Deck 39: Elementary Particle Physics

Question 1

In a scattering experiment,an alpha particle initially with 8.00 MeV of kinetic energy can approach the nucleus of an unknown element to within 20.0 fm.If the only force between the alpha particle and the nucleus of the unknown element is the electric force,then what initial kinetic energy is required for a the alpha particle to approach within 30.0 fm of the nucleus?

A)4.67 MeV
B)6.00 MeV
C)5.33 MeV
D)5.67 MeV

Answer 1

5.33 MeV

Question 2

Compared to the elementary charge,Planck charge is about 12 times larger.

A)False
B)True

Answer 2

True

Question 3

The closest distance,r_min to a gold nucleus an alpha particle can get is 38.9 fm.The kinetic energy of the alpha particle is

A)5.85 MeV.
B)12.1 MeV.
C)7.24 MeV.
D)16.8 MeV.
E)0 MeV.

Answer 3

5.85 MeV.

Question 4

A 5.00 MeV alpha particle is incident on a lead nucleus.Because of the Coulomb force between them,the alpha particle will only approach the nucleus to a minimum distance,r_min.Determine r_min.

A)32.5 fm
B)47.2 fm
C)51.0 fm
D)60.3 fm

Question 5

The order of magnitude of the background radiation intensity at the end of the radiation-dominated era (10¹¹ s)was

A)10⁹ W/m².
B)10¹⁰ W/m².
C)10¹¹ W/m².
D)10¹² W/m².
E)10¹³ W/m².

Question 6

An alpha particle is incident on a lead nucleus.Because of the Coulomb force between them,the alpha particle will only approach the nucleus to a minimum distance of 32.5 fm.Determine the kinetic energy initial kinetic energy of the alpha particle.

A)8.66 MeV
B)7.27 MeV
C)5.00 MeV
D)9.18 MeV

Question 7

In a scattering experiment,an alpha particle initially with 8.00 MeV of kinetic energy can approach the nucleus of an unknown element to within 20.0 fm.If the only force between the alpha particle and the nucleus of the unknown element is the electric force,then how close would it approach if its initial kinetic energy was 4.00 MeV instead?

A)10.0 fm
B)20.0 fm
C)40.0 fm
D)80.0 fm

Question 8

Of the fundamental bosons,which has the greatest mass?

A)W boson
B)Z boson
C)Higgs Boson
D)gluon

Question 9

The closest distance,r_min to a gold nucleus a 4.00 MeV alpha particle can get is

A)16.2 fm.
B)24.7 fm.
C)32.4 fm.
D)44.5 fm.
E)56.9 fm.

Question 10

The order of magnitude of the background radiation intensity at the end of the radiation-dominated era was 10¹¹ W/m².How long after the big bang did the radiation dominant era end?

A)10¹⁰ s
B)10¹² s
C)10⁹ s
D)10¹¹ s
E)10¹³ s

Question 11

Which particle below has the largest mass?

A)neutral pi-meson (pion)
B)neutral k-meson (kaon)
C)proton
D)neutron

Question 12

Which particle below has the smallest mass?

A)neutral pi-meson (pion)
B)neutral k-meson (kaon)
C)proton
D)neutron

Question 13

Protons with kinetic energy of 1.6 MeV scatter off a lead (Pb)nuclei in a foil target.Each Pb nucleus contains 82 protons.If both the incoming protons and the Pb nuclei can be treated as point objects,what is the differential scattering cross section for the protons to scatter off the Pb nuclei at an angle of 25 ^$\circ$ from their initial velocity?

A)8.4 * 10^-12 m²/sr
B)1.6 * 10^-25 m²/sr
C)2.3 * 10^-15 m²/sr
D)5.7 * 10^-27 m²/sr
E)6.4 * 10^-22 m²/sr

Question 14

Determine the approximate probing distance of a photon with a minimum energy of 4.0 keV.

