C2a: Hadronic Matrix Elements and Exclusive Semileptonic Decays

In this project we will improve the theoretical predictions for various exclusive semileptonic b-decay processes, including new classes of decay modes where precision calculations have not been available so far. Starting point for the evaluation of exclusive b-hadron decays are the light-cone distribution amplitudes (LCDAs) that parametrize the essential hadronic infor- mation in the light-cone sum rule (LCSR) and QCD factorization (QCDF) approaches. With these methods the (generalized) form factors that describe the semileptonic transition into single hadrons or multi-hadron final states can be investigated. The results of this project are essential for precise determinations of the fundamental parameters |Vub| and |Vcb| appearing in the Cabbibo-Kobayashi-Maskawa matrix, and for tests of the Standard Model against New Physics in charged-current (CC) transitions.

1. Factorization and Light-Cone Distribution Amplitudes
   • 2- and 3-particle LCDAs of the B-meson
   • Implications for B → γlν, B− → μ−ν ̄μ+μ− decays
   • Theoretical properties of quasi-distribution amplitudes
2. Theoretical Development of QCD Sum Rules and Related Methods
   • Interplay of sum rules and unitarity bounds
   • 1/mQ power corrections to B → D(∗) form factors ◦ Form factors for semileptonic Bc transitions
3. New Channels and Multi-Hadron Final States
   • B → ππlν and Bs → Kπlν decays
   • Semileptonic decays of heavy baryons
   • Heavy-to-heavy and heavy-to-light decays of Bc
4. Inclusive Rate from the Sum over Exclusive Channels
   • Realistic description of B → D + nπ contributions ◦ Excited states contributing to b → ulν