Deck 43: Elementary Particle

Question 1

The Feynman diagram shows the weak interaction of a neutrino (ν) and a neutron (n), mediated by a W⁺ particle. The interaction produces an electron (e^-) and another particle. What is the other particle? FIGURE 43-2

A)a positron (e⁺)
B)a pion (π⁺)
C)a proton (p)
D)a quark
E)an anti-neutron

Answer 1

a proton (p)

Question 2

Which of the following is not considered to be one of the four fundamental forces?

A)the gravity force
B)the meson force
C)the weak nuclear force
D)the strong nuclear force
E)the electromagnetic force

Answer 2

the meson force

Question 3

The neutrino has

A)enormous rest mass, positive charge, and spin quantum number 1/2.
B)enormous rest mass, no charge, and spin quantum number 1.
C)negligible rest mass, negative charge, and spin quantum number 1.
D)negligible rest mass, no charge, and spin quantum number 1/2.
E)none of the given answers

Answer 3

negligible rest mass, no charge, and spin quantum number 1/2.

Question 4

What happens to the cyclotron frequency of a charged particle if the radius of its path doubles?

A)It quadruples.
B)It triples.
C)It doubles.
D)It halves.
E)It does not change.

Question 5

The reaction p + → e⁺ + γ is not possible because

A)angular momentum cannot be conserved in such a reaction.
B)baryon number is not conserved in such a reaction.
C)lepton number is not conserved in such a reaction.
D)charge is not conserved in such a reaction.
E)The statement is not true; the reaction is possible.

Question 6

The reaction p + e^- → + e⁺ is not possible because

A)the baryon number is not conserved.
B)the lepton number is not conserved.
C)the angular momentum cannot conserved.
D)the charge is not conserved.
E)The statement is untrue; the reaction is possible.

Question 7

The quantum of the gravitational force is the

A)muon.
B)graviton.
C)pion.
D)quark.
E)newton.

Question 8

The decay: n → p + e^- + v_e does not occur as it would violate conservation of

A)baryon number.
B)mass.
C)charge.
D)lepton number.
E)angular momentum.

Question 9

If both 30-GeV electrons and 30-GeV protons are used to probe the nucleus, which has the shorter wavelength?

A)They are the same.
B)the electrons
C)the protons
D)It depends on the nucleus probed.
E)They are never the same.

Question 10

The exchange particles for the weak force are very massive (about 100 times as massive as a proton). This would lead one to expect that the weak force would

A)act over a very long range.
B)act over a very short range.
C)only act on very massive particles.
D)only act on very light particles.
E)be transmitted at the speed of light.

Question 11

The force between two quarks increases with separation.

Question 12

What combination of quarks produces a proton and what are the electric charges on these quarks, expressed in terms of e?

Question 13

What combination of quarks produces a neutron and what are the electric charges on these quarks, expressed in terms of e?

Question 14

The competition between the electrostatic force between the protons in a nucleus and the strong nuclear force determines whether a nucleus is stable.

Question 15

The strong nuclear force acts only on neutral particles.

Question 16

What happens to the cyclotron frequency of a charged particle if its speed doubles?

A)It quadruples.
B)It triples.
C)It doubles.
D)It halves.
E)It does not change.

Question 17

The Feynman diagram shows two electrons approaching each other, interacting, and then leaving each other. What particle is being exchanged during the interaction? FIGURE 43-1

A)pion
B)meson
C)virtual photon
D)neutrino
E)W particle

Question 18

Quarks can only have a charge of +(2/3)e or -(1/3)e, while antiquarks can only have charges of -(2/3)e or +(1/3)e.

Question 19

The strong nuclear force is how many times as strong as the gravitation force?

A)10³⁸
B)1 (They are the same.)
C)2
D)100
E)10⁶

Question 20

One reason a photon could not create an odd number of electrons and positrons is that such a process would

A)not conserve charge.
B)not conserve energy.
C)require photon energies that are not attainable.
D)result in the creation of mass.
E)result in the destruction of mass.

Question 21

The proton composition by quarks is

A)u d.
B)uud.
C)udd.
D)u
.
E)u d.

Question 22

Which of the following combinations of quarks can form a particle with a unit charge, a baryon number of zero, and a minimum angular momentum of zero?

A)u
B)udd
C) d
D)uud
E)ud

Question 23

A proton is an example of

A)a lepton.
B)a meson.
C)a baryon.
D)a gauge boson.
E)none of the above.

Question 24

A photon is an example of

A)a lepton.
B)a meson.
C)a baryon.
D)a gauge boson.
E)hadrons.

