arXiv subjects

Norihisa Watanabe

Publications and source records attributed to Norihisa Watanabe.

7 recordsLinked to original sources

arXiv2018

PHOTON-2017 conference proceedings

This document collects the proceedings of the PHOTON 2017 conference ("International Conference on the Structure and the Interactions of the Photon", including the 22th "International Workshop on Photon-Photon Collisions", and the "International Workshop on High Energy Photon Colliders") held at CERN (Geneva) in May 2017. The latest experimental and theoretical developments on the topics of the PHOTON conference series are covered: (i) $γ\,γ$ processes in e$^+$e$^-$, proton-proton (pp) and nucleus-nucleus (AA) collisions at current and future colliders, (ii) $γ$-hadron interactions in e$^\pm$p, pp, and AA collisions, (iii) final-state photon production (including Standard Model studies and searches beyond it) in pp and AA collisions, and (iv) high-energy $γ$-ray astrophysics. These proceedings are dedicated to the memory of Maria Krawczyk.

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arXiv2015

ME-PS matching in the simulation of multi-jet production in hadron collisions using a subtraction method

The subtraction method for the matching between the matrix element (ME) and parton shower (PS), that has been developed for combining 0-jet and 1-jet production processes in association with electroweak-boson production in hadron collisions, is extended to multi-jet production. In order to include multi-jet MEs, we have to address the soft-gluon divergence together with the collinear divergence. We introduce an approximation which simultaneously reproduces both divergences in a form suitable for application to our subtraction method. The alteration in the subtraction can be compensated by applying an appropriate correction to corresponding non-radiative events. We demonstrate that $W$ + 0, 1, and 2 jet production processes can be consistently combined using the developed matching method.

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arXiv2014

Higgs production in $e$ and real $γ$ collision

We investigate the Standard Model Higgs boson production in $e^-γ$ collision. The electroweak one-loop contributions to the scattering amplitude for $e^-γ\rightarrow e^-H$ are calculated and expressed in analytical form. We analyze the cross section for the Higgs production in $e^-γ$ collision for each combination of polarizations of the initial electron and photon beams. The feasibility of observing the Higgs boson in $e^-+γ\rightarrow e^-+b+{\overline b}$ channel is examined.

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arXiv2013

Higgs Production in Two-Photon Process and Transition Form Factor

The Higgs production in the two-photon fusion process is investigated where one of the photons is off-shell while the other one is on-shell. This process is realized in either electron-positron collision or electron-photon collision where the scattered electron or positron is detected (single tagging) and described by the transition form factor. We calculate the contributions to the transition form factor of the Higgs boson coming from top-quark loops and W-boson loops. We then study the $Q^2$ dependence of each contribution to the total transition form factor and also of the differential cross section for the Higgs production.

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arXiv2013

One loop integration with hypergeometric series by using recursion relations

General one-loop integrals with arbitrary mass and kinematical parameters in $d$-dimensional space-time are studied. By using Bernstein theorem, a recursion relation is obtained which connects $(n+1)$-point to $n$-point functions. In solving this recursion relation, we have shown that one-loop integrals are expressed by a newly defined hypergeometric function, which is a special case of Aomoto-Gelfand hypergeometric functions. We have also obtained coefficients of power series expansion around 4-dimensional space-time for two-, three- and four-point functions. The numerical results are compared with LoopTools for the case of two- and three-point functions as examples.

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arXiv2013

The real photon structure functions in massive parton model in NLO

We investigate the one-gluon-exchange ($αα_s$) corrections to the real photon structure functions $W_{TT} $, $W_{LT}$, $W_{TT}^{a} $ and $W_{TT}^τ$ in the massive parton model. We employ a technique based on the Cutkosky rules and the reduction of Feynman integrals to master integrals. We show that a positivity constraint, which is derived from the Cauchy-Schwarz inequality, is satisfied among the unpolarized and polarized structure functions $W_{TT}$, $W_{TT}^a$ and $W_{TT}^τ$ calculated up to the next-to-leading order in QCD.

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arXiv2012

The polarized photon structure function $g_1^γ(x,Q^2)$ in massive parton model in NLO

We investigate the one-gluon-exchange ($αα_s$) corrections to the polarized real photon structure function $g_1^γ(x,Q^2)$ in the massive parton model. We employ a technique based on the Cutkosky rules and the reduction of Feynman integrals to master integrals. The NLO contribution is noticeable at large $x$ and does not vanish at the threshold of the massive quark pair production due to the Coulomb singularity. It is found that the first moment sum rule of $g_1^γ$ is satisfied up to the NLO.

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