1. Particles energy states
Particles decay, transform, change, behave like waves, emit energy and absorb energy as if they are energy states.
Particles include electrons, protons, neutrons, pions, kaons, J, D, Upsilon, sigma, rho, etc., some have strange names.
The study of particles is called particle physics or high-energy physics.
Particle studies proposed a standard model with a few fundamental components for all matter.
Particles interact with via a force, and each force has a carrier. Fynman diagrams neatly represent these interactions.
See particleadventure.org/particleadventure/other/othersites.html for more info
Particles

2. Particles particles and antiparticles
Antiparticles of electrons, positrons, have been introduced in the discussion of beta decay.
Theory about particles and antiparticles is simple and symmetric. Particles and antiparticles have the same mass, but opposite electric charge, and magnetic moment.
Some questions regarding particles:
Do all particles have corresponding antiparticles as do electrons?
Do neutral particles such as neutrons have antiparticles?
Particles

3. The Particle-antiparticle Concept
Dirac's energy equation from Einstein's equation
E = m c2 = m0 c2 (1 - (v/c)2)-1
E 2 = (m c2)2
= m02 c 4/(1-(v/c)2)
From this, he has
(m c2)2 - m 2 v 2c 2 = m02 c 4
Thus, (p = m v)
E 2 = p 2 c 2 + (m0 c 2)2
Therefore
E + = [p 2 c 2 + (m0 c 2)2]1/2
E - = -[p 2 c 2 + (m0 c 2)2 ]1/2
Ignore the formula box if you find the equations hard to follow.
Dirac combined theory of relativity with quantum mechanics to get a theory, that predicted a new state for an electron whose energy becomes more negative as the electron increases speed. He worked out the wave functions for such a positive electron, and called it antiparticle.
Particles

4. The Particle-antiparticle Concept (continue)
In a vacuum, all negative-energy states are occupied, and positive energy states are empty. Fully occupied or unoccupied states are unobservable
A pair of particle and antiparticle
Singly occupied states are observable
Particles

5. Particle Antiparticle Annihilation
Unstable particle-antiparticle pair
Return of particle to negative-energy state
Particle-antiparticle annihilated
2hv
Particles

6. Discovery of Antiparticle
C.D. Anderson observed tracks of positive electrons in his cloud chamber in 1932, and called them positrons, antiparticle suggested by Dirac.
Particles

7. Generalizing the Antiparticle Concept
In particle physics, every particle has a corresponding antiparticle.  A particle and its antiparticle have identical mass and spin.
A particle and its antiparticle have opposite signs for nearly all non-zero quantities such as: electric charge, (abstract) flavor, electron number, muon number, tau number, and baryon number.
We call commonly observed particles such as protons, neutrons, and electrons "matter" particles, and their antiparticles are “antimatter”
Matter: anything built from quarks, negatively charged leptons and left-hand neutrinos
Antimatter: anything built from antiquarks, positively charged leptons and right-handed neutrinos.
Particles

8. annihilation and pair production
At the ends of positron tracks, two tracks appeared due to gamma photons in annihilation.
A year later, electron-positron pair productions were observed at track ends of high-energy photons.
Particles

9. Generalized annihilation and pair production
Whenever sufficient energy is available to provide the mass(energy), a particle and its antiparticle can be produced together, obeying the conservation laws in all processes.
When a particle collides with its antiparticle, they may annihilate – they disappear and combine into a boson (a carrier particle of interaction forces).
The boson may decay (change to) into other particles and antiparticles.
Particles

10. The discovery of protons and antiprotons
The discovery was made by observing a bubble chamber photo of antiproton annihilation.
Antiproton: same mass as proton, 932 MeV. present in accelerators and cosmic rays annihilated with proton to give a set of starburst of particles (pions).
p + p  4 p– + 4 p+
Particles

11. Eight (8) pions were produced in this process.
The actual bubble chamber photograph of an antiproton (entering from the bottom of the picture) colliding with a proton at rest and annihilating.
Eight (8) pions were produced in this process.
One decayed into a m+ and a n. The positive and negative pions curve different ways in the magnetic field.
Particles

12. The Discovery of Antineutrons
This bubble-chamber picture, taken in 1958, demonstrated the existence of the antineutron, n.
At the point marked by the arrow, an incoming antiproton beam particle undergoes the `charge exchange' reaction p + p --> n + n The kinetic energy of the interacting antiproton is estimated to be ~50 MeV.
The n formed in the process travels an actual distance of 9.5 cm before annihilating in a characteristic `annihilation star‘. n + p --> 3 p p-
The energy released is > 1500 MeV.
See L. E. Agnew et al, Phys. Rev., 110 (1958) 994
Particles

