Modern Physics Letters A

The 40 years old Standard Model, the theory of particle physics, seems to describe all experimental data very well. All of its elementary particles were identified and studied apart from the Higgs boson until 2012. For decades, many experiments were built and operated searching for it, and finally, the two main experiments of the Large Hadron Collider (LHC) at CERN, CMS and ATLAS, in 2012 observed a new particle with properties close to those predicted for the Higgs boson. In this paper, we outline the search story: the exclusion of the Higgs boson at the Large Electron Positron (LEP) collider, and its observation at LHC.

The near threshold π^- p →ηn reaction is studied within an effective Lagrangian approach and the isobar model. By considering the contributions from s- and u-channel nucleon pole and N*(1535) resonance, the total and differential cross-sections of the π^- p →ηn reaction near threshold are calculated. Our theoretical results can fairly reproduce the current experimental data. It is also shown that while the center-of-mass energy lies in the range from the reaction threshold up to 1.65 GeV, s-channel N*(1535) resonance plays the dominant role. The effect from nucleon pole is found to be small but the interference terms between the N*(1535) resonance and the nucleon pole are significant. The contributions from t-channel processes are negligible in the present calculation.

We have studied nuclear structure and reaction properties of Ne, Mg and Si isotopes, using relativistic mean field (RMF) densities, in the framework of Glauber model. Total reaction cross-section σ_R for Ne isotopes on ¹²C target have been calculated at incident energy 240 MeV. The results are compared with the experimental data and with the recent theoretical study [W. Horiuchi et al., Phys. Rev. C 86, 024614 (2012)]. Study of σ_R using deformed densities have shown a good agreement with the data. We have also predicted total reaction cross-section σ_R for Ne, Mg and Si isotopes as projectiles and ¹²C as target at different incident energies.

We consider the production of a single top quark in association with a W boson at LHeC based γp collider. We compute the cross-section for the process γp→WtX with the anomalous Wtb and Wtbγ couplings. We find that the sensitivities to anomalous couplings of top quark are shown to be comparable, even better than the ones obtained from direct searches at hadron colliders.

We calculate the lowest order quantum gravity contributions to QED beta function in an effective field theory picture with a momentum cutoff. We use a recently proposed four-dimensional improved momentum cutoff that preserves gauge and Lorentz symmetries. We find that there is nonvanishing quadratic contribution to the photon two-point function but that does not lead to the running of the original coupling after renormalization. We argue that gravity cannot turn gauge theories asymptotically free.

We consider wormhole solutions in five-dimensional Kaluza–Klein gravity in the presence of a massless ghost four-dimensional scalar field. The system possesses two types of topological nontriviality connected with the presence of the scalar field and of a magnetic charge. Mathematically, the presence of the charge appears in the fact that the S³ part of a spacetime metric is the Hopf bundle S³ →S² with fiber S¹. We show that the fifth dimension spanned on the sphere S¹ is compactified in the sense that asymptotically, at large distances from the throat, the size of S¹ is equal to some constant, the value of which can be chosen to lie, say, in the Planck region. Then, from the four-dimensional point of view, such a wormhole contains a radial magnetic (monopole) field, and an asymptotic four-dimensional observer sees a wormhole with the compactified fifth dimension.