Feasibility study of measuring $b\to s\gamma$ photon polarisation in $D^0\rightarrow K_1(1270)^- e^+\nu_e$ 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.