arXiv subjects

Hisaki Hatanaka

Publications and source records attributed to Hisaki Hatanaka.

At least 37 records · Page 2Linked to original sources

arXiv2016

AdS/QCD approach to the scale-invariant extension of the standard model with a strongly interacting hidden sector

In this paper, we revisit a scale-invariant extension of the standard model (SM) with a strongly interacting hidden sector within AdS/QCD approach. Using the AdS/QCD, we reduce the number of input parameters to three, {\it i.e.} hidden pion decay constant, hidden pion mass and $\tanβ$ that is defined as the ratio of the vacuum expectation values (VEV) of the singlet scalar field and the SM Higgs boson. As a result, our model has sharp predictability. We perform the phenomenological analysis of the hidden pions which is one of the dark matter (DM) candidates in this model. With various theoretical and experimental constraints we search for the allowed parameter space and find that both resonance and non-resonance solutions are possible. Some typical correlations among various observables such as thermal relic density of hidden pions, Higgs boson signal strengths and DM-nucleon cross section are investigated. We provide some benchmark points for experimental tests.

hep-ph↗

arXiv2015

Oblique corrections from less-Higgsless models in warped space

The Higgsless model in warped extra dimension is reexamined. Dirichlet boundary conditions on the TeV brane are replaced with Robin boundary conditions which are parameterized by a mass parameter $M$. We calculate the Peskin-Takeuchi precision parameters $S$, $T$ and $U$ at tree level. We find that to satisfy the constraints on the precision parameters at $99 \%$ [$95 \%$] confidence level (CL) the first Kaluza-Klein excited $Z$ boson, $Z'$, should be heavier than 5 TeV [8 TeV]. The Magnitude of $M$, which is infinitely large in the original model, should be smaller than 200 GeV (70 GeV) for the curvature of the warped space $R^{-1}=10^{16}$ GeV ($10^{8}$ GeV) at $95\%$ CL. If the Robin boundary conditions are induced by the mass terms localized on the TeV brane, from the $99\%$ [$95\%$] bound we find that the brane mass interactions account for more than $97\%$ [$99\%$] of the masses of $Z$ and $W$ bosons. Such a brane mass term is naturally interpreted as a vacuum expectation value of the Higgs scalar field in the standard model localized on the TeV brane. If so, the model can be tested by precise measurements of $HWW$, $HZZ$ couplings and search for 1st Kaluza-Klein excited states.

hep-ph↗

arXiv2015

A Three-Loop Neutrino Model with Global $U(1)$ Symmetry

We study a three-loop induced neutrino model with a global $U(1)$ symmetry at TeV scale, in which we naturally accommodate a bosonic dark matter candidate. We discuss the allowed regions of masses and quartic couplings for charged scalar bosons as well as the dark matter mass on the analogy of the original Zee-Babu model, and show the difference between them. We also discuss the possibility of the collider searches, in which future like-sign electron liner collider could be promising.

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

Polyakov loops and the Hosotani mechanism on the lattice

We explore the phase structure and symmetry breaking in four-dimensional SU(3) gauge theory with one spatial compact dimension on the lattice ($16^3 \times 4$ lattice) in the presence of fermions in the adjoint representation with periodic boundary conditions. We estimate numerically the density plots of the Polyakov loop eigenvalues phases, which reflect the location of minima of the effective potential in the Hosotani mechanism. We find strong indication that the four phases found on the lattice correspond to SU(3)-confined, SU(3)-deconfined, SU(2) x U(1), and U(1) x U(1) phases predicted by the one-loop perturbative calculation. The case with fermions in the fundamental representation with general boundary conditions, equivalent to the case of imaginary chemical potentials, is also found to support the $Z_3$ symmetry breaking in the effective potential analysis.

hep-lat↗

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

Hosotani mechanism on the lattice

We explore the phase structure and symmetry breaking in four-dimensional SU(3) gauge theory with one spatial compact dimension on the lattice in the presence of fermions in the adjoint and fundamental representations with general boundary conditions. The eigenvalue phases of Polyakov loops and the associated susceptibility are measured on 16^3 x 4 lattice. We establish a correspondence between the phases found on the lattice and the gauge symmetry breaking by the Hosotani mechanism.

hep-lat↗

arXiv2013

Thermal Phase Transition in the SO(5) x U(1) Gauge-Higgs Unification with 126GeV Higgs

We study the phase structure of the gauge theories in the space-time with one compact dimension, where the gauge symmetry can be broken by the Hosotani mechanism. As the extra dimension, we consider the SO(5) x U(1) gauge-Higgs unification in the Randall-Sundrum space-time which reproduce the 126 GeV Higgs mass. It is found that the thermal phase transition of the electroweak symmetry is almost second order and the critical temperature is around 160 GeV for z_L < 10^7 and n_F=3.

