Recoil Mass of Leptons from Z

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The final states of mainly come from the (Higgs-strahlung), where means charged leptons, as shown in the below

The boson can be constructed by the invariant mass of di-lepton, and the Higgs can be constructed by the recoil mass of the . This method of construction of Higgs is independent to how Higgs decays, and allows us measure the cross-section model indepently. You can find more details at Cross section and Higgs mass measurement with Higgsstrahlung at the CEPC.

Event Selection

The lepton candidates are selected by the criterion

Then di-lepton candidates are selected by the criterion

If there are multiple combinations, the combination with smallest is selected. Once the di-lepton is constructed, the recoil mass is calculated by

The Plots

The invariant mass of di-muon

The recoil mass of di-muon

The invariant mass of di-electron

The recoil mass of di-electron