Pion Form Factor in the NLC QCD SR approach

We present results of a calculation of the electromagnetic pion form factor within a framework of QCD Sum Rules with nonlocal condensates and using a perturbative spectral density which includes \mathcal{O}(\alpha_s) contributions.Comment: 9 pages, 2 figures (embedded). Talk presented by the second author at the Workshop on Physics of Fundamental Interactions, Institute of High Energy Physics, Protvino, Russia, 22--25 December 200

Taming Landau singularities in QCD perturbation theory: The analytic approach 2.0

The aim of this topical article is to outline the fundamental ideas underlying the recently developed Fractional Analytic Perturbation Theory (FAPT) of QCD and present its main calculational tools together with key applications. For this, it is first necessary to review previous methods to apply QCD perturbation theory at low spacelike momentum scales, where the influence of the Landau singularities becomes inevitable. Several concepts are considered and their limitations are pointed out. The usefulness of FAPT is discussed in terms of two characteristic hadronic quantities: the perturbatively calculable part of the pion's electromagnetic form factor in the spacelike region and the Higgs-boson decay into a $b\bar b$ pair in the timelike region. In the first case, the focus is on the optimization of the prediction with respect to the choice of the renormalization scheme and the dependence on the renormalization and the factorization scales. The second case serves to show that the application of FAPT to this reaction reaches already at the four-loop level an accuracy of the order of 1%, avoiding difficulties inherent in the standard perturbative expansion. The obtained results are compared with estimates from fixed-order and contour-improved QCD perturbation theory. Using the brand-new Higgs mass value of about 125 GeV, measured at the Large Hadron Collider (CERN), a prediction for $\Gamma_{H\to b\bar{b}}=2.4 \pm 0.15 {\rm MeV}$ is extracted.Comment: v3: 23 pages, 7 figures, Invited topical article published in Particles and Nuclei with update using the CERN Higgs discovery. Abridged version presented as plenary talk at International Conference on Renormalization Group and Related Topics (RG 2008), Dubna, Russia, September 1 - 5, 2008. v4 typo in Eq. (3) correcte

Pion Form Factor in QCD: How to Calculate?

We discuss the pion form factor calculation in QCD.We shortly consider the main points of the nonlocal condensate QCD sum rule approach and show its results for the pion form factor, $F_\pi(Q^2)$. These results are compared with predictions of the perturbative and lattice QCD. Then we consider the Local Duality (LD) approach for the pion FF in QCD and show that for $Q^2\gtrsim 2$ GeV$^2$ the main parameter of the approach, namely, $s_0^{\text{LD}}(Q^2)$ should grow with $Q^2$ rather than be a constant.Comment: 25 pages (in Russian), 9 figures, talk at the Baikal Summer School on Particle Physics and Astrophysics, Bol'shie Koty (Irkutsk reg.), July 7--14, 2010 (SPIRES Conf Num: C10/07/06.1), corresponds to the last part of the Doctor-Nauk Thesis (defended 24.12.2009 at Bogoliubov Lab. of Theoretical Physics, JINR; approved by the Supreme Attestation Committee of the Russian Federation on 12.03.2010

Evolution of the understanding of psoriasis and therapeutic approaches used to manage such patients. BCD-085 is the first Russian genetically-engineered biological preparation for the treatment of patients suffering from psoriasis

This review paper discusses the systemic character of psoriasis. For medical specialists, it is of crucial importance to understand that psoriasis is not exclusively a skin disease; rather, it is pathogenetically connected with the development of a number of comorbid conditions. This fact has a practical significance in terms of choosing therapeutic strategies for managing patients with medium and severe dermatoses characterized by relapses and comorbid conditions. The long-term use of systemic medications in such cases, including genetically engineered biological ones, seems to be theoretically reasonable, since it facilitates control over the main clinical manifestations of the disease.This paper presents information on the innovative Russian drug — BCD-085-inhibitor IL17 — and its effects on the key stages of psoriasis immunopathogenesis. The efficacy and safety of this drug for patients with moderate and severe psoriasis are discussed.BCD-085 is found to exhibit a fast and high therapeutic response in terms of the PASI75, PASI90, PASI100 and sPGA indexes during the first 12 weeks of therapy. According to the available data, BCD-085 is characterized by a favourable safety profile and the absence of immunogenicity from the clinical standpoint