Question 25

The greater the width of a resonance,

A)the greater the rest energy of the resonance.
B)the greater the lifetime of the resonance.
C)the lower the rest energy of the resonance.
D)the shorter the lifetime of the resonance.
E)None of the above answers are correct.

Question 26

What is the quark composition of a Λ°?

A)uud
B)uus
C)uds
D)uss
E)udd

Question 27

When a quark emits or absorbs a gluon, the quark changes

A)its charge.
B)its mass.
C)its color.
D)into an antiquark.
E)none of the above

Question 28

An electron is an example of

A)a lepton.
B)a meson.
C)a baryon.
D)a gauge boson.
E)hadrons.

Question 29

The π⁺ meson composition by quarks is

A)ud.
B) d.
C)u .
D)
.
E)none of the above

Question 30

Composite particles that are composed of a quark and antiquark pair are called

A)leptons.
B)hadrons.
C)mesons.
D)bosons.
E)baryons.

Question 31

A quark is

A)a constituent of a nucleon.
B)a constituent of a hadron.
C)an elementary particle.
D)all of the given answers.

Question 32

Composite particles that are composed of three quarks are called

A)leptons.
B)hadrons.
C)mesons.
D)bosons.
E)baryons.

Question 33

A neutron is an example of

A)a lepton.
B)a meson.
C)a baryon.
D)a gauge boson.
E)none of the above.

Question 34

Hadrons are divided into two subgroups called

A)baryons and leptons.
B)leptons and mesons.
C)mesons and baryons.
D)nucleons and gauge bosons.
E)mesons and gauge bosons.

Question 35

Which of the following particles is not stable?

A)photon
B)electron
C)tau neutrino
D)muon
E)proton

Question 36

The number of different kinds of leptons, including antiparticles as different, is

A)4.
B)6.
C)8.
D)2.
E)12.

Question 37

Particles that do not interact via the strong force but do interact via the weak nuclear force (and presumably by the much weaker gravitation force) are called

A)gauge bosons.
B)leptons.
C)baryons.
D)mesons.
E)hadrons.

Question 38

What is the charge, baryon number, and minimum angular momentum for the udd combination of quarks?

A)1, 0,
B)0, 1,
C)1, 1,
D)0, 0, 0
E)0, 0,

Question 39

One of the particle groups listed below includes two other groups on the list. Which group is it?

A)leptons
B)hadrons
C)mesons
D)bosons.
E)baryons

Question 40

Given that a reaction n + π⁺ → p can occur and that the quark composition of the neutron is udd and that of the proton is uud, what must be the quark composition of the π⁺ meson?

A)u
B) d
C)d
D)u
E)none of the above

Question 41

If a new force were discovered that had a range on the order of 10^-18 meters:
(a) predict the mass of the exchange particle.
(b) how long is conservation of energy violated in the exchange of this particle?

Question 42

Is the following decay permissible? Σ⁺ → Λ° + π⁺

A)Yes.
B)No, because charge is not conserved.
C)No, because mass is created.
D)No, because lepton number is not conserved.

Question 43

Consider a particle composed of quarks.
(a) The negative pion is composed of what combination of up and down quarks?
(b) Is the negative pion a baryon or meson?
(c) Is the negative pion a lepton or a hadron?

Question 44

The voltage across the dees of a cyclotron is 30,000 V. How many revolutions do the protons go through in reaching 21 MeV kinetic energy?

A)more than 2 x 10⁶
B)1400
C)700
D)350
E)35

Question 45

A cyclotron of radius 0.25 m accelerates protons in a 1.7-T magnetic field. What is the frequency for the applied alternating voltage?

A)0.26 MHz
B)2.6 MHz
C)26 MHz
D)260 MHz
E)2600 MHz

Question 46

What is the wavelength of a 20-GeV alpha particle?

A)0.25 fm
B)0.063 fm
C)0.099 fm
D)less than 10^-18 m
E)0.50 fm

Question 47

If electrons are accelerated from rest in a 30 MeV tandem Van de Graaff Accelerator, what is their final kinetic energy?

A)15 MeV
B)20 MeV
C)30 MeV
D)40 MeV
E)60 MeV

Question 48

A significant step in "unifying" the forces of nature was the discovery that two of the so-called fundamental forces were two parts of a single force. The two forces that were so unified were

A)the electromagnetic force and the weak force.
B)the electromagnetic force and the strong nuclear force.
C)the electromagnetic force and the gravity force.
D)the weak force and the strong nuclear force.
E)the weak force and the gravity force.

Question 49

Scientists hope that some day they will be able to produce a theory which will combine the strong force, the weak nuclear force, and electromagnetism. This theory has been called

A)The Grand Unified Theory.
B)The Theory of Everything.
C)The Unified Field Theory.
D)The Electroweak Theory.
E)The Electrostrong Theory.

