Modern Physics Letters A

In this brief review, we summarize the current theoretical knowledge of heavy quarkonium inclusive decays, with emphasis on recent progress made in the framework of QCD effective field theories. In the appendix, we list the imaginary parts of the matching coefficients of dimensions six and eight NRQCD four-fermion operators as presently known.

In this brief review, we summarize the new developments on the description of gluon radiation by energetic quarks traversing a medium as well as the observable consequences in high-energy heavy-ion collisions. Information about the initial state is essential for a reliable interpretation of the experimental results and will also be reviewed. Comparison with experimental data from RHIC and expectation for the future LHC will be given.

The interaction of a magnetic flux vortex with weak external fields is considered in the framework of the Abelian Higgs model. The approach is based on the calculation of the zero-mode excitation probability in the external field. The excitation of the field configuration is found perturbatively. As an example we consider the effect of interaction with an external current. The linear in the scalar field perturbation is also considered.

The electron and muon number violating muonium–antimuonium oscillation process can proceed provided that neutrinos have nonzero masses and mix among the various generations. Modifying the Standard Model only by the inclusion of singlet right-handed neutrino fields and allowing for general neutrino masses and mixings, the leading order matrix element contributing to this process is computed. For the particularly interesting case where the neutrino masses are generated by a seesaw mechanism with a very large Majorana mass M_R≫M_W, it is found that both the very light and very heavy Majorana neutrinos each give comparable contributions to the oscillation time scale proportional to . Present experimental limits set by the non-observation of the oscillation process sets a lower limit on M_R of roughly of order 10⁴ GeV.

The perturbative renormalization group for light-front QCD Hamiltonians produces a logarithmically rising inter-quark potential already in second order, when Fock sectors with effective (constituent) gluons are truncated. In this approach the quark self-interaction renders states unphysical if they are not color singlets. There is a question if this mechanism solves the problem of too strong color van der Waals forces between heavy quarkonia, which emerge in potential models not directly derivable from QCD. This article shows that such forces do exist in this approach, and estimates their strength with the result that they are on the border of exclusion, while more advanced calculation is possible.

We evaluate the total cross-sections of top-charm associated production induced by SUSY–QCD FCNC at the LHC within the general unconstrained MSSM framework. Our results show that these production rates may be as large as a few pb for favorable parameter values allowing by current precise experiments. It means that the LHC may produce abundant events of this process, and the SUSY FCNC effects through the above process may be observable in the future experiments.

We study the Lorentz and CPT violating effects on the ratio where BR_LorVio (BR_SM) is the branching ratios coming from the Lorentz violating effects (the SM), for the decays H⁰→f⁺f^- (f = quarks and charged leptons) and H⁰→ZZ(W⁺W^-). We observe that these new effects are too small to be detected, especially for f⁺f^- output, since the corresponding coefficients are highly suppressed at the low energy scale.