Light Cone Sum Rules for gamma* N -> Delta Transition Form Factors

A theoretical framework is suggested for the calculation of gamma* N -> Delta transition form factors using the light-cone sum rule approach. Leading-order sum rules are derived and compared with the existing experimental data. We find that the transition form factors in a several GeV region are dominated by the ``soft'' contributions that can be thought of as overlap integrals of the valence components of the hadron wave functions. The ``minus'' components of the quark fields contribute significantly to the result, which can be reinterpreted as large contributions of the quark orbital angular momentumComment: 38 pages, 10 figures; some typos fixed and references added, to appear in Phys. Rev.

Mass Spectrum in SQCD and Problems with the Seiberg Duality. Another Scenario

N=1 SQCD with SU(N_c) colors and N_F flavors of light quarks is considered within the dynamical scenario which assumes that quarks can be in two different phases only. These are: a) either the HQ (heavy quark) phase where they are confined, b) or they are higgsed, at the appropriate values of parameters of the Lagrangian. The mass spectra of this (direct) theory and its Seiberg's dual are obtained and compared, for quarks of equal or unequal masses. It is shown that in all cases when there is the additional small parameter at hand (it is 0<(3N_c-N_F)/N_F << 1 for the direct theory, or its analog 0<(2N_F-3N_c)/N_F << 1 for the dual one), the mass spectra of the direct and dual theories are parametrically different. A number of other regimes are also considered.Comment: 30 pages, purely technical improvements for readers convenienc

Light Cone Sum Rules for the pi0-gamma*-gamma Form Factor Revisited

We provide a theoretical update of the calculations of the pi0-gamma*-gamma form factor in the LCSR framework, including up to six polynomials in the conformal expansion of the pion distribution amplitude and taking into account twist-six corrections related to the photon emission at large distances. The results are compared with the calculations of the B-> pi l nu decay and pion electromagnetic form factors in the same framework. Our conclusion is that the recent BaBar measurements of the pi0-gamma*-gamma form factor at large momentum transfers are consistent with QCD, although they do suggest that the pion DA may have more structure than usually assumed.Comment: 20 pages, 14 figures, 5 table

Light-cone Distribution Amplitudes of Xi and their Applications

We present the light-cone distribution amplitudes of the Xi baryons up to twist six on the basis of QCD conformal partial wave expansion to the leading order conformal spin accuracy. The nonperturbative parameters relevant to the DAs are determined in the framework of the QCD sum rule. The light-cone QCD sum rule approach is used to investigate both the electromagnetic form factors of Xi and the exclusive semileptonic decay of Xi_c as applications. Our estimations on the magnetic moments are $\mu_{\Xi^0}=-(1.92\pm0.34)\mu_N$ and $\mu_{\Xi^-}=-(1.19\pm0.03)\mu_N$. The decay width of the process Xi_c->Xi e^+\nu_e is evaluated to be $\Gamma=8.73\times10^{-14}{GeV}$, which is in accordance with the experimental measurements and other theoretical approaches.Comment: 23 pages, 8 figures, version to appear in Phys. Rev.

The ρ\rho Meson Light-Cone Distribution Amplitudes of Leading Twist Revisited

We give a complete re-analysis of the leading twist quark-antiquark light-cone distribution amplitudes of longitudinal and transverse $\rho$ mesons. We derive Wandzura-Wilczek type relations between different distributions and update the coefficients in their conformal expansion using QCD sum rules including next-to-leading order radiative corrections. We find that the distribution amplitudes of quarks inside longitudinally and transversely polarized $\rho$ mesons have a similar shape, which is in contradiction to previous analyses.Comment: 21 pages, latex2e, requires a4wide.sty and epsf.sty, 6 PS figures include

