Optimizing Higgs factories by modifying the recoil mass

Abstract

It is difficult to measure the $WW$-fusion Higgs production process ($e^{+}{e}^{-}\to \nu \bar{\nu }h$) at a lepton collider with a center of mass energy of 240-250 GeV due to its small rate and the large background from the Higgsstrahlung process with an invisible $Z$ ($e^{+}{e}^{-}\to hZ,Z\to \nu \bar{\nu }$). We construct a modified recoil mass variable, $m_{\mathrm{recoil}}^p$, defined using only the 3-momentum of the reconstructed Higgs particle, and show that it can better separate the $WW$-fusion and Higgsstrahlung events than the original recoil mass variable $m_{\mathrm{recoil}}$. Consequently, the $m_{\mathrm{recoil}}^p$ variable can be used to improve the overall precisions of the extracted Higgs couplings, in both the conventional framework and the effective-field-theory framework. We also explore the application of the $m_{\mathrm{recoil}}^p$ variable in the inclusive cross section measurements of the Higgsstrahlung process, while a quantitive analysis is left for future studies.

Comments: 25 pages, 8 figures