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

Abstract

We report a sensitive study of measuring b → sγ photon polarisation in D 0 → K 1 (1270) − e + ν e with an integrated luminosity of 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 → 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 × 10 −2 by performing a two-dimensional angular analysis in D 0 → K 1 (1270) − e + ν e . Combining with measurements of up-down asymmetry in B → K 1 γ, the photon polarisation in b → sγ can be determined model-independently.

Electromagnetic form factors of $Λ$ hyperon in the vector meson dominance model and a possible explanation of the near-threshold enhancement of the $e^+e^- \to Λ\barΛ$ reaction

“…The proposed formalism attribute the e + e − → Λ Λ non-vanishing cross sections near threshold to be the contribution of a new narrow vector meson X(2232), which could be the peak structure seen in the e + e − → K + K − K + K − and e + e − → φK + K − reactions at √ s = 2.2324 GeV. It is expected that this conclusion can be distinguished and may be tested by the future experiments with improved precision at BESIII or the planned Super tau-charm Facility at China [58][59][60].…”

Feasibility Study of $D_s^+ \to τ^+ ν_τ$ Decay and Test of Lepton Flavor Universality with Leptonic $D_s^+$ Decays at STCF

“…Utilizing the signal MC samples, three categories of detector responses are studied with the help of the fast simulation software package, where the detailed information are elaborated below. a. Tracking efficiency In the fast simulation, two dimensional distributions of transverse momentum P T and polar angle cosθ are used to characterize the tracking efficiency, since they are correlated with the level of track bending and hit positions of tracks in the tracker system [39]. The reconstruction efficiency will be affected due to stronger electromagnetic multiple scattering, electric field leakage, energy loss, and so on.…”