Spring Semester 2012 Final Oral Exam – 15.06.2012 1.
2.
3.
Weak interactions −
−
1.  Is reaction
µ →e + γ
allowed? Justify. 2.  Specify any additional particles needed in the following reactions and draw the Feynman diagrams τ + → µ + + ?
νe + p → ?
€
Mass parabola, odd-­‐mass nuclei 1.  Comment the figure “excess mass =f(Z)” and discuss the decay sequences €
2.  Use the A=111 isobars (attached figure) 3.  Write down the different beta-­‐decay reactions and draw Feynman diagrams of the basic processes. Neutrino mass 1.  How is beta-­‐decay used to set a limit on the electron-­‐neutrino mass? 2.  What is the current status of neutrino mass? Oscillations, Double-­‐beta decay, … 111
45
Rb
111
51
Sb
111
46
Pd
111
50
Sn
111
47
Ag
111
49
In
111
48
Cd
€
1.
CP violation 1.  How was CP violation discovered in 1964 in K0-­‐decays? 2.  Interpretation? 3.  How is CP violation incorporated into the Standard Model? 2.
Mass parabola, even-­‐mass nuclei 1.  Comment the figure “excess mass =f(Z)” and discuss the decay sequences. 2.  Use the A=102 isobars (attached figure). Which nuclei are beta-­‐stable? 3.  In particular discuss the – in principle – possible transition (A,Z) →(A,Z - 2)
3.
102
46
Pd + ?→102
44 Ru + ?
New physics? 82
82
1.  2-­‐beta decays have been observed; e.g. 34
36
Se→
Kr + 2e − + 2ν e . What is special with neutrino-­‐less 2-­‐beta decay? Feynman graph? Consequences? €
2.  Any other theoretical idea requiring violation of well-­‐established quantum numbers? €
•
o
Even-­‐even nuclei (data) -­‐ Upper curve (SEMF) Odd-­‐odd nuclei (data) -­‐ Lower curve (SEMF) 1.
Strong interaction 1.  Describe QCD and its main predictions. 2.  What kind of hadrons exist in nature and how does QCD account for them? Hint: only some quark combinations are observed in nature. 3.  Compare the following + − reactions (Feynman + − diagrams, signature in detectors) e e →qq γγ and e e →qq gg
2.
Nuclear models 1.  Present €
briefly the Fermi-­‐gas model. 2.  Success and limitations? 3.  What does the Shell Model improve? 3.
Solar neutrinos 1.  Which and how are neutrinos produced in Sun? 2.  How are they detected on Earth 1.
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.  What is the parity and charge conjugation of mesons? 3.  Deduce the meson families expected for the first 3 quarks (u,d,s) and for L=0, as well as the corresponding JPC 2.
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 3.
Solar neutrinos and neutrino oscillations? 1.  What is known as the solar neutrino problem and how is it solved? 2.  What are the consequences? 1.
QED vs QCD 1.  Compare some properties of the photon and the gluon 2.  What is the behavior of the coupling constants at high/low energies? 3.  Compare the following reactions (Feynman diagrams, signature in detectors) gg →gg and γγ →γγ
2.
Charge distribution and spatial extension of nucleus 1.  Comment the results of electron-­‐Nucleus scattering – see figure attached €
2.  What is the interpretation of the minima? Why not zeros? 3.  How to probe matter density of nuclei? 3.
Atmospheric neutrinos and neutrino oscillations 1.  How are neutrinos produced in atmosphere? 2.  What is the atmospheric neutrino anomaly and how is it explained? 3.  Consequences? 1.
Weak gauge bosons 1.  How are W+, W-­‐ and Z0 bosons produced in p-­‐pbar collisions? Feynman diagrams? 2.  Discuss decays of the W boson; how often does the W decay into jets? Into leptons? 2.
Semi-­‐empirical mass formula and nuclear stability 1.  Describe the various terms of the SEMF (VSCAP) 2.  What is the main prediction? 3.  Limitations? 3.
The electron-­‐antineutrino was discovered in 1955 at a nuclear reactor 1.  How are antineutrinos produced in a reactor? Feynman graph. 2.  How was the discovery made? Process and Feynman graph? 3.  Detection principle? 1.
Higgs field and Higgs boson 1.  What is the role of the Higgs mechanism? 2.  How would the Higgs boson be produced in e+e-­‐ collisions? 3.  What are the main decay channels of a Higgs of mass 100 GeV ? What about a 200 GeV Higgs? 2.
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? 3.
In asymmetric B-­‐factories, B-­‐meson pairs are produced through 1.
What is the principle of measurement of CP asymmetry using the following final state. (Note that it is important to know the flavor of the decaying B) 1.
Higgs Search at LHC 1.  The main Higgs production mechanism in pp-­‐collisions is gluon-­‐gluon fusion. Draw the Feynman diagram. 2.  Although the Higgs boson couples to massive particles, it can decay to a pair of photons. How come? Draw the Feynman diagram(s). 2.
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.  Any observable signatures of q-­‐g-­‐plasma? 3.
QED and WI have been unified into the so-­‐called Electroweak force. 1.  How would QCD be incorporated in a so-­‐called grand unification (GUT)? 2.  What would be the consequences? Temperature
ρ0"
baryon density
1.
The tau-­‐lepton and leptonic numbers 1.  Consider tau-­‐pair production in e+e-­‐ collisions. Draw the Feynman diagram. e +e − →τ +τ −
2.  What are the 2 leptonic decays of the tau? Feynman diagrams? 3.  Assuming the 2 taus decay differently, what would be the final state? €in the detector? Comment. 4.  What is “seen” 2.
Quark-­‐gluon plasma 1.  What is it? 2.  Discuss “jet-­‐quenching” 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 GUT 2.  What are the (Sakharov) conditions to explain matter-­‐antimatter in the Universe? Justify. €
1.
The Z weak neutral boson 1.  What are the possible decays of the Z-­‐boson? 2.  To a first approximation, how often does a Z decay to hadron-­‐jets? To charged leptons? To neutrinos? 3.  Deduce how the LEP-­‐I e+e-­‐ collider (COM energy ~91GeV) could set limit on the number of light neutrinos? How light? 2.
Strong nuclear force 1.  Give a simple potential accounting for the nuclear force 2.  Describe QCD briefly. Can it be applied to nuclei? Argue. 3.
Nature of neutrinos: Dirac or Majorana or both? 1.  What are the conditions to observe double beta-­‐decay, a higher order weak interaction process? 2.  What are the conditions for neutrino-­‐less double beta decay to happen? Feynman diagram.