International Journal of Modern Physics A

The kaon system has been a privileged observatory for the discovery and the study of the violations of fundamental discrete symmetries, elucidating the role of such phenomena within the present successful theory of particle physics. Its peculiar characteristics from an experimental and a theoretical point of view make this system an ideal one for the investigation of elusive asymmetries. An overview of recent measurements is presented, as well as a discussion of the rich future plans for high-precision measurements with several different approaches.

We study the production of the vector U-unparticle stuff and a single photon in decays of a dilaton. The signals of an unparticle can be detected through the missing energy and momentum distribution carried away by U once it was produced in radiative decay of a dilaton. The continuous energy spectrum of the emitted photons encoding the recoil unparticle can be measured in precision studies of rare decays of the dilaton or Higgs-boson after their discoveries.

In this paper we study the effects of black hole mass on the absorption cross-section for a massive scalar field propagating in a five-dimensional topological Chern–Simons black hole at the low-frequency limit. We consider the two branches of black hole solutions (α = ±1) and we show that, if the mass of black hole increase the absorption cross-section decreases at the zero-frequency limit for the branch α = -1 and for the other branch, α = 1, the behavior is opposite, if the black hole mass increase the absorption cross-section increases. Also we find that beyond a certain frequency value, the mass black hole does not affect the absorption cross-section.

In this paper we apply the Functional Renormalization Group Equation (FRGE) to the noncommutative scalar field theory proposed by Grosse and Wulkenhaar. We derive the flow equation in the matrix representation and discuss the theory space for the self-dual model. The features introduced by the external dimensionful scale provided by the noncommutativity parameter, originally pointed out in R. Gurau and O. J. Rosten, J. High Energy Phys.0907, 064 (2009), are discussed in the FRGE context. Using a technical assumption, but without resorting to any truncation, it is then shown that the theory is asymptotically safe for suitably small values of the ϕ⁴ coupling, recovering the result of M. Disertori et al., Phys. Lett. B649, 95 (2007). Finally, we show how the FRGE can be easily used to compute the one-loop beta-functions of the duality covariant model.

We consider the λSUSY model, a version of the NMSSM with large λH₁H₂S coupling, relaxing the approximation of large singlet mass and negligible mixing of the scalar singlet with the scalar doublets. We show that there are regions of the parameter space in which the lightest pseudoscalar can be relatively light, with unusual consequences on the decay pattern of the CP-even Higgs bosons and thus on the LHC phenomenology.

We study non-Abelian flavor symmetries on orbifolds, S¹/Z₂ and T²/Z₃. Our extra dimensional models realize D_N, Σ(2N²), Δ(3N²) and Δ(6N²) including A₄ and S₄. In addition, one can also realize their subgroups such as Q_N, T₇, etc. The S₃ flavor symmetry can be realized on both S¹/Z₂ and T²/Z₃ orbifolds.

The model-independent constraints on the Abelian Z′ couplings from the LEP data are applied to estimate the Z′ production in experiments at the Tevatron and LHC. The Z′ total and partial decay widths are analyzed. The results are compared with model-dependent predictions and present experimental data from the Tevatron. If we assume the 1–2σ hints from the LEP data to be a signal of the Abelian Z′ boson, then the Tevatron data constrain the Z′ mass between 400 GeV and 1.2 TeV.

We present new results concerning the masses and the decay widths of the most interesting hybrid meson states taking as inputs the gluon mass m_g and the nonperturbative QCD running coupling constant α_s(0) coming from both LQCD and SDE recent estimations.

Since our universe is a system with the temperature so it is interesting to investigate the effects of temperature in the brane-world theories. In this paper we consider the effect of temperature on a real scalar field with potential V(ϕ) = -½aϕ² + ¼bϕ⁴ in a flat extra dimension. We find analytical expressions for the coefficients of the potential. We study the effect of the temperature on the domain wall (thick brane solution). We find an expression for the critical temperature which separates a symmetric phase from the broken symmetry phase. By inclusion of fermions, we also investigate temperature effect on the localization of fermions in extra dimension. It is found that the inclusion of fermion reduces the critical temperature.

The recent BaBar measurements of the γγ*→π⁰ transition form-factor show spectacular deviation from perturbative QCD prediction for large spacelike Q² up to 34 GeV². When plotted against Q², Q²F(Q²) shows steady increase with Q² in contrast with the flat Q² behavior predicted by perturbative QCD, and at 34 GeV² is more than 50% larger than the QCD prediction. Stimulated by the BaBar measurements, we revisit our previous paper on the cancellation of anomaly effects in high energy processes Z⁰→π⁰γ, e⁺e^- → π⁰γ and apply our results to the γ*γ→π⁰ transition form-factor measured in the e⁺e^- → e⁺e^-π⁰ process with one highly virtual photon. We find that, the transition form-factor F(Q²) behaves as and produces a striking agreement with the BaBar data for Q²F(Q²) with m = 132 MeV which also reproduces very well the CLEO data at lower Q².

We improve the previous study of the Klein–Gordon equation in a noncommutative space–time as applied to the hydrogen atom to extract the energy levels, by considering the second-order corrections in the noncommutativity parameter. Phenomenologically we show that noncommutativity is the source of Lamb shift corrections.

A novel attempt has been made to probe the QCD phase boundary by using the experimental data for transverse momenta of ϕ mesons produced in nuclear collisions at AGS, SPS and RHIC energies. The data are confronted with simple thermodynamic expectations and lattice QCD results. The experimental data indicate a first-order phase transition, with a mixed phase stretching the energy density between ~1 and 3.2 GeV/fm³ corresponding to SPS energies.