The mass of the photon is assumed to be zero, but experiments put only an upper limit of

Why did Yukawa conclude that the particle mediating the strong force should have nonzero mass?

How can we follow the tracks of individual particles?

How are baryons fundamentally different from leptons?

What coordinates are changed under the inversion processes P and T?

Why are we unlikely to observe an isolated quark?

Describe the relation between the strong force and the nuclear force.

Whats the role of gluons?

Classify (a) mesons and (b) baryons as fermions or bosons, and relate your classification to the particles quark compositions.

Name the fundamental force involved in (a) binding of a proton and a neutron to make a deuterium nucleus; (b) decay of a neutron to a proton, an electron, and a neutrino; (c) binding of an electron and a proton to make a hydrogen atom.

What forces are unified in the electroweak theory?

What forces would be unified by GUTs?

Why do we need higher-energy particle accelerators to explore fully the standard model?

How can Hubbles law hold without the universe having a center?

Is it possible for a charged particle to be its own antiparticle?

Describe the origin of the cosmic microwave background.

Explain how particle accelerators can help us understand the early universe.

What medical diagnostic procedure makes use of the fact that every particle has an antiparticle? What particle/antiparticle pair is involved?

The radiation that we observe as the cosmic microwave background started out largely as infrared. Why is it now the microwave background?

How long could a virtual photon of 633-nm red laser light exist without violating conservation of energy?

Some scientists have speculated on a possible fifth force, with a range of about 100 m. Following Yukawas reasoning, what would be the mass of the field particle mediating such a force?

Write the equation for the decay of a positive pion to a muon and a neutrino, being sure to label the type of neutrino. (Hint: The positive muon is an antiparticle.)

Use Table 39.1 to find the total strangeness before and after the decay and use your answer to determine which force is involved in this reaction.

The particle is a neutral nonstrange meson that can decay to a positive pion, a negative pion, and a neutral pion. Write the reaction for this decay, and verify that it conserves charge, baryon number, and strangeness.

Are either or both of these decay schemes possible for the tau particle: (a) (b)

Is the interaction allowed? If not, what conservation law does it violate? p 1 p S p 1 p1

Determine the quark composition of the

The Eightfold Way led Gell-Mann to predict a baryon with strangeness Determine this particles quark composition.

The and have quark compositions uus and dds, respectively. Are the and each others antiparticles? If not, give the quark compositions of their antiparticles.

Estimate the volume of the 50,000 tons of water used in the Super Kamiokande experiment shown in Fig. 39.8.

Estimate the temperature in a gas of particles such that the thermal energy kT is high enough to make electromagnetism and the weak force appear as a single phenomenon.

Repeat Exercise 30 for the energy of grand unification.

Express the Hubble constant in SI units.

Find the distance to a galaxy that is receding from us at

Find the recession speed of a galaxy 300 Mly from Earth.

What would be the age of the universe, assuming constant expansion rate, if the Hubble constant were 25 km/s/Mly?

The mass of the photon is assumed to be zero, but experiments put only an upper limit of on the photon mass. What would the range of the electromagnetic force be if the photon mass were actually at this upper limit?

Which of the reactions (a) and (b) is not possible, and why not?

Both the neutral kaon and the neutral meson can decay to a pionantipion pair. Which of these decays is mediated by the weak force? How can you tell?

Some grand unification theories suggest that the decay may be possible, in which case all matter may eventually become radiation. Are (a) baryon number and (b) electric charge conserved in this hypothetical proton decay?

Consider systems described by wave functions that are proportional to the terms (a) (b) and (c) where and z are the spatial coordinates. Which pairs of these systems could be transformed into each other under a parity-conserving interaction?

The particle is an uncharmed meson that nevertheless includes charmed quarks. Determine its quark composition.

List all the possible quark triplets formed from any combination of up, down, and charmed quarks, along with the charge of each.

The Tevatron at Fermilab accelerates protons to energy of 1 TeV. (a) How much is this in joules? (b) How far would a 1-g mass have to fall in Earths gravitational field to gain this much energy?

(a) Whats the relativistic factor for a 7-TeV proton in the Large Hadron Collider? (b) Find an accurate value for the protons speed.

How long, as measured in the lab frame, does it take a 7-TeV proton to circle the 27-km circumference of the Large Hadron Collider?

Estimate the critical density of the universe.

Estimate the diameter to which the Sun would have to be expanded for its average density to be the critical density found in Problem 46.

A baryon called the neutral lambda particle has mass Find the minimum speed necessary for the particles in a protonantiproton collider to produce lambda antilambda pairs.

A so-called muonic atom is a hydrogen atom with the electron replaced by a muon; the muons mass is 207 times the electrons. Find (a) the size and (b) the ground-state energy of a muonic atom.

(a) By what factor must the magnetic field in a proton synchrotron be increased as the proton energy increases by a factor of 10? Assume the protons are highly relativistic, so (b) By what factor must the diameter of the accelerator be increased to raise the energy by a factor of 10 without changing the magnetic field?

A galaxys spectral line, normally at 486.1 nm, appears at 495.4 nm. (a) Use the Doppler shift of Chapter 14 to find the galaxys recession speed, and (b) infer the distance to the galaxy. Is it appropriate to use Chapter 14s nonrelativistic Doppler formulas in this case?

At the time the cosmic microwave background radiation originated, the temperature of the universe was about 3000 K. What were (a) the median wavelength of the newly formed radiation (Equation 34.2b) and (b) the corresponding photon energy?

Many particles are far too short-lived for their lifetimes to be measured directly. Instead, tables of particle properties often list width, measured in energy units and indicating the width of the distribution of measured rest energies. For example, the has mass 91.18 GeV and width 2.5 GeV. Use the energytime uncertainty relation to estimate its corresponding lifetime.

A mix of particles starts with equal numbers of the three types of sigma particles listed in Table 39.1. Find the relative portion of each after (a) and (b) Give your answer in a reference frame in which the particles are at rest.

You pick up an old astronomy book and read that the Hubble constant is 17 km/s/Mly. You know that todays more accurate value is 22.7 km/s/Mly. Use the simplified reasoning of Example 39.2 to compare the ages for the universe implied by these two values of

A friend believes the universe is very young, less than 10,000 years old. Based on Hubbles law, how would you argue that the universe is older? What would the Hubble constant be for a million-year-old universe?

Your roommate is writing a science-fiction novel set very far in the future, 60 Gy after the Big Bang. One of the characters is a cosmologist, and your roommate wants to know what the cosmologist will measure for the Hubble constant. Whats your answer, assuming a steady expansion rate?

The negative pion usually decays into a negative muon and one other particle. The other particle could be a. a proton. b. an antineutrino. c. a neutrino. d. an up quark.

In the cancer-treatment experiments described in the passage, for which pions is it energetically easiest to be captured by a nucleus? a. b. c. d. Energetically, capture is equally likely for all three pions.

The lifetime of charged pions is 26 ns. The length of an accelerators biomedical beam line, from the point where pions are created to the patient, could be at most about a. 800 m long. b. 80 m long. c. 8 m long. d. 80 cm long.

The quark composition of the negative pion is a. b. c. d.