[填空题]
If a proton is moving aaqi 4 i0tr3fy-4bgw8/;tvu lg.cl 4slt very high speed, so that its kinetic energy is much greater than ib; /lu .8l44ctgsgw lvts 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, ahrio 2z;)my2rgsyno4 t /l+n+n extremely large momentum), there is no way to conserve both energy and momentum duringo++r)ygnlozthy 2;in 2 r /sm4 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.
