A topological defect in the form of the Abrikosov–Nielsen–Olesen vortex in the space of an arbitrary dimension is considered as a gauge-flux-carrying tube that is impenetrable for quantum matter. The charged scalar matter field is quantized in the vortex background with the perfectly rigid (Neumann) boundary condition imposed at the side surface of the vortex. We show that a current circulating around the vortex is induced in the vacuum, if the Compton wavelength of the matter field exceeds the transverse size of the vortex considerably. The vacuum current is periodic in the value of the gauge flux of the vortex, providing a quantum-field-theoretical manifestation of the Aharonov–Bohm effect. The vacuum current leads to the appearance of an induced vacuum magnetic flux that, for some values of the tube thickness, exceeds the vacuum magnetic flux induced by a singular vortex filament. The results are compared to those obtained earlier in the case of the perfectly reflecting (Dirichlet) boundary condition imposed at the side surface of the vortex. It is shown that the absolute value of the induced vacuum current and the induced vacuum magnetic flux in the case of the Neumann boundary condition is greater than in the case of the Dirichlet boundary condition.
Despite the undeniable success of the standard model of particle physics (SM), there are some phenomena that the SM cannot explain. These phenomena indicate that the SM has to be modified. One of the possible ways to extend the SM is to introduce heavy neutral leptons (HNLs). To search for HNLs in intensity Frontier experiments, one has to consider HNL production both in two-body and three-body decays of some mesons. We verified the possibility of using the parton level PYTHIA default matrix elements (without the form-factor formalism) to calculate HNL production in three-body semileptonic decays of B and D mesons in the experimentally interesting mass range of the produced HNLs. We conclude that this approach is quite suitable for the estimation of the sensitivity region for HNLs in the intensity Frontier experiments, provided one uses suitable parton level PYTHIA default matrix elements. Our study was driven by the usage of such an approximation by the SHiP collaboration. We conclude that in this case the parton level PYTHIA default matrix elements could have been chosen more appropriately.
We consider the vacuum polarization of a charged scalar matter field outside the tube with magnetic flux inside. The tube is impenetrable for quantum matter, and the perfectly rigid (Neumann) boundary condition is imposed at its surface. We write expressions for the induced vacuum energy density for the case of a space with arbitrary dimension and for an arbitrary value of the magnetic flux. We do the numerical computation for the case of a half-integer flux value in the London flux units and the (2 + 1)-dimensional space-time. We show that the induced vacuum energy of the charged scalar matter field is induced, if the Compton wavelength of the matter field exceeds the transverse size of the tube considerably. We show that the vacuum energy is periodic in the value of the magnetic flux of the tube, providing a quantumfield-theoretical manifestation of the Aharonov–Bohm effect. The dependencies of the induced vacuum energy upon the distance from the center of the tube for different values of its thickness are obtained. The results are compared to those obtained earlier in the case of the perfectly reflecting (Dirichlet) boundary condition. It is shown that the value of the induced vacuum energy density in the case of the Neumann boundary condition is greater than in the case of the Dirichlet boundary condition.
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