arXiv subjects

Noriaki Kitazawa

Publications and source records attributed to Noriaki Kitazawa.

59 records · Page 4Linked to original sources

arXiv1996

An analysis on a supersymmetric chiral gauge theory with no flat direction

The low energy effective theory of the N=1 supersymmetric SU(5) gauge theory with chiral superfields in the 5* and 10 representations is constructed. Instead of postulating the confinement of SU(5) (confining picture), only the confinement of its subgroup SU(4) is postulated (Higgs picture), and the effective fields are SU(4)-singlet but SU(5)-variant. The classical scalar potential which ensures unique supersymmetric vacuum at the classical level is incorporated into the Kaehler potential of the effective fields. We show that supersymmetry and all other global symmetry are spontaneously broken. The scales of these symmetry breaking and the particle spectrum including Nambu-Goldstone particles are explicitly calculated, and no large scale hierarchy is found.

hep-th↗

arXiv1996

Majorana Neutrinos as the Dark Matters in the Cold plus Hot Dark Matter Model

A simple model of the Majorana neutrino with the see-saw mechanism is studied, assuming that two light neutrinos are the hot dark matters with equal mass of 2.4 eV in the cold plus hot dark matter model of cosmology. We find that the heavy neutrino, which is the see-saw partner with the remaining one light neutrino, can be the cold dark matter, if the light neutrino is exactly massless. This cold dark matter neutrino is allowed to have the mass of the wide range from 5.9 x 10^2 eV to 2.2 x 10^7 eV.

hep-ph↗

arXiv1995

Extended technicolor contribution to the Zbb vertex

We show that the flavor-diagonal gauge boson of the extended technicolor theory contributes with opposite sign to the standard model correction for the $Zbb$ vertex. This mechanism can naturally explain the deviation of the LEP result from the standard model prediction for the partial width $Γ(Z \rightarrow b{\bar b})$. A smaller value of the QCD coupling, $α_s(m_Z) \simeq 0.115$, is then preferred by the $Γ(Z \rightarrow \mbox{hadron})$ data, which is consistent with both the recent Lattice-QCD estimate and the Particle Data Group average.

hep-ph↗

arXiv1994

Model independent determination of |Vub| in heavy meson effective thoery

We propose a strategy of the model-independent determination of the Kobayashi-Maskawa matrix element $|V_{ub}|$ within the framework of the heavy meson effective theory. The effective theory is model-independent, since no assumption on the dynamics is introduced except for the symmetry of QCD. Although the effective theory can only be applied to the decay process with soft pions, high detection efficiency on the soft pions in the future B-factories makes this theory effective. The two exclusive processes, $B \rightarrow πl ν$ and $B \rightarrow ππl ν$, are used to determine the value of $|V_{ub}|$, under the condition that the values of the decay constants of $B$ and $B^*$ mesons are given.

hep-ph↗

arXiv1994

Tumbling and Technicolor Theory

The extended technicolor theory is a candidate of the physics beyond the standard model. To explain the mass hierarchy of the quarks and leptons, the extended technicolor gauge symmetry must hierarchically break to the technicolor gauge symmetry. Tumbling gauge theory is considered as a candidate of the dynamics of such hierarchical symmetry breaking, since the sequential self-breaking of the gauge symmetry (``tumbling'') can be expected in that theory. It is well known that the extended technicolor theory induces too strong flavor-changing neutral current interactions to be consistent with the experiments. This problem can be solved if the technicolor dynamics is the special one with very large anomalous dimension of the composite operator ${\bar T}T$ composed by the technifermion field $T$. Two types of the models with large anomalous dimension have been proposed. One is the gauge theory with slowly running coupling, another is the gauge theory with strong four fermion interaction. It is expected that the large anomalous dimension is realized in the tumbling gauge theory. In this thesis we systematically estimate the strength of the effective four fermion interactions induced in the tumbling gauge theory

hep-ph↗