Exam 31: Particle Physics

The rest-energy of the Z⁰ boson is 96 GeV.Using this information,find the maximum length of time a virtual Z⁰ can exist,in accordance with the uncertainty principle $\Delta E \Delta t = \hbar / 2$ .(1 eV = 1.6 *10^-19 J. )

Of the following leptons,which has the greatest rest energy?

The minimum energy needed to produce a positron is

A model for how repulsive forces between two particles can be mediated by a third particle would be

Which of the following reactions violates conservation of strangeness?

In this course we have seen that baryons have inertial and gravitational mass,intrinsic angular momentum,and other internal properties that have been given names like baryon number,strangeness,charm,etc.The Standard Model's explanation for these properties of baryons is that

According to the Hubble law,where H = 17 km/s/10⁶ lightyears,what is the velocity of recession of a quasar at a distance of 2 billion lightyears from Earth?

The strong nuclear interaction has a range of approximately 0.70 *10^-15 m.It is thought that an elementary particle is exchanged between the protons and neutrons,leading to an attractive force.Utilize the uncertainty principle $\Delta E \Delta t = \hbar / 2$ to estimate the mass of the elementary particle if it moves at nearly the speed of light.

Particles composed of quarks are

Name at least one conservation law that prevents each of the following reactions: a) $\pi$ ^- + p $\rightarrow$$\Sigma$ ⁺ + $\pi$$\degree$ b) p $\rightarrow$ $\pi$ ⁺ + $\pi$ ⁺ + $\pi$ ^-

The decay $\pi ^ { - } \rightarrow \mu ^ { - } + \bar { v } _ { \mu } + \bar { \nu } _ { e }$ is not possible because

The three quarks in any baryon must all have different

If the quark content of the proton,p,is uud,the quark content of the antiproton, $\overline{p}$ is

An electron and a positron (antielectron),both nearly at rest,collide.What particle(s)is(are)produced?

The particle $\Delta$ ⁺⁺ has an electric charge twice that of the proton and baryon number +1.Strangeness,charm,bottomness and topness are all 0.Its quark composition must be

The attractive force between protons and neutrons in the nucleus is brought about by the exchange of a virtual pi-meson (m _$\pi$ = 140 MeV/c²).Estimate the longest time a virtual $\pi$ ⁰ can exist,in accordance with the uncertainty principle $\Delta E \Delta t = \hbar / 2$ .(1 eV = 1.6 *10 ^{- 19} J. )

According to string theory,six space-time dimensions cannot be measured except as quantum numbers of internal particle properties because they are curled up in size of the order of

The omega-minus particle decays $\Omega ^ { - } \rightarrow X ^ { 0 } + \pi ^ { - }$ with the X⁰ and the $\pi$ ^- eventually decaying into stable baryon(s)and lepton(s).Utilizing conservation laws,which of the following is the correct accounting of the decay products?

A proton and an antiproton each with total energy of 400 GeV collide head-on.What is the total energy (particles + energy)released?

In the standard model of the expansion of the universe,the total energy of a standard mass m is assumed to be zero.When we solve the resulting energy equation for the critical mass density of the universe,we find that the critical mass density is given by