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Particle Phyics Uni
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| Question | Answer |
|---|---|
| Name some rules for Feynman diagrams | 1. Time flows from left to right. 2. Particle in and particle out. 3. Vertices represent point of interaction, EM, weak, strong. 5. Must follow conservation laws. |
| What is the Standard Model? | Describes the three forces; EM, weak, strong and classifies all known elementary particles. |
| Name all four elementary particle families. | Quarks, Leptons, Gauge Bosons and Scalar Bosons. |
| Give examples on what properties the fundamental particles have. | Mass, charge, color charge, spin. |
| Name all six quarks , their charge and spin . Do it in the order of the generations. | G1: up, u: q = +2/3, down, d: q = -1/3. G2: charm, c: q = +2/3, strange, s: q = -1/3. G3: top, t: q = +2/3, bottom, b: q = -1/3. All spin 1/2. |
| Why is the top quark so special? | VERY heavy(heavier than some atoms). Does not form hadrons, decays too quickly. Couples to the Higgs Boson. |
| What is a hadron? | Particles made of quarks.Held together by the strong force. |
| What problem did the bottom quark help solve? | CP(conjugation-parity) violation. Involves B mesons.(and K?) |
| What is confinement and why does it happen? | No free quarks or gluons. More energetically favourable to be in confinement. |
| Hadrons are split into two groups. What are these and what makes them different? | Mesons* are made up of quark+antiquark. Baryons are made up of either 3 quarks or 3 anti-quarks. |
| There are two terms that specify the spin of particles. What are these? What particles are included? | Bosons(integer spin): Photons, W,Z bosons, Gluon, Higgs, Mesons. Fermions(half-odd integers):Baryons, Leptons., Quarks |
| Hadrons are ___ neutral. | Hadrons are color neutral. |
| What colors to quarks have? | Red, green, blue and the respective anti-colors as well. |
| What are quark mass states and flavor states? | u,c,t are mass states. d^f, s^f, b^f are flavor states. Each quark flavor is associated with a different mass, and these masses are not equal. |
| Mention something about B mesons and CP violation. | B mesons can oscillate between their matter and antimatter states, a phenomenon known as B-meson mixing. The rates of these oscillations can be different for matter and antimatter B mesons, leading to CP violation. |
| What are favored transitions and why are the favored? | Involves smaller CKM elements>more likely to occur. Same/neighbour quark generations. |
| What are supressed transitions and why are they not favored? | Involves largerCKM elements>lesslikely to occur. Different quark generations. |
| What are jets and how do they occur? | Relates to confinement of quarks gluons. Trying to separate them > more favorable to create q-anti q pairs instead > creates a stream of new quark pairs > this is the jet. Excludes top quark! |
| Give quark composition of all 3 of the pions. | π0 = uu^- - dd^- / sqrt(2). π+ = ud^-. π- = u^-d |
| Give quark composition of the proton and neutron, as well as their anti particles. | p = uud. n = udd. p ^- = u^-u^-d^-. n^- = u^-d^-d^-. |
| Give quark composition of all four Kaons. | K+ = us^-. K- = u^-s. K0 = ds^-. K0^- = d^-s. |
| Give quark composition of all lambda and it's anti particle. | Λ = uds. Λ^- = u^-d^-s^-. |
| What are quarkonias and Give quark composition of the phi, J/Ψ and Υ. | Quarkonias are quark-antiquark pairs. Φ = ss^-. J/Ψ = cc^-. Υ = bb^-. |
| Give quark composition of the delta and omega baryons. Clue: 3 in total, one double positive, two negative. Bonus, what is the charge for them? | Δ++ = uuu, q=+2. Δ- = ddd, q=-1. Ω- = sss, q=-1. |
| Give quark composition of all four D mesons. | D+ = cd^-. D- = c^-d. D0 = cu^-. D0^- = c^-u |
| Give quark composition of all four B mesons. | B+ = ub^-. B- = u^-b. B0 = db^-. B0^- = d^-b |
| What is the experimental evidence of color? | e+e- collisions. Ratio of produced hadrons muons correspond to factor 3, 3 colors. |
| What is the theoretical evidence of color? | Contradiciton Pauli Exclusion, quark theory. Pauli says wave function is anti-symmetric, quark said symmetric. Solution: introduce more degrees of freedom(color) > wavef. symmetric changing quarks and anti-symmetric when changing color. |
| What is the experimental evidence of quarks? | Inelastic scattering experiment. Formula of the cross section independent of momentum transfer, indicated that scattering was occuring off a point like charged particle inside proton. |
| What is the experimental evidence of gluons? | e+e- collisions, annhiliation gave quark-antiquark. Jets created. Sometimes there were 3 jets(thought 2), was possible to obtain gluon bremstrahlung. Gluon would split into quarks > more jets. |
| What are leptons and name them all(in the order of their families). | Elementary particles, respond only to electromagnetic force, weak force, and gravitational force, are not affected by strong force. Electron, electron neutrino. Muon, muon neutrino. Tau, tau neutrino. Plus their anti particles. |
| What is the charge of all leptons? | All -1 but neutrinos neutral. Anti leptons +1. |
| What force do the neutrinos interact with? Name something about their mass and speed. | Weak force(gravity too but irrelevant). VERY light particles and propagate almost speed of light. |
| What can the Tau decay into that is a bit special? | Hadrons. Most probable: pions + neutrino. |
| What are the three different type of neutrinos called? And what are they mixes of? | 3 flavors, is a mix of 3 mass states. |
| What is neutrino mixing? | The 3 flavor states couple to the W,Z bosons and the mass eigenstates have a definite mass. Particles that we observe through interactions with the other leptons, e,m,t, are linear combinations of the mass states. |
