7.3 the structure of matter - wikispacesthe+structure... · 7.3 the structure of matter 2 quarks...
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7.3 The Structure of Matter 2 Quarks Leptons & Antiparticles.notebook
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May 18, 2016
Particles are either:
FUNDAMENTAL (meaning they have no internal structure)
OR COMPOSITE (meaning they are composed of some combination of the fundamental particles)
THE ELECTRON, THE NEUTRINO AND THE QUARKS ARE FUNDAMENTAL.
ATOMS, NUCLEI, PROTONS, AND NEUTRONS—THESE ARE ALL COMPOSITE.
7.3 The Structure of MatterQuarks, leptons & their antiparticles
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7.3 The Structure of Matter
Quarks and leptons, are fundamental particles. They are not thought to be composed of any smaller particles.
Hadrons, such as protons and neutrons, are composed of quarks. All of these matter particles are referred to as Fermions.
Quarks, leptons & their antiparticles
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7.3 The Structure of MatterLeptons & their antiparticles
Leptons are fundamental particles such as the electron. They are called leptons as they are considered to be lightweights, although the muon is as massive as a meson and the tau has a greater mass than a gold atom.Leptons do not feel the strong force. They only feel the weak force (beta minus decay is a good example) and the electromagnetic force. With each lepton there is an associated Neutrino. Neutrinos only feel the weak force as they have no charge.The only stable lepton is the electron. The muon and the tau are highly unstable with very short life times.
7.3 The Structure of Matter 2 Quarks Leptons & Antiparticles.notebook
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7.3 The Structure of MatterHadrons Baryons Hadrons are composite particles made of
quarks. Although individual quarks have fractional electrical charges, they combine such that hadrons have a net integer electric charge (1, 1 or 0).
Quarks, like leptons are fundamental particles which build up matter. The class of Hadron called Baryons consist of 3 quarks. Baryons build up nuclei.
Using your table in your formula booklet, work out the charge of each baryon on the left.
Λ
p p
n
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7.3 The Structure of MatterHadrons Mesons Mesons are hadrons that are made up
of one quark and one antiquark.
Mesons come in many different varieties. Three of them are pi mesons (pions), K mesons (kaons) and J/ψ mesons (psi/J).
A quark and its own antiquark particle annihilate each other so their lifetime is very short.
Using your table in your formula booklet, work out the charge of each baryon on the left.
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7.3 The Structure of Matter
Mesons
Mesons can be positively or negativelycharged or neutral. The charge is represented by a superscript number after the symbol for the meson. The symbols for the pi and K mesons are: π+, π–, π0, K+, K–, K0.
K mesons have some unusual properties that led to them being called ‘strange particles’ (contain a strange quark).
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7.3 The Structure of MatterQuarks, leptons & their antiparticles
Adding up the charge or strangeness for the quarks composing a hadron gives the charge or strangeness (the strange quark) of that hadron.
A hadron composed of two up quarks and a down quark (proton) would have charge 2/3 + 2/3 – 1/3 = +1 and strangeness 0.
7.3 The Structure of Matter 2 Quarks Leptons & Antiparticles.notebook
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7.3 The Structure of Matter
Build a MesonMesons are hadrons that are subatomic particles composed of one quark and one antiquark
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7.3 The Structure of Matter
Build a Baryon Three quark combinations are called baryons
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7.3 The Structure of Matter
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7.3 The Structure of MatterAnnihilation & Pair Production
Eo = rest energy
min energy of each photon is hfmin
The relationship between mass and energy can be seen when particles with mass become a massless photon (annihilation) or vice versa (pair production).
Annihilation
Pair Production
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7.3 The Structure of MatterQuantities conserved in particle interactions
A Baryon can not change into a lepton, Baryon numbers help to make that distinction if we only consider charge, a baryon could make that change.