Spring Semester 2014 Final Oral Exam – 4/5.06.2014 !
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1.
Quarks 1.  Give two evidences supporting the quark hypothesis. + −
2.  Draw the Feynman diagrams for top production in e e →tt
3.  How does top decay? Give one experimental signature of the process above and the threshold centre of mass energy to observe it. €
2.
Mass parabola, odd-­‐mass nuclei 1.  Comment the attached figure “excess mass =f(Z)” and discuss the decay sequences of the A=111 isobars. 2.  Write down the relevant reactions – one example per kind. 3.
Neutrino mass 1.  How is beta-­‐decay used to set a limit on the electron-­‐neutrino mass? Discuss Tritium decay. 2.  What is the current status of neutrino masses? !
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CP violation 1.  What is a K0 and how does it decay? 2.  How was CP violation discovered in 1964 in K0-­‐decays. 3.  Formalism? 2.
Spin and parity of nuclei 1.  What is the spin and parity of the radioisotope 179F? (figure available) 2.  The first excited state has JP=1/2-­‐. Suggest 2 possible configurations of that state. 3.
New physics? 82
82
1.  2-­‐beta decays have been observed; e.g. 34
36
Se→
Kr + 2e − + 2ν e . Feynman graph? 2.  What is special with neutrino-­‐less 2-­‐beta decay? Feynman graph? 3.  Consequences? €
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Strong interaction 1.  What kind of hadrons exist in nature and how does QCD account for them? 2.  Give one way of measuring the strong coupling constant αs in e+e-­‐ collisions. 3.  Compare the following reactions (Feynman diagrams, signature in detectors) and infer the main differences between αs and αqed . qq →qq γγ and qq →qq gg
2.
Nuclear models 1.  Present the Fermi-­‐gas model. Success and limitations? €
2.  What does the Shell Model improve? How? 3.
Solar neutrinos and oscillations 1.  Which neutrino flavors are produced in Sun and how? 2.  Give the steps to obtain the oscillation probability. Discuss its parameters and how to set limits on the neutrino mass. !
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According to the quark model, mesons are quark-­‐antiquark bound states and baryons 3-­‐quark bound states. 1.  What is the relation between electric charge, isospin and hypercharge 2.  Apply to the lowest-­‐mass mesons made of the first 3 quarks (u,d,s). What is the corresponding JPC ? 3.  Compare the decay widths of the charged pion and kaon into muon-­‐neutrino final state. 2.
Nuclear models 1.  Present the nuclear shell model and explain how magic numbers are predicted. 2.  Predict spin and parity of 4120Ca – make use of the attached scheme. 3.
Solar neutrinos and neutrino oscillations? 1.  Which reactions are responsible for neutrino production in the Sun? 2.  How are they detected on Earth? Feynman diagram of reaction? Principle. !
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QCD properties 1.  Give 2 evidences for the existence of the color quantum number. 2.  What is the gluon and how was it discovered? 3.  Compare the following reactions (Feynman diagrams, signature in detectors). Draw conclusion on the behavior of the electromagnetic and strong coupling constants. gg →gg and γγ →γγ
2.
Spin and parity of nuclei 1.  What is the spin and parity of the radioisotope 179F? €
2.  The first excited state has JP=1/2-­‐. Suggest 2 possible configurations of that state. 3.
Atmospheric neutrinos and neutrino oscillations 1.  How are neutrinos produced in atmosphere? Which flavors? 2.  What is the outcome of the Super Kamiokande experiment? !
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Weak gauge bosons 1.  How are W+, W-­‐ bosons produced in proton-­‐proton collisions? 2.  Compare W production in pp and ppbar: at low and at very high energies. 3.  How often does the W decay into jets? Into leptons? You may want to write all possible decays first. 2.
Semi-­‐empirical mass formula and nuclear stability 1.  Describe the various terms of the Semi Empirical Mass Formula 2.  What is the main prediction? 3.  Limitations? 3.
Neutrino discovery 1.  Which flavor(s) of neutrinos is/are produced in a reactor? In the Sun? 2.  How was the first discovery made? Process and Feynman graph? Detection principle? !
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2.
