (~10 0 ) –Poor res in (~70 0 !) –Offset depends on pointing position: Offset angle Apparent signal exit radius Lunar radius Apparent Signal Origin Inverse Likelihood We require a further parameter to constrain

LUNASKA The Lunar Cherenkov Technique: From Parkes Onwards 14 Using Signal Polarisation Detecting Polarisation –Cherenkov signals are linear polarised –Polarisation aligns with shower track –Some distortion by refraction & roughness –Will restrict arrival direction, esp. in

LUNASKA The Lunar Cherenkov Technique: From Parkes Onwards 15 Signal Polarisation: Simulation Results Results for and -Beam –Combined resolution ~10 0 x10 0 –Weak energy dependence –Similar for cosmic rays At lower frequencies: –Roughness decreases (better resolution) –Cherenkov cone is wider (worse resolution) –Combined effect: worse resolution. –The effective aperture to high energy particles is greater. How can we get around this?

LUNASKA The Lunar Cherenkov Technique: From Parkes Onwards 16 Using Spectral Information We need to measure, the angle to the shower axis This can be derived from the observed signal spectrum Dependence: Spectral Information: Angle from Cherenkov cone Angular Dependence The Cherenkov cone has finite width, Hence uncertainty in the arrival direction. is larger at low frequencies: How to eliminate this uncertainty?

LUNASKA The Lunar Cherenkov Technique: From Parkes Onwards 17 Determining Particle Type Spectral Information Cosmic rays interact at the surface Neutrinos penetrate deep into the regolith Regolith absorbs radio-waves Signal strength (V/m/MHz) Frequency (GHz) Shower depth (absorption lengths at 1 GHz) Cosmic Rays vs Neutrinos Both should produce detectable pulses Both interact with similar geometries How can they be distinguished?

LUNASKA The Lunar Cherenkov Technique: From Parkes Onwards 18 The Square Kilometre Array Minimal Specifications: 1 km 2 collecting area at 1.4 GHz Frequency range 100 MHz to 25 GHz Wide Bandwidths (up to 4 GHz) Resolving power < 0.1 arcsec at 1.4 GHz Proposed locations: South Africa or Australia Timeline 2009Final technology decision 2010 Construction of prototypes begin 2014Construction of full array begins 2020First observations with full SKA ‘The International Radio Telescope for the 21 st Century’

LUNASKA The Lunar Cherenkov Technique: From Parkes Onwards 19 Summary Part 2 UHE Particle Astronomy with the Lunar Cherenkov Technique Arrival direction can be reconstructed on an individual event basis using –Apparent signal origin (can be done for marginal events; requires long baselines) –Polarisation (accuracy depends on signal/noise) –Measurement of the spectrum (requires broad bandwidths) Cosmic rays and neutrinos can be distinguished with a broad-bandwidth instrument Neutrino energies will be hard/impossible to determine for most events (unknown inelasticity). Simultaneous observations over a wide frequency range are critical. The Square Kilometre Array Potentially an extremely powerful instrument for UHE particle astronomy Technology/design decisions being made now We require the radio-astronomy community to be convinced by this technique (pre-2009 observation would help!). We’re not that kind of lunatic!