Novel Model-Independent Approach to Explore New Physics in Five-body Semileptonic Decays

Substantial contribution of the tensor current in semileptonic decays is regarded as a clear signal for new physics. In this work, we propose a model-independent approach to unambiguously test contribution of the tensor current in semileptonic five-body decays $\bar{D}_{(s)}/\bar{B}_{(s)}\to V\ell\bar{\nu}_{\ell}\,(\ell=e,\mu,\tau)$ with $V\to \pi^0\pi^+\pi^-$, where $V$ denotes vector particles. We derive three parameters associated with the angular asymmetry, which are always equal to one in the Standard Model regardless the data of form factor but will deviate if contribution of the tensor current doesn't vanish. The outcomes have potential applications in precisely testing the Standard Model and searching for new physics. Relevant measurements can be performed using data collected by BESIII, Belle~II, and LHCb.