Particle Physics
40 questions tagged Particle Physics — spanning every one of the seven Ws.
What is the Higgs boson?
The Higgs boson is a fundamental particle linked to the field that gives other particles mass. It was discovered at CERN in 2012, confirming a 1964 prediction.
What is antimatter?
Antimatter is made of particles with the opposite charge to ordinary matter. When matter and antimatter meet, they annihilate in a burst of pure energy.
What Is a Neutrino?
A neutrino is an electrically neutral, nearly massless subatomic particle that interacts with matter only through the weak nuclear force and gravity, making it extraordinarily difficult to detect.
What is baryogenesis?
Baryogenesis is the process that may have produced the small excess of matter over antimatter in the early Universe. Without it, the Universe could have ended up mostly as radiation.
What is a gauge boson?
A gauge boson is a particle that carries one of the fundamental forces in nature. Examples include photons, gluons, and the W and Z bosons.
What is the Standard Model of particle physics?
The Standard Model is the theory that describes the known fundamental particles and three of the four fundamental forces. It does not include gravity.
What is the Higgs field?
The Higgs field is an all-pervading quantum field that gives certain particles mass through their interaction with it. It is central to the Standard Model.
When was the first evidence of the Higgs boson announced?
On 4 July 2012, CERN announced the discovery of a new particle consistent with the Higgs boson.
When was the Standard Model of particle physics completed?
The Standard Model was essentially completed in the 1970s, with the discovery of the tau lepton in 1975 and the bottom quark in 1977.
When was the first neutrino detected?
In 1956, Clyde Cowan and Frederick Reines announced the first detection of the neutrino.
When were the W and Z bosons discovered?
In 1983, CERN experiments discovered the W and Z bosons, confirming the electroweak theory.
When was the first evidence for neutrino oscillation reported?
In the 1990s, experiments such as Super-Kamiokande reported strong evidence that neutrinos change flavor.
Which fundamental force is mediated by the W and Z bosons?
The weak nuclear force is mediated by the W and Z bosons. These particles were discovered in 1983 at CERN.
Which fundamental force changes quarks from one type to another in beta decay?
The weak force changes quark flavor in beta decay. For example, a down quark can turn into an up quark.
What is quantum chromodynamics?
Quantum chromodynamics, or QCD, is the theory that describes the strong interaction between quarks and gluons. It explains how protons, neutrons, and other hadrons are built.
What is a proton?
A proton is a positively charged particle found in the nucleus of an atom. It is made of quarks and is one of the main building blocks of ordinary matter.
When was the Higgs boson discovered?
In 2012, CERN’s ATLAS and CMS collaborations announced the discovery of a Higgs-like particle. It was later confirmed as the Higgs boson.
Where is the Large Hadron Collider built?
The Large Hadron Collider is built at CERN, on the France–Switzerland border near Geneva. Its 27-kilometer ring lies underground in a tunnel about 100 meters deep on average.
Where is the Higgs boson studied at the Large Hadron Collider?
It is studied in detectors such as ATLAS and CMS at CERN near Geneva. The Higgs boson was announced there in 2012 after collisions in the LHC.
Which fundamental force is described by quantum chromodynamics?
The strong nuclear force is described by quantum chromodynamics, or QCD. QCD explains how quarks interact through gluons.
Which force is thought to be mediated by gluons?
The strong nuclear force is mediated by gluons. Gluons bind quarks together inside protons and neutrons.
Whose idea explained the strong force inside the atomic nucleus using color charge?
Murray Gell-Mann helped develop the quark model and color-based ideas of the strong interaction. His work led to modern quantum chromodynamics.
Whose model unified electricity, magnetism, and the weak force?
Abdus Salam helped develop electroweak theory in the 1960s. The theory unifies the electromagnetic and weak interactions.
Whose work predicted the existence of the positron before it was seen?
Paul Dirac predicted antimatter in 1928. The positron was discovered a few years later in 1932.
Whose discovery identified the carrier of the strong force between quarks?
Murray Gell-Mann’s framework and later quantum chromodynamics identified gluons as the force carriers. These particles bind quarks together.
Whose discovery revealed the antiproton?
Emilio Segrè and Owen Chamberlain discovered the antiproton in 1955. It confirmed the existence of antimatter counterparts to ordinary particles.
Whose calculations predicted the Higgs boson before it was found?
Peter Higgs helped propose the mechanism that gives particles mass in 1964. The Higgs boson was discovered at CERN in 2012.
Whose discovery showed that neutrinos have mass?
Takaaki Kajita led major results from Super-Kamiokande in 1998 showing neutrino oscillations. Those oscillations imply that neutrinos have mass.
Whose discovery helped establish the first evidence for a neutrino?
Clyde Cowan and Frederick Reines detected the neutrino experimentally in 1956. The particle had been proposed decades earlier by Wolfgang Pauli.
How do particle accelerators help test the fundamental forces?
They smash particles together at very high energies so physicists can see force carriers and new particles. Higher energy means probing smaller distances.
How does the Higgs field give particles mass?
Particles interacting with the Higgs field behave as if they have inertia, and the Higgs boson is the field’s detectable particle. The Higgs boson was discovered at CERN in 2012.
Why do some particles have electric charge while others do not?
Electric charge is a fundamental property of certain particles, built into the laws of physics rather than caused by something simpler. Charged particles interact with electromagnetic fields; neutral ones do not, or do so only weakly.
When was the Higgs boson first proposed?
It was proposed in 1964, in papers by several physicists including Peter Higgs.
When was antimatter first predicted?
Antimatter was first predicted in 1928 by Paul Dirac.
When was the positron first discovered?
It was first observed in 1932 by Carl Anderson.
When was the first observation of beta decay energy loss explained with the neutrino idea?
Wolfgang Pauli proposed the neutrino in 1930, and Enrico Fermi developed the beta-decay theory in 1933–1934.
When was the first evidence for the existence of quarks published?
Strong evidence was published in 1968 from deep inelastic scattering experiments at SLAC.
Where is the world’s best-known neutrino beam sent from?
One of the best-known neutrino beams is produced at Fermilab near Chicago, Illinois. It sends particles toward detectors in long-baseline experiments.
Which force is the only one that can change one type of quark into another?
The weak nuclear force can change quark flavour, turning one type into another. That is why it can cause radioactive beta decay.
Which force is mediated by gluons?
The strong nuclear force is mediated by gluons. Gluons carry the color charge that binds quarks together.