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

TL;DR

This study explores the potential to measure photon polarization in the rare decay process $b o s o ext{gamma}$ via $D^0$ decays at the future Super Tau Charm Facility, aiming for high sensitivity and model-independent results.

Contribution

It demonstrates the feasibility of measuring $b o s o ext{gamma}$ photon polarization through $D^0$ decay analysis with high statistical sensitivity at STCF.

Findings

Expected over 61,000 signal events at 1 ab$^{-1}$ luminosity.

Estimated statistical sensitivity of $1.5 imes 10^{-2}$ for the asymmetry ratio.

Photon polarization can be determined model-independently by combining measurements.

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.