- How do cosmic-ray-produced muons reaching sea level serve as experimental proof of time dilation?
Quarks and the Quark Model
The fundamental constituents of hadrons and their classification.
- What is spontaneous symmetry breaking, and why can a system's ground state be less symmetric than the laws governing it?
- Why did the Nobel Committee wait until 2008 to award Nambu a prize for work from the early 1960s?
- What connection does Nambu's early work have to the later development of string theory?
- How did the curvature of the mystery particle's track in a magnetic field rule out both a proton and an electron?
- What did Isidor Rabi mean when he asked 'Who ordered that?' about the muon?
- Why is the muon considered unnecessary to the structure of ordinary matter?
- How long does a muon exist before it decays, and where do muons come from?
- How did Stern's anomalous proton measurement eventually point toward the proton having internal structure rather than being a point particle?
- What problem did Yukawa's predicted particle solve about the force holding the nucleus together?
- How long did it take experimentalists to confirm Yukawa's 1935 prediction, and how did they find the particle?
- What made Yukawa's 1949 Nobel significant beyond the physics itself?
- Why did detecting Yukawa's predicted meson require going to high altitudes?
- How did the pion's track differ from the muon tracks that had misled earlier researchers?
- What is parity, and why had physicists assumed it held for every force in nature?
- How did Chien-Shiung Wu's cobalt-60 experiment prove that the weak force does not respect left-right symmetry?
- Why was Chien-Shiung Wu excluded from the 1957 Nobel Prize despite performing the decisive experiment?
- What did I. I. Rabi mean by calling parity violation the most startling result in physics since the neutron?
- What problem in particle physics — an 'embarrassment' of subatomic particles — did the quark model try to solve?
- Where did Murray Gell-Mann get the name 'quark,' and why did he think the word fit?
- What name did George Zweig propose independently for the same particles, and why didn't it survive?
- What experimental evidence at SLAC in the late 1960s confirmed that quarks were physically real?
- What contradiction in gauge theory made it necessary to explain how the W and Z bosons could have mass?
- What is CP symmetry, and why had physicists assumed it applied to every physical process?
- What did Cronin and Fitch observe in neutral kaon decays at Brookhaven that violated CP symmetry?
- Why does the small CP violation found in 1964 help explain why matter outnumbers antimatter in the universe?
- In what sense did Cronin and Fitch's result remain without a full explanation even decades later?
- Why did the growing catalogue of hadron resonances seem bewildering before the quark model existed?
- What problem did Gell-Mann's Eightfold Way solve for particle physics?
- Where did the name 'quark' actually come from?
- How was the omega-minus baryon used to test the quark model?
- Why is the quark model considered a precondition for the Standard Model?
- How did Stern's measurement of the proton's magnetic moment anticipate the discovery of quarks?
- How did two independent teams using completely different experimental methods discover the same particle in the same weekend?
- Why did the J/ψ particle end up with two names instead of one?
- What made the J/ψ particle's unusually long lifetime so surprising to physicists at the time?
- How did discovering the J/ψ particle confirm the existence of the charm quark?
- What made the W and Z boson mass predictions such a bold bet for the theory?
- What did Cronin and Fitch observe in neutral kaon decays that violated the assumed symmetry between matter and antimatter?
- How small was the CP violation Cronin and Fitch measured, and why did such a tiny effect matter so much?
- Why does CP violation help explain why the universe contains matter at all instead of nothing but photons?
- What did the Glashow-Salam-Weinberg electroweak theory predict about the W and Z bosons before they were observed?
- How did Carlo Rubbia and Simon van der Meer use proton-antiproton collisions at the CERN Super Proton Synchrotron to find the W and Z bosons?
- Why was it considered unusually fast for Rubbia and van der Meer to receive the Nobel Prize the year after their discovery?
- What are the W and Z bosons and why did the electroweak theory require an accelerator powerful enough to produce them?
- What did the 1983 detection of the W and Z bosons confirm about the Standard Model?
- What did the Brookhaven experiment reveal about the muon neutrino versus the electron neutrino?
- Why does the existence of paired neutrino flavours imply that matter comes in generations?
- What other areas of physics did Feynman contribute to beyond quantum electrodynamics?
- What did the SLAC experiments observe when electrons bounced backward off protons, and why did that rule out a smooth proton?
- How did James Bjorken's predictions guide the interpretation of the electron-proton scattering data?
- Why couldn't quarks simply be seen directly in a detector, and what had to be inferred instead?
- What in Martin Perl's SLAC data pointed to a completely new charged lepton rather than an error in the apparatus?
- Why didn't the Standard Model predict the existence of the tau lepton?
- Why did it take two decades after its prediction to actually find the top quark?
- How heavy is the top quark compared to the other five quarks, and why does that matter?
- Why does the top quark's extremely short lifetime make it easier to measure precisely?
- What did it mean for atmospheric muon-neutrinos to 'oscillate' into tau-neutrinos as they passed through the Earth?
- What is asymptotic freedom, and why does it mean quarks behave as if free at short distances?
- How did Kobayashi and Maskawa predict the existence of two undiscovered quarks from an asymmetry in particle decays?
- Why would the universe contain nothing but radiation if matter and antimatter had been produced in perfectly equal amounts?
- When was the sixth and final predicted quark, the top quark, actually confirmed experimentally?
- What did Murray Gell-Mann propose in 1964 about the internal structure of protons and neutrons?
- Where did Gell-Mann get the word 'quark,' and why did he choose it?
- What did Yang and Lee argue in 1956 about parity conservation in the weak nuclear force that no one had tested?
- How did Chien-Shiung Wu's experiment confirm that parity is violated in weak interactions?
- What is the muon's magnetic moment (g-2), and why do virtual particles alter it?
- Why does the gap between the Standard Model's prediction and the measured muon g-2 value matter for finding new physics?
- What experiments at CERN, Brookhaven, and Fermilab contributed to measuring the muon's magnetic moment over three decades?
- What is asymptotic freedom, and how did David Gross's work on it explain quark behavior at short distances?