A)1.3 * 10⁴ fm
B)3.7 * 10⁴ fm
C)4.9 * 10⁴ fm
D)5.1 * 10⁴ fm
E)1.3 * 10⁹ fm

Question 15

The W bosons,having a mass of 80.403 GeV/c² are elementary bosons for the electroweak interaction.The order of magnitude of the range of the corresponding weak interaction is

A)10^-16 m.
B)10^-17 m.
C)10^-18 m.
D)10^-19 m.
E)10^-20 m.

Question 16

In the Standard Model of elementary particle physics,how many fermions are there? Include both particles and anti-particles.

A)3
B)4
C)12
D)24

Question 17

Which particles are always comprised of some number of quarks greater than one?

A)fermions
B)bosons
C)hadrons
D)gravitons

Question 18

Of the fundamental bosons,which has the smallest mass?

A)W boson
B)Z boson
C)Higgs Boson
D)gluon

Question 19

A 5.00 MeV alpha particle is incident on a lead nucleus.Because of the Coulomb force between them,the alpha particle will only approach the nucleus to a minimum distance, .If the kinetic energy of the alpha particle is decreased,will the particle's distance of approach increase,or remain the same?

A)increase
B)decrease
C)remain the same

Question 20

Determine the approximate minimum energy of a photon if a probing distance of 1.3 * 10⁴ fm is desired.

A)4.0 keV
B)18 keV
C)8.0 keV
D)12 keV
E)15 keV

Question 21

What is the maximum range of the Higgs boson? The Higgs has a spin of 0,a mass of 125 GeV/c² (2.23 * 10^-25 kg)and zero electrical charge.

A)1.6 * 10^-18 m
B)7.1 * 10^-17 m
C)5.8 * 10^-14 m
D)6.7 * 10^-12 m
E)infinity

Question 22

Two particles interact through the weak force by exchanging a Z boson,which has a rest mass of 91 GeV/c².If energy fluctuations given by the Heisenberg uncertainty principle which produced the Z boson allow it to exist only for short times,estimate the maximum range of the weak force.

A)4 * 10^-22 m
B)3 * 10^-20 m
C)2 * 10^-18 m
D)6 * 10^-16 m
E)7 * 10^-14 m

Question 23

Protons with kinetic energy of 1.6 MeV scatter off a lead (Pb)nuclei in a foil target.Each Pb nucleus contains 82 protons.If both the incoming protons and the Pb nuclei can be treated as point objects and the differential scattering cross section for the protons to scatter off the Pb nuclei is 3.2 * 10^-27 m²/sr,what is the scattering angle relative to their initial velocity?

A)57 ^$\circ$
B)35 ^$\circ$
C)50 ^$\circ$
D)70 ^$\circ$
E)25 ^$\circ$

Question 24

The differential scattering cross section for particles to scatter by 60 ^$\circ$ off a 1 mm² area target is 1.5 * 10^-18 m²/sr.A detector with an area of 2.0 cm² is placed 1.0 m away from the target in order to detect particles that have been scattered at 60 ^$\circ$ .If 2 * 10¹⁸ particles hit the target every second,how many will strike the detector every second?

A)100
B)300
C)600
D)1000
E)2000

Question 25

As the early universe began to cool,what was the neutron/proton ratio at a temperature of 20 billion Kelvin?

A)0.14
B)0.5
C)1.1
D)2.1
E)10.4

Question 26

If a newly discovered boson has a maximum range of 7.1 * 10^-17 m,a spin of 0 and zero electrical charge,what is its mass?

A)78.9 GeV/c²
B)34.2 GeV/c²
C)125 GeV/c²
D)2.78 GeV/c²
E)150 GeV/c²

Question 27

Which of the following formed latest in the universe?

A)quarks
B)protons and neutrons
C)hydrogen atoms
D)helium nuclei
E)gluons

Question 28

How many elementary fermions are known to exist in the universe (not including their anti-particles)?

