International Journal of Modern Physics A

The paper deals with an approach to the model-independent searching for the Z' gauge boson as a virtual state in scattering processes. The relations between the Z' couplings to fermions covering a wide class of models beyond the Standard Model are found and used. They reduce in an essential way the number of parameters to be fitted in experiments. Special observables which uniquely pick out the Z' at energies of LEP and ILC colliders in different leptonic processes are introduced and the data of LEP experiments are analyzed. The Z' couplings to leptons and quarks are estimated at 95% confidence level. At this level, the LEP data are compatible with the existence of the Z' with the mass m_Z′ ~ 1–1.2 TeV. These estimates may serve as a guide for experiments at the Tevatron and/or LHC. A comparison with other approaches and results is given.

We first discuss the problem of mass hierarchy and review briefly the main Beyond the Standard Model (BSM) proposals. We then describe the framework of strings, branes and large extra dimensions and give the main experimental predictions in both particle accelerators and microgravity experiments testing gravity at short distances. Finally, we present some models based on intersecting branes and discuss the issue of Standard Model embedding.

This lecture concerns the properties of strongly interacting matter (which is described by Quantum Chromodynamics) at very high energy density. I review the properties of matter at high temperature, discussing the deconfinement phase transition. At high baryon density and low temperature, large N_c arguments are developed which suggest that high baryonic density matter is a third form of matter, Quarkyonic Matter, that is distinct from confined hadronic matter and deconfined matter. I finally discuss the Color Glass Condensate which controls the high energy limit of QCD, and forms the low x part of a hadron wave function. The Glasma is introduced as matter formed by the Color Glass Condensate which eventually thermalizes into a Quark Gluon Plasma.

A nonperturbative effective model is derived for the Higgs sector of the Standard Model which is described by a simple scalar theory. The renormalized couplings are determined by the derivatives of the Gaussian effective potential that are known to be the sum of infinite bubble graphs contributing to the vertex functions. A good agreement has been found with strong coupling lattice simulations when a comparison can be made.

The heavy T-quark is one of the most crucial ingredients in the left–right twin Higgs model, which is introduced to cancel the largest contribution of the Standard Model top quark to the Higgs boson mass at one-loop level. In this paper, we study the relevant single heavy T-quark production processes, the 2 → 2 partonic processes of qb → q'T and , the 2 → 3 partonic processes of and at the CERN LHC. Our numerical results show that the 2 → 3 process can be quite important, as its cross-section is about 60% of that for the 2 → 2 process at the LHC. We also show the p_T distribution and the rapidity distributions for out-going particles. For the 2 → 3 process, the production rate of the final state can be larger than 100 fb with reasonable values of the free parameters. The possible signatures of the heavy T-quark might be detected via the process at the LHC.

It is shown that in the scheme with a rotating fermion mass matrix (i.e. one with a scale-dependent orientation in generation space) suggested earlier for explaining fermion mixing and mass hierarchy, the theta angle term in the QCD action of topological origin can be eliminated by chiral transformations, while giving still nonzero masses to all quarks. Instead, the effects of such transformations get transmitted by the rotation to the CKM matrix as the KM phase giving, for θ of order unity, a Jarlskog invariant typically of order 10^-5, as experimentally observed. Strong and weak CP violations appear then as just two facets of the same phenomenon.

We consider the so-called "eV seesaw" scenario, with right-handed Majorana mass M_R at eV order, extended to four lepton generations. The fourth generation gives a heavy pseudo-Dirac neutral lepton, which largely decouples from other generations and is relatively stable. The framework naturally gives three active and three sterile neutrinos. We update a previous numerical analysis of a 3+3 study of the LSND anomaly, taking into account the more recent results from the MiniBooNE experiment. In particular, we study the implications for the third mixing angle sin² θ₁₃, as well as CP violation. We find that current data do not seriously constrain more than one sterile neutrinos.

The Technicolor (TC) model is a dynamical theory without fundamental scalars. Due to the pseudo-Goldstone bosons, there exist some new flavor-changing (FC) couplings in the TC model which can contribute to the production rates of some FC processes. In this paper, we study the production process in the one-generation technicolor model (OGTM) at the ILC, i.e. . We find that the cross section with the OGTM's contributions can be largely enhanced and the signal should be observable at the ILC. Our predictions can be viewed as valid estimates of other TC models. Therefore, the process may provide a unique window for studying the TC theory.

In this paper we consider the Casimir energy and force of massless Majorana fermions and vector bosons between parallel plates. The vector bosons satisfy perfect electric conductor boundary conditions, while the Majorana fermions satisfy bag and chiral boundary conditions. We consider various piston configurations containing one vector boson and one fermion. We make use of supersymmetry, broken on the boundaries, to explain the number of fields that appear in all the studied cases. The effect of chiral boundary conditions in a fermion–boson system is investigated. Concerning the supersymmetry issue and the vanishing of the Casimir energy, we study a massive Dirac fermion–scalar boson system with bag and specific Robin type boundary conditions for which the Casimir energy vanishes. Finally, a two-scalar-boson system between parallel plates is presented in which the singularities vanish in the total Casimir energy.

We calculate the lowest-order corrections to the static potential for both the generalized Born–Infeld electrodynamics and an Euler–Heisenberg-like model, in the presence of a constant external magnetic field. Our analysis is carried out within the framework of the gauge-invariant but path-dependent variables formalism. The calculation reveals a long-range correction (-type) to the Coulomb potential for the generalized Born–Infeld electrodynamics. Interestingly enough, in the Euler–Heisenberg-like model, the static potential remains Coulombian. Therefore, contrary to popular belief, the quantized truncated action and the truncated quantized action do not commute at all.

Multiple solutions exist in many experimental situations where several interfering amplitudes are summed to fit experimentally measured distributions, such as cross sections, mass spectra, and/or angular distributions. We show a few examples where multiple solutions are found, but only one solution is reported in publications. Since there is no standard rule for choosing one among the solutions as the physics one, we propose a simple rule that agrees with what has been adopted in previous literature: the solution corresponding to the minimal magnitudes of the amplitudes must be the physical solution. We suggest testing this rule in future analyses.