[填空题]
If a proton is movin ui+j n.pa5)ehvehd. v327 aqag at very high ndto yss4 a);d1(con11:z.9 qcv dxqp speed, so that its kinetic energy is much greater than its rest eavyt.d1dq4d1:ns;p)s1c cx n oo zq 9(nergy ($mc^2$), 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 kinyfe0w,s+n 7 m 0xly.xfetic energy (and, thus, an extremely large momentum), there is no way to conserve both energy and momentum duringw700f.,mf +xsel ynxy such a decay $( \text{p} \to \text{n} + \pi^+ )$. 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.
