Stars as Laboratories for Fundamental Physics - MPP Theory Group

378 Chapter 10
error for simplicity. This yields
S 17 (0)/eV b =
{ 14.7 ± 3.7 TL93,
9.8 ± 2.0 BP95,
(10.21)
to be compared with the world average 22.4 ± 2.1 (Sect. 10.2.3). While
the discrepancy is severe, one would still be hard-pressed to conclude
with a reasonable degree of certainty that the solar neutrino problem
is not just a nuclear physics problem.
10.5.2 Beryllium Flux
The Kamiokande solar neutrino problem may be explained by a low
S 17 (0) factor, perhaps in conspiration with lower-than-standard opacities
that cause the central solar temperature to be lower than expected.
In this case the spectral shape would remain unchanged, leading to an
unambiguous prediction for the neutrino signal that must be caused by
8 B neutrinos in the chlorine and gallium detectors. This contribution
may be subtracted from the Homestake and SAGE/GALLEX data, respectively,
to obtain a measurement of the remaining neutrino sources
(Tab. 10.10)—see Kwong and Rosen (1994). Moreover, the predicted pp
and pep signals in these detectors do not seem to involve any significant
uncertainties so that they may be subtracted as well, effectively leading
to a measurement of the flux of 7 Be and CNO-neutrinos (Tab. 10.10).
These fluxes are then found to be formally negative; they are consistent
with zero within the experimental measurement errors.
These remaining fluxes inferred from the chlorine and gallium experiments
are to be compared with the predictions for the 7 Be and CNO
neutrinos. In Tab. 10.10 the predictions of BP95 are shown; those of
TL93 and other authors are similar. Bahcall (1994b) has compiled the
predictions for the 7 Be flux from a heterogeneous set of 10 solar models
by different authors whose predictions agree to within ±10%—there is
a broad consensus on the standard value of this flux. Therefore, the
errors of the predictions are much smaller than the experimental ones,
leaving one with a very significant discrepancy between the predicted
and observed flux both at Homestake and at SAGE/GALLEX, even if
one were to ignore the CNO contributions entirely.
In the analysis of Hata and Haxton (1995) which uses the GALLEX
source experiment as a constraint on the gallium absorption cross section,
it is found that at the 99% CL the measured 7 Be flux is less
than 0.3 of the BP95 prediction. This high significance of the beryllium
problem relies on the assumption that all solar neutrino experi-