Higgs boson 1.  How is the Higgs boson produced in e+e-­‐ and pp collisions? Give one Feynman diagram for each. 2.  What are the 3 main decay channels of a Higgs of mass 126 GeV ? What about a 380 GeV Higgs? Discuss nuclear fission within the Liquid Drop model 1.  Which term of SEMF plays a crucial role? 2.  How different are 23592U and 23892U with respect to fission? In asymmetric B-­‐factories, B-­‐meson pairs are produced through 3.
e + e − → Υ( 4s) → B 0 B 0
Give Feynman diagrams of the decay of the B0 and B0bar mesons to final states involving a charged pion and a charged kaon 2.  What is is the principle of measurement of CP asymmetry using the following final state? B 0 / B 0 → J/ψ K s
1.
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Higgs Search at LHC 1.  The main Higgs production mechanism in pp-­‐collisions is gluon-­‐gluon fusion. Draw the Feynman diagram(s). 2.  Although the Higgs boson couples to massive particles, it can decay to a pair of gluons. Draw the Feynman diagram(s). 3.  Discuss the CMS and ATLAS discovery of the Higgs into photon-­‐pairs. Why is this channel easier than the gluon pair above? QCD predicts a new state of matter 1.  What are the conditions for a quark-­‐gluon plasma? 2.  Comment the phase diagram – see figure attached 3.  What is jet quenching? Grand Unification Theories – GUT 1.  Which symmetry is behind GUT? What about Supersymmetry? 2.  Give details about 2 important predictions? !
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Bottom quark production and decay 1.  Consider b-­‐quark-­‐pair production in e+e-­‐ collisions. Draw the Feynman diagram(s) of the reaction e +e − →bb
2.  Give a semi-­‐leptonic decay of each b flavour ? Feynman diagrams? Comment? 3.  Assuming the 2 b-­‐quarks decay differently, what would be the final state and €
experimental signature? 2.
Quark-­‐gluon plasma 1.  What is it? Comment the phase diagram – see figure attached . 2.  Discuss strangeness suppression as signature of quark-­‐gluon plasma 3.
p → π 0e + ; π 0 → γγγ
Which quantum numbers are not conserved in: 1.  Draw Feynman graphs leading to proton decay in Grand Unification (GUT). 2.  What is the experimental signature? €
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The Z weak neutral boson
1.  What are all possible decays of the Z-boson?
2.  Explain how the LEP-I e+e- collider experiments (COM energy ~91±3
GeV) set a limit on the number of light neutrinos? How light?
3.  Feynman graph for e+e- à ZZ? What is the threshold of this reaction?
2.
Strong nuclear force
1.  Give a simple potential accounting for the nuclear force.
2.  What is quark-gluon plasma in the framework of QCD.
3.  Tell about one signature of QGP. 3.
Nature of neutrinos: Dirac or Majorana?
2.  What are the conditions for neutrino-­‐less double beta decay to happen? Feynman diagram. 3.  How is Tritium beta-­‐decay used to set a limit on the electron neutrino? !
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The Higgs boson 1.  What are possible decays of a 126-­‐GeV Higgs boson? Draw Feynman graph of the decay into 4 leptons. 2.  How is it produced at LHC? 3.  Discuss its observation in 4-­‐leptons by ATLAS and CMS Mass parabola, even-­‐mass nuclei 1.  Comment the attached figure “excess mass =f(Z)” and discuss the decay sequences of the A=102 isobars. Which nuclei are beta-­‐stable? 2.  In particular discuss the possible transition (A,Z) →(A,Z - 2)
102
46
Pd + ?→102
44 Ru + ?
Atmospheric neutrinos and oscillations? 1.  How are atmospheric neutrinos produced? 2.  Explain why most of neutrinos stem from pion decays. (Compare pion and kaon decays to muon+neutrino). €
3.  What is the atmospheric neutrino anomaly and how was it solved? !
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The Higgs boson 1.  What are possible decays of a 126-­‐GeV Higgs boson? Draw Feynman graphs of the decay into 2 photons. 2.  How is it produced at LHC? 3.  Discuss its observation in 2 photons by ATLAS and CMS: Mass parabola, odd-­‐mass nuclei 1.  Comment the attached figure “excess mass =f(Z)” and discuss the decay sequences of the A=111 isobars. 2.  Write down the different beta-­‐decay reactions – one example per kind. Solar neutrinos 1.  What is the production mechanism of solar neutrinos? 2.  How are they detected on the Earth? Feynman diagram and detection principle. !
