In its salt-enhanced phase (results published in 2005), SNO measured the following…

PHYSICS · Multi-part · Fermi University Physics · Particle Physics & Quantum Fields · Flavour, neutrinos and CP violation · Flavour, neutrinos and CP violation

Symmetry and Flavour, Ch Neutrino masses, mixing and oscillations

Problem

In its salt-enhanced phase (results published in 2005), SNO measured the following solar 8^8B neutrino fluxes, in units of 106 cm−2s−110^6\,\mathrm{cm^{-2}s^{-1}}: charged-current ϕCC=1.68\phi_{\rm CC}=1.68 (the reaction νed→ppe−\nu_ed\to ppe^-, sensitive to νe\nu_e only) and neutral-current ϕNC=4.94\phi_{\rm NC}=4.94 (the reaction νxd→pnνx\nu_xd\to pn\nu_x, equally sensitive to all active flavours). The Standard Solar Model predicts a total 8^8B flux ϕSSM=(5.05±0.91)×106 cm−2s−1\phi_{\rm SSM}=(5.05\pm0.91)\times10^6\,\mathrm{cm^{-2}s^{-1}}. ((a)) Find the electron-neutrino flux ϕe\phi_e and the combined muon-plus-tau flux ϕμτ\phi_{\mu\tau} arriving at Earth. ((b)) Compute the electron-neutrino survival probability Pee=ϕCC/ϕNCP_{ee}=\phi_{\rm CC}/\phi_{\rm NC}. ((c)) Compare ϕNC\phi_{\rm NC} with ϕSSM\phi_{\rm SSM} and state what this comparison shows about the Standard Solar Model, independently of any assumption about neutrino oscillation. ((d)) Explain why the neutral-current measurement, rather than the charged-current deficit alone, is what rules out a mundane error in the solar model as the explanation for the missing νe\nu_e.

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