Higher Twist Effects in Proton-Proton Collisions

In this article, we investigate the contribution of the high twist Feynman diagrams to the large-$p_T$ pion production cross section in proton-proton collisions and we present the general formulae for the high and leading twist differential cross sections. The pion wave function where two non-trivial Gegenbauer coefficients $a_2$ and $a_4$ have been extracted from the CLEO data, two other pion model wave functions, $P_2$, $P_3$, the asymptotic and the Chernyak-Zhitnitsky wave functions are used in the calculations. The results of all the calculations reveal that the high twist cross sections, the ratios $R$, $r$, the dependence transverse momentum $p_T$ and the rapidity $y$ of pion in the $\Phi_{CLEO}(x,Q^2)$ wave function case is very close to the $\Phi_{asy}(x)$ asymptotic wave function case. It is shown that the high twist contribution to the cross section depends on the choice of the meson wave functions.Comment: 28 pages 18 figures RevTex

Kaon Distribution Amplitude from QCD Sum Rules

We present a new calculation of the first Gegenbauer moment $a_1^K$ of the kaon light-cone distribution amplitude. This moment is determined by the difference between the average momenta of strange and nonstrange valence quarks in the kaon. To calculate $a_1^K$, QCD sum rule for the diagonal correlation function of local and nonlocal axial-vector currents is used. Contributions of condensates up to dimension six are taken into account, including $O(\alpha_s)$-corrections to the quark-condensate term. We obtain $a_1^K=0.05\pm 0.02$, differing by the sign and magnitude from the recent sum-rule estimate from the nondiagonal correlation function of pseudoscalar and axial-vector currents. We argue that the nondiagonal sum rule is numerically not reliable. Furthermore, an independent indication for a positive $a_1^K$ is given, based on the matching of two different light-cone sum rules for the $K\to\pi$ form factor. With the new interval of $a_1^K$ we update our previous numerical predictions for SU(3)-violating effects in $B_{(s)}\to K$ form factors and charmless (B) decays.Comment: a comment and a reference added, version to appear in Phys.Rev.D, 17 pages, 7 figure

Leading-twist pion and kaon distribution amplitudes in the gauge-invariant nonlocal chiral quark model from the instanton vacuum

We investigate the leading-twist light-cone distribution amplitudes for the pion and kaon based on the gauge-invariant nonlocal chiral quark model from the instanton vacuum in the presence of external axial-vector currents. We find that the nonlocal contribution from the gauge invariance has much effects on the pion distribution amplitudes, while it changes mildly the kaon ones. We also study the Gegenbauer moments of the distribution amplitudes and compare them with the empirical analysis of the CLEO data.Comment: 14 pages, 10 figure

Outage probability for soliton transmission

PACS. 78.55.Qr – Amorphous materials; glasses and other disordered solids. PACS. 05.40.-a – Fluctuation phenomena, random processes, noise, and Brownian motion. Abstract. – We study the interplay between amplifier noise and birefringent disorder in the case of strongly nonlinear (soliton) type of transmission in optical fibers. Assuming both noise and disorder to be weak, we evaluate the probability distribution function (PDF) of the Bit-Error-Rate (BER) for the values of BER that are much larger than the typical (average) value. The PDFtail that describes probability of the system outage shows log-normal shape, strongly dependent on the fiber length. We also discuss a simple timing shift technique capable of the outage compensation. Nonlinear information transmission in optical fibers when elementary bits are represented by optical solitons constitutes a promising technology that has been a subject of intensive research over the past decades [1, 2]. In idealfibers, the information carried by the solitons would be transmitted without any loss. In practice, however, various impairments lead to information loss. Amplifier noise and birefringent disorder represent the two major impairments in both linear and nonlinear transmission regimes. The noise generated by spontaneous emissio

Plasma Injectors Based on Rotating Gliding Discharge with Reverse Vortex Flow with Liquid Electrode

The researched plasma-liquid system was developed to create discharge that is compliant with industrial requirements. Current-voltage characteristics of discharge and their dependence on interelectrode dis-tance are obtained. The main components of plasma are presented based on spectroscopy results. Meas-ured electron, vibrational and rotational temperatures prove that system is able to generate non-equilibrium discharge plasma at atmospheric pressure without severe electrode erosion