Deck 46: Particle Physics and Cosmology

Question 1

Which of the following reactions violates conservation of strangeness?

A) Ω⁻ → 3γ
B)

C)

D)

E)

Answer 1

Ω⁻ → 3γ

Question 2

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?

A) 0.75 c
B) 0.33 c
C) 0.55 c
D) 0.11 c
E) 0.93 c

Answer 2

0.11 c

Question 3

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

A) the baryons are states of something more elementary that can exist in multiple quantum states.
B) the leptons are states of something more elementary that can exist in multiple quantum states.
C) photons are states of something more elementary that can exist in multiple quantum states.
D) according to the Heisenberg Uncertainty Principle quantum numbers are indeterminate.
E) quarks are states of something more elementary that can exist in multiple quantum states.

Answer 3

the baryons are states of something more elementary that can exist in multiple quantum states.

Question 4

Which of the following decays violates conservation of lepton number?

A)

B)

C)

D)

E)

Question 5

If a K⁰ meson at rest decays in 0.89 × 10−¹⁰ s, how far will a K⁰ meson moving at 0.96 c travel through a bubble chamber?

A) 17 cm
B) 1.1 cm
C) 53 cm
D) 42 mm
E) 9.2 cm

Question 6

The minimum energy needed to produce a positron is

A) 3 MeV
B) 2 MeV
C) 1 MeV
D) 4 MeV
E) 0.51 MeV

Question 7

Which of the following particle reactions cannot occur?

A) p + p → p + p + p +

B) p +
→ 2γ
C) π⁺ + p → K⁺ + Σ⁺
D) γ + p → n + π⁰
E) e− + e⁺ → 2γ

Question 8

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

A) zero
B) 400 Gev
C) 800 GeV
D) 1 600 GeV
E) 2 400 GeV

Question 9

Particles composed of quarks are

A) photons.
B) leptons.
C) neutrinos.
D) W and Z bosons.
E) baryons and mesons.

Question 10

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 to estimate the mass of the elementary particle if it moves at nearly the speed of light.

A) 140 MeV/c², a pion
B) 511 keV/c², an electron
C) 96 GeV/c², a Z boson
D) 500 MeV/c², a K meson
E) 106 MeV/c², a muon

Question 11

The law of conservation of baryon number is that

A) the total number of baryons and leptons is conserved.
B) the total number of baryons is conserved.
C) the (number of baryons) − (number of antibaryons) is conserved.
D) the total number of quarks is conserved.
E) the (number of baryons) + (number of antibaryons) is conserved.

Question 12

Which of the following reactions cannot occur?

A) n → p + e− +

B) p + n → p + p +

C) μ⁻ → e− +
+
μ
D) π⁻ → μ⁻ + νμ
E) π⁺ → μ⁺ +

Question 13

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

A) A person on a skateboard pushing against a wall.
B) two people in two canoes throwing a ball back and forth.
C) two people in two canoes each pulling on one end of a rope.
D) two people in two skateboards giving each other a shove.
E) two people in two skateboards each pulling on one end of a rope.

Question 14

The attractive force between protons and neutrons in the nucleus is brought about by the exchange of a virtual pi-meson (mπ = 140 MeV/c²). Estimate the longest time a virtual π⁰ can exist, in accordance with the uncertainty principle . (1 eV = 1.6 × 10−¹⁹ J.)

A) 2.4 × 10−²⁴ s
B) 6.9 × 10−²⁷ s
C) 3.3 × 10−¹⁸ s
D) 2.4 × 10−²¹ s
E) 1.6 × 10−¹⁹ s

Question 15

The following reaction can occur by the strong interaction: π⁰ + n → K⁺ + Σ⁻. If the quark composition of the n is (udd), the π° is ( ), and the composition of the K⁺ is ( ), find the quark composition of the Σ⁻.

A) sss
B) uds
C) dds
D)

E)

Question 16

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 . (1 eV = 1.6 × 10−¹⁹ J.)

A) 3.4 × 10−²⁷ s
B) 7.5 × 10−³⁰ s
C) 2.4 × 10−²⁴ s
D) 1.9 × 10−²¹ s
E) 6.3 × 10−⁵ s

Question 17

Which one of the following is not true of neutrinos?

A) They have no charge.
B) They have no spin.
C) One type of neutrino may change into another type of neutrino.
D) They are leptons.
E) They do not take part in strong nuclear interactions.

Question 18

All particles can be classified into

A) Leptons and quarks
B) Hadrons and leptons
C) Baryons and leptons
D) Mesons and Baryons

Question 19

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

A) One photon of energy 1.02 MeV
B) Two photons of energy 511 keV
C) A pi-meson
D) A K-meson and an anti-neutrino

Question 20

The omega-minus particle decays with the X⁰ and the π⁻ 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)

B)

C)

D)

Question 21

A photon with an energy of Eγ = 2.090 0 GeV creates a proton-antiproton pair in which the proton has a kinetic energy of 95.0 MeV. What is the kinetic energy of the antiproton? (m_pc² = 938.3 MeV)

Question 22

If the quark content of the proton, p, is uud, the quark content of the antiproton, is

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

Question 23

A K⁰ particle at rest decays into a π⁺ and a π⁻. What will be the speed of each of the pions? The mass of the K⁰ is 497.7 MeV/c² and the mass of each π is 139.6 MeV/c².

Question 24

The acceleration (or deceleration) of the expansion of the universe is determined by

A) the standard matter, baryons and leptons.
B) the dark matter in the universe.
C) the dark energy in the universe.
D) all of the above.
E) only (b) and (c) above.

Question 25

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

A) 10−³⁵ m.
B) 10−¹⁵ m.
C) 10−¹⁰ m.
D) 10−⁸ m.
E) 10−³ m.

Question 26

A Σ⁺ particle, composed of uus quarks, has the same ____ as a proton.

A) baryon number and charm.
B) baryon number and electric charge.
C) baryon number and strangeness.
D) baryon number, electric charge, and charm.
E) electric charge and strangeness.

Question 27

The three quarks in any baryon must all have different

A) baryon number.
B) color charge.
C) electric charge.
D) lepton number.
E) spin.

Question 28

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

A)

B)

C)

D)

E)

Question 29

Calculate the range of the force that might be produced by the virtual exchange of a proton. (m_p = 1.67 × 10−²⁷ kg, h = 6.626 × 10−³⁴ J ⋅ s)

Question 30

The decay is not possible because

A) L_e is not conserved.
B) Lμ is not conserved.
C) quark number is not conserved.
D) all of the above are not conserved.
E) only L_e and Lμ are not conserved.

Question 31

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

A)
.
B)
.
C)
.
D)
.
E)
.

Question 32

The particle Δ⁺⁺ 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

A) uuu.
B) uud.
C) udd.
D)
.
E)
.

Question 33

Name at least one conservation law that prevents each of the following reactions:
a)
π⁻ + p → Σ⁺ + π°
b)
p → π⁺ + π⁺ + π⁻

Question 34

The particle reaction cannot occur because

A) electric charge is not conserved.
B) strangeness is not conserved.
C) baryon number is not conserved.
D) all of the above are not conserved.
E) both (a) and (b) above are not conserved.