Solar neutrino

For some experiments, the solar neutrino flux and the rate of decay of the proton being extreme examples, tire count rate is so small that observation times of months or even years are required to yield rates of sufficiently small relative uncertainty to be significant. For high count rate experiments, the limitation is the speed with which the electronics can process and record the incoming infomiation. 

Neutrino deficit Subatomic particles predicted to be released by the nuclear reactions on the Sun and should be detected on Earth. The number of neutrinos observed on Earth is much less than predicted by the models of solar nuclear fusion. 

The capability of neutralizing daughter ions emitted by a parent atom in nuclear decay would result in practical realization of ULLC for solar neutrino detection, weak interaction physics, cosmochronology, geophysics, environmental research, and other important applications. 

Fig. 5.3. Energy spectrum of solar neutrinos predicted from a standard solar model (e.g. Bahcall et al. 1982), omitting the undetectably small flux due to the CNO cycle. Fluxes are in units of cm-2 s-1 MeV-1 for continuum sources and cm-2 s-1 for line sources. Detectors appropriate in various energy ranges are shown above the graph. Courtesy J.N. Bahcall.

Table 5.3. Outline of stellar structure and evolution Solar neutrino fluxes expected and detected in different experiments ... 

Table 5.4. Solar neutrino fluxes from heavy water experiments...

The site of the r-process is also not clear, but it seems that the conditions needed to reproduce Solar-System r-process abundances may hold in the hot bubble caused by neutrino winds in the immediate surroundings of a nascent neutron star in the early stages of a supernova explosion (see Fig. 6.10). Circumstantial evidence from Galactic chemical evolution supports an origin in low-mass Type II supernovae, maybe around 10 M (Mathews, Bazan Cowan 1992 Pagel Tautvaisiene 1995). Another possibility is the neutrino-driven wind from a neutron star formed by the accretion-induced collapse of a white dwarf in a binary system (Woosley Baron 1992) leading to a silent supernova (Nomoto 1986). In stars with extreme metal-deficiency, the heavy elements sometimes display an abundance pattern characteristic of the r-process with little or no contribution from the s-process, and the... 

Fig. 6.10. Results of a dynamical calculation of the r-process in the hot neutrino bubble inside a 20 Mq supernova (continuous curve) compared to the observed Solar-System abundance distribution (filled circles). After Woosley etal. (1994). Courtesy Brad Meyer.

First results from SNO heavy-water experiment announced, giving definitive solution of solar neutrino problem. 

LOOKING INSIDE THE EARTH WITH SOLAR AND SUPERNOVA NEUTRINOS AN ANALYTIC APPROACH... 

Abstract For the case of small matter effects V perturbation theory using e = 2V E/ Am2 as the expansion parameter. We derive simple and physically transparent formulas for the oscillation probabilities in the lowest order in e which are valid for an arbitrary density profile. They can be applied for the solar and supernova neutrinos propagating in matter of the Earth. Using these formulas we study features of averaging of the oscillation effects over the neutrino energy. Sensitivity of these effects to remote (from a detector), d > PE/AE, structures of the density profile is suppressed. 

For the LMA parameters the oscillations of solar and supernova (low energy) neutrinos inside the Earth occur in the vacuum (kinetic) energy dominating regime. This means that the matter potential V is much smaller than the kinetic energy of the neutrino system ... 

Neutrino oscillations in the weak matter effect regime have been discussed extensively before [1-13], in particular, for the solar and supemovae neutrinos propagating in the matter of the Earth. The previous work has been done mainly in the approximation of constant density profile which consists of several layers with constant density. 

Looking inside the Earth with solar and supernova neutrinos An analytic approach 407... 

The probability of u2 —> u, transition relevant for the solar neutrino oscillations in the Earth can be obtained immediately from the unitarily condition ... 

The results can be applied for the solar and supernova (low energy) neutrinos crossing the Earth. 

Luminous matter has revealed dark matter, but the new substance remains obscure. What is it made from Is it perhaps composed of known forms of matter Only partly Is dark matter made up of microscopic particles If the answer is affirmative, we may suppose that this unknown form of energy penetrates and permeates the galaxies, the Solar System and even our own bodies, just as neutrinos pass through us every second without affecting us in any way. And like the neutrinos, these unknown particles would hardly interact at all with ordinary matter made from atoms. To absorb its own neutrinos, a star with the same density as the Sun would have to measure a billion solar radii in diameter. Luminous and radiating matter is a mere glimmer to dark matter. 

Neutrinos inform us almost instantaneously of what is happening in the Sun s core. However, the main interest of this solar cardiograph is hardly to detect some failure in the Sun s cycle. In capturing solar neutrinos, the aim of contemporary physics is rather to catch the Sun in the act of nuclear transmutation. By measuring the neutrino flux, we may check our understanding of the Sun as a whole and at the same time analyse the relationship between this strange particle and more commonplace forms of matter. 

Fig. 5.3. Solar neutrino spectrum and detection ranges of the various underground neutrino observatories. The main part of the emission comes from the proton-proton reaction. About 3000 bilhon neutrinos pass through this figure every second. These neutrinos left the Sun eight minutes and two seconds earlier.

Each time a proton changes into a neutron in the Sun s core, a neutrino flies out and crosses the whole enormous body of the star as though there were nothing there. The Earth is a transparent ball for solar neutrinos and we are continually visited by these invisible beings. 

Five experiments have so far detected solar neutrinos. These are Homestake (USA), GALLEX, SAGE, KAMIOKANDE and SUPERKAMIOKANDE, all set up down mines or tunnels. Detected fluxes agree qualitatively with theoretical predictions, both in numbers and energies. We may say that we have basically understood how the Sun shines. The same set of nuclear reactions invoked to explain the solar luminosity does give rise to neutrinos. 

Table 5.1. Solar neutrinos confronting prediction with detection. The unit of flux is the SNU, or solar neutrino...

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