Unbiased analysis of CLEO data at NLO and pion distribution amplitude

We discuss different QCD approaches to calculate the form factor F^{\gamma^*\gamma\pi}(Q^2) of the \gamma^*\gamma\to\pi^{0} transition giving preference to the light-cone QCD sum rules (LCSR) approach as being the most adequate. In this context we revise the previous analysis of the CLEO experimental data on F^{\gamma^*\gamma\pi}(Q^{2}) by Schmedding and Yakovlev. Special attention is paid to the sensitivity of the results to the (strong radiative) \alpha_s-corrections and to the value of the twist-four coupling \delta^2. We present a full analysis of the CLEO data at the NLO level of LCSRs, focusing particular attention to the extraction of the relevant parameters to determine the pion distribution amplitude, i.e., the Gegenbauer coefficients a_2 and a_4. Our analysis confirms our previous results and also the main findings of Schmedding and Yakovlev: both the asymptotic, as well as the Chernyak--Zhitnitsky pion distribution amplitudes are completely excluded by the CLEO data. A novelty of our approach is to use the CLEO data as a means of determining the value of the QCD vacuum non-locality parameter \lambda^2_q = / =0.4 GeV^2, which specifies the average virtuality of the vacuum quarks.Comment: 25 pages, 5 figures, 4 tables; format and margins corrected to fit page size; small changes in the text and correction of misprint

Synthesis of Novel 1,2,3-Thiadiazoles

This work was supported by the Russian Foundation for Basic Research, project 17-03-00641

Extended analytic QCD model with perturbative QCD behavior at high momenta

In contrast to perturbative QCD, the analytic QCD models have running coupling whose analytic properties correctly mirror those of spacelike observables. The discontinuity (spectral) function of such running coupling is expected to agree with the perturbative case at large timelike momenta; however, at low timelike momenta it is not known. In the latter regime, we parametrize the unknown behavior of the spectral function as a sum of (two) delta functions; while the onset of the perturbative behavior of the spectral function is set to be 1.0-1.5 GeV. This is in close analogy with the "minimal hadronic ansatz" used in the literature for modeling spectral functions of correlators. For the running coupling itself, we impose the condition that it basically merges with the perturbative coupling at high spacelike momenta. In addition, we require that the well-measured nonstrange semihadronic (V+A) tau decay ratio value be reproduced by the model. We thus obtain a QCD framework which is basically indistinguishable from perturbative QCD at high momenta (Q > 1 GeV), and at low momenta it respects the basic analyticity properties of spacelike observables as dictated by the general principles of the local quantum field theories.Comment: 15 pages, 6 figures; in v2 Sec.IV is extended after Eq.(48) and refs.[51-52] added; v2 published in Phys.Rev.D85,114043(2012

Vector meson couplings to vector and tensor currents in extended NJL quark model

A simple explanation of the dynamic properties of vector mesons is given in the framework of extended Nambu - Jona-Lasinio quark model. New mass relations among the hadron vector resonances are derived. The results of this approach are in good accordance with the QCD sum rules, the lattice calculations and the experimental data.Comment: 4 pages, 2 figure

Gravitational and higher-order form factors of the pion in chiral quark models

The gravitational form factor of the pion is evaluated in two chiral quark models and confronted to the recent full-QCD lattice data. We find good agreement for the case of the Spectral Quark Model, which builds in the vector-meson dominance for the charge form factor. We derive a simple relation between the gravitational and electromagnetic form factors, holding in the considered quark models in the chiral limit. The relation implies that the gravitational mean squared radius is half the electromagnetic one. We also analyze higher-order quark generalized form factors of the pion, related to higher moments in the symmetric Bjorken X-variable of the generalized parton distribution functions, and discuss their perturbative QCD evolution, needed to relate the quark-model predictions to the lattice data. The values of the higher-order quark form factors at t=0, computed on the lattice, also agree with our quark model results within the statistical and method uncertainties.Comment: 12 pages, 4 figures, discussion and references adde

Annihilation effects in B→ππB \to \pi\pi from QCD Light-Cone Sum Rules

Using the method of QCD light-cone sum rules, we calculate the $B \to \pi\pi$ hadronic matrix elements with annihilation topology. We obtain a finite result, including the related strong phase. Numerically, the annihilation effects in $B\to \pi\pi$ turn out to be small with respect to the factorizable emission mechanism. Our predictions, together with the earlier sum rule estimates of emission and penguin contributions, are used for the phenomenological analysis of $B\to \pi\pi$ channels. We predict a $\Delta I=1/2$ transition amplitude which significantly differs from this amplitude extracted from the current data.Comment: two references added, a few misprints corrected, 38 pages, 29 figure