En anglais

The particle catalogue and its rules

Science · Quantum & Modern Physics · ages 20-22

Name ______________________ Date ____________

Photons and gluons are massless. Which statement correctly distinguishes electromagnetism from the strong interaction?
- Photons allow long-range electromagnetism; gluon interactions confine quarks.
- Photons confine electrically charged particles; gluons allow isolated color charges.
- Photon and gluon masses alone explain why both interactions end at nuclear distances.
Which assignment matches the carriers of the three Standard Model interactions?
- Strong: photons; electromagnetic: gluons; weak: W and Z
- Strong: gluons; electromagnetic: photons; weak: W and Z
- Strong: W and Z; electromagnetic: photons; weak: gluons
The muon belongs to generation 3 of the charged leptons.
Circle one: True False
Which statement gives the conventional valence-quark descriptions of a proton and a positive pion?
- Proton: up, up, antidown; positive pion: up, down.
- Proton: up, up, down; positive pion: up, antidown.
- Proton: up, down, down; positive pion: down, antiup.
Test proton -> positron + photon using charge, baryon number B and total lepton number L only. Which statement describes the tallies?
- Charge and B change; total L balances.
- Charge and total L change; B balances.
- B and total L change; charge balances.
In a massive-exchange model, carrier Y has three times X's mass. X's range is 6 x 10^-18 m. Estimate Y's range in units of 10^-18 m. Enter the numerical coefficient.
Answer: ______________
Test strangeness only for proton + neutral pion -> neutral lambda + positive pion, proposed as a strong reaction. The proton and pions have S = 0; the lambda has S = -1. What follows?
- The strong route is forbidden; a weak route needs other checks.
- The strong route passes; a weak route is forbidden by this tally.
- Every possible route passes because baryon number stays unchanged.
A student says most proton mass is the sum of its three valence quarks' Higgs-generated masses. Which source actually accounts for most proton mass?
- Only the Higgs masses of its three valence quarks.
- A Higgs drag force that slows the whole proton.
- The energy of its quark and gluon fields.

Answer key

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The particle catalogue and its rules W1-mt_GYB4UMS0D9-s1

Photons allow long-range electromagnetism; gluon interactions confine quarks. · Photon exchange gives electromagnetism no intrinsic finite range. Massless gluons do not imply isolated quarks: the color interaction has confinement.
Strong: gluons; electromagnetic: photons; weak: W and Z · Gluons carry the strong interaction, photons carry electromagnetism, and W and Z bosons carry the weak interaction.
False · The muon is the generation-2 charged lepton. The tau is the generation-3 charged lepton.
Proton: up, up, down; positive pion: up, antidown. · The proton has conventional valence content uud. A positive pion has an up quark and an antidown quark. These do not count all constituents.
B and total L change; charge balances. · Charge stays +1. B changes from 1 to 0, and total L changes from 0 to -1. The proposal fails both number checks used here.
2 · Range varies inversely with carrier mass. Tripling mass divides range by 3: 6/3 = 2, giving 2 x 10^-18 m.
The strong route is forbidden; a weak route needs other checks. · Initial S is 0 + 0 = 0. Final S is -1 + 0 = -1. Strong reactions conserve S, so the stated strong route is forbidden. Other routes need further checks.
The energy of its quark and gluon fields. · Higgs coupling gives quarks mass, but their masses account for only a small part of proton mass. Most comes from quark and gluon field energy.