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J/ψ particle 1.  How was it discovered? Give Feynman graph(s) of production in e+e-­‐ and decay to leptons. 2.  What are its quantum numbers (JPC)? 3.  Explain why the particle is very narrow (width Γ~90 keV instead of ~100MeV for normal hadrons)? Nuclear models 1.  Present briefly the nuclear shell model and explain how magic numbers are predicted. 2.  Predict spin and parity of 3717Cl – make use of the attached scheme. Nature of neutrinos: Dirac or Majorana? 2.  What are the conditions for neutrino-­‐less double beta decay to happen? What about normal double beta decay? Feynman diagrams. !
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Time-­‐reversal violation in kaon decays 1.  K0 production in low energy proton antiproton annihilations proceeds through pp →K −π + K 0 . What about anti-­‐K0? 2.  How do K0 and anti-­‐K0 decay semi-­‐leptonically? Feynman graphs? 3.  Explain how CPlear experiment measured T-­‐violation. Conclusions? €
2.  α decay 1.  Draw a schematic diagram of the potential energy of an α particle as a function of its distance r from the centre of the nucleus. Discuss α decay. 2.  Explain why fast neutrons are needed to induce fission of 238U, contrary to 235U. 3.  Atmospheric neutrinos and oscillations? 1.  How are atmospheric neutrinos produced? 2.  How are they detected in Super Kamiokande and what is the outcome of the experiment? 1.
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Pion decays 1.  How do the charged and neutral pions decay? Give Feynman diagrams. 2.  Compare the decay widths of the charged pion into electron and muon final states 2.
Nuclear models 1.  Present briefly the Fermi-­‐gas model. 2.  Success and limitations? 3.  What does the Shell Model improve? 3.
Grand UnificationTheories, Supersymmetry 1.  What is the symmetry behind SUSY? Give 2 prediction of the theory. 2.  Discuss one possible proton decay. Feynman diagram and experimental detection principle. !
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Muon decay 1.  How does the muon decay? Feynman diagram? 2.  What is particular with muons produced in pion decays at rest? Consequences? 3.  Discuss Parity (P) and C-­‐parity (C ) violations in muon decay. Consequences? Charge distribution and spatial extension of nucleus 1.  Comment the results of electron-­‐Nucleus scattering – see figure attached. What is the interpretation of the minima? Why not zeros? 2.  How to probe matter density of nuclei? Neutrino oscillations 1.  Give the steps to calculate the oscillation probability. 2.  Discuss the oscillation parameters and how limits on the neutrino mass can be inferred. !
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2.
3.
According to the quark model, mesons are quark-­‐antiquark bound states and baryons 3-­‐quark bound states. 1.  What is the relation between electric charge, isospin and hypercharge? 2.  For mesons, what are the allowed JPC ? 3.  Deduce the meson families expected for the first 3 quarks (u,d,s) and for L=1 Nuclear models 1.  Present briefly the nuclear shell model and explain how magic numbers are predicted. 2.  Predict spin and parity of 178O – make us of the attached scheme Solar neutrinos and neutrino oscillations? 1.  How are solar neutrinos detected? 2.  What is the solar neutrino problem and how is it confirmed on Earth? !
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According to the quark model, mesons are quark-­‐antiquark bound states and baryons 3-­‐quark bound states. 1.  What is the relation between electric charge, isospin and hypercharge? 2.  For Baryons, what are the allowed JPC ? 3.  Deduce the baryon families expected for the first 3 quarks (u,d,s) and for L=0. 2.
α decay 1.  Draw a schematic diagram of the potential energy of an α particle as a function of its distance r from the centre of the nucleus. Discuss α decay. 2.  Explain why fast neutrons are needed to induce fission of 238U, contrary to 235U. 3.
Oscillations 1.  Compare neutrino oscillations and K0-­‐K0bar oscillations. 2.  Give Feynman graph of oscillation in the kaon and D-­‐meson systems. !
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Charged pion decay at rest 1.  How does the charged pion decay? Feynman diagram(s). 2.  Compare the decays to muon and to electron? 3.  Discuss parity, C-­‐parity and CP in pion decay. 2.
Confinement and Quark-­‐gluon plasma 1.  Discuss asymptotic freedom and confinement. 2.  Comment the phase diagram – see figure attached. 3.  Discuss “jet-­‐quenching” as signature of quark-­‐gluon plasma 3.
Strangeness and Oscillations 1.  Describe the neutral kaon system. 2.  Give Feynman graphs of oscillations in the kaon and D-­‐meson systems. !
