International Journal of Modern Physics A

Several dynamical symmetries of the Dirac Hamiltonian are reviewed and the conditions under which such symmetries hold are considered. These include relativistic spin and orbital angular momentum symmetries, SO(4)×SU_σ(2) symmetry for generalized relativistic hydrogen atom that includes an extra Lorentz scalar potential, SU(3)×SU_σ(2) symmetry for the relativistic simple harmonic oscillator. The energy spectrum in each case is calculated from group-theoretic considerations.

The present status of theoretical and experimental studies of muon capture reactions on light nuclei is reviewed. In particular, the recent results for the two reactions ^{2H(μ-,ν_μ)nn} and ³He(μ^-, ν_μ)³H are presented, and the unresolved discrepancies among different measurements and calculations, open problems, and future developments are discussed.

A self-consistent global fitting method based on the Markov Chain Monte Carlo technique to study the dark matter (DM) property associated with the cosmic ray electron/positron excesses was developed in our previous work. In this work we further improve the previous study to include the hadronic branching ratio of DM annihilation/decay. The PAMELA data are employed to constrain the hadronic branching ratio. We find that the 95% (2σ) upper limits of the quark branching ratio allowed by the PAMELA data is ~0.032 for DM annihilation and ~0.044 for DM decay, respectively. This result shows that the DM coupling to pure leptons is indeed favored by the current data. Based on the global fitting results, we further study the neutrino emission from DM in the galactic center. Our predicted neutrino flux is some smaller than previous works since the constraint from γ-rays is involved. However, it is still capable to be detected by the forthcoming neutrino detector such as IceCube. The improved points of the present study compared with previous works include: (1) the DM parameters, both the particle physical ones and astrophysical ones, are derived in a global fitting way, (2) constraints from various species of data sets, including γ-rays and antiprotons are included, and (3) the expectation of neutrino emission is fully self-consistent.

In a wino LSP scenario the annihilation cross-section of winos gravitationally bound in galaxies can be boosted by a Sommerfeld enhancement factor which arises due to the ladder of exchanged W bosons between the initial states. The boost factor obtained can be in the range S ≃10⁴ if the mass is close to the resonance value of M ≃4 TeV. In this paper we show that if one takes into account the Sommerfeld enhancement in the relic abundance calculation then the correct relic density is obtained for 4 TeV wino mass due to the enhanced annihilation after their kinetic decoupling. At the same time the Sommerfeld enhancement in the χχ→W⁺ W^- annihilation channel is sufficient to explain the positron flux seen in PAMELA data without significantly exceeding the observed antiproton signal. We also show that (e^-+e⁺) and γ-ray signals are broadly compatible with the Fermi-LAT observations. In conclusion we show that a 4 TeV wino DM can explain the positron and antiproton fluxes observed by PAMELA and at the same time give a thermal relic abundance of CDM consistent with WMAP observations.

Using the four best measured moduli of the flavor mixing matrix (|V_ud|, |V_us|, |V_cd|, |V_cs|), the Jarlskog invariant J(V), and the quark masses at M_Z energy scale as experimental constraints, a statistical comparison of three different types of quark mass matrices in the physical basis is performed. The mass matrices in question are the Chaturvedi–Gupta–Sánchez-Colón (CGS), the Fritzsch and the Gupta–Rajpoot types. With nine parameters the best fits are obtained using a Gupta–Rajpoot-type matrix while with seven parameters the best fits are obtained using the CGS-type matrix. The stability of our analysis with respect to evolution of the quark masses is also presented.

We combine the Bethe–Salpeter method with the ³P₀ model to describe OZI-allowed two body meson decays. In this combined method, the relativistic wave functions defined in the Salpeter equation show up in the decay amplitude of the ³P₀ model automatically. We apply the method to OZI-allowed ϒ(4S, 5S, 6S) two body decays. The results are roughly consistent with the experimental data and the predictions of ϒ(6S) decays are given.

It is investigated what constraints are imposed on the so-called yukawaon model when we regard quarks and leptons as of SU(5) (i = 1, 2, 3: index of U(3) family symmetry). In past yukawaon models, the effective Yukawa coupling constants are given by vacuum expectation values of fields Y_f ("yukawaons") as . In order to build a model without a cutoff scale Λ, vector-like fields are introduced in addition to the conventional quarks and leptons. The U(3) family symmetry is broken at 〈Y_f〉~10¹³GeV.

We consider an supersymmetric gauge theory on a curved space. We try to generalize Pestun's localization calculation on the four-sphere to a more general class of curved spaces. We calculated the Q-exact term to localize the path-integral, and when it becomes positive-definite, we obtain a configuration where the path-integral localizes. We also evaluate the super-Yang–Mills action in this configuration.

Besides the SM-like Higgs boson h, the left–right twin Higgs (LRTH) model predicts the existence of three additional Higgs bosons: one neutral Higgs ϕ⁰ and a pair of charged Higgs bosons ϕ^±. In this paper, we focus on the study of the triple Higgs production at the ILC, i.e. e⁺e^-→ϕ⁰ ϕ⁺ϕ^- and e⁺e^-→hhϕ⁰. We present the production cross-sections and the distributions of the various observables, such as, the distributions of the energy and the transverse momenta of neutral and charged Higgs bosons, the differential cross-section of the invariant mass of final Higgs bosons pair, and the production angle distributions of neutral Higgs boson and charged Higgs boson. Our numerical results show that, for the processes e⁺e^-→ϕ⁰ϕ⁺ϕ^- and e⁺e^-→hhϕ⁰, the production rates are at the level of 10^-1 fb with reasonable parameter values while the resonance production cross-section can be significantly enhanced and reach several tens fb. The signatures for signals and corresponding standard model backgrounds are also investigated for the decay mode .

Although our compact form of energy relation is correct, there is an error in the last energy relation reported in our recent paper, which is here corrected.