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Chapter 33: Q9CQ (page 1210)
Theorists have had spectacular success in predicting previously unknown particles. Considering past theoretical triumphs, why should we bother to perform experiments?
Scientists bother to perform experiments to validate the theories and provide live proof for their theories.
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Massless particles must travel at the speed of light, while others cannot reach this speed. Why are all massless particles stable? If evidence is found that neutrinos spontaneously decay into other particles, would this imply they have mass?
The primary decay mode for the negative pion \({\pi ^{\rm{ - }}} \to {{\rm{\mu }}^{\rm{ - }}}{\rm{ + }}{{\rm{\bar \upsilon }}_{\rm{\mu }}}\).
(a) What is the energy release in \({\rm{MeV}}\) in this decay?
(b) Using conservation of momentum, how much energy does each of the decay products receive, given the \({\pi ^{\rm{ - }}}\) is at rest when it decays? You may assume the muon antineutrino is massless and has momentum \(p = \frac{{{E_\nu }}}{c}\), just like a photon.
Suppose you are designing a proton decay experiment and you can detect \({\rm{50}}\) percent of the proton decays in a tank of water.
(a) How many kilograms of water would you need to see one decay per month, assuming a lifetime of \({\rm{1}}{{\rm{0}}^{{\rm{31}}}}{\rm{ y}}\)?
(b) How many cubic meters of water is this?
(c) If the actual lifetime is \({\rm{1}}{{\rm{0}}^{{\rm{33}}}}{\rm{ y}}\), how long would you have to wait on an average to see a single proton decay?
What evidence is cited to support the contention that the gluon force between quarks is greater than the strong nuclear force between hadrons? How is this related to color? Is it also related to quark confinement?
What length track does a \[{{\rm{\pi }}^{\rm{ + }}}\]traveling at 0.100c leave in a bubble chamber if it is created there and lives for \[{\rm{2}}{\rm{.60 \times 1}}{{\rm{0}}^{{\rm{ - 8}}}}{\rm{\;s}}\]? (Those moving faster or living longer may escape the detector before decaying.)
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