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Katsuji Yamamoto

Publications and source records attributed to Katsuji Yamamoto.

31 records · Page 2Linked to original sources
arXiv2003

Lepton flavor violation with supersymmetric Higgs triplets in TeV region for neutrino masses and leptogenesis

Lepton flavor violating processes such as μ\to 3e and μ\to e γare investigated with supersymmetric Higgs triplet pair Δand \bar Δin the light of neutrino masses and experimentally verifiable leptogenesis. The Higgs triplet mass M_Δis expected to be in the range of 1 - 100 TeV. The branching ratios of these charged lepton decays are evaluated in terms of M_Δand the coupling f L ΔL of Higgs triplet Δwith lepton doublet pairs L L, which is proportional to the neutrino mass matrix. They may be reached in the future collider experiments. In particular, the μ\to 3e decay would be observed indicating the existence of Higgs triplets with M_Δ\sim 1 - 100 TeV for | f | \sim 0.1 - 1, while the μ\to e γdecay can be significant irrespective of M_Δin the supersymmetric model due to the flavor violation in the slepton mass matrices induced by the renormalization effects.

hep-ph↗
arXiv2003

Teleportation-based number state manipulation with number sum measurement

We examine various manipulations of photon number states which can be implemented by teleportation technique with number sum measurement. The preparations of the Einstein-Podolsky-Rosen resources as well as the number sum measurement resulting in projection to certain Bell state may be done conditionally with linear optical elements, i.e., beam splitters, phase shifters and zero-one-photon detectors. Squeezed vacuum states are used as primary entanglement resource, while single-photon sources are not required.

quant-ph↗
arXiv2003

Leptogenesis via multiscalar coherent evolution with supersymmetric neutrino see-saw

A novel scenario of leptogenesis is investigated in the supersymmetric neutrino see-saw model. The right-handed sneutrino $ {\tilde N} $ and the $ ϕ$ field in the $ {\tilde L} H_u $ direction of the slepton and Higgs doublets start together coherent evolution after the inflation with right-handed neutrino mass $ M_N $ smaller than the Hubble parameter of inflation. Then, after some period the motion of $ {\tilde N} $ and $ ϕ$ is drastically changed by the cross coupling $ M_N h_ν{\tilde N}^* ϕϕ$ from the $ M_N N N $ and $ h_νN L H_u $ terms, and the significant asymmetries of $ {\tilde N} $ and $ {\tilde L} $ are generated. The $ {\tilde L} $ asymmetry is fixed later by the thermal effect as the lepton number asymmetry for baryogenesis, while the $ {\tilde N} $ asymmetry disappears through the decays $ {\tilde N} \to {\bar L} {\bar{\tilde H}}_u, {\tilde L} H_u$ with almost the same rate but opposite final lepton numbers.

hep-ph↗
arXiv2002

Maximal entanglement of squeezed vacuum states via swapping with number-phase measurement

We propose a method to refine entanglement via swapping from a pair of squeezed vacuum states by performing the Bell measurement of number sum and phase difference. The resultant states are maximally entangled by adjusting the two squeezing parameters to the same value. We then describe the teleportation of number states by using the entangled states prepared in this way.

quant-ph↗
arXiv2002

Flat manifold leptogenesis in the supersymmetric standard model

Flat manifold leptogenesis a la Affleck-Dine is investigated with the slepton and Higgs fields, L, H_u, H_d, in the supersymmetric standard model. The multi-dimensional motion of these scalar fields is realized in the case that the L H_u and H_u H_d directions are comparably flat with the relevant non-renormalizable superpotential terms. Soon after the inflation, the lepton number asymmetry appears to fluctuate due to this multi-dimensional motion involving certain CP violating phases. Then, it is fixed to some significant non-zero value for the successful baryogenesis when the scalar fields begin to oscillate with rotating phases driven by the quartic coupling from the superpotential term h_e L H_d e^c with h_e \sim 10^-5 - 10^-3. The Hubble parameter H_osc at this epoch for the completion of leptogenesis is much larger than the gravitino mass m_3/2 \sim 10^3 GeV. The thermal terms may even play a cooperative role in this scenario of early leptogenesis. The lightest neutrino mass can be 10^-4 eV, if the reheating temperature is allowed to be 10^10 GeV.

hep-ph↗
arXiv2001

Affleck-Dine leptogenesis with triplet Higgs

We study an extension of the supersymmetric standard model including a pair of electroweak triplet Higgs $Δ$ and ${\bar Δ}$. The neutrinos acquire Majorana masses mediated by these triplet Higgs fields rather than the right-handed neutrinos. The successful leptogenesis for baryogenesis can be realized after the inflation through the Affleck-Dine mechanism on a flat manifold consisting of $Δ$, ${\bar Δ}$, ${\tilde e}^c$ (anti-slepton), even if the triplet Higgs mass $M_Δ$ is much larger than the gravitino mass $m_{3/2} \sim 10^3 {\rm GeV}$. Specifically, due to the effects of the potential terms provided with the superpotential terms $M_Δ{\bar Δ} Δ$, $(λ_{L /} / 2M) {\bar Δ} {\bar Δ} e^c e^c$, $(λ_Δ/ 2M) {\bar Δ} Δ{\bar Δ} Δ$ ($λ_{L /} / λ_Δ\sim 0.3 - 3$), the phases of $Δ$, ${\bar Δ}$, ${\tilde e}^c$ are rotated at the time with the Hubble parameter $H \sim M_Δ$, producing generally the asymmetry with fraction $ε_L \sim 0.1$. If $M_Δ$ is large enough, this early leptogenesis can be completed before the thermal effects take place.

