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The Subatomic Zoo

The Subatomic Zoo. Atomic Physics. Physicists believe (hope?) they will eventually show that these are all different manifestations of single fundamental force (aka Grand Unified Theory or GUT). strong nuclear force is very large over a short distance (x10 -8 m) which is the size of a nucleus

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The Subatomic Zoo

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  1. The Subatomic Zoo Atomic Physics

  2. Physicists believe (hope?) they will eventually show that these are all different manifestations of single fundamental force (aka Grand Unified Theory or GUT).

  3. strong nuclear force is very large over a short distance (x10-8m) which is the size of a nucleus - to separate the parts of the nucleus, scientists need very large energies • cosmic rays – energies of 102 – 1014 MeV - are EM photons protons, - antiprotons, electrons positrons, alpha particles

  4. Subatomic Particles ( > 300) • Muons – unstable particles having similar properties to electrons but 207 x the mass • Discovered in cosmic rays observed in cloud chambers • Pion – unstable particle – 270 x mass of the electron

  5. The Large Hadron Collider at CERN can accelerate protons to an energy of about 7 TeV (7 x 1012 eV) each, or lead nuclei to about 574 TeV per nucleus. • Beams of protons, moving in opposite directions, will be collided (each beam moving very close to c). http://www.youtube.com/watch?v=j50ZssEojtM • CERN on Wikipedia

  6. CERN and the movies • In the movie Angles and Demons, a container with ½ g of antimatter is stolen from CERN, to be used as a bomb which would produce a sizable boom. • CERN does produce antimatter, but much less than ½ g. (x 10-14g)

  7. Two Separate Families • Leptons – subatomic particles that do not interact by means of the strong nuclear force • eg) electrons, neutrinos, muons • Hadrons – subatomic particles that do interact by means of the strong nuclear force • eg) protons and neutrons

  8. Hadrons are divided into 2 groups based upon spin 1. Mesons – hadron with an integer spin eg(0, 1, or 2) eg) pion 2. Baryons- hadron with a half integer spin eg (1/2, 3/2) eg) proton or neutron

  9. Text: p. 842 – 843 tables • *Fermions – a particle with a half integer spin – all leptons and baryons • Bosons – a particle with an integer spin

  10. Mass of Subatomic Particles • Too small to be measured in kg • Measured in energy/speed squared • Based upon:

  11. Reminder: Converting units • 1. Mass into u (atomic mass units-amu) 2. Atomic mass units into Energy 3. Energy into eV.

  12. Masses of subatomic particles are expressed in MeV/c2 • Eg) electron Divide charge by speed of light squared Divide mass by 1 u Divide mass in kg by 1.78x10-36 • Eg) proton

  13. Quark • any group of fermions or fundamental particles in hadrons

  14. Quarks for real • Hadrons(protons and neutrons) are believed to be composed of 3 smaller particles • All known hadrons were first believed to be composed of these particles and their antiparticles

  15. Charge on Quarks • Quarks have fractional charges of 1/3 or 2/3 the charge of an electron or proton • Scattered electrons suggested the mass and charge of a proton were concentrated in 3 centers • Only protons and neutrons contain up and down quarks

  16. Composition of a Proton and Neutron • The proton and neutron are both made up of three quarks. Proton: up up down (uud)     charge = +2/3 +2/3 -1/3 = +1 Neutron: down down up  (udd)    charge = -1/3 -1/3 +2/3 = 0

  17. Example • A hypothetical hadron has a charge of +2. Determine the up and down quarks that make up this hadron. Up: +⅔ e Down = -⅓ e • +⅔ e + +⅔ e ++⅔ e = +2 • particle composition: uuu

  18. Some other examples • Pion : (πo): uu • Pion (π+ ) : ud • sigma-plus (Σ+ ) : uus • sigma-minus (Σ− ) : dds • anti-proton (p− ) : uud • See page 847

  19. Beta Decay Using Quarks and Leptons • Beta decay emits a high energy electron or positron • β- decay – neutron transforms into a proton and an electron and antineutrino ( ) are emitted • Change is:

  20. The decay is actually described as Virtual mediating particle that decays into an electron and a antineutrino

  21. β+ Decay • β+ decay – proton transforms into a neutron and a positron and a neutrino are emitted • Change is:

  22. Diagrams to describe Beta Decay

  23. Quark version: • In beta plus decay an up quark changes into down quark while in beta minus decay an down quark changes into a up quark. NOTE: The "mass" of the up and down quarks is 360 MeV. Three of them in a proton gives a mass of 1080 MeV. The mass of the proton is around 930 MeV giving a sort of binding energy of 150 MeV.

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