Mohamad-Ziad Charif - Antares

Figure 3.1: The neutral current (NC), charged current (CC) and total cross sectionof neutrinos (left) and anti-neutrinos (right), with matter as a function of theneutrino energy.ν µ + N/P → ν µ + Xν τ + N/P → ν τ + XHowever, since the NC cross-section is about an order of magnitude lower thanthe CC cross-section, the most significant signature of a neutrino comes from thelatter. Since the nuclear interaction length is less than one meter, we would expectthe hadronic shower signature to dissipate before having a chance to be detectedif it was produced far from our apparatus, henceforth the accompanying leptonoffers a higher chance for detection inside a medium such as water.We would expect a charged particle (our corresponding lepton) with relativisticspeeds to dissipate its energy in several ways:3.1.1 Bremsstrahlung radiationBremsstrahlung radiation is an electromagnetic radiation emitted by a chargedparticle when it decelerates under the influence of the electrical field of anothercharged particle (Figure 3.2 ). In this case the first particle would be our leptonand the second the atomic nucleus of the matter of our environment (ex: water).However, its contribution to the total energy dissipated [87] depends on the massof the lepton or implicitly on its flavor, it depends on γ 6 or γ 4 as seen in eq 3.3& 3.4 (γ is the Lorentz factor) and we have γ ∼ m −1 . So we can see that thismradiation is more important for an electron than for a muon or a tau. µm e∼ 200m τm µ∼ 17 so the Bremsstrahlung contribution to a muon who has the same energyas an electron would be between 9 and 13 orders of magnitude lower.34