QED factorization for eXclusive semi-leptonic B-meson decays

Exclusive semi-leptonic B decays provide an important laboratory for measuring fundamental parameters of the Standard Model (SM), or to search for yet unknown particles and interactions.

Various tensions between experimental measurements and SM predictions have been guiding the theoretical efforts over the past years.To draw reliable conclusions from the anticipated experimental high-precision data for such decays in the coming years, requires a rigorous study of sub-leading corrections that have been neglected so far.

With the proposed action, the researcher aims to investigate the impact of so-called structure-dependent electromagnetic corrections to kinematic distributions in semi-leptonic B decays, using modern Effective Field Theory and factorization methods.

A systematic study of QED corrections along these lines is a relatively new field of research, and in certain cases revealed surprising enhancement mechanisms not captured in a pointlike-meson description.

An analysis of these effects in semi-leptonic transitions at the differential level is ambitious, and phenomenologically interesting.

Photon couplings between the charged leptons and the meson constituents might lead to enhanced effects in rates or angular distributions.

Uncertainties from novel hadronic parameters must be added to clean ratios with reduced hadronic uncertainties.Conceptually, factorization is achieved using of Soft-Collinear Effective Theory and Heavy-Quark Effective Theory.

The analysis of these decay amplitudes require modern sub-leading power techniques to deal with technical difficulties such as endpoint singularities.The action is subdivided into four work-packages (WP): Factorization theorems for charged and neutral-current semi-leptonic transitions are derived in WP1 and WP2, respectively.

Novel concepts regarding the treatment of endpoint-singularities are developed in WP3, and WP4 aims at a collinear-photon inclusive 'jet-like' treatment of electronic channels.