Question 1
The attractive force between protons and neutrons in the nucleus is brought about by the exchange of a virtual pi-meson (
mπ = 140 MeV/
c2). Estimate the longest time a virtual
π0 can exist, in accordance with the uncertainty principle

. (1 eV = 1.6
× 10
−19 J.)
◦
2.4 × 10−24 s
◦
6.9 × 10−27 s
◦
3.3 × 10−18 s
◦
2.4 × 10−21 s
◦
1.6 × 10−19 s
Question 2
The decay

is not possible because
◦
Le is not conserved.
◦
Lμ is not conserved.
◦
quark number is not conserved.
◦
all of the above are not conserved.
◦
only Le and Lμ are not conserved.