Λ particle is a subatomic particle that can decay spontaneously into a proton and a negatively charged pion： (a) In a certain experiment the outgoing proton and pion were observed, both traveling in the same direction along the positive x axis with momenta pp = 581 MeV/c and pπ = 256 MeV/c in the laboratory frame. Find the rest mass of the Λ particle (expressed in units of MeV/c 2 ). The rest masses of p and π − are given by mp = 938 MeV/c 2 and mπ = 140 MeV/c 2 , respectively. [Note: 1 eV (electron volt)= 1.602×10−19 J; 1 MeV/c2= 1.78×10−30 kg.] (b) Determine the energy and momentum of the proton in the reference frame of pion. (c) As a consistency check, determine the rest mass of proton by evaluating the scalar product of the 4-momentum of proton in the frame of pion.

Λ particle is a subatomic particle that can decay spontaneously into a proton and a negatively charged pion： (a) In a certain experiment the outgoing proton and pion were observed, both traveling in the same direction along the positive x axis with momenta pp = 581 MeV/c and pπ = 256 MeV/c in the laboratory frame. Find the rest mass of the Λ particle (expressed in units of MeV/c 2 ). The rest masses of p and π − are given by mp = 938 MeV/c 2 and mπ = 140 MeV/c 2 , respectively. [Note: 1 eV (electron volt)= 1.602×10−19 J; 1 MeV/c2= 1.78×10−30 kg.] (b) Determine the energy and momentum of the proton in the reference frame of pion. (c) As a consistency check, determine the rest mass of proton by evaluating the scalar product of the 4-momentum of proton in the frame of pion.