Distributions for tau neutrino interactions observed through the decay $\tau \to \mu {\nu }_{\tau }{\bar{\nu }}_{\mu }$

Abstract

We investigate the problem of identifying ${\nu }_{\tau }$-induced reactions in large neutrino telescopes. We concentrate on events with tracks and showers where the respective energies $E_{\mu }$ and $E_X$ are measured separately. Then we compute analytically and numerically event distributions in two variables $r_l=E_X/E_l$ and $y^{\prime }=E_{\text{X}}/(E_{\mu }+E_X)$. We find that the $y^{\prime }$-distribution is especially useful because in the ${\nu }_{\tau }$-induced reactions the distribution has a minimum at $y^{\prime }=0.75$ and then increases as $y^{\prime }\to 1$. This is different in ${\nu }_{\mu }$-induced reactions where the $y^{\prime }$-distribution decreases monotonically. The results are demonstrated with figures where one can estimate the required sensitivity of the experiments. Another attractive property is that in several ratios the neutrino flux factorizes and drops out. We hope the results of this article will be useful for searches of tau (anti)neutrinos of energies above 100 GeV to several TeV in the present and planned large volume neutrino telescopes.

Comments: 16 pages, 4 figures. The shorter version will be published in Physics Letters B; details of the calculations appear in v1