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Search: authors:"Hiroshi Yokoya"

8 papers found.
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Top-quark mass from the diphoton mass spectrum

We calculate the \(gg\rightarrow \gamma \gamma \) amplitude by including the \(t\bar{t}\) bound-state effects near their mass threshold. In terms of the non-relativistic expansion of the amplitude, the LO contribution is an energy-independent term in the one-loop amplitude. We include the NLO contribution described by the non-relativistic Green function and part of the NNLO ...

Search for Higgs portal DM at the ILC

Higgs portal dark matter (DM) models are simple interesting and viable DM models. There are three types of the models depending on the DM spin: scalar, fermion and vector DM models. In this paper, we consider renormalizable, unitary and gauge invariant Higgs portal DM models, and study how large parameter regions can be surveyed at the International Linear Collider (ILC) experiment ...

Simplified DM models with the full SM gauge symmetry: the case of t-channel colored scalar mediators

The general strategy for dark matter (DM) searches at colliders currently relies on simplified models. In this paper, we propose a new t-channel UV-complete simplified model that improves the existing simplified DM models in two important respects: (i) we impose the full SM gauge symmetry including the fact that the left-handed and the right-handed fermions have two independent ...

Probing CP violation in e + e − production of the Higgs boson and toponia

We study the CP violation in the Higgs boson and toponia production process at the ILC where the toponia are produced near the threshold. With the approximation that the production vertex of the Higgs boson and toponia is contact, and neglecting the P-wave toponia, we analytically calculated the density matrix for the production and decay of the toponia. Under these assumptions, ...

LHC Run-I constraint on the mass of doubly charged Higgs bosons in the same-sign diboson decay scenario

In this letter, we study the latest bound on the mass of doubly charged Higgs bosons, $H^{\pm \pm }$, assuming that they dominantly decay into a diboson. The new bound is obtained by comparing the inclusive searches by the ATLAS Collaboration [ATLAS Collaboration, J. High Energy Phys. 1503, 041 (2015)] for events with a same-sign dilepton using the latest 20.3 fb$^{-1}$ data at the ...

Bound-state effects on kinematical distributions of top quarks at hadron colliders

Yukinari Sumino 1 Hiroshi Yokoya 0 0 Theory Unit, Physics Department , CERN, CH-1211 Geneva, Switzerland 1 Department of Physics, Tohoku University , Sendai 980-8578, Japan First we present a

Single Longitudinal-Spin Asymmetries in Lepton-Pair Production at RHIC and J-PARC

We study the single longitudinal-spin asymmetries in lepton-pair production with large transverse-momentum at RHIC and J-PARC experiments. Asymmetries in the azimuthal angular distribution of a lepton can arise from an absorptive part of the production amplitudes. We reconsider the one-loop calculation for the absorptive part of the production amplitudes in perturbative QCD and ...