Evaluation of measurement accuracy of $h\to {\tau }^{+}{\tau }^{-}$ branching ratio at the ILC with $\sqrt{s}=250$ GeV and 500 GeV

Abstract

We evaluate the measurement accuracy of the branching ratio of $h\to {\tau }^{+}{\tau }^{-}$ at $\sqrt{s}=250$ GeV and 500 GeV at the ILC with the ILD detector simulation. For the $\sqrt{s}=250$ GeV, we assume the Higgs mass of $M_h=120$ GeV, branching ratio of $\mathrm{Br}(h\to {\tau }^{+}{\tau }^{-})=8.0$, beam polarization of $P(e^{-},e^{+})=(-0.8,+0.3)$, and integrated luminosity of $\int Ldt=250\mathrm{f}{\mathrm{b}}^{-1}$. The Higgs-strahlung process $e^{+}{e}^{-}\to Zh$ with $Z\to e^{+}{e}^{-}$, $Z\to {\mu }^{+}{\mu }^{-}$, $Z\to q\bar{q}$ mode are analyzed. The measurement accuracy is calculated to be $\Delta (\sigma \cdot \mathrm{Br})/(\sigma \cdot \mathrm{Br})=3.5$. The scaled result to $M_h=125$ GeV is estimated to be $4.2$. For the $\sqrt{s}=500$ GeV, we assume the Higgs mass of $M_h=125$ GeV, branching ratio of $\mathrm{Br}(h\to {\tau }^{+}{\tau }^{-})=6.32$, beam polarization of $P(e^{-},e^{+})=(-0.8,+0.3)$, and integrated luminosity of $\int Ldt=500\mathrm{f}{\mathrm{b}}^{-1}$. The Higgs-strahlung process $e^{+}{e}^{-}\to Zh$ with $Z\to q\bar{q}$ mode and $WW$-fusion process $e^{+}{e}^{-}\to {\nu }_e\overline{{\nu }_e}h$ are analyzed. The measurement accuracy is calculated to be $\Delta (\sigma \cdot \mathrm{Br})/(\sigma \cdot \mathrm{Br})=5.7$ for Higgs-strahlung with $Z\to q\bar{q}$ and $7.5$ for $WW$-fusion.

Comments: 11 pages, 23 figures, 9 tables