Particle Physics - A2 - OCR

Particle Physics - A2 - OCR

1. Hadrons

   • Baryons
     • Nucleons - protons and neutrons
     • All baryons decay to protons
     • Baryon number
       • the number of baryons in a reaction never changes
       • The proton and neutron each have a baryon number of 1
   • Mesons
     • They are unstabe
     • Baryon number
       • All mesons have a baryon number of 0 as they aren't baryons
     • Pions and Kaons
       • Pions are the lightest mesons
         • There are 3 types with different charges - π0, π+, and π−
       • Kaons are heavier and more unstable
         • There are also 3 types with different charges - K+, K0, K−
   • Hadrons are particles that are held together by strong nuclear force

2. Letptons

   • Leptons do not feel the strong nuclear force.
   • There are 3 types of Lepton - electron, muon and tau which all have a leton number of 1
     • the electron, muon and tau all have a charge of -1
     • Neutrinos - these have almost zero mass and zero electric charge
       • each types of lepton has a neutrino form as well, with a charge of 0
       • they have the same lepton number as the non neutrino form though

3. Anti particles

   • Every particle has an anti particle, that will have opposite charge, but the same lepton or baryon number
   • Mesons are their own antipartices
   • Energy can be converted into matter as E=mc2
     • However, when energy is converted into matter, you will produce equal amounts of anti matter and matter
   • Particle-Antiparticle Pair is produced from a single photon, if there is enough energy
   • Pair Annihilation happens when a particle meets an antiparticle, all the mass is converted to energy
     • For instance an electron and positron will combine to form a gamma ray

4. Quarks

   • Quarks are the fundamental particles, that make hadrons
     • There are many types - up, down and strange (the ones to know) and a few others called top,bottom and charm
     • Baryons are made from 3 quarks
       • Protons-uud
       • Neutron-udd
       • antiprotons and antineutrons are made up of the equivalent antiquarks
   • Antiparticles are made up of antiquarks
     • Note: antiquarks have the opposite charge and baryon number!
   • Quarks have charge and a baryon number - strange also has a strangeness value of 1
     • Charge: Up=+2/3 Down=-1/3 Strange=-1/3
     • Baryon Number: all =+1/3
   • Mesons are a quark and an antiquark
     • Pions are made from up and down quarks
     • Kaons have strangeness