Search for New Physics in the Semileptonic D_{l4} Decays, D->K \pi l \nu

TL;DR

This paper investigates potential new physics effects, such as CP violation and decay rate modifications, in semileptonic D_{l4} decays by considering scalar interactions and analyzing intermediate state contributions.

Contribution

It introduces a detailed analysis of scalar-exchange interactions in D_{l4} decays, including constraints on new couplings within specific beyond Standard Model frameworks.

Findings

Only the lowest K* state significantly contributes among intermediate states.

Constraints on complex scalar couplings are derived within multi-Higgs and leptoquark models.

Higher excited states are negligible in the decay process.

Abstract

New physics effects through the direct CP violation and the decay rate change are investigated in the semileptonic $D_{l4}$ decays, $D^\pm\to K\pi l^\pm \nu$, by including a scalar-exchange interaction with a complex coupling. In the decay process, we included various excited states as intermediate states decaying to the final hadrons, $K+\pi$, and found that among the intermediate states only the lowest state ($K^*$) is dominant and the other higher excited states are negligible, contrary to the $B_{l4}$ decays. We also obtained constraints on the new complex coupling within the multi-Higgs doublet model and the scalar leptoquark models.