XXth International Conference on Neutrino Physics and Astrophysics
S.N.Dobrovolsky
Long-Wavelength Transition Radiation Application for High-Energy
Neutrino Detection
Recently, the number of experiments concerned with investigations of
ultrahigh-energy cosmic ray neutrinos striking the Earth's or Moon's
soil has been performed [1,2]. Electromagnetic showers in a media are
expected to set up centimeter coherent Transition and Cherenkov
radiation. Generation of coherent long-wavelength transition and
Cherenkov radiation is caused by the charge asymmetry in
electromagnetic particles cascade ("Askaryan effect"). For
wavelengths larger than shower size the radiation intensity will be
proportional to the squared number of excess electrons in cascade, in
contrast to the linear dependence for shorter wavelength region. This
effect gives the tool for neutrino detection problem. Some new
searches of radio-frequency emission by particles cascades resulted by
high-energy cosmic particles from the lunar regolith and Antarctic ice
are planned now [2]. The theoretical background for implications of
coherent transition radiation for high-energy neutrino detection
problem is proposed. We have showed that for performed experiments
[2] (typical electron's energies in cascade 30-100MeV), as well
transversal as longitudinal sizes of region where radiation is formed
can reach some meters or tens of meters correspondingly. Therefore,
for "forward" direction, detector will be placed in the "formation
region". We showed that the strong distortion for well-known results
caused by the interference between own electrons field and fields of
transition radiation will occur [3]. Moreover, it is shown, that for
various detectors' arrangements and various angles of observation the
sufficiently different situation connected with electron's fields or
transition radiation fields dominating will observe. Both effect of
small-size detector and effect of finite transversal size of
experimental setup aren't considered earlier for this problem. We
have obtained the simple analytical formulae for "forward"
electromagnetic energy flux through the detector place in the
formation region. Taking into account these effects can help to the
more correct experimental data analyzing for the performed and planned
neutrino detection experiments.
References
1. G.M.Frichter, J.P.Ralston & D.W.McKay,
"Radio-frequency emission from electromagnetic cascades",
Phys. Rev. D 53 (1996) 1684.
2. P.Gorham et al.,
"Radio-frequency measurements of coherent transition and cherenkov
radiation: implications for high-energy neutrino detection",
hep-ex/0004007
3. S.N.Dobrovolsky & N.F.Shul'ga,
"On the distrubution of long-wave transition and diffraction radiation
by relativistic electrons in the formation zone",
Proc. 5-th International Symposium RREPS 01, Lake Aya,
Russia, Sept. 2001, p35.