夸克

Negatively charged electron circles around in circular orbits Much more massive nucleus contains electrically neutral neutrons and positively charged protons Simplified View of Atom Extended View  Electron is still fundamental particle (lepton)  Proton and neutron now thought of as being collection of quarks and the gluons hold them together

夸克是什麼 ? 物質是由基本費米子 (Fermions) 叫夸克 (quarks) 和 輕子 (Leptons) 組成的。這些費 米子的相亙作用力是經由交換 波色子 (Bosons) 所產生的。

 Matter and energy are interchangeable  Matter can be converted to energy by E=mc 2, where m is the mass of the matter being converted (in kg), c is the speed of light (3 x 10 8 m/s), and E is the amount of energy (in J). For example a 1kg block, if converted entirely into energy would be 9x10 12 kJ (about 21 megatons of TNT or 1600 Hiroshima nuclear bombs!)  Mass no longer needs to be conserved because it can become energy  Energy does not need to be conserved because it can become mass  Instead, the sum of mass and energy (mass energy) is conserved There are four different forces governing all interactions and each force is transmitted through its force particle GGravity (graviton) EElectromagnetism (photon) WWeak Force (Weak Nuclear Force) (weak gauge bosons) SStrong Force (Strong Nuclear Force) (gluon)

Three Groups of Elementary Particles Bosons – particles that transmit forces (Gluon is responsible for Strong interactions) Leptons – particles that do not participate in Strong interactions Quarks – particles that individually participate in Strong interactions, cannot be individually isolated

夸克 Rest Mass ( MeV/c 2 ) Charge Date Discovered Up 52/31968 Down9-1/31968 Strange 170-1/31964 Charm 14002/31974 Bottom4400-1/31977 Top /31995

Mass? How do you find the mass of a particle you can’t isolate? Physicists find the apparent mass of a quark based on its tendency to be accelerated.

Accelerators Electric fields accelerate the proton and anti-protons in opposite directions Magnetic fields keep the particles in a circular path Electric fields accelerate the proton and anti-protons in opposite directions

In the case of the up and down quarks, the most salient evidence was in the inelastic scattering of electrons aimed at neutrons or protons, suggesting a substructure of each The existence of the strange quark was postulated when research was being conducting with proton-nucleus collisions. The “lambda” particle (discovered in 1947) produced from these collisions could not have been made up of only up and down quarks based on color neutrality, mass, and charge The psi/J particle discovered in 1974 could not have been made from the existing 3 quarks for similar reasons. Even more energetic proton collisions yielded the upsilon particle, which was concluded to be made of bottom quarks for similar reasons.

The top quark was discovered by analyzing the particles it very quickly decays into

A Proton/Anti-Proton Collision

Kind of…. The quark model is the best explanation for the observed phenomena, but no quark has ever been directly observed because of…  Quarks are bound very tightly inside larger particles meaning it takes a lot of energy to separate them  If you put energy into the system, it produces quark-antiquark pairs long before there is enough energy to separate a quark A Proton Energy is put into the proton to separate a quark Before there is enough energy to separate the quark, the energy goes into producing quark- antiquark mesons

"Truth decays into beauty, while beauty soon becomes merely charm. Charm ends up as strangeness, and even that doesn't last, but up and down are forever." - The Laws of Physics (James Walden) Top and bottom were allegedly called “truth” and “beauty” at one point, which made the above quote a valid description of quark behavior Apparently, the names “truth” and “beauty” were too quaint even for the physicists who study them – the ‘t’ and ‘b’ came to stand for “top” and “bottom” instead The name is said to have been taken by Murray Gell-Mann from the novel Finnegan's Wake by James Joyce. The line in which the word “quark” appears is, “Three quarks for Muster Mark…”. Gell-Mann received the 1969 Nobel prize for his work in quantum physics.

資料來源 Deutches Electronen-Synchotron, © 2003, Deutches Electronen-Synchotron, © 2003, Raycomm.com, Peter Bancel, © 2003, html Raycomm.com, Peter Bancel, © 2003, html html html “ The Elegant Universe ”, NOVA Public Broadcasting Service (PBS), © 2003, “ The Elegant Universe ”, NOVA Public Broadcasting Service (PBS), © 2003, Stanford Linear Accelerator Center, © 2003, Stanford Linear Accelerator Center, © 2003, Fermi National Accelerator Laboratory, © 2001, Fermi National Accelerator Laboratory, © 2001, HyperPhysics, © 2000 CR Nave, Georgia State University, HyperPhysics, © 2000 CR Nave, Georgia State University, “ Rutherford Atomic Model ”, Encyclopedia Britannica online, © “ Rutherford Atomic Model ”, Encyclopedia Britannica online, ©