Motivations for semileptonic charm physics
Semileptonic decays are accessible to experiment...
- Cabbibo-allowed decays have large branching ratios
- and easily distinguishable signals
And to theory.
- Fully-explicit decay rate can be calculated from first principles (eg Feynman diagrams)
- No final-state interactions to worry about!
- QCD complications are contained in form factors
- 1 (+1) for pseudoscalar-l-n
- 3 (+1) for vector-l-n
- Form factors can be predicted...
- And measured.
- Shape measurement determines form factor ratios for vector-l-n
- Branching ratio measures absolute FF scale times VCS, VCD
Measurements + FF predictions can determine CKM matrix elements