Nuclear Physics Question: Why do the heavy nuclei clump above the red line ? Hint: What are the competing interactions ? Ans: Attractive Strong Interaction and repulsive Coulomb interaction. Easier to add neutrons when there is a large Coulomb repulsion. Question: Which are β+ or β- emitters ?

Question : Which of the following has the most stable isotopes: N odd, Z odd 2) N odd, Z even 3) N even, Z even 4) N even, Z odd Remember the shell model and Pauli exclusion principle.

Today’s plan Chapter 8 on oscillations Return homework and quizzes. Quiz review More on the weak interaction: CKM matrix Warm up material on mixing (Chapter 8). Quiz on Weak Interactions (Friday April 14th) Chapter 8 on oscillations and mixing of mesons on Wednesday. “Warm up” material today.

Quiz 6:

Question: Why is the J/ψ so narrow (factor of 50) ? Hint if needed. Ans: OZI suppression and running of αS

Upsilon(1S), Upsilon(2S), Upsilon(3S) can only decay through 3 gluons and hence their widths are strongly suppressed. Upsilon(4S) can decay to pairs of B-anti B mesons (hence it is quite broad) Similarly, the J/ψ(1S), ψ(2S) are narrow while the ψ(3S) is above threshold for decay to D Dbar and is broad.

Review: Recall only 4 interactions possible.

Review: PDG Plot Ratio of 0.45; valence quarks are fractionally charged with some sea contribution

Review: Dimensional arguments for neutrino fixed target Note GF ~ 1/E2 and s ~E2 . Now calculate s in the fixed target neutrino nucleon scattering. Another example, e+e- hadrons or e+e- μ+ μ- Here alpha is dimensionless and sigma~L2

Review question: Draw the dominant Feynman diagrams for the decay of the top quark ? Hint: There are two classes of final states: those with quarks and those with leptons Hint: Does t ->s or t->d ?

Note that Vus and Vcd are singly Cabibbo suppressed.

Big Bang Theory Episode Whiteboard by David Saltzberg

How to observe top quark decay at the Tevatron Question: How is the LHC different ? Ans: Gluon-Gluon fusion rather than quark-antiquark

Measurement of Vub Two methods: use an exclusive bu decay mode or inclusive bu Question: Can you draw the Feynman diagram for this decay mode (show the couplings) Question: What would be an “inclusive” bu decay ?

Inclusive measurement of Vub Look for leptons with momenta beyond the kinematic limit for bc decay

https://arxiv.org/pdf/hep-ex/0202019.pdf CLEO collaboration at CESR in Ithaca, NY

Inclusive measurements of V_ub (CKM example)

Weak Interaction Review Problem The former has a branching fraction of 100% and the latter is 16%. The muon lifetime is 2.2 microseconds. Calculate the tau lifetime. Hint: the tau mass is 1776 MeV and the muon mass is 105.6 MeV Another hint: How does the width of the weak leptonic decay depend on its mass ? (Use weak interaction and dimensional analysis)

Weak Interaction Review Problem The former has a branching fraction of 100% and the latter is 16%. The muon lifetime is 2.2 microseconds. Calculate the tau lifetime. How do we get the tau lifetime from the width ?

Weak Interaction Review Question Muons have the same electromagnetic charge and weak interactions as electrons and yet a muon with an energy of a few GeV passes through an iron slab while an electron of the same energy does not. Explain why. Ans: Electrons bremsstrahlung and produce electromagnetic showers 2.5 GeV electron in liquid argon

Weak Interaction Review question: Find the valence quark composition, dependence on CKM matrix elements and relative rates of the following processes (order them by strength). Hint: B0 = bbar d or anti-B0= b dbar

Feynman diagram for process 1) Can you draw the Feynman diagram for process 4) ? (Hint it is Cabibbo suppressed).

Feynman diagrams for process 3)

Find the valence quark composition, dependence on CKM matrix elements and relative rates of the following processes.

Warm-up for Chapter 8 (neutral mesons’ oscillation and CP violation) Neutral mesons such as the K0 or B0 may transform into their anti-particles (anti-K0, anti-B0) and vice versa. Question: Which interaction is responsible for this phenomena called “mixing” ? Why Ans: Weak interaction, these are ΔS= 2 or ΔB=2 transitions. 2nd order processes ! Question: Are these strong, weak or EM processes ? Ans: Weak; strangess changing. Question: Are the decay process strong, weak or EM ? Why

Neutral kaon are produced by the strong interaction but decay by the weak interaction. This is described by simple time-dependent quantum mechanics. The strong interaction eigenstates differ from the weak interaction eigenstates. They are linear combinations.

Question: How much do the KS and KL lifetimes differ Question: How much do the KS and KL lifetimes differ ? What is the mass difference in milli-electron volts ?