Investigations show that most cosmic rays were fast moving protons or small nuclei. They collide with gas atoms in the atmosphere, and create particles and antiparticles that can be detected on ground level. Some new types that were discovered were:
1) Muon: or heavy electron, negatively charged with a rest mass over 200 times the rest mass of an electron
2) Pion: or pi meson, positively or negatively charged or neutral and has a rest mass greater than a muon but less than a proton
3) Kaon: or K meson, positively or negatively charged or neutral and has a rest mass greater than a pion but still less than a proton
K mesons decay into muons and antineutrinos or antimuons and neutrinos
Charged pi mesons decay into muons and antineutrinos or anti muons and neutrinos
Muons and antimuons decay into electrons and antineutrinos or positrons and neutrinos
The decay always ibeys the conservation rules for energy and for charge.
Classifying particles and antiparticles
Particle Charge Antiparticle Charge Rest energy Interaction
proton +1 Antiproton -1 938 strong, electromagnetic
neutron 0 antineutron 0 939 strong
electron -1 positron +1 0.511 weak, electromagnetic
neutrino 0 antineutrino 0 0 weak
pi meso +1,0,-1 ............ -1,0,+1 140;135;140 strong, electromagnetic
muon -1 antimuon +1 106 weak, electromagnetic
K meson +1,0,-1 ............. -1,0,+1 494;498;494 strong, electromagnetic
Hadrons and Leptons
Hadrons are particles and antiparticles that can interact through the strong interaction
Leptons are particles and antiparticles that do not interact through the strong interaction
Leptons interact through the weak interaction and through the electromagnetic interaction if charged
Hadrons interact through the strong interaction and through the electromagnetic interaction if charged. Apart from the proton which is stable, hadrons decay through the weak interaction
The large hadron collider is a ring shaped accelerator that boosts the kinetic energy of the charged particles in the ring at several places round it. When they collide with other particles:
1) the total energy of the particles amd antiparticles before the collision= their rest energy + their kinetic energy
2) the total energy of the new particles and antiparticles after the collision = their rest energy + their kinetic energy
Using conservation of energy
the rest energy of the products=total energy before- the kinetic energy of the products
Baryons and Mesons
Baryons are protons and all other hadrons that decay into protons, either directly or indirectly
Mesons are hadrons that do not include protons in their decay products. In other words K mesons and pi mesons are not Baryons.
Matter and antimatter
Lepton Collisions and Neutrino Types
Leptons and antileptons can interact to produce hadrons. An electron-positron annihilation event can produce a quark and an antiquark whu=ich move away in opposite directions, producing lots of hadrons in each direction.
Muon and Electron neutrinos
Leptons can change into other leptons through the weak interaction and can be produced or annihilated in particle- antiparticle interactions.
1) in an interaction between a lepton and a hadron, an neutrino or antineutrino can change into or from a corresponding charged lepton.
2) in muon decay, the muon changes into a muon neutrino.In addition, an electron and an electron neutrino are created to conserve charge.
In any change, the total lepton number before the change is equal to the total lepton number after the change. In other words, the lepton number is conserved in any change.
Quarks and antiquarks - Strangeness
To explain why certain reactions were not observed, a strangeness number was introduced for each particle and antiparticle so that strangeness is always conserved in strong interactions. Non strange particles ( proton , neutron, pi meson, leptons) were assigned zero strangeness
Strangeness is always conserved in a strong interaction.
There are 3 different types of quarks and their corrosponding antiquarks. Up, Down and Strange.
Up Down Strange Antiup Antidown Antistrange Charge +2/3 -1/3 -1/3 -2/3 +1/3 +1/3
Strangeness 0 0 -1 0 0 +1
Quark Combinations and beta decay
Mesons are hadrons and consist of one quark and one antiquark.
Baryons and antibaryons are hadrons that consist of 3 quarks for a baryon, and 3 antiquarks for an antibaryon.
In beta- decay a down quark changes into an up quark
In beta+ decay an up quark changes into a down quark
1) Conservation of energy and conservation of charge apply to all changes in science
2) Conservation rules used only for particle and antiparticle interaction and decays are particle counting rules, based on what reactions are observed:
a) Conservation of lepton numbers- in any change the total lepton is the same before and after the change
b) Conservation of strangeness- in any strong interaction, strangeness is always conserved