In particle physics, one is usually able to track charged particles like protons
ID: 1793688 • Letter: I
Question
In particle physics, one is usually able to track charged particles like protons and electrons. The properties of neutral particles like neutrons and neutrinos (and Higgs bosons) must be deduced from their effects on charged particles. Suppose that a proton is observed in a particle detector. It enters the detector with a speed of vo = 2.0 . 105 m/s and interacts with a neutral particle. The proton is deflected by an angle of 60° and its speed f. to vo 1.0-105 m/s is reduced by hal A proton has a mass of m 1.67. 10-27 kg. What is the approximate mass of the neutral particle?Explanation / Answer
mp = mass of proton = 1.67 x 10-27
mn = mass of neutron = ?
vpi = initial velocity of proton = 2 x 105 m/s
vpf = final velocity of proton = 1 x 105 Cos60 = 0.5 x 105 m/s
vni = initial velocity of neutron = 0 m/s
vnf = final velocity of neutron = ? m/s
using conservation of momentum
mp vpi + mn vni = mp vpf + mn vnf
(1.67 x 10-27 ) (2 x 105) + (mn) (0) = (1.67 x 10-27 ) (0.5 x 105) + mn vnf
mn vnf = 2.51 x 10-22
vnf = 2.51 x 10-22 /mn eq-1
using conservation of kinetic energy
mp v2pi + mn v2ni = mp v2pf + mn v2nf
(1.67 x 10-27 ) (2 x 105)2 + (mn) (0)2 = (1.67 x 10-27 ) (0.5 x 105)2 + mn (2.51 x 10-22 /mn )2
mn = 1.006 x 10-27 kg