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↗

arXiv2012

SUSY breaking scales in the gauge-Higgs unification

In the $SO(5) \times U(1)$ gauge-Higgs unification in the Randall-Sundrum (RS) warped space the Higgs boson naturally becomes stable. The model is consistent with the current collider signatures only for a large warp factor $z_L > 10^{15}$ of the RS space. In order for stable Higgs bosons to explain the dark matter of the Universe the Higgs boson must have a mass $m_h = 70 \sim 75$ GeV, which can be obtained in the non-SUSY model with $z_L \sim 10^5$. We show that this discrepancy is resolved in supersymmetric gauge-Higgs unification where a stop mass is about $300 \sim 320 $GeV and gauginos in the electroweak sector are light.

hep-ph↗

arXiv2011

Gauge-Higgs Unification in Lifshitz Type Gauge Theory

We discuss the gauge-Higgs unification in a framework of Lifshitz type gauge theory. We study a higher dimensional gauge theory on R^{D-1}\times S^{1} in which the normal second (first) order derivative terms for scalar (fermion) fields in the action are replaced by higher order derivative ones for the direction of the extra dimension. We provide some mathematical tools to evaluate a one-loop effective potential for the zero mode of the extra component of a higher dimensional gauge field and clarify how the higher order derivative terms affect the standard form of the effective potential. Our results show that they can make the Higgs mass heavier and change its vacuum expectation value drastically. Some extensions of our framework are briefly discussed.

hep-ph↗

arXiv2010

Radiative and Semileptonic B Decays Involving Higher K-Resonances in the Final States

We study the radiative and semileptonic B decays involving a spin-$J$ resonant $K_J^{(*)}$ with parity $(-1)^J$ for $K_J^*$ and $(-1)^{J+1}$ for $K_J$ in the final state. Using the large energy effective theory (LEET) techniques, we formulate $B \to K_J^{(*)}$ transition form factors in the large recoil region in terms of two independent LEET functions $ζ_\perp^{K_J^{(*)}}$ and $ζ_\parallel^{K_J^{(*)}}$, the values of which at zero momentum transfer are estimated in the BSW model. According to the QCD counting rules, $ζ_{\perp,\parallel}^{K_J^{(*)}}$ exhibit a dipole dependence in $q^2$. We predict the decay rates for $B \to K_J^{(*)} γ$, $B \to K_J^{(*)} \ell^+ \ell^-$ and $B \to K_J^{(*)}ν\barν$. The branching fractions for these decays with higher $K$-resonances in the final state are suppressed due to the smaller phase spaces and the smaller values of $ζ^{K_J^{(*)}}_{\perp,\parallel}$. Furthermore, if the spin of $K_J^{(*)}$ becomes larger, the branching fractions will be further suppressed due to the smaller Clebsch-Gordan coefficients defined by the polarization tensors of the $K_J^{(*)}$. We also calculate the forward backward asymmetry of the $B \to K_J^{(*)} \ell^+ \ell^-$ decay, for which the zero is highly insensitive to the $K$-resonances in the LEET parametrization.

hep-ph↗

arXiv2009

Radiative and Semileptonic B Decays Involving the Tensor Meson K_2^*(1430) in the Standard Model and Beyond

We study semileptonic and radiative B decays involving the strange tensor meson K_2^*(1430) in the final state. Using the large energy effective theory (LEET) techniques, we formulate the B \to K_2^* transition form factors in large recoil region. All the form factors can be parametrized in terms of two independent LEET parameters ζ_\perp and ζ_\parallel. The magnitude of ζ_\perp is estimated from the data for Br(B \to K_2^*(1430)γ). Assuming a dipole q^2-dependence for the LEET parameters and ζ_\parallel/ζ_\perp = 1.0 \pm 0.2, we investigate the decays B \to K_2^* \ell^+ \ell^- and B \to K_2^* ν\barν, where the contributions due to $ζ_\parallel are suppressed by m_{K_2^*}/m_B. For the B \to K_2^* \ell^+ \ell^- decay, in the large recoil region where the hadronic uncertainties are considerably reduced, the longitudinal distribution d F_L/ds is reduced by 20-30 % due to the flipped sign of c_7^eff compared with the standard model result. Moreover, the forward-backward asymmetry zero is about 3.4 GeV^2 in the standard model, but changing the sign of c_7^eff yields a positive asymmetry for all values of the invariant mass of the lepton pair. We calculate the branching fraction for B \to K_2^* ν\barν in the standard model. Our result exhibits the impressed resemblance between B \to K_2^*(1430) \ell^+\ell^-, ν\barν and B \to K^*(892) \ell^+ \ell^-, ν\barν.

hep-ph↗

arXiv2008

K1(1270)-K1(1400) Mixing Angle and New-Physics Effects in B to K1 l+ l- Decays

We study semileptonic B meson decays B to K_1(1270) l^+ l^- and K_1(1400) l^+ l^- (l=e, mu, tau), where the strange P-wave mesons, K_1(1270) and K_1(1400), are the mixtures of the K_{1A} and K_{1B}, which are the 1^3P_1 and 1^1P_1 states, respectively. We show that the ratio R_l = Br(B to K_1(1400) l^+ l^-)/Br(B to K_1(1270) l^+ l^-), insensitive to new-physics parameters, is suitable for determining the K_1(1270)-K_1(1400) mixing angle, theta_{K_1}. The forward-backward asymmetry shows a weak theta_{K_1}-dependence for B to K_1(1270) mu^+ mu^-, but relatively strong for B to K_1(1400) mu^+ mu^-. We investigate model-independent new-physics corrections to operators relevant to the b to s l^+ l^- electroweak-penguin and weak-box diagrams. Furthermore, for the B to K_1(1270) mu^+ mu^- decay the position of the forward-backward asymmetry zero, which is almost independent of the value of theta_{K_1}, can be dramatically changed under variation of new-physics parameters.