| What are neutrino oscillations? And what does is say about neutrinos? (specifically it's mass?) | Neutrinos change from one flavor to another as they propagate through space. This phenomenon is a clear indication that neutrinos have non-zero masses, |
| There's a specific particle that the neutrino does not couple to. And a certain field it doesn't interact with. Which one? | Does not couple to higgs boson or interact with higgs field., because they are left handed(spin opposite momentum). |
| How are the quark/neutrino mass states related to the flavor states? What has this to do with Cabibbo mixing? | Mass states are rotated with respect to flavor states by cabibbo angle > flavor states are linear combinations of mass states > give different coupling constants g > cabibbo mixing. |
| What are force carriers? Name all five(six) and what force they correspond to. | Particles that mediate the fundamental forces between other particles in the universe. Gluons(strong), photons(EM), Z and W+- bosons(weak), Higgs(higgs field). |
| The force carriers are split into two groups, what groups? | Gauge bosons(gluons, photons, W+-, Z) and Scalar bosons(Higgs). |
| The Higgs boson does something to other particles, what? What are the exceptions? | Gives mass to the fundamental particles, except photon. And neutrino? |
| Give some characteristics of the gluon. | q=0, spin=1, color change = 8 linearly indep. types (+1 = 9 total). Short range, size of nucleus, very strong here. . Couples to itself. |
| What is QCD? | Quantum chromodynamics, theory of the strong interaction between quarks mediated by gluons. |
| What is asymptotic freedom? | According to QCD, quarks and gluons behave almost like free particles when they are close together within a hadron. Strong force gets weaker the closer quarks and gluons are. In contrast to other forces. |
| What is screening? | In QED the EM attraction between two particles is weaker at large distances. |
| What is anti-screening? | In QCD the strong attraction between two particles is weaker at short distances. |
| What are coupling constants? | Parameters that determine strength of interactions between particles. |
| Explain something about the running of the coupling constant. | ”Run” = changes with energy scale of interaction. Ex: Short distances > small coupling constant > asymptotic freedom. Long distances > large coupling constant > confinement. |
| Give some characteristics of the photon. | q=0, spin 1, no color charge, infinite range but strength decreases with distance, moves at speed of light. |
| What is QED? | Quantum electrodynamics, theory of the EM interaction between charged particles mediated by photons. |
| Give some general characteristics of the W+- and Z bosons. | q for W+- = +-1, q for Z = 0. Spin=1. VERY heavy. Super short range, short lifetime. Interacts with all fermions. |
| Give some more characteristics of the W+- boson. | Is it's own antiparticle. Emission of W+- lowers/raises charge by one unit and alters spin one unit. Can change type of particle, ex quarks(couples to flavored states). |
| Give some more characteristics of the Z boson, specifically flavor changing neutral currents. | Emission of Z boson can *only* change spin, momentum and energy of other particle. never flavor. Flavor changing neutral currents strictly forbidden. |
| What is the electroweak interaction? | Very high energies EM and weak forces very similar, combine to electroweak. |
| Give some characteristics of the Higgs boson. | q=spin=color charge=0. Decays very quickly, often Z+photon. VERY large, larger than W+- and Z. Couples to itself, like gluon. Produced by the quantum excitation of the Higgs field. |
| What is the Higgs field? | Scalar field with two neutral, two charged components, form a complex doublet. It's potential makes it exist *everywhere* > via Higgs mechanism gives mass to particles. |
| State something about the electroweak symmetry and symmetry breaking. | Electroweak symmetry described by gauge symmetry. Low energies > breaks > mass to W+-, Z and no mass to photon. Highs mechanism and boson that is responsible for the symmetry breaking. |
| How many degress of freedom does the Higgs field have? | Four. Three mass for W+, W-, Z and one for Higgs. |
| What is a particle accelerator? | Device that uses electromagnetic fields to propel charged particles to high speeds and energiest that are directed and collided with other particles to study fundamental properties of matter and the universe. |
| What is a particle detector? | Device designed to detect and measure the properties of subatomic particles, such as electrons, protons, neutrons, and various types of mesons and bosons. |
| Give general key components of a particle accelerator. | Charged Particles, Electric Fields, Magnetic Fields, Linear Accelerators (Linacs), Circular Accelerators, Colliders, Applications. |
| Give general key components of a particle detector. | Tracking Detectors, Calorimeters, Muon Detectors, Particle Identification Detectors, Magnetic Fields, Trigger Systems, Shielding. |
| ATLAS | A Toroidal LHC ApparatuS. General purpose detector. |
| CMS | Compact Muon Selenoid. General purpose detector. |
| ALICE | A Large Ion Collider Experiment. Heavy-ion collisions, quark-gluon plasma. |
| LHCb. | Large Hadron Collider beauty. Differences between matter, antimatter using b quarks. |
| Explain the four main components of ATLAS. | Muon spectrometer, hadronic calorimeter, EM calorimeter, tracking. |
| What do gluons carry that quarks also do? | Gluons also carry color charge, carry both color+anticolor same time. |
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marlinm0220
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