Feasibility study of measuring $$b\rightarrow s\gamma $$ b → s γ photon polarisation in $$D^0\rightarrow K_1(1270)^- e^+\nu _e$$ D 0 → K 1 ( 1270 ) - e + ν e at STCF

Abstract

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