13. Particles and the standard model
Two types of fundamental particles are leptons and quarks. Charged particles interact via gauge bosons, and quarks via strong-force carriers called gluons.
Particles

14. The Standard Model Leptons Quarks
Particles are grouped into families – leptons and quarks.
Leptons
Quarks
Electron e-neutrino
Up Down
These are found inside 3rd generation matters
muon m -neutrino
Charm Strange
tau t -neutrino
Top Bottom
The Standard Model (a theory?) is the name given to the current theory of fundamental particles and how they interact.
Particles

15. Crossing Symmetry in Particle Interactions
In a particle interaction A + B  C + D energy (and mass), momentum, baryon number, lepton number, and charge are conserved.
The crossing symmetry suggests that any of the particles can be replaced by its antiparticle on the other side of the interaction A  B + C + D (X is antiparticle of X) A + C  B + D C  D + A + B C + D  A + B
The crossing symmetry allows us to see different phenomena as the same interaction.
Particles

16. quarks as fundamental particles
The study of particles, their relationships and classification led to the idea that some fundamental particles smaller than protons and neutron exist.
A mathematical theories support their existence.
The fundamental particles are called quarks.
Particles

17. mesons and baryons Mesons and baryons are collectively called hadrons.
Mesons consist of a quark and antiquark.
Baryons consist of three quarks.
Relations of some mesons and baryons are shown here.
Particles

18. properties of mesons
Name Symbol Mass* Lifetime (s)
Pi-zero p e-16 Pi-plus p e-8 Pi-plus p e-8
K-zero K e-8 to 1e-10 K-plus K e-8 K-zero K e-8
J/psi J/ e cc# D-zero D e cu D-plus D e cd Upsilon Y e bb
* mass in MeV #quarks
Discovery in 1974 of J confirmed the charm (c) quark. D’s were discovered in 1976, and upsilon in 1977, conformed the bottom (b) quark.
Particles

19. discovery of mesons kaons and pions
Particles

20. decays of kaons K0  2  or  p+ + p–
K+ + + v or  p+ + p0 or  p+ + p++ p– or  p0 + e+ + ve
K– – +  or  p– + p0 or  p– + p++ p– or  p0 + e– + ve
o   +  p +  e+ + e p –  e– + e
Particles

21. four forces and force carriers
Particles interact with each other via a force. Particles responsible for the delivery of force are force carriers.
Feynman invented a method to represent the interaction.
Gravity, electromagnetic (e & m), weak, and strong are the 4 forces, each has its type of carriers.
Particles

22. four types of force carriers
Gravity e & m weak strong
Carrier graviton photon W+, W-, Z gluons (g)
Mass MeV ~0
Charge , -1, 0 0
Spin unknown
strength 1e /137 1e
Decay of weak force carriers half-life 1e-25 s
W  e,n; m,n; t,n
Z  e+,e-; m+,m-
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23. Feynman diagrams
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24. Particles

25. The Standard Model of Fundamental Particles and Interactions Chart
copyright 1999 by the Contemporary Physics Education Project. We grant permission for teachers and students to print these copyrighted images for their personal or classroom use.
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26. Particles

27. Particles

28. Particles

29. Neutron Beta Decay
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30. Particles

31. skills acquired for particles
describe the concept of particles and antiparticles
explain energy aspects of particles and antiparticles
explain how positron was discovered
specify properties of antiparticles - particularly positrons
explain annihilation reactions
describe the standard model in terms of fundamental particles
show organization and components of mesons
forces and force carriers
draw Fynman diagrams
Particles

32. Particles – energy states
Particles decay, transform, change, behave like waves, emit energy and absorb energy as if they are energy states.
Particles include electrons, protons, neutrons, pions, kaons, J, D, Upsilon, sigma, rho, etc., some have strange names.
The study of particles is called particle physics or high-energy physics.
Particle studies reveal a standard model with few fundamental components for all matter.
Particles interact with via a force, and each force has a carrier. Fynman diagrams neatly represent these interactions.
Particles

33. Ingredients for a Midnight Snack
Particles

34. SCI270 Midterm Examination Room Assignment for Feb. 11, 2004
Room ID number start with
P-150 (50) 0000xxxx – 2006xxxx
P-313 (50) 2007xxxx – 2011xxxx
P-145 (100) 2012xxxx – 9999xxxx
Particles