Two-photon exchange in leptophilic dark matter scenarios

In leptophilic scenarios, dark matter interactions with nuclei, relevant for direct detection experiments and for the capture by celestial objects, could only occur via loop-induced processes. If the mediator is a scalar or pseudo-scalar particle, which only couples to leptons, the dominant contribution to dark matter-nucleus scattering would take place via two-photon exchange with a lepton triangle loop. The corresponding diagrams have been estimated in the literature under different approximations. Here, we present new analytical calculations for one-body two-loop and two-body one-loop interactions. The two-loop form factors are presented in closed analytical form in terms of generalized polylogarithms up to weight four. In both cases, we consider the exact dependence on all the involved scales, and study the dependence on the momentum transfer. We show that some previous approximations fail to correctly predict the scattering cross section by several orders of magnitude. Moreover, we quantitatively show that form factors in the range of momentum transfer relevant for local galactic dark matter, can be significantly smaller than their value at zero momentum transfer, which is the approach usually considered.

Photon and leptons induced processes at the LHC

We study a few basic photon- and lepton-initiated processes at the LHC which can be computed using the recently developed photon and lepton parton densities. First, we consider the production of a massive scalar particle initiated by lepton-antilepton annihilation and photon-photon fusion as representative examples of searches of exotic particles. Then we study lepton-lepton scattering, since this Standard-Model process may be observable at the LHC. We examine these processes at leading and next-to-leading order and, using the POWHEG method, we match our calculations to parton shower programs that implement the required lepton or photon initial-states. We assess the typical size of cross-sections and their uncertainties and discuss the preferred choices for the factorization scale. These processes can also be computed starting directly from the lepto-production hadronic tensor, leading to a result where some collinear-enhanced QED corrections are missing, but all strong corrections are included. Thus, we are in the unique position to perform a comparison of results obtained via the factorization approach to a calculation that does not have strong corrections. This is particularly relevant in the case of lepton-scattering, that is more abundant at lower energies where it is affected by larger strong corrections. We thus compute this process also with the hadronic-tensor method, and compare the results with those obtained with POWHEG. Finally, for some lepton-lepton scattering processes, we compare the size of the signal to the main quark-induced background, which is double Drell-Yan production, and outline a preliminary search strategy to enhance the signal to background ratio.

Rotating frame effects and potential on a relativistic scalar particle in Kaluza–Klein theory

The effects of uniform rotation on a relativistic scalar particle that interacts with a Cornell-type potential in background space–time described by the Kaluza–Klein theory are analyzed and the gravitational analogue of the Aharonov–Bohm effect is observed. Furthermore, linear confinement of a relativistic scalar particle was also discussed. We see a coupling between the angular velocity of the rotating frame [Formula: see text] and the angular momentum eigenvalue [Formula: see text] which shows the Sagnac-type effect.

The study of the generalized Klein–Gordon oscillator in the context of the Som–Raychaudhuri space–time

In this paper, we study the relativistic scalar particle described by the Klein–Gordon equation that interacts with the uniform magnetic field in the context of the Som–Raychaudhuri space–time. Based on the property of the biconfluent Heun function equation, the corresponding Klein–Gordon oscillator and generalized Klein–Gordon oscillator under considering the Coulomb potential are separately investigated, and the analogue of the Aharonov–Bohm effect is analyzed in this scenario. On this basis, we also give the influence of different parameters including parameter [Formula: see text] and oscillator frequency [Formula: see text], and the potential parameter [Formula: see text] on the energy eigenvalues of the considered systems.

A functional approach to the next-to-eikonal approximation of high energy gravitational scattering

The Fradkin–Schwinger functional methods to represent a Green function in an external gravitational field are used to study the eikonal and the next-to-eikonal limit, including the nonlinear gravitational interactions, of the scattering amplitudes of an ultra-relativistic scalar particle on a static super-massive scalar target in the nearly forward limit. The functional approach confirms the exponentiation of the leading eikonal which also applies to the first non-leading power in the energy of the light particle, moreover includes the interaction at impact parameter much larger than the Schwarzschild radius associated with the center of mass energy in the ultra-relativistic limit.

Effects of Lorentz Symmetry Breaking and External Potential on a Relativistic Scalar Particle

In this paper, a relativistic scalar particle under Lorentz symmetry breaking effects in the presence of a scalar potential is investigated. We introduce the scalar potential by modifying the mass via transformation M → M+S(r) in the wave equation and analyze the behaviour of a scalar particle. We see that the analytical solution to the KleinGordon equation can be achieved, and the energy eigenvalues and the wave function depends on the Lorentz symmetry breaking parameters as well as potential

Effects of Linear Central Potential Induced by Lorentz Symmetry Violation framework and Cornell-type Non-electromagnetic Potential on Spin-0 Scalar Particles

The relativistic quantum dynamics of a spin-0 scalar particle under the effects of the violation of Lorentz symmetry in the presence of a non-electromagnetic potential is analyzed. The central potential induced by the Lorentz symmetry violation is a linear electric and constant magnetic field and, analyze the effects on the eigenvalues and the wave function. We see there is a dependence of the linear charge density on the quantum numbers of the system

Linear Confinement of a Relativistic Spin-0 scalar Particle under Lorentz Symmetry Violation Effects

In this work, linear confinement of a relativistic scalar particle under the effects of Lorentz symmetry violation is investigated. We introduce a scalar potential by modifying the mass via transformation M → M + S(r) in the wave equation, and analyze the effects on the eigenvalues and the wave function. We see that the solution of the bound state to the wave equation can be achieved, and the energy eigenvalues and the wave function modified by the Lorentz symmetry breaking parameters as well as potential

Linear Confinement of a Scalar Particle Under Linear Central Potential Induced by the Effects of Violation of Lorentz Symmetry framework

The relativistic quantum motion of a scalar particle under the effects of violation of the Lorentz symmetry in the presence of a linear confining potential is investigated. We see that the solution of the bound state to the modified Klein-Gordon equation can be obtained and a quantum effect characterized by the dependence of the magnetic field on the quantum numbers of the system is observed