A)1
B)3
C)6
D)10
E)12

Question 29

Protons scatter off a lead (Pb)nuclei in a foil target.Each Pb nucleus contains 82 protons.If both the incoming protons and the Pb nuclei can be treated as point objects and the differential scattering cross section for the protons to scatter off the Pb nuclei at an angle of 25 ^$\circ$ relative to their initial velocity is 3.2 *10^-26 m²/sr,what is the initial kinetic energy of the protons?

A)2.8 MeV
B)3.5 MeV
C)3.2 MeV
D)1.6 MeV
E)4.2 MeV

Question 30

Which Feynman diagram shows an electron-proton scattering,e^- + p $\rarr$ e^- + p mediated by a photon exchange?

A)
B)
C)
D)

Question 31

An electron (m=9.11 * 10^-31 kg)interacts with a positron and a single photon is emitted.Find the smallest possible frequency for this photon.

A)8.2 * 10¹¹ Hz
B)6.8 * 10¹⁸ Hz
C)1.3 * 10²⁰ Hz
D)2.5 * 10²⁰ Hz
E)This reaction cannot occur because of conservation laws.

Question 32

If the energy of the virtual photon mediating an electron-proton scattering,e^- + p $\rarr$ e^- + p,is 1.1 * 10^-20 J,what is the range of this electromagnetic interaction?

A)0.01 µm
B)3 µm
C)2 mm
D)1 cm

Question 33

The proton beam at the Large Hadron Collider (LHC)at CERN can reach a luminosity of 10³⁴ cm^-2s^-1 (this means that in a 1 cm² area,10³⁴ protons encounter each other every second).A cross section for collisions of the order of 1 pb (picobarn)provided evidence of the Higgs boson.If the accelerator runs without interruption,approximately how many of these Higgs events can one expect in one year at the LHC?

A)3 * 10⁵ Higgs events per year
B)1 * 10⁴ Higgs events per year
C)400 Higgs events per year
D)6 * 10⁶ Higgs events per year
E)2000 Higgs events per year

Question 34

What is the correct expression for the Planck length?

A)
B)
C)
D)

Question 35

What is the correct expression for the Planck mass?

A)
B)
C)
D)

Question 36

A 3.8-MeV proton is fired directly at a uranium nucleus (Z = 92).What is the closest that this proton can get to the uranium nucleus?

A)2.7 * 10^-15 m
B)9.3 * 10^-15 m
C)1.2 * 10^-14 m
D)3.5 * 10^-14 m
E)4.6 * 10^-14 m

Question 37

Which of the following particles does not have an integer spin?

A)photon
B) $\pi$ meson
C) $\varepsilon$ meson
D) $\upsilon$ _e lepton

Question 38

What is the maximum wavelength of a photon that can produce a proton/anti-proton pair? The mass of a proton is 1.67 * 10^-27kg.

A)5.0 * 10^-19 m
B)1.0 * 10^-18 m
C)6.6 * 10^-16 m
D)1.3 * 10^-15 m
E)There is no upper limit.

Question 39

What is the correct expression for the Planck time?

A)
B)
C)
D)

Question 40

What is the correct expression for the Planck temperature?

A)
B)
C)
D)

Question 41

A particle composed of two down quarks and one strange quark dds is a baryon with strangeness -1.Its total charge is

A)-3e.
B)-2e.
C)-1e.
D)+1e.

Question 42

An electron-positron pair traveling towards each other with a speed of v with respect to their center of mass,collide and annihilate according to e^- + e⁺ $\rarr$ $\gamma$ + $\gamma$ .An observer at rest with respect to the center of mass of the electron-positron pair,detects two photons each of wavelength 380 fm.What was the speed,v prior to the collision?

A)0.976 c
B)0.923 c
C)0.950 c
D)0.995 c
E)0.988 c

Question 43

A virtual Z particle is emitted in a weak interaction.The range of the interaction is

A)1 * 10^-14 m.
B)4 * 10^-15 m.
C)5 * 10^-16 m.
D)2 * 10^-18 m.