Question 50

A deuteron has the same charge as a proton but approximately twice the proton mass. Suppose deuterons are being accelerated in a cyclotron in an orbit of radius 75 cm at a frequency of 8.0 MHz. What magnetic field is needed?

A)0.011 T
B)0.11 T
C)1.1 T
D)11 T
E)111 T

Question 51

The color charge of leptons is

A)violet.
B)red.
C)blue.
D)zero.
E)green.

Question 52

An electron undergoes a collision with a proton. In the center of mass system, the energy of the electron is 4000 MeV. What is the energy of the electron in the lab system, where the proton is at rest before the collision?

A)34 GeV
B)37 GeV
C)40 GeV
D)43 GeV
E)46 GeV
F)52 GeV

Question 53

When a positronium atom (electron + positron) decays, it emits two photons. What are the energies of the photons?

A)0.511 MeV and 1.022 MeV
B)0.225 MeV and 1.022 MeV
C)0.225 MeV and 0.285 MeV
D)0.256 MeV and 0.256 MeV
E)0.511 MeV and 0.511 MeV

Question 54

The Large Hadron Collider is expected to produce protons with kinetic energy 7 TeV. What is the speed of these protons?

A)less than 0.9000 c
B)0.9500 c
C)0.9990 c
D)greater than 0.9999 c
E)0.9000 c

Question 55

An electron with an energy of 20 GeV (3.20 × 10^-9 J) moving in the +x direction collides head on with a stationary proton. After the collision, the electron travels in the -x direction. What is the momentum of the electron after the collision? Note that this is an ultrarelativistic collision so that the energy of the moving masses can be approximated by the expression E ≈ pc. The mass of a proton is 1.67 × 10^-27 kg and that of an electron is 9.11 × 10^-31kg.

A)2.5 × 10^-19 kg∙m/s
B)5.0 × 10^-19 kg∙m/s
C)1.1 × 10^-17 kg∙m/s
D)2.2 × 10^-17 kg∙m/s
E)2.7 × 10^-22 kg∙m/s

Question 56

What is the wavelength of a 2.0-GeV electron?

A)1.2 fm
B)0.62 fm
C)0.099 fm
D)less than 10^-18 m
E)2 fm

Question 57

A cyclotron of radius 0.25 m accelerates protons in a 1.7-T magnetic field. What is the kinetic energy of the protons when they leave the cyclotron?

A)3.7 keV
B)7.8 keV
C)8.7 keV
D)7.8 MeV
E)8.7 MeV

Question 58

A cyclotron operates at 10 MHz. What magnetic field is needed to accelerate protons?

A)0.12 T
B)0.25 T
C)0.66 T
D)1.3 T
E)1.5 T

Question 59

Suppose you were to try to create a proton-antiproton pair by annihilation of a very high energy photon. The proton and the anti-proton have the same masses, but opposite charges. What energy photon would be required?

A)1.022 MeV
B)12.2 MeV
C)1880 MeV
D)940 MeV
E)223 MeV

Question 60

A cyclotron is designed with a magnet that produces 1.2 T. When refurbished, the magnet is replaced by one that produces 1.5 T. How does the kinetic energy developed by the protons change compared to the previous energy developed?

A)It increases by 25%.
B)It decreases by 25%.
C)It increases by 56%.
D)It decreases by 56%.
E)It does not change.

Question 61

The number of quarks in a deuteron (²H) is

A)1.
B)2.
C)3.
D)4.
E)6.

Question 62

Which of the following cannot occur?

A)π⁺ → μ⁺ + v_μ
B)π° → 2γ
C)π⁺ + p → K⁺ + Σ⁺
D)π^- + p → n + γ
E)Σ^- → π^- + p

Question 63

If a resonance had a width of 100 keV, what would be the corresponding lifetime associated with the particle?

A)7 × 10^-24 s
B)7 × 10^-21 s
C)2 × 10^-20 s
D)4 × 10^-20 s
E)7 × 10^-23 s

Question 64

Which of the following can occur?

A)π⁺ → μ⁺ + v_μ
B)p + n → p + p +
C)K⁺ → π°
D)μ^- → e^- + v_e + v_μ
E)K⁺ → 2π°

Question 65

Is the following decay allowed? Σ⁺ → p + π⁺

A)Yes.
B)No, because charge is not conserved.
C)No, because mass is created.
D)No, because lepton number is not conserved.

Question 66

Is the following decay allowed? π° → μ⁺ + v_μ

A)Yes.
B)No, because charge is not conserved.
C)No, because mass is created.
D)No, because lepton number is not conserved.