Precision Higgs boson mass determination at lepton colliders

We demonstrate that a measurement of the Bjorken process e + e − , µ + µ − → ZH in the threshold region can yield a precise determination of the Higgs boson mass. With an integrated luminosity of 100 fb −1 , it is possible to measure the Higgs mass to within 60 MeV (100 MeV) for m H = 100 GeV (150 GeV). One of the triumphs of the LEP program was the measurement of the Z-boson mass to two MeV. Expectations are also quite good for the measurement of the W-boson mass (M W) and the top quark mass (m t) in the future, perhaps achieving precision of order 10 MeV for M W and 2 GeV for m t at the Tevatron and the LHC [1]. Precise values for M W and m t can also be obtained at lepton colliders by measuring the ℓ + ℓ − → W W and ℓ + ℓ − → tt (ℓ = e or µ) threshold cross sections, as illustrated by measurements of W-pair production at LEP center-of-mass energy √ s = 161 GeV [2]. These measurements will allow an indirect prediction for the Higgs boson mass (m H) and will test the consistency of the Standard Model (SM) at the two-loop level once m H is known.