[填空题]
If a proton is moving at very high speed, so that id vs)5ew2b7j cts pg,jpnt1 2i pws.39lakinetic energy is much greatlw1p tp.s9gpiajn,2 3er than its rest energy ($mc^2$), can it then decay via $p \to n + \pi^+$?
参考答案: no
本题详细解析: No, even if the proton has an extremely large kinetic energy (and, thus, an ext+,0 kdqjf- ortremely large momentum), there is no way to conserve both energy and momentum during such a decay jft-rk dq,o0+$( \text{p} \to \text{n} + \pi^+ )$. Observed from the rest frame of the proton, the decay is energetically impossible, and so it is energetically impossible in every other reference frame as well. In the frame in which the proton is moving fast, the decay products must move very fast as well in order to conserve momentum, and with this constraint, there will still not be enough energy to make the decay energetically possible.
