Corrections to the generalized vector dominance due to diffractive rho_3 production

The idea of the vector dominance is still in use in various analyses of experimental data of photon-hadron reactions. It makes sense, therefore, to recast results of microscopic calculations of such reactions in this language. Here we present the diffractive DIS $\rho_3$ production as a specific correction to the generalized vector dominance. We perform a coupled channel analysis of spin-orbital excitations in diffractive photoproduction and reiterate the point that rho_3 in diffractive DIS will be sensitive to a novel aspect of diffraction.Comment: 12 pages, 2 figure

Production of orbitally excited vector mesons in diffractive DIS

Within the k_t-factorization framework, we study diffractive production of orbitally excited vector mesons and compare it with the production of radial excitations, focusing on the rho(1450)/rho(1700) case. At small Q^2, orbital excitation of light quarkonia is found to dominate over radial excitations in diffractive production. We predict strong suppression of the production of orbital excitations by longitudinal photons, which leads to very small sigma_L/sigma_T ratio. At small Q^2, the s-channel helicity violating transitions contribute \sim 10-15% of the transverse cross section and \sim 50% of the longitudinal cross section. We also study mixing between radial and orbital excitations and determine strategies towards clarification of S-wave/D-wave assignment to rho(1450) and rho(1700) mesons. The results are compared with the experimental data available, and predictions for future experiments are given.Comment: 9 pages, 5 figure

Two-Higgs-doublet model from the group-theoretic perspective

In the two-Higgs-doublet model, different Higgs doublets can be viewed as components of a generic "hyperspinor". We decompose the Higgs potential of this model into irreducible representations of the SU(2) group of transformations of this hyperspinor. We discuss invariant combinations of the Higgs potential parameters lambda_i that arise in this decomposition and provide simple and concise sets of conditions for the hidden Z_2-symmetry, Peccei-Quinn symmetry, and explicit CP-conservation in 2HDM. We show that some results obtained previously by brute-force calculations are reduced to simple linear algebraic statements in our approach.Comment: 10 pages; v3: expanded section on consequences, added subsections on CP-conservation, PQ symmetry, RG evolution; v4: misprints corrected; to appear in Physics Letters

A new type of CP symmetry, family replication and fermion mass hierarchies

We study a two-Higgs-doublet model with four generalised CP symmetries in the scalar sector. Electroweak symmetry breaking leads automatically to spontaneous breaking of two of them. We require that these four CP symmetries can be extended from the scalar sector to the full Lagrangian and call this requirement the principle of maximal CP invariance. The Yukawa interactions of the fermions are severely restricted by this requirement. In particular, a single fermion family cannot be coupled to the Higgs fields. For two fermion families, however, this is possible. Enforcing the absence of flavour-changing neutral currents, we find degenerate masses in both families or one family massless and one massive. In the latter case the Lagrangian is highly symmetric, with the mass hierarchy being generated by electroweak symmetry breaking. Adding a third family uncoupled to the Higgs fields and thus keeping it massless we get a model which gives a rough approximation of some features of the fermions observed in Nature. We discuss a number of predictions of the model which may be checked in future experiments at the LHC.Comment: 24 pages. Version published in EPJC. Minor changes as suggested by the refere

The longitudinal cross section of vector meson electroproduction

We analyze electroproduction of light vector mesons (V=rho, phi and omega) at small Bjorken-x in the handbag approach in which the process factorizes into general parton distributions and partonic subprocesses. The latter are calculated in the modified perturbative approach where the transverse momenta of the quark and antiquark forming the vector meson are retained and Sudakov suppressions are taken into account. Modeling the generalized parton distributions through double distributions and using simple Gaussian wavefunctions for the vector mesons, we compute the longitudinal cross sections at large photon virtualities. The results are in fair agreement with the findings of recent experiments performed at HERA and HERMES.Comment: 27 pages, 20 figures, using LATEX with graphic

The γγ→J/ψJ/ψ\gamma \gamma \to J/\psi J/\psi reaction and the J/ψJ/ψJ/\psi J/\psi pair production in exclusive ultraperipheral ultrarelativistic heavy ion collisions