hep-ph↗

arXiv2008

$B \to K_1 γ$ Decays in the Light-Cone QCD Sum Rules

We present a detailed study of $B\to K_1(1270) γ$ and $B\to K_1(1400) γ$ decays. Using the light-cone sum rule technique, we calculate the $B\to K_{1A} (1^3P_1)$ and $B\to K_{1B} (1^1P_1)$ tensor form factors, $T_1^{K_{1A}}(0)$ and $T_1^{K_{1B}}(0)$, where the contributions are included up to the first order in $m_{K_1}/m_b$. We resolve the sign ambiguity of the $K_1(1270)$--$K_1(1400)$ mixing angle $θ_{K_1}$ by defining the signs of decay constants, $f_{K_{1A}}$ and $f_{K_{1B}}^\perp$. From the comparison of the theoretical calculation and the data for decays $B\to K_1 γ$ and $τ^-\to K_1^-(1270)ν_τ$, we find that $θ_{K_1}=-(34\pm 13)^\circ$ is favored. In contrast to $B\to K^* γ$, the hard-spectator contribution suppresses the $B\to K_1(1270) γ$ and $B\to K_1(1400) γ$ branching ratios slightly. The predicted branching ratios are in agreement with the Belle measurement within the errors. We point out that a more precise measurement for the ratio $R_{K_1}={\cal B}(B\to K_1(1400)γ)/{\cal B}(B\to K_1(1270)γ)$ can offer a better determination for the $θ_{K_1}$ and consequently the theoretical uncertainties can be reduced.

hep-ph↗

arXiv2008

(Pseudo-) Scalar Operators in the MSSM and B to phi K^*, K eta(') Decays

We study the effect of b to s sbar s scalar/pseudoscalar operators, originating from penguin diagrams of neutral Higgs bosons in the MSSM, in B to K eta(') and B to phi K^* decays. These operators can be Fierz-transformed into tensor operators, and the resultant tensor operators could affect the transverse polarization amplitudes in B to phi K^* decays. We find that only when the weak annihilations in B to phi K^* into account, the polarization puzzle can be resolved, so that new physics effects are strongly suppressed and no more relevant to the enhancement of the transverse modes in B to phi K^* decays.

hep-ph↗

arXiv2007

Pseudoscalar and Scalar Operators of Higgs-Penguins in the MSSM and B to phi K^*, K eta(') Decays

We study the effect of b to s sbar s scalar/pseudoscalar operators in B to K eta('), phi K^* decays. In the minimal supersymmetric standard model (MSSM), such scalar/pseudoscalar operators can be induced by the penguin diagrams of neutral Higgs bosons. These operators can be Fierz-transformed into tensor operators, and the resultant tensor operators could affect the transverse polarization amplitudes in B to phi K^* decays. A combined analysis of the decays B to phi K^* and B to K eta('), including b to s sbar s scalar/pseudoscalar operators and their Fierz-transformed tensor operators originated from the MSSM, is performed. Our study is based on the followings: (1) Assuming that weak annihilations in B to phi K^* is negligible and the polarization puzzle is resolved by Fierz-transformed tensor operators, it results in too large coefficients of scalar/pseudoscalar operators, such that the resulting B to K eta(') branching fractions are much larger than observations. (2) When we take the weak annihilations in B to phi K^* into account, the polarization puzzle can be resolved. In this case, new physics effects are strongly suppressed and no more relevant to the enhancement of the transverse modes in B to phi K^* decays.

hep-ph↗

arXiv2007

Radiatively Induced Spontaneous Symmetry Breaking by Wilson Line in a Warped Extra Dimension

We investigate the dynamical gauge-Higgs unification in the Randall-Sundrum (RS) space-time. We study the dynamical gauge-Higgs unification in the SU(2) gauge theory with a bulk fermion in the RS space-time. We evaluate the contribution from fermion loop to the one-loop effective potential with respect to the Wilson-line phase, and study the dynamical gauge symmetry breaking. We also apply this mechanism of the gauge symmetry breaking to the electroweak gauge-Higgs unification in the RS space-time. Especially we numerically studied a SU(3)_w gauge model as a toy model of electroweak gauge-Higgs unification in the RS space-time. We introduce an adjoint fermion into the model to break the gauge symmetry and to obtain the U(1)_em electromagnetic symmetry. We found that in this model the ratio of Z-boson mass to W-boson varies with respect to the Wilson-line phase even at the tree level. We also propose a dynamical mechanism of tuning the ratio m_Z/m_W to the experimental value 91.2GeV/80.4GeV=1.13 by introducing bulk scalars or bulk fermions with twisted boundary conditions. In these models the Higgs can vary in mass between zero and 290GeV.

hep-th↗