Search

The article provides information on a study on Higss pair production. It discusses a fully exclusive simulation of gluon fusion Higgs pair production based on matrix element matching. The study concludes that matched samples offer a state-of-the-art accurate exclusive description of the final state.

At hadron colliders, the leading production mechanism for a pair of photons is from quark-antiquark annihilation at the tree level. However, due to large gluon-gluon luminosity, the loop-induced process gg→γγ provides a substantial contribution. In particular, the amplitudes mediated by the top quark become important at the tt̄ threshold and above. In this paper we present the first complete computation of the next-to-leading order (NLO) corrections (up to αS³) to this process, including contributions from the top quark. These entail two-loop diagrams with massive propagators whose analytic expressions are unknown and have been evaluated numerically. We find that the NLO corrections to the top-quark induced terms are very large at low diphoton invariant mass m(γγ) and close to the tt̄ threshold. The full result including five massless quarks and top quark contributions at NLO displays a much more pronounced change of slope in the m(γγ) distribution at tt̄ threshold than at LO and an enhancement at high invariant mass with respect to the massless calculation. [ABSTRACT FROM AUTHOR]

At hadron colliders, the leading production mechanism for a pair of photons is from quark-antiquark annihilation at the tree level. However, due to large gluon-gluon luminosity, the loop-induced process gg→γγ provides a substantial contribution. In particular, the amplitudes mediated by the top quark become important at the tt̄ threshold and above. In this paper we present the first complete computation of the next-to-leading order (NLO) corrections (up to αS³) to this process, including contributions from the top quark. These entail two-loop diagrams with massive propagators whose analytic expressions are unknown and have been evaluated numerically. We find that the NLO corrections to the top-quark induced terms are very large at low diphoton invariant mass m(γγ) and close to the tt̄ threshold. The full result including five massless quarks and top quark contributions at NLO displays a much more pronounced change of slope in the m(γγ) distribution at tt̄ threshold than at LO and an enhancement at high invariant mass with respect to the massless calculation. [ABSTRACT FROM AUTHOR]

We study multi-Higgs final states in vector boson fusion (VBF) processes at the LHC and at future proton-proton colliders, focusing on the prospects for measurements at 27 and 100 TeV. We use an effective Lagrangian which includes higher-dimensional operators in the mass eigenstates which are relevant to VBF processes and relate this to specific parametrizations and models for new physics in the Higgs sector. We derive theoretical constraints on the parameter space from the unitarity of 2→n scattering amplitudes and apply the results to VV→hh and hhh processes, where V=W, Z. As a result, we present constraints on differential distributions as appropriate to the study of VV→hh and hhh processes. [ABSTRACT FROM AUTHOR]

The effective coupling of the Higgs boson to a gluon pair is one of the most important parameters to test the Standard Model and search for the new physics beyond. In this paper, we propose several new observables based on the jet energy profile to extract the effective coupling. The statistical uncertainties of the effective coupling extracted by using new observables are derived and estimated based on the simulation at the future e+e- collider for 250 GeV center-of-mass energy and 5 ab-1 integrated luminosity. We found that the statistical uncertainties of effective coupling via the optimized observable can reach about 1.6% in the channels of a Z boson decaying to lepton pairs and is reduced by 52% compared to the relevant uncertainties in the conventional approach. These new observables potentially can be helpful for the measurement of effective coupling at future e+e- colliders. [ABSTRACT FROM AUTHOR]

Since the discovery of the Higgs boson at the Large Hadron Collider, a future electron-position collider has been proposed for precisely studying its properties. We investigate the production of the Higgs boson at such an e+e- collider associated with a Z boson, and calculate for the first time the mixed QCD-electroweak corrections to the total cross sections. We provide an approximate analytic formula for the cross section and show that it reproduces the exact numeric results rather well for collider energies up to 350 GeV. We also provide numeric results for √s = 500 GeV, where the approximate formula is no longer valid. We find that the O(ααs) corrections amount to a 1.3% increase of the cross section for a center-of-mass energy around 240 GeV. This is significantly larger than the expected experimental accuracy and has to be included for extracting the properties of the Higgs boson from the measurements of the cross sections in the future. [ABSTRACT FROM AUTHOR]