arXiv subjects

Shuichiro Funatsu

Publications and source records attributed to Shuichiro Funatsu.

22 records · Page 2Linked to original sources

arXiv2016

$H\to Zγ$ in the gauge-Higgs unification

The decay rate of the Higgs decay $H \to Z γ$ is evaluated at the one-loop level in the $SO(5)\times U(1)$ gauge-Higgs unification. Although an infinite number of loops with Kaluza-Klein states contribute to the decay amplitude, there appears the cancellation among the loops, and the decay rate is found to be finite and non-zero. It is found that the decay rate is well approximated by the decay rate in the standard model multiplied by $\cos^2θ_H$, where $θ_H$ is the Aharonov-Bohm phase induced by the vacuum expectation value of an extra-dimensional component of the gauge field.

hep-ph↗

arXiv2014

Dark matter in the $SO(5)\times U(1)$ gauge-Higgs unification

In the $SO(5) \times U(1)$ gauge-Higgs unification the lightest, neutral component of $n_F$ $SO(5)$-spinor fermions (dark fermions), which are relevant for having the observed unstable Higgs boson, becomes the dark matter of the universe. We show that the relic abundance of the dark matter determined by WMAP and Planck data is reproduced, below the bound placed by the direct detection experiment by LUX, by a model with one light and three heavier ($n_F=4$) dark fermions with the lightest one of a mass from 2.3$\,$TeV to 3.1$\,$TeV. The corresponding Aharonov-Bohm phase $θ_H$ in the fifth dimension ranges from 0.097 to 0.074. The case of $n_F=3$ ($n_F = 5, 6$) dark fermions yields the relic abundance smaller (larger) than the observed limit.

hep-ph↗

arXiv2014

LHC signals of the $SO(5)\times U(1)$ gauge-Higgs unification

Signatures of the $SO(5)\times U(1)$ gauge-Higgs unification at LHC and future colliders are explored. The Kaluza-Klein (KK) mass spectra of $γ, Z, Z_R$ and the Higgs self-couplings obey universality relations with the Aharonov-Bohm (AB) phase $θ_H$ in the fifth dimension. The current data at low energies and at LHC indicate $θ_H <0.2$. Couplings of quarks and leptons to KK gauge bosons are determined. Three neutral gauge bosons, the first KK modes $Z_R^{(1)}$, $Z^{(1)}$, and $γ^{(1)}$, appear as $Z'$ bosons in dilepton events at LHC. For $θ_H = 0.114$, the mass and decay width of $Z_R^{(1)}$, $Z^{(1)}$, and $γ^{(1)}$ are (5.73TeV, 482GeV), (6.07TeV, 342GeV), and (6.08TeV, 886GeV), respectively. For $θ_H = 0.073$ their masses are 8.00TeV$\sim$8.61TeV. An excess of events in the dilepton invariant mass should be observed in the $Z'$ search at the upgraded LHC at 14TeV.

hep-ph↗

arXiv2013

Novel universality and Higgs decay H -> γγ, gg in the SO(5) x U(1) gauge-Higgs unification

The SO(5) x U(1) gauge-Higgs unification in the Randall-Sundrum warped space with the Higgs boson mass m_H=126 GeV is constructed. An universal relation is found between the Kaluza-Klein (KK) mass scale $m_{KK}$ and the Aharonov-Bohm (AB) phase $θ_H$ in the fifth dimension; $m_{KK} \sim 1350 GeV/(sin θ_H)^{0.787}$. The cubic and quartic self-couplings of the Higgs boson become smaller than those in the standard model (SM), having universal dependence on $θ_H$. The decay rates H -> γγ, gg are evaluated by summing contributions from KK towers. Corrections coming from KK excited states are finite and about 0.2% (2%) for $θ_H= 0.12 (0.36)$, branching fractions of various decay modes of the Higgs boson remaining nearly the same as in the SM. The signal strengths of the Higgs decay modes relative to the SM are $\sim cos^2 θ_H$. The mass of the first KK $Z$ is predicted to be $5.9 (2.4)$TeV for $θ_H= 0.12 (0.36)$. We also point out the possible enhancement of $Γ(H -> γγ)$ due to the large $U(1)_X$ charge of new fermion multiplets.

hep-ph↗