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PERSPECTIVES OF THE RADIO ASTRONOMICAL DETECTION OF EXTREMELY HIGH ENERGY NEUTRINOS BOMBARDING THE MOONR.D. Dagkesamanskii1) , I.M. Zheleznykh2) and V.A. Matveev 3)1) – Pushchino Radio Astronomy Observatory of the Lebedev Physical Institute, Russian Academy of Sciences 2) – Institute for Nuclear Research, Russian Academy of SciencesVLVνT-09
INTRODUCTION-1 • UHE cosmic rays could be used not only as a tool for particle physics, but also as a diagnostic of some astrophysical processes and as a probe of cosmological models. • However, the problem of detecting of UHE cosmic rays belongs to the very difficult observational tasks. • The difficulties are increased when the detection of the UHE neutrinos is considered. Target volumes of corresponding detectors should be of about 109 m3 and even more.
INTRODUCTION-2 • Construction of cubic kilometer targets is very expensive as well as very difficult problem. So, one of the ways to increase the volumes is to use some natural targets. • Amongst the natural targets that now used for SHE cosmic neutrinos detection are: - Earth’s atmosphere, - Lake and sea waters, - Ice massifs, - Moon regolith – the subject of this talk/
RAMAND- and RAMHAND-types EXPERIMENTS • The idea to use the Moon as a giant cosmic target for SHE-neutrinos detection (Radio-Moon Hadrons And Neutrinos Detector, i.e. RAMHAND-project [1]) likes to Radio Antarctic Muons And Neutrinos Detector RAMAND-type experiment’s [2] one. • The both types experiments are based on Askaryan’s effect [3, 4]: coherent Cherenkov emission of the negative charged cascades in dense dielectric. • Askaryan’s conclusion was confirmed in excellent SLAC experiment by Peter Gorham, Dave Saltzberg and their colleagues [5]. _______________________________________________ 1. R.D.Dagkesamanskii and I.M.Zheleznykh (1989). 2. G.A.Gusev and I.M.Zheleznykh (1983) 3-4. G.A.Askaryan (1961, 1965). 5. P.Gorham, D.Saltzberg et al. (2000).
PARKS AND GOLDSTONE EXPERIMENTS • First attempt to realize i.e. RAMHAND-type experiment had been undertaken in Parks Radio Observatory by USA/Australian team in mid-1990th. There was 12-hous on-Moon exposition (T.H.Hankins, R.D.Ekers, and J.D.O’Sullivan, 1996). • Second RAMHAND-type experiment (GLUE) was made by P.Gorham, D.Saltzberg, et al. (2000) with 70-metr and 34-meter dishes of the Goldstone DSN station. More than 120-hours exposition and no one expected event (P.W.Gorham et al., 2004).
KALYAZIN EXPERIMENT-1 • Pushchino Radio Astronomy Observatory team started the monitoring of the Moon from 2002. Some of the first observations were made with our 22-meter dish, but the most fruitful results have been obtained with Kalyazin 64-meter radio telescope of the Moscow Power Institute. • Multi-frequency feed system of Kalyazin 64-meter radio telescope is very important advantage. Indeed, delay of the signal at lower frequency due to dispersion in the Earth ionosphere could be used to separate the signal from the Moon from local interferences. • Both circular polarizations of two main frequencies (1.4 and 2.3 GHZ) is registered. Trigger recording system register all suspicious events with 2 ns time resolution.
KALYAZIN EXPERIMENT-2 • Some results of our observations with Kalyazin 64-meter dish were published in 2005(A.R.Bereznyak et al., 2005). • After 2005 our receiver and recording systems were upgraded. New sensitivity was about the same as in GLUE-experiment. Now the total on-Moon exposition with the new sensitivity is about 150 hours, that is also similar to GLUE data. • No one expected event was registered during our observations with Kalyazin radio telescope, too.
The antenna beamwidths are ~11' at 1.4 GHz and ~7' at 2.3 GHz. The expected events should be near the limb of the Moon, so the pointing was at 14' apart from the center of the MoonPosition of the antenna beams on the Moon
Our main results- Today the total “live-time on the Moon” is slightly more than 150 hrs with threshold level of 3500 Jy. - With this “exposition” we also had not found any reliable radio pulse similar to Cherenkov emission pulse. - So, our sensitivity and exposition are close to GLUE one. However, combined estimate of the upper limit to the SHE neutrino flux is more conservative than GLUE’s one. Certainly, it is mainly due to our less optimistic estimate of the effective target volume . Another (additional) cause: it could be due to different slopes adopted for neutrino spectrum above 1020eV or differences in some other model parameters.
How to improve our estimates ? Here is some of the obvious ways:1. Increasing the “live-time on the Moon” (i.e. make more and more observations). 2. Increasing the sensitivity (use wider receiver bandwidths and coincidence schemes). 3. Reduce the thresholds and use some kind statistic analysis of the suspicious events. All these ways are rather hard.
SOME OTHER PERSPECTIVES 1. To optimize observational frequency range. NuMoon experiment. Possibilities of Indian GMRT and Ooty radio telescopes. 2. To observe more time during the AGNs occultations by the Moon. (Some correlation was found between the direction to nearby AGNs and SHE cosmic ray’s arrival directions. (Australian team). 3. Lunar Orbital Radio Detector proposed by LPI team (V.Tsarev et al., 2005). 3. International cooperation similar to that proposed by I.Zheleznykh in 1988.
Active galactic nuclei are the sources of cosmic SHE neutrinos.
LORDLunar Orbital Radio Detector • Huge target mass Veff ~ 105 (km.w.e.)3 • Lunar satellite: • Very favorable background conditions • Short (and variable) distance – high signal
International cooperationThe possible scheme of international cooperative observaions proposed by I.Zheleznykh in 1988. Such observations will be very useful: they improve sensitivity, increase the reliability of results, and even could help us to determine the direction to the UHE neutrino source.
