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Today, however, charm production experiments give a consistent set of data, and are compatible
with QCD calculations to next-to-leading order [11]. This has removed the impetus
to look for unconventional mechanisms of charm production, and has motivated a detailed
study of atmospheric neutrinos within perturbative QCD [12].
In Fig. 1 I have collected some of the expected astrophysical neutrino signals and several
predictions for the high energy atmospheric background. The astrophysical signals shown
are the diffuse fluxes from blazars estimated by Dar and Shaviv [13], Protheroe [14], and
Mannheim [15], and the neutrino emission from the galactic interstellar medium as calculated
by Domokos et al. [16]. The conventional atmospheric background is from Lipari [17], and
the prompt neutrino fluxes are from Zas et al. (ZHVa for model A, ZHVe for model E) [4],
Volkova et al. (VFGS) [9], Bugaev et al. (BNSZ) [10], Gonzalez-Garcia et al. (GGHVZ) [7],
and Thunman et al. (TIG) [12]. Also indicated are the upper limits on the prompt neutrino
flux from MACRO [18] and AKENO [19]. Although these limits exclude the highest prediction
ZHVa, the remaining uncertainty in the prompt neutrino background is still a factor of 100.
Since the high-energy atmospheric neutrino background may be a nuisance to the detection
of astrophysical diffuse neutrino fluxes, it may be of value to decrease the uncertainty in the
predictions. The best way would be a detection of the associated prompt muons, maybe
through larger air shower arrays. A second option would be to increase the precision of the
theoretical inputs, for example through better measurement of the charm production cross
section and the charm semileptonic decay rates, which is under way/under project in high
statistics charm production experiments. At last, it may happen that we have to wait for the
neutrino telescopes themselves to know the high energy atmospheric neutrino background.
References
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[5] L.V. Volkova, Yad. Fiz. 31 (1980) 1510 [Sov. J. Nucl. Phys. 31 (1980) 784].
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al., Phys. Rev. Lett. 77 (1996) 2388.
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