Question 44

What is the wavelength of a photon that has the minimum energy necessary to produce an electron-positron pair?

A)1.2 pm
B)2.4 pm
C)7.6 pm
D)91 nm
E)120 nm

Question 45

What is the electric charge of a particle with a quark content of dsb?

A)-2
B)-1
C)0
D)+1
E)+2

Question 46

An electron-positron pair traveling towards each other with a speed of 0.95 c with respect to their center of mass,collide and annihilate according to e^- + e⁺ $\rarr$ $\gamma$ + $\gamma$ .Assuming the observer is at rest with respect to the center of mass of the electron-positron pair,what is the wavelength of the photons?

A)340 fm
B)380 fm
C)760 fm
D)1200 fm
E)2400 fm

Question 47

An electron-positron pair traveling towards each other with a speed of v with respect to their center of mass,collide and annihilate according to e^- + e⁺ $\rarr$ $\gamma$ + $\gamma$ .An observer at rest with respect to the center of mass of the electron-positron pair,detects two photons each of frequency 5.13 * 10²⁰ Hz .What was the speed,v prior to the collision?

A)0.983 c
B)0.971 c
C)0.991 c
D)0.942 c
E)0.959 c

Question 48

An electron-positron pair traveling towards each other with a speed of 0.95 c with respect to their center of mass,collide and annihilate according to e^- + e⁺ $\rarr$ $\gamma$ + $\gamma$ .Assuming the observer is at rest with respect to the center of mass of the electron-positron pair,what is the frequency of the photons?

A)9.89 * 10¹⁹ Hz
B)9.02 * 10¹⁸ Hz
C)5.13 * 10²⁰ Hz
D)7.25 * 10¹⁹ Hz
E)3.95 * 10²⁰ Hz

Question 49

According to most Grand Unified Theories,the lifetime of a proton is

A)10¹⁰ years.
B)10¹⁵ years.
C)10²¹ years.
D)10³⁰ years

Question 50

Which of the following particles has a quark content of udd?

A)proton
B)neutron
C)electron
D)pion
E)kaon

Question 51

Suppose a neutral rho meson (rest mass 770 MeV/c²)decays at rest into two oppositely charged pions (rest mass 139.5 MeV/c²).What is the momentum of each pion?

A)305 MeV/c
B)196 MeV/c
C)359 MeV/c
D)402 MeV/c

Question 52

Which of the following particles has a quark content of uud?

A)proton
B)neutron
C)electron
D)pion
E)kaon

Question 53

A proton and an antiproton at rest annihilate to create two gamma photons.The wavelength of the photons is

A)5.91 fm.
B)3.24 fm.
C)1.32 fm.
D)0.78 fm.

Question 54

Suppose an eta meson (rest mass 547 MeV/c²)decays at rest into two photons.What is the wavelength of one of the photons?

A)2.3 fm
B)2.3 pm
C)4.5 fm
D)4.5 pm
E)More information is needed.

Question 55

Considering only the four lightest quarks,u,d,s,c,of all the possible combinations of mesons one can make,what proportion have strangeness 1?

A)25%
B)44%
C)19%
D)38%
E)other

Question 56

The decay of a neutron into a proton and electron (n $\rarr$ p + e^-)is not allowed because of which one of the following conservation laws?

A)electric charge
B)spin angular momentum
C)energy
D)lepton number
E)Both B and D are correct.

Question 57

According to the standard model of particle physics,what conservation laws,if any,are violated in the nuclear reaction ?

A)electron lepton and muon lepton number
B)charge conservation
C)energy conservation
D)None are correct.

Question 58

In the Feynman diagram for proton-neutron scattering shown in the figure,what is the virtual particle?

A)W⁺
B)K ^$\circ$
C)g
D) $\pi$ ^-
E) $\pi$ ⁺

Question 59

Considering only the three lightest quarks,u,d,s,of all the possible combinations of baryons one can make,what fraction have non-zero strangeness?

A)60%
B)70%
C)33%
D)66%
E)other