Topical seminar: LCSR application to D+ → π+ℓ+ℓ-

by Dr. Anshika Bansal (Siegen U.)

Thursday 12 Dec 2024, 12:00 → 13:00 Europe/Madrid

1001-Primera-1-1-1 - Paterna. Seminario (Universe)

Flavour Changing Neutral Currents (FCNCs) in the Standard Model (SM) arise only at loop level, making them important probes for New Physics (NP). However, unlike bottom FCNCs (eg. b → sℓ+ℓ-), the charm FCNCs (eg. c → uℓ+ℓ-) are dominated by long distance (LD) effects due to strong GIM suppression, posing significant challenges.

In this talk we will explore these challenges focusing on D+ → π+ℓ+ℓ- decays which can be realised as the combination of the singly Cabibbo suppressed (SCS) weak transitions with the electromagnetic emission of the lepton pair. We study these LD effects using the framework of Light Cone Sum Rules (LCSR) and make predictions for the differential widths for these decays. Our findings suggest that the weak annihilation contribution are dominant, with negligible loop contributions.

Finally, I relate these decays to other Cabibbo favoured and doubly Cabibbo suppressed, D(s) → Pℓ+ℓ- (P = π, K, ...) decays through flavour symmetries. As a byproduct, I further discuss Ds+ → π+ℓ+ℓ- which is not an FCNC but shares the topologies with D+ → π+ℓ+ℓ- and can therefore be useful in better understanding of LD dynamics involved.