Feasibility study of measuring $b\to s\gamma$ photon polarisation in $D^0\to K_1(1270{)}^{-}{e}^{+}{\nu }_e$ at STCF

Abstract

We report a sensitive study of measuring $b\to s\gamma$ photon polarisation in $D^0\to K_1(1270{)}^{-}{e}^{+}{\nu }_e$ with an integrated luminosity of $\mathcal{L}$ = 1 ab${}^{-1}$ at a center-of-mass energy of 3.773 GeV at future Super Tau Charm Facility. More than 61,000 signals of $D^0\to K_1(1270{)}^{-}{e}^{+}{\nu }_e$ are expected. Based on a fast simulation software package, the statistical sensitivity for the ratio of up-down asymmetry is estimated to be $1.5\times 10^{-2}$ by performing a two-dimensional angular analysis in $D^0\to K_1(1270{)}^{-}{e}^{+}{\nu }_e$. Combining with measurements of up-down asymmetry in $B\to K_1\gamma$, the photon polarisation in $b\to s\gamma$ can be determined model-independently.