In the decay ^ 64 Cu → ^ 64 Ni + e^ + + , the maximum kinetic...

The total disintegration energy ($Q$-value) is shared between the positron and the neutrino, neglecting the recoil of the daughter nucleus.

Q = K_\max(e^{+}) = 0.650 \text{ MeV}

When the positron has a kinetic energy $K_{e^{+}} = 0.150 \text{ MeV}$, the energy of the neutrino is:

$E_{\nu} = Q - K_{e^{+}} = 0.650 \text{ MeV} - 0.150 \text{ MeV} = 0.500 \text{ MeV}$

Converting this energy to Joules:

$E_{\nu} = 0.500 \times 10^{6} \times 1.6 \times 10^{-19} \text{ J} = 8.0 \times 10^{-14} \text{ J}$

For a neutrino, the relationship between energy and momentum is the same as that for a photon, $E_{\nu} = p_{\nu} c$.

$p_{\nu} = \dfrac{E_{\nu}}{c} = \dfrac{8.0 \times 10^{-14}}{3 \times 10^{8}} \text{ kg m s}^{-1}$

$p_{\nu} \approx 2.67 \times 10^{-22} \text{ kg m s}^{-1}$