Weak nuclear force (also calledweak forceOr weak interaction)Fundamental forceThe other three are strong nuclear force, electromagnetic force and gravitational force.Subatomic particleOfRadioactive decayIt is caused by it. One of the stars is calledHydrogen fusionIt also initiates the process of.Weak interactionWill affect allFermion, i.e. allspinHalf odd number of particles.
Weakly interacting particles: W and Z bosons - internal structure model diagram
stayParticle physicsOfStandard modelThe theory of weak interaction points out thatW and Z bosonsThe weak force is caused by the emission (or absorption) of bosons, so it is aNon-contact force。The most famous of these launches isBeta decay, it isradioactivityA performance of.Heavy particles are unstable in nature. Since Z and W bosons are much heavier than protons or neutrons, the interaction distance of weak interaction is very short.This interaction is called "weak" because the probability of beta decay is much lower than that of strong interaction, which means that its general intensity ratioelectromagnetismandStrong nuclear forceSeveral weakOrder of magnitude。Most particles will decay through weak interaction after a period of time.The weak interaction has a unique characteristic that isquarkTaste changes - other interactions cannot do this.In addition, it will destroyParity symmetryandCP symmetry。The flavor change of quarks enables quarks to“taste”Interchangeable.
The earliest description of weak force is in the 1930s, which is fourFermionContact interactingFermi theory: Contact refers to no operating distance (i.e. completely physical contact).But now it is better to describe it in terms of a field with an effective distance, although that distance is very short.In 1968, electromagnetic and weak interaction were unified. They are two aspects of the same force, now calledWeak current interaction。
Weak interaction in theBeta decayIs the most obvious in hydrogen productionDeuteriumandheliumThe process (energy source of star thermonuclear reaction) is also very obvious.Radiocarbon datingThis is the decayCarbon-14Decay through weak interactionNitrogen - 14。It can also createRadiant cold light, common inSuperheavy hydrogenLighting;Has also createdBeta voltThis application field (Beta rayThe electrons of are used as current).
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The weak interaction has several characteristics as follows:
The only interaction that can change the quark flavor.
The only commandParityNonconservative interactions.So it's also the only violationCP symmetryInteraction.
There are two kinds of weak interactions.The first is called“Load flow interaction”Because the particles responsible for transmitting it are charged（W+or W −）β decay is caused by it.The second is called“Neutral current interaction”, because the particles responsible for transmitting it,Z boson , is neutral (not charged).
Load flow interaction
In one of the load current interactions, the chargedLepton(e.g. electron or muon, with charge of − 1) can absorbW+Boson(the charge is+1), and then converted into the correspondingneutrino(The charge is 0), and the type (generation) of neutrinos (electrons, μ and τ) is consistent with that of leptons before interaction.
Neutral current interaction
In neutral current interaction, a quark or lepton (such as an electron or muon) emits or absorbs a neutralZ boson 。For example:
Like the W boson, the Z boson also decays rapidly, such as:
According to the weak electricity theory, when the energy is very high, there are four kinds of masslessGauge bosonFields, which are similar to photons, have a complex vectorHiggs fieldDouble state.However, when the energy is low, gauge symmetry will appearSpontaneous breakage, become electromagnetically interactingU(1)Symmetry (one of the Higgs fields hasVacuum expectation）。Although thisSymmetry breakingThree massless bosons will be generated, but they will fuse with three photon like fields, soHiggs mechanismWill bring quality to them.These three fields become the weakly interacting W+, W − and Z bosons, while the fourth gauge field remains massless, that is, the photon of electromagnetic interaction.
On March 14, 2013, the European Organization for Nuclear Research issued a press release, officially announcing the detection of a new particle, the Higgs boson.