We calculate the cross section for the $\gamma \gamma \to J/\psi J/\psi$ process. Two mechanisms are considered: box (two-loop) diagrams of the order of $O(\alpha_{em}^2 \alpha_s^2)$ and two-gluon exchange of the order of $O(\alpha_{em}^2 \alpha_s^4)$. The first mechanism is calculated in the heavy-quark non-relativistic approximation while the second case we also include the effects of quantum motion of quarks in the bound state. The box contribution dominates at energies close to the threshold ($W <$ 15 GeV) while the two-gluon mechanism takes over at $W >$ 15 GeV. Including the bound-state wave function effects for the two-gluon exchange mechanism gives a cross section 0.1 - 0.4 pb, substantially smaller than that in the non-relativistic limit (0.4 - 1.6 pb). We also find a strong infrared sensitivity which manifests itself in a rather strong dependence on the mass for the $t$-channel gluons. The elementary cross section is then used in the Equivalent Photon Approximation (EPA) in the impact parameter space to calculate the cross section for $^{208}Pb+^{208}Pb \to ^{208}Pb + J/\psi J/\psi + ^{208}Pb$ reaction. Distributions in rapidity of the $J/\psi J/\psi$ pair and invariant mass of the pair are shown.Comment: 15 pages, 11 figure

QCD factorization for forward hadron scattering at high energies

We consider the QCD factorization of DIS structure functions at small x and amplitudes of 2->2 -hadronic forward scattering at high energy. We show that both collinear and k_T-factorization for these processes can be obtained approximately as reductions of a more general (totally unintegrated) form of the factorization. The requirement of ultraviolet and infrared stability of the factorization convolutions allows us to obtain restrictions on the fits for the parton distributions in k_T- and collinear factorization.Comment: 18 pages, 10 figures In the present version misprints found in the prevcious version are corrected and some more details are explaine

Unitarity Corrections to the Proton Structure Functions through the Dipole Picture

We study the dipole picture for the description of the deep inelastic scattering, focusing on the structure functions which are driven directly by the gluon distribution. One performs estimates using the effective dipole cross section given by the Glauber-Mueller approach in QCD, which encodes the corrections due to the unitarity effects associated with the saturation phenomenon. We also address issues about frame invariance of the calculations when analysing the observables.Comment: 16 pages, 8 figures. Version to be published in Phys. Rev.

Использование SPR биосенсора при поиске прототипов лекарственных средств на примере цитохрома Р450(51) в качестве белка-мишени

The development of the integral platform “From Gene to Lead”, consolidated computer methods, bioinformatics researches, and experimental approaches, significantly accelerated and optimized base structure search in the field of drug design. The necessity of the experimental verification of hundreds virtual structure hypothesis (results of molecular data base selections or de novo construction) requires demands the usage of the high-through out and sensitive methods for validation possible interaction between numerous of selected compounds and particular molecular targets and evaluation of affinity, kinetics and thermodynamics. Surface plasmon resonance (SPR) technology makes it possible to solve all these problems. In this article the methodical aspects of the optical SPR-biosensor usage in the field of drug prototypes selection are described using the human cytochrome P450(51) catalyzing one of the key step of cholesterol biosynthesis as an example.Интеграция различных компьютерных, биоинформатических и экспериментальных технологий в единую платформу, покрывающую путь “от гена до прототипа лекарства”, значительно ускорила и оптимизировала поиск базовых структур для создания новых лекарственных препаратов. При этом необходимость экспериментальной проверки найденных компьютерными методами сотен структурных гипотез, представляющих собой выборки из молекулярных баз данных или сконструированных de novo соединений, требует привлечения быстрых и чувствительных скрининговых методов анализа их возможных взаимодействий с белком-мишенью. А в случае позитивного результата и возможности количественной оценки аффинности, кинетики и термодинамики межмолекулярного взаимодействия. Технология поверхностного плазмонного резонанса (SPR) позволяет решать все перечисленные задачи. В данной статье рассматриваются методические аспекты применения оптического SPR биосенсора для поиска прототипов лекарственных средств на примере цитохрома Р450(51) человека, катализирующего ключевую стадию биосинтеза холестерина