A proposal on complementary determination of the electro-weak mixing angles $\mathrm{si}{\mathrm{n}}^2{\theta }_{\mathrm{W}}$ at a super Z-factory

Abstract

A proposal on determination of the effective electro-weak mixing angle $\mathrm{si}{\mathrm{n}}^2{\theta }_{\mathrm{eff}}^{\mathrm{f}}(\mathrm{f}=\mathrm{c},\mathrm{b})$ at a super Z-factory (an $e^{+}{e}^{-}$ collider designed with the possible highest luminosity and running around the center mass energy $\sqrt{s}=m_Z$) is proposed. It is to determine how the effective mixing angles depend on the flavors, especially the flavors $c$, $b$ (with the determined effective ones, the electro-weak mixing angles $\mathrm{si}{\mathrm{n}}^2{\theta }_{\mathrm{W}}^{\mathrm{f}}(\mathrm{f}=\mathrm{c},\mathrm{b})$ of Standard Model can be derived out precisely). The key point of the proposal is that at such a super Z-factory, via measuring the forward-backward ($A_{FB}$), left-right ($A_{LR}$) and combined left-right forward-backward ($A_{LR}^{FB}$) asymmetries of the produced doubly heavy-flavored hadrons (such as $B_c$, $B_c^{\ast }$ and the baryons $H_{Q{Q}^{\prime }q}$: ${\Xi }_{cc}$, ${\Xi }_{bc}$ and ${\Xi }_{bb}$ etc) in the relevant production processes $e^{+}{e}^{-}\to B_c+\cdots$ and $e^{+}{e}^{-}\to H_{Q{Q}^{\prime }q}+\cdots$ one may complement the final determination of the mixing angle $\mathrm{si}{\mathrm{n}}^2{\theta }_{\mathrm{W}}^{\mathrm{f}}(\mathrm{f}=\mathrm{c},\mathrm{b})$ of Standard Model. The advantage of the proposed way to determine the effective electro-weak mixing angles is that the doubly heavy flavor(s) and the out-going direction of the produced doubly-heavy hadron can be experimental determined precisely, i.e. there are no such errors caused by missing identification of the heavy flavor(s) and by determining the so-called thrust axis of the produced jets, which can not be avoided in the early determination at LEP-I and SLC.

Comments: 9 pages, 7 figures