Patrick Janot edited 13311371905442115.tex  almost 11 years ago

Commit id: 924fbf73bc32b4b1e12d228d95e869c31a96eeb5

deletions | additions      

       

With the sole 240 GeV data, TLEP is therefore able to determine the Higgs boson decay width with a precision of the order of 3\% in this channel. As indicated in Ref.~\cite{cite:ILCTDR}, it takes five additional years of data at $\sqrt{s} = 500$ GeV for the ILC to reach a precision of 6\% on the same quantity, with the ${\rm H \to b\bar b}\nu\bar\nu$ final state produced via WW fusion. This measurement can be performed in a very similar manner at TLEP at $\sqrt{s} = 350$ GeV, as is described in the next paragraph. To a lesser extent, the $\epemto {\rm H}\nu\bar\nu$ cross section can also be measured at $\sqrt{s} = 240$ GeV, which in turns improves the total width precision at this energy down to 2\%.  The $\ell^+\ell^-{\rm H}$ final state and the distribution of the mass recoiling against the lepton pair can also be used to directly measure the invisible decay width of the Higgs boson, when in events where  the Higgs boson decay products escape undetected. If observed, the Higgs boson invisible branching fraction can be measured with an absolute precision of 0.25\% with the TLEP data at 240 GeV. If not observed, a 95\% C.L. upper limit of 0.5\% can be set on this branching fraction.