Modern Physics Letters A

In this brief review, we discuss the viability of a multi-dimensional geometrical theory with one compactified dimension. We discuss the case of a Kaluza–Klein (KK) fifth-dimensional theory, addressing the problem by an overview of the astrophysical phenomenology associated with this five-dimensional (5D) theory. By comparing the predictions of our model with the features of the ordinary (four-dimensional (4D)) Relativistic Astrophysics, we highlight some small but finite discrepancies, expectably detectible from the observations. We consider a class of static, vacuum solutions of free electromagnetic KK equations with three-dimensional (3D) spherical symmetry. We explore the stability of the particle dynamics in these spacetimes, the construction of self-gravitating stellar models and the emission spectrum generated by a charged particle falling on this stellar object. The matter dynamics in these geometries has been treated by a multipole approach adapted to the geometric theory with a compactified dimension.

We present a formulation of the operator product expansion that is infrared finite to all orders in the attendant massless non-Abelian gauge theory coupling constant which we will oftentimes associate with the QCD theory. We actually have the QCD theory as our primary objective in view of the operation of the LHC at CERN. We make contact in this way with the recently introduced IR-improved DGLAP-CS theory and point-out phenomenological implications accordingly, with an eye toward the precision QCD theory for LHC physics.

We study the anisotropy in the arrival directions of Pierre Auger Observatory (PAO) ultra-high-energy cosmic rays (UHECRs), using the point source correlational angular distance distribution (CADD). The result shows that the anisotropy is characterized by one prominent excess region and one void region. The excess region is located near the Centaurus A direction, supporting that the Centaurus A is a promising UHECR source. The void region near the south pole direction may be used to limit the diffuse isotropic background contribution.

We verify that quadratic divergences stemming from gravitational corrections to quantum electrodynamics (QED) which have been conjectured to lead to asymptotic freedom near Planck scale are arbitrary (regularization dependent) and compatible with zero. Moreover, we explicitly show that such arbitrary term contributes to the beta function of QED in a gauge dependent way in the gravitational sector.

The problem of normalization related to energy-dependent potentials is examined in the context of the path integral approach, and a justification is given. As examples, the harmonic oscillator and the hydrogen atom (radial) where, respectively the frequency and the Coulomb's constant depend on energy, are considered and their propagators determined. From their spectral decomposition, we have found that the wave functions extracted are correctly normalized.

We calculate the destructive interference factors between the Higgs decay H→γγ produced in gluon-fusion and the Standard Model (SM) continuum gg→γγ process, as a function of the scattering angle in the center-of-mass frame of the final two photons. The interference factors are studied with the selections based on the acceptance criteria of the ATLAS and CMS H→γγ searches at the LHC. The result shows that the destructive interference is only at an order of 2.5% for the SM Higgs analysis at the LHC. The factors are almost the same for the same Higgs mass hypothesis but with different proton–proton collisions at , 8 TeV, 13 TeV and 14 TeV. The destructive interference is far below the present uncertainty on the total cross-section prediction of Higgs, which is about 15% used at the LHC. A destructive interference factor of -2.5% is suggested to be used in the H→γγ analysis at the LHC, due to the effect from the interference for this decay channel.

Recently the ATLAS and CMS experiments at the LHC have found a Higgs-like boson h with a mass around 125 GeV from several decay modes. The decay mode h →γγ is one of the most important modes in studying whether h is actually the Standard Model (SM) Higgs boson. Current data indicate that h→γγ has a branching ratio larger than the SM prediction for h being identified as the SM Higgs boson. To decide whether the h discovered at the LHC is the SM Higgs boson, more data are needed. We study how γγ collider can help to provide some of the most important information about the Higgs boson properties. We show that a γγ collider can easily verify whether the enhanced h →γγ observed at the LHC hold. Different models can be tested by studying Higgs boson decay to γZ. Studying angular distribution of the γγ through on-shell production of h and its subsequent decays into a γγ pair can decide whether the Higgs-like boson h at the LHC is a spin-0 or a spin-2 boson.