The problems of simple elementary weakly interacting massive particles (WIMPs) appeal to extend the physical basis for nonbaryonic dark matter. Such extension involves more sophisticated dark matter candidates from physics beyond the Standard Model (BSM) of elementary particles. We discuss several models of dark matter, predicting new colored, hyper-colored or techni-colored particles and their accelerator and non-accelerator probes. The nontrivial properties of the proposed dark matter candidates can shed new light on the dark matter physics. They provide interesting solutions for the puzzles of direct and indirect dark matter search.

We analyze an extension of the Standard Model with an additionalSU(2)hypercolor gauge group keeping the Higgs boson as a fundamental field. Vectorlike interactions of new hyperquarks with the intermediate vector bosons are explicitly constructed. We also consider pseudo-Nambu–Goldstone bosons caused by the symmetry breakingSU(4)→Sp(4). A specific global symmetry of the model with zero hypercharge of the hyperquark doublets ensures the stability of a neutral pseudoscalar field. Some possible manifestations of the lightest states at colliders are also examined.

We study processes with unstable particles in intermediate time-like states. It is shown that the amplitudes squared of such processes factor exactly in the framework of the model of unstable particles with continuous masses. Decay widths and cross sections can then be represented in a universal factorized form for an arbitrary set of interacting particles. This exact factorization is caused by specific structure of propagators in the model. We formulate the factorization method and perform a phenomenological analysis of the factorization effects. The factorization method considerably simplifies calculations while leading to compact and reasonable results.

We adopt the vector-meson-dominance approach to investigate $Q^2$-evolution of $NR$-transition form factors ($N$ denotes nucleon and $R$ an excited resonance) in the first and second resonance regions. The developed model is based upon conventional $\gamma NR$-interaction Lagrangians, introducing three form factors for spin-$3/2$ resonances and two form factors for spin-$1/2$ nucleon excitations. Lagrangian form factors are expressed as dispersionlike expansions with four or five poles corresponding to the lowest excitations of the mesons $\rho (770)$ and $\omega (782)$. Correct high-$Q^2$ form-factor behavior predicted by perturbative QCD is due to phenomenological logarithmic renormalization of electromagnetic coupling constants and linear superconvergence relations between the parameters of the meson spectrum. The model is found to be in good agreement with all the experimental data on $Q^2$-dependence of the transitions $N\Delta (1232)$, $NN(1440)$, $NN(1520)$, $NN(1535)$. We present fit results and model predictions for high-energy experiments proposed by JLab. Besides, we make special emphasis on the transition to perturbative domain of $N\Delta (1232)$ form factors.

We consider the most general two-loop massless correlator I(n ₁ , n ₂ , n ₃ , n ₄ , n ₅; x, y; D) of two composite vertices with the Bjorken fractions x and y for arbitrary indices {n _i } and space-time dimension D; this correlator is represented by a “kite” diagram. The correlator I({n _i }; x, y; D) is the generating function for any scalar Feynman integrals related to this kind of diagrams. We calculate I({n _i }; x, y; D) and its Mellin moments in a direct way by evaluating hypergeometric integrals in the α representation. The result for I({n _i }; x, y; D) is given in terms of a double hypergeometric series — the Kampé de Férriet function. In some particular but still quite general cases it reduces to a sum of generalized hypergeometric functions ₃ F ₂. The Mellin moments can be expressed through generalized Lauricella functions, which reduce to the Kampé de Férriet functions in several physically interesting situations. A number of Feynman integrals involved and relations for them are obtained.

We calculate the gauge invariant Drell-Yan-like hadron tensors. In connection with new COMPASS results, we predict the new single spin asymmetry which probes gluon poles together with chiral-odd and time-odd functions. The relevant pion production as a particular case of the Drell-Yan-like process has been discussed. For the meson-induced Drell-Yan (DY) process, we model an analog of the twist-3 distribution function, which is a collinear function in inclusive channel, by means of two noncollinear distribution amplitudes which are associated with exclusive channel. This modeling demonstrates the fundamental duality between different factorization regimes.