hep-ph↗
arXiv2000

Lepton flavor violation in the supersymmetric standard model with vectorlike leptons

Lepton flavor violating processes are obtained from the mixing between ordinary leptons and vectorlike SU(2)_L doublet leptons which may originate in E_6. The effects of this lepton mixing are, however, suppressed naturally by the hierarchy of the charged lepton masses. In the supersymmetric model, significant effects of lepton flavor violation may appear rather through slepton mixing, which is in the present case generated by radiative corrections with ordinary-exotic lepton couplings. We are especially interested in the mu -> e gamma decay. In the model without the bare mass term of vectorlike leptons, the supersymmetric contributions are rather suppressed due to the approximate U(1)_e X U(1)_mu. It is, however, remarkable that they are substantially enhanced by tan^6 beta. Then, B(mu -> e gamma) might be comparable to the experimental bound for large tan beta. In the model with the bare mass term, much larger contributions are obtained through slepton mixing. These investigations show that the supersymmetric effects on lepton flavor violation due to the vectorlike leptons can be observed in the near future experiments.

hep-ph↗
arXiv2000

Quark mixings and flavor changing interactions with singlet quarks

Aspects of the quark mixings and flavor changing interactions are investigated in electroweak models with singlet quarks. The effects on the ordinary quark mixing are determined in terms of the quark masses and the parameters describing the mixing between the ordinary quarks q and the singlet quarks Q (q-Q mixing). Some salient features arise in the flavor changing interactions through the q-Q mixing. The unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) matrix within the ordinary quark sector is violated, and the flavor changing neutral currents (FCNC's) appear both in the gauge and scalar couplings. The flavor changing interactions are calculated appropriately in terms of the q-Q mixing parameters and the quark masses, which really exhibit specific flavor structures. It is found that there are reasonable ranges of the model parameters to reproduce the ordinary quark mass hierarchy and the actual CKM structure even in the presence of q-Q mixing. Some phenomenological effects of the singlet quarks are also discussed. In particular, the scalar FCNC's may be more important in some cases, if the singlet quarks as well as the extra scalar particles from the singlet Higgs fields have masses $\sim$ 100 GeV -- 1 TeV.

hep-ph↗
arXiv1999

Quantum analysis of Rydberg atom cavity detector for dark matter axion search

Quantum calculations are developed on the dynamical system consisting of the cosmic axions, photons and Rydberg atoms which are interacting in the resonant microwave cavity. The time evolution is determined for the number of Rydberg atoms in the upper state which are excited by absorbing the axion-converted and thermal background photons. The calculations are made, in particular, by taking into account the actual experimental situation such as the motion and uniform distribution of the Rydberg atoms in the incident beam and also the spatial variation of the electric field in the cavity. Some essential aspects on the axion-photon-atom interaction in the resonant cavity are clarified by these detailed calculations. Then, by using these results the detection sensitivity of the Rydberg atom cavity detector is estimated properly. This systematic quantum analysis enables us to provide the optimum experimental setup for the dark matter axion search with Rydberg atom cavity detector.

hep-ph↗
arXiv1997

Flavor nonconservation and CP violation from quark mixings with singlet quarks

Flavor nonconserving and CP violating effects of the quark mixings are investigated in electroweak models incorporating singlet quarks. Especially, the D^0 - {\bar D}^0 mixing and the neutron electric dipole moment, which are mediated by the up-type quark couplings to the neutral Higgs fields, are examined in detail for reasonable ranges of the quark mixings and the singlet Higgs mass scale. These neutral Higgs contributions are found to be comparable to or smaller than the experimental bounds even for the case where the singlet Higgs mass scale is of the order of the electroweak scale and a significant mixing is present between the top quark and the singlet quarks.

hep-ph↗
arXiv1997

Flavor-Nonconservation and CP-Violation with Singlet Quarks

Some aspects are considered on the flavor-nonconservation and $ CP $-violation arising from the quark mixings with singlet quarks. In certain models incorporating the singlet quarks, the contributions of the quark couplings to the neutral Higgs fields may become more significant than those of the neutral gauge interactions. Then, they would provide distinct signatures for new physics beyond the standard model in various flavor-nonconserving and $ CP $-violating processes such as the neutron electric dipole moment, $ D^0 $-$ {\bar D}^0 $, $ K^0 $-$ {\bar K}^0 $, $ B^0 $-$ {\bar B}^0 $, $ b \to s γ$, and so on.

hep-ph↗
arXiv1995

Neutron electric dipole moment in a supersymmetric model with singlet quarks

The neutron electric dipole moment is investigated in a supersymmetric electroweak model admitting $ {\rm SU(2)}_W $ singlet and $ Q = -1/3 $, say $ D $-type, quarks. Significant $ CP $ violating phases appear in the coupling between the singlet $ D $-type quarks and the ordinary $ d $-type quarks. Then, through the $ d $-$ D $ mixing effects on the squark mass terms the gluino one-loop diagrams provide naturally the contributions $ \sim 10^{-26} e~{\rm cm} $ comparable to the current experimental bound on the neutron electric dipole moment. The $ CP $ violation in the $ d $-$ D $ coupling would also be relevant for the electroweak baryogenesis.

hep-ph↗