Multidimensional tunneling between potential wells at non degenerate minima

We consider tunneling between symmetric wells for a 2-D semi-classical Schr\"odinger operator for energies close to the quadratic minimum of the potential V in two cases: (1) excitations of the lowest frequency in the harmonic oscillator approximation of V; (2) more general excited states from Diophantine tori with comparable quantum numbers.Comment: 6 pages, 1 figure, Conference Days on Diffraction 2014, Saint Petersburg, Russi

Higher twist nucleon distribution amplitudes in Wandzura-Wilczek approximation

We derive the higher twist (four and five) nucleon distribution amplitudes in the Wandzura-Wilczek approximation. Our method is based on an analysis of the conformal expansion of nonlocal operators in the spinor formalism.Comment: 10 page

Non local lagrangians(I): the pion

We define a family of non local and chirally symmetric low energy lagrangians motivated by theoretical studies on Quantum Chromodynamics. These models lead to quark propagators with non trivial momentum dependencies. We define the formalism for two body bound states and apply it to the pion. We study the coupling of the photon and W bosons with special attention to the implementation of local gauge invariance. We calculate the pion decay constant recovering the Goldberger-Treiman and the Gell-Mann-Oakes-Renner relations. We recover a form of the axial current consistent with PCAC. Finally we study the pion form factor and we construct the operators involved in its parton distribution.Comment: Latex, 25 pages with 15 figures; added references for introduction and section

Gluon poles and photon distribution amplitudes in Drell-Yan-like processes

We calculate the hadron tensor related to the photon-induced Drell-Yan process, with incoming nucleon being transversally polarised. We predict the new single spin asymmetry which probes gluon poles and which is expressed in terms of photon (both chiral-odd and chiral-even) distribution amplitudes and chiral-odd nucleon function stemming from the nucleon transverse polarization.Comment: 6 pages, 3 figures; Appendix has been adde

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

Do L3 data indicate the existence of an isotensor meson ?

The QCD analysis of the hard exclusive production of $\rho^+\rho^-$ and $\rho^0\rho^0$ mesons in two photon collisions shows that the recent experimental data obtained by the L3 Collaboration at LEP can be understood as a signal for the existence of an exotic isotensor resonance with a mass around $1.5 {\rm GeV}$.Comment: 3 pages, 2 figures; Presented at Photon2005, Warsaw, Polan