Physics with ILD
The Tevatron and LHC experiments are anticipated to see the Higgs boson and possibly new physics phenomenaa such as supersymmetry and extra dimensions. The precision measurements at the ILC will be crucial for identifying the correct model and mechanisms of nature.
The response of the ILD detector has been simulated for many physics processes, some of which are quoted below. See the ILD Letter of Intent for a full review of physics measurement prospects with ILD.
Higgs boson mass
The measurement of the Higgs boson mass using the reaction e+e- -> ZH is considered. The Z boson will be identified by its decay into a pair of muons or electrons. Assuming the Higgs mass to be 120 GeV and 250 fb-1 of data at the center-of-mass energy of 250 GeV with polarized electron (+30%) and positron (-80) beams, the measurement precision of the Higgs mass is estimated to be 32 MeV which is independent of its decay modes. The e+e- -> ZH cross section can be measured with a precision of 2.5%.
Higgs boson branching fractions
The branching fractions of the Higgs boson can be used to measure the strength of the interaction between the Higgs boson and other particles to test the hypothesis of the Standard Model, in which the interaction strength is assumed to be linearly proportional to the mass of the other particle. The branching fractions of the Higgs decays to a pair of quarks or gluons will be measured using the e+e- -> ZH channel, with the Z boson identified by its decay into a pair of leptons, neutrinos, and quarks. Assuming 250 fb-1 of data at the center-of-mass energy of 250 GeV, the measurement accuracy of the branching fractions is estimated to be 2.7% for H->bb, 12% for H->cc, and 29% for H->gg.