ΔπN\Delta\pi N coupling constant in light cone QCD sum rules

We employ the light cone QCD sum rules to calculate $\Delta\pi N$ coupling constant by studying the two point correlation function between the vacuum and the pion state. Our result is consistent with the traditional QCD sum rules calculations and it is in agreement with the experimental value.Comment: 8 pages, latex, 2 figure

Deep Inelastic Scattering Beyond Perturbation Theory

I discuss possibilities to observe the instanton-induced contributions to deep inelastic scattering which correspond to nonperturbative exponential corrections to the coefficient functions in front of parton distributions of the leading twist.Comment: Talk given at the Leipzig workshop on High Energy Physics, Kyffhaeuser, September 20-24,1993, LATEX, 12 pages, 3 figures included as uu-encoded file, MPI-Ph/93-7

Electroproduction of Resonances at Large Momentum Transfers

Measurements of transition form factors for the electro-excitation of nucleon resonances in the Q^2=5-14 GeV^2 region can provide one with the information on quark wave functions at small transverse separations. In particular a comparison of form factors for the states of opposite parity can give insight in the mechanisms of chiral symmetry breaking. I discuss perspectives of the theoretical description of such reactions using a combination of lattice calculations and light-cone sum rulesComment: 10 pages, 5 figures. Contribution to the Proceedings of the 4th Workshop on Exclusive Reactions at High Momentum Transfer, May 18-21, 2010 Thomas Jefferson National Accelerator Facility Newport News, Virginia US

Handbook of Higher Twist Distribution Amplitudes of Vector Mesons in QCD

We give a summary of existing results on higher twist distribution amplitudes of vector mesons in QCD. Special attention is payed to meson mass corrections which turn out to be large. A ``shopping list'' is presented of most important nonperturbative parameters which enter distribution amplitudes.Comment: Talk presented by V.M. Braun at 3rd workshop ``Continuous Advances in QCD'', Minneapolis, MN, USA, April 16--19, 1998; 17 pages, 2 figures, requires sprocl.sty (included

The 24-Cell and Calabi-Yau Threefolds with Hodge Numbers (1,1)

Calabi-Yau threefolds with h^11(X)=h^21(X)=1 are constructed as free quotients of a hypersurface in the ambient toric variety defined by the 24-cell. Their fundamental groups are SL(2,3), a semidirect product of Z_3 and Z_8, and Z_3 x Q_8.Comment: 22 pages, 3 figures, 3 table

Nucleon Form Factors and Distribution Amplitudes in QCD

We derive light-cone sum rules for the electromagnetic nucleon form factors including the next-to-leading-order corrections for the contribution of twist-three and twist-four operators and a consistent treatment of the nucleon mass corrections. The essence of this approach is that soft Feynman contributions are calculated in terms of small transverse distance quantities using dispersion relations and duality. The form factors are thus expressed in terms of nucleon wave functions at small transverse separations, called distribution amplitudes, without any additional parameters. The distribution amplitudes, therefore, can be extracted from the comparison with the experimental data on form factors and compared to the results of lattice QCD simulations. A selfconsistent picture emerges, with the three valence quarks carrying 40%:30%:30% of the proton momentum.Comment: 27 pages, 7 figures uses revte

Ultraviolet dominance of power corrections in QCD?

I explain current theoretical ideas on higher-twist (hadronization) corrections to physical observables in QCD.Comment: 7 pages, LATEX, no figures; Presented at 5th International Conference on Physics Beyond the Standard Model, Balholm, Norway, 29 Apr - 4May 199

Nucleons on the light-cone: Theory and phenomenology of baryon distribution amplitudes

This is a short review of the theory and phenomenology of baryon distribution amplitudes, including recent applications to the studies of nucleon form factors at intermediate momentum transfers using the light-cone sum rule approach.Comment: 16 pages, talk at CAQCD2006, Minneapoli

Electroproduction of the N∗(1535)N^\ast(1535) nucleon resonance in QCD

Following the 12 GeV upgrade, a dedicated experiment is planned with the Hall B CLAS12 detector at Jefferson Lab, with the aim to study electroproduction of nucleon resonances at high photon virtualities up to $Q^2 = 12$ GeV$^2$. In this work we present a QCD-based approach to the theoretical interpretation of these upcoming results in the framework of light-cone sum rules that combine perturbative calculations with dispersion relations and duality. The form factors are thus expressed in terms of $N^\ast(1535)$ light-front wave functions at small transverse separations, called distribution amplitudes. The distribution amplitudes can therefore be determined from the comparison with the experimental data on form factors and compared to the results of lattice QCD simulations. The results of the corresponding next-to-leading order calculation are presented and compared with the existing data. We find that the form factors are dominated by the twist-four distribution amplitudes that are related to the $P$-wave three-quark wave functions of the $N^\ast(1535)$, i.e. to contributions of orbital angular momentum.Comment: 12 pages, 3 figures. arXiv admin note: text overlap with arXiv:1310.1375 (2 typos corrected 1 reference updated