Modern Studies of the Atom

1. Modern Studies of the Atom

2. Hideki Yukawa- 1935- Theorized that a particle passes back and forth between protons and neutrons to hold the nucleus together. Predicted the existence of a particle called a meson (also known as pions). The meson was observed in 1947.

3. Enrico Fermi-1934- Theorized that a neutral particle is emitted during beta decay which he called the neutrino. Cs →  Ba  +  e−  +  ν (beta decay) electron neutrino Neutrino- tiny neutron – Observed in 1956

4. Radioactive Decay _________ Alpha _______ Beta _____ Gamma

5. Paul Dirac -late 1920s Theorized that electrons should be expected in two energy states, one positive and one negative. He called these antiparticles. Antiparticles-Mirror image of each particle. Particle have the same mass but the opposite charge.(ie: electron and positron)

6. Annihilation Depends on frequency When Matter meets antimatter annihilation occurs. Energy and radiation is given off. http://www.youtube.com/watch?v=fT2TSL5Q0s8

7. Pair Production When gamma rays pass close to nucleus, a particle and antiparticle are formed.(requires 1.02MeV or more of energy)

8. The Standard Model Particles made of quarks electrons Protons and neutron

9. QUARKS • Fundamental particle of the standard model. • 6 types or flavors. • Have charge. • Can’t exist on their own. • Make up Baryons and Mesons.

10. TERMS Hadrons- anything composed of quarks Mesons-subatomic particles composed of a quark and antiquark. Baryons- particles formed by three quarks. Includes protons and neutrons. Leptons- Doesn’t have quarks. Includes electrons, muons, Tau, neutrino and antiparticles.

11. QUARKS Up (u) +2/3 Down(d) -1/3 Charm (c) +2/3 Strange(s) -1/3 Top (t) +2/3 Bottom (b) -1/3

12. DATES OBSERVED up- 1964 Down- 1964 Strange- 1964 Charm-1975 Bottom- 1977 Top- 1995

13. Neutrons are made of 2 down quarks and one up quark. (udd) (+2/3) + (-1/3) + (-1/3) = 0 Protons are made of 2 up quarks and one down quark. (uud) (+2/3)+(+2/3)+(-1/3) = +1

15. Strong Force-Short range force that holds quarks together in the nucleus and keeps protons in nucleus Electromagnetic force- Attractive and repulsive force between charges. Binds the electrons to the nucleus.

16. Weak Force-Responsible for formation of elements and release of nuclear energy and beta decay. Gravitational force-Weakest of four forces. Force due to the mass of the atom.

18. Gluon- the exchange particle between quarks http://www.youtube.com/watch?v=V0KjXsGRvoA

19. Higgs Boson The Higgs Boson is the only Standard Model particle that has not been observed. The Higgs boson would help explain the origin of mass in the universe. If the Higgs boson exists, it completes the standard model. http://www.youtube.com/watch?v=x4BzBvk0MXk

20. PARTICLE ACCELERATORS Cyclotron- E.O. Lawrence accelerated protons to a very high speed and projected them into a stationary target.

21. Synchrotron Similar to a Cyclotron. Particle experience a higher magnetic field therefore moves at a higher speed. Fermi National Accelerator Lab- Batavia Illinois- Tevatron- 4miles wide- Accelerates protons to 99.9% speed of light. Uncovered the top quark

22. Linear Accelerator Particles are accelerated as they pass through a series of conductors. Longest is in Palo Alto California. Its 3.3 km long and buried 7.6m underground.

23. Particle Colliders Instead of a stationary target, this aims two high speed particles at each other and detects particles that are emitted. CERN- French-Swiss collider that is sponsored by 19 European countries in hopes of locating the Higgs-Boson particle. (17miles wide and 574ft deep) http://www.youtube.com/watch?v=dw3KuNgD-jE

24. Standard Model Limitations

25. The standard model doesn’t predict the mass of the fundamental particles that make up luminous matter. • Doesn’t predict the existence of dark matter • Key particles have not been directly observed. Their existence is inferred by experimental observations. • 1% discrepancy in how the neutrino behaves. Due to results, they feel there may be an unknown force or particle influencing it.

26. Dark Matter • Dark matter is matter that doesn’t emit or scatter light or other electromagnetic radiation. It cannot be directly detected. Dark matter is believed to make up 83% of the matter in the universe and 23% of the mass-energy. • Regular Matter makes up only 17% of all matter. http://www.youtube.com/watch?v=rJQtbKaZmMY

27. Dark Matter is not…. • Is not in the form of mass that we see. • is not made up of baryons. We know this because we would be able to detect baryonic clouds by their absorption of radiation passing through them. • dark matter is not antimatter, because we do not see the unique gamma rays that are produced when antimatter annihilates with matter.

28. Unanswered questions • Does the Higgs Boson particle exist? What are the implications if it does not? Is there only one type of them? • Are protons absolutely stable? If not, then what is the proton‘s half-life? • Why is there now more detectable matter than antimatter in the universe?

29. More questions • What governs the transition of quarks and gluons into mesons and baryons? • What is the nature of the nuclear force that binds protons and neutrons into stable nuclei and rare isotopes?