Production Of Higgs Boson And Heavy Quarkonium At The Future Electron-Positron Colliders

The standard model(SM)of particle physics has achieved great successes since its establishment.Most of the SM predictions have been tested by experiments.In July 2012,the European Organization for Nuclear Research(CERN)announced the discovery of a 125 GeV new boson.The experimental results show this new boson should be the long-sought Higgs boson in SM.This landmark discovery makes up for the last puzzle of SM,and opens a new era in particle physics.It is of the highest priority to determine the properties of this Higgs-like boson,in order to penetrate into the mechanism of electroweak symmetry breaking,and to seek the hints of new physics.Some electron-positron colliders,for example the International Linear Collider(ILC),the Future Circular Collider(FCC-ee),the Circular Electron Positron Collider(CEPC)and the Super B factory(SuperKEKB),have been proposed to precisely test the SM predictions.Compared with the hadron colliders,the electron-positron collid-ers are expected to be environmentally clean,and their luminosities will be improved greatly.These high-precision measurements also pose new challenges to theoretical predictions.In this thesis,we focus on some phenomenological analyses for these fu-ture electron-positron colliders.In Chap.2,the Higgsstrahlung process,e+e-?HZ,is studied.The electroweak-QCD correction to e+e-? HZ is evaluated at next-to-next-to-leading order(NNLO).We show the technique details and list the numeric results for the differential(total)cross sections of the HZ associated production.We give a detailed error analysis by varying the values of the input parameters.The electroweak-QCD correction turns out to be large,around 1%of the leading order(LO)result,well above the projected experimen-tal(sub)percent accuracy for the ?(HZ)measurement,thus should be incorporated in future confrontations with the experimental data.In Chap.3,we study the inclusive h,production at the Super B factory,Su-per KE KB.The numeric result shows that the inclusive production of h,is dominated by the color-octet mechanism at LO,and its next-to-leading order(NLO)correction turns out to be very large,with a K-factor of 1.8.The endpoint divergences appear in the energy spectrum of h,at NLO,indicating the failure of fixed-order perturbative expansion at the endpoint.With the aid of the soft-collinear effective theory(SCET),we resum the endpoint singularities to NLL order.Together with our NLO results,we finally get a well-behaved energy spectrum for the inclusive hc production.In Chap.4,we evaluate the rare decays of the Higgs boson into vector meson(J/?,?)plus a Z boson and into double pseudoscalar heavy quarkonia(?c,?b).The numeric results show that the branching ratios for these rare decays are small.The branching ratios are around 10-6?10-5 for the decays of Higgs boson into vector meson plus a Z boson and 10-11?10-10 for the decays of Higgs boson into double pseudoscalar heavy quarkonia.The tiny branching ratios make these rare decays difficult to measure at the present or future colliders.The predictions of SM will be tested in the future electron-positron colliders with very high precision,which may help to solve the plight of SM and even find some hints of new physics.We expect our theoretical predictions could be tested in the near future.