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Neutrino electron scattering −
−
−
−
1.  Feynman diagrams of reactions v e e
→
v e e and v e e → ve e
2.  Compare the (electron) angular distributions? 3.  Consequence on the total cross sections? 2.
Charge distribution and spatial extension of nucleus 1.  Describe Rutherford scattering 2.  Comment the results of electron-­‐Nucleus scattering – see figure attached Double beta decay 1.  What are the possibilities? Feynman graphs. 2.  Consequences? 3.
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Flavour oscillations and CP violation. 1.  Discuss flavour “conservation” in weak interactions. 2.  Give example of B0 and D0 semi-­‐leptonic decays. Feynman graphs. 3.  Draw Feynman diagrams of oscillations. B 0 ↔ B 0 ; D 0 ↔ D 0
2.
Confinement and Quark-­‐gluon plasma 1.  Discuss asymptotic freedom and confinement. 2.  Discuss “jet-­‐quenching” as signature of quark-­‐gluon plasma 3.
Lepton number and baryon nomber + −
+ −
1.  Is the process e µ →
µ e allowed in the Standard Model? Feynman graph. 2.  Discuss possibilities for simultaneous violation of lepton and baryon number beyond SM. Example of process. !
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CP violation in B-­‐decays 1.  What are B0d–mesons and how do they decay to a Kπ final state? 2.  How was this process used to measure CP violation? 3.  Experimental status and measurement principle. Mass parabola, even-­‐mass nuclei 1.  Comment the attached figure “excess mass =f(Z)” and discuss the decay sequences of the A=102 isobars. (A,Z) →(A,Z - 2)
2.  Discuss the possible transition 102
102
Pd
+
?→
46
44 Ru + ?
3.  New physics? 2.  Why is the proton stable? € Theory predict? Process? 3.  What does Grand Unification 4.  Describe the experimental situation: principle and outcome. 2.
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Weak decays of B mesons 1.  How do the following decays proceed? Feynman graphs? B − → D 0 K *− and B − → D 0 ρ −
2.
3.
Γ ( B − → D 0 K *− )
Estimate the ratio of the two decay widths Γ ( B− → D 0 ρ − )
Compare CP violation expected in B mesons and in K mesons. 2.
3.
Spin and parity of nuclei 1.  What is the spin and parity of the radioisotope 179F? 2.  The first excited state has JP=1/2-­‐. Suggest 2 possible configurations of that state. New physics? 2.  Why is the proton stable? 3.  What does Grand Unification Theory predict? Process? 4.  Describe the experimental situation: principle and outcome. !
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Standard Model interactions 1.  Which of processes 1,2,3 are allowed? 2.  If yes, Feynman graphs and interaction at work? 3.
e+ + e− → γ + γ
(1)
e+ + e− → ν e + ν e
(2)
e+ + e− → g + g
(3)
Propose another collider to observe any of the not-­‐allowed reactions above. 2.
3.
Charge distribution and spatial extension of nucleus 1.  Comment the results of electron-­‐Nucleus scattering – see figure attached. What is the interpretation of the minima? Why not zeros? 2.  How to probe matter density of nuclei? SM and beyond 2.  Give two experimental facts that suggest physics beyond the SM? 3.  Tell about one possible solution which addresses these shortcomings. 4.  Tell about an experiment to check such idea / solution? !
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Weak decays of D mesons 1.  How do the following decays proceed? Feynman graphs? D 0 → K +π – and D 0 → K – π +
2.
3.
Estimate the ratio of the two decay widths Compare mixing in D mesons and in K mesons. (
Γ (D
Γ D 0 → K +π –
0
→ π +K –
)
)
2.
Spin and parity of nuclei 1.  What is the spin and parity of the radioisotope 179F? 2.  The first excited state has JP=1/2-­‐. Suggest 2 possible configurations of that state. 3.
Running coupling constants and Unification 1.  What is the difference between electromagnetic and strong interactions? 2.  What about weak interactions? 3.  Discuss the possibility of unification of all 3 forces. 111
45
Rb
111
51
Sb
111
46
Pd
111
50
Sn
111
47
Ag
111
49
In
111
48
Cd
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•
o
Even-­‐even nuclei (data) -­‐ Upper curve (SEMF) Odd-­‐odd nuclei (data) -­‐ Lower curve (SEMF) €
Q(x) = d(x) + u(x)
Q (x) = d (x) + u (x)
Qv (x) ≡ Q(x) − Q (x)
Temperature
ρ0"
baryon density