P-parity of charmed particles from associative photoproduction of D and D^*-mesons

We suggest to measure the triple polarization correlations in the exclusive associative charm particle photoproduction, vector gamma + vector p --> vector Lambda_c^{++} bar{D^0} with linearly polarized photons, as a method to determine the P-parity of the charmed D-meson. The dependence of these correlations on the parity P(N Lambda_c D) can be predicted in model independent way. The t-dependence of the differential cross section for vector meson photoproduction, gamma + p --> Lambda_c^{++} bar{D^{*0}}, in a model based on D-exchange, is also sensitive to P(N Lambda_c D).Comment: 11 pages, 1 figur

Model independent properties of two-photon exchange in elastic electron proton scattering

We derive from first principles, as the C-invariance of the electromagnetic interaction and the crossing symmetry, the general properties of two-photon exchange in electron-proton elastic scattering. We show that the presence of this mechanism destroys the linearity of the Rosenbluth separation.Comment: 12 pages, no figures- Corrected misprints, changes in P. 7. No changes in conclusion

Relativistically invariant analysis of polarization effects in exclusive deuteron electrodisintegration process

A general formalism for the calculation of the differential cross section and polarization observables, for the process of deuteron electrodisintegration, is developed in the framework of relativistic impulse approximation. A detailed analysis of the general structure of the differential cross section and polarization observables for the $e^-+d\to e^-+n+p$ reaction is derived, using the formalism of the structure functions. The obtained expressions have a general nature and they hold in the one--photon--exchange mechanism, assuming P--invariance of the hadron electromagnetic interaction. The model of relativistic impulse approximation is introduced and the final state interaction is taken into account by means of the unitarization of the helicity amplitudes. A detailed description of the unitarization procedure is also presented. Using different parametrizations of the deuteron wave functions, the following polarization observables are calculated in the kinematical region of quasi--elastic deuteron electrodisintegration: the asymmetry for the scattering of longitudinally polarized electrons on a polarized deuteron target, the proton and neutron polarizations (for longitudinally polarized electron beam or vector--polarized deuteron target). The sensitivity to the neutron electric form factor is also thorougly investigated. The predictions of the model are compared with the results of recent polarization measurements and a good agreement with the existing experimental data has been obtained.Comment: 90 pages, 17 figure

PP-parity of charm and strange particles in electroproduction processes, in collinear regime

We show that definite polarization observables for the simplest electroproduction processes, $\ell+N\to \ell+B(1/2^\pm)+M(0^\pm)$, $B=Y(\Lambda, \Sigma$ or $Y_c$-hyperon, $\Theta^+$-pentaquark) and $M=K$, $\bar{K}$ or $D$, are sensitive to the relative P-parity $\pi(B)$ of the NBM-system. The interference of the longitudinal and transversal amplitudes for the collinear regime of the processes $\gamma^*+N\to B+M$($\gamma^*$ is the virtual photon) - at any value of momentum transfer squared and excitation energy of the $BM$-system - generates model independent relations between analyzing powers (in unpolarized lepton scattering by polarized target), from one side, and the components of the produced baryon $B$ polarization. It is important to stress that these relations depend on the above mentioned P-parity, and constitute a model independent method for the determination of unknown parities of strange and charm particles.Comment: 4 page

Precise method for the determination of the neutron electric form factor based on a relativistic analysis of the process $d(e,e'n)p

We generalize the recoil polarization method for the determination of the proton form factor to the case of the disintegration of vector polarized deuterons by longitudinally polarized electrons, $\vec d(\vec e, e'n)p$. We suggest to measure for this reaction, in the kinematics of quasi-elastic $en$-scattering, the ratio $R_{xz}=A_x/A_z$ of the asymmetries induced by the $x$- and $z$-components of the deuteron vector polarization. In the framework of the relativistic impulse approximation the ratio $R_{xz}$ is sensitive to $G_{En}$ in a wide interval of momentum transfer squared, whereas it depends weakly on the details of the $np$-interaction and on the choice of the deuteron wave function. Moreover, in the range $0.5\le Q^2\le$1.5 GeV$^2$, the ratio $R_{xz}$ shows a smooth dependence on $Q^2$, making the analysis simpler.Comment: 7 pages, 4 figs, 1 tabl

Polarization observables in the processes p+p→Θ++Σ+p+p\to \Theta^+ +\Sigma^+ and n+p→Θ++Λ0n+p\to \Theta^+ +\Lambda^0, for any spin and parity of the Θ+\Theta^+-hyperon in the threshold region

Using the symmetry properties of the strong interaction, such as the Pauli principle, the P-invariance, the conservation of the total angular momentum and isotopic invariance, we establish the spin structure of the threshold matrix elements for the processes $p+p\to \Theta^+ +\Sigma^+$ and $n+p\to \Theta^+ +\Lambda^0$, in a model independent way, which applies to any spin and parity of the $\Theta^+$-hyperon in the near threshold region. We predict the double spin observables for these processes, such as the dependence of the differential cross section on the polarizations of the colliding nucleons, and the coefficients of polarization transfer from a nucleon beam or target to the produced $\Sigma^+$ or $\Lambda^0$ hyperon. We prove that these observables are sensitive to the P-parity of the $\Theta^+$ baryon, for any value of its spin. As an example of dynamical considerations, we analyzed these reactions in the framework of K-meson exchange.Comment: 14 pages 1 figur

Polarization phenomena in elastic e∓Ne^{\mp}N scattering, for axial parametrization of two-photon exchange

We analyze polarization phenomena for elastic lepton-nucleon scattering, parametrizing the $2\gamma$-exchange contribution, as the product of lepton and nucleon axial vector currents, that correspond to $C=+1$ exchange in the annihilation channel. We found two combinations of polarization observables (one for three T-odd observables and another one - for five T-even observables), which allow to measure the ratio $G_E(Q^2)/G_M(Q^2)$ of nucleon electromagnetic form factors in model independent