Atmospheric neutrinos  Solar Neutrinos  New neutrino physics?

Future experiments

In Table  the main characteristics of the future experiments are listed

Table:

 

Experiment	Reaction	Experimental  method	Threshold  (MeV)	Expected  start-up	Statistics  [full SSM]
Superkamiokande	$\nu_{x}e^- \rightarrow \nu_{x}e^-$	C events	5.	already running	65/d
SNO	$\nu_e d \rightarrow ppe^-$	C events	5.	1997	20/d
	$\nu_{x}d \rightarrow \nu pm$			1999?	7/d
Borexino	$\nu_{x}e^- \rightarrow \nu_{x}e^-$	liquid scint.	0.25	1999	50/d
ICARUS	$\nu_{x}e^- \rightarrow \nu_{x}e^-$	liquid Ar	5.	1999	0.8/d
	$\nu_{e} Ar \rightarrow K^{*} e^-$				2/d

 

 

All these experiments have big problems for the background. Borexino has carried out the experiment C.T.F. (Counting Test Facility) just to demonstrate the feasibility of the experiment for what concerns the radiopurity of the detecting materials SNO and Borexino are surely in condition to give a very good contribution to the clarification of the problem of the solar neutrino oscillation, the first for what concerns the study of the neutral currents, the second one for the analysis of the ⁷Be flux and its time variation. To be more specific we discuss what it can be expected from the experiments in the next few years in terms of flux, energy spectrum, time variations. In term of flux if for instance we assume the SMA as correct, SNO and Borexino are able to rule out completely the LMA and Borexino also the V.O. region. If the V.O. hypothesis is assumed correct, SNO and Borexino can rule out the SMA. The study of the energy spectrum in the ⁸B region at an energy higher than 5 MeV (Superkamiokande, SNO) could disentangle the possible contribution from the oscillations but this analysis is hard in the case of the elastic scattering, where the differences are only few percent. The seasonal variation can be well studied by Borexino, because the ⁷Be neutrino is monoenergetic; all the $\Delta m^2$ vs sin $^{2} \vartheta$ plane can be explored. Finally both the ⁸B and the ⁷Be fluxes can give origin to the day/night effect; its detection could be easier in the ⁸B region. Three further experiments have to be mentioned GNO, Hellaz and Supermunu. GNO (Gallium Neutrino Observatory) is just a prolongation of Gallex with increased volume and an upgrading of the analysis devices (proportional counters). In this way the Gallex collaboration planes to depress both the statistical and the systematical errors. Two new experiments, still in R$\&$D phase, are Supermunu and Hellaz. Both are based on gas TPC's. Hellaz planes to use a 2000 m³ TPC filled with He-CH₄ at 5-10 bars, cooled at 77 K. The resolution in angle and in energy should be very good ( $\sigma_\vartheta \sim$35 mrad and $\sigma (E_{\nu})/E_{\nu} \sim 2-4 \%$). The energy threshold should be $\sim$ 100 KeV. Supermunu is similar to Hellaz, but it should employ CF₄. We can conclude that there is a good chance that the solar neutrino problem should be solved in the first years of the 21st century. Experiments on ⁷Be neutrinos, on neutral current events and on time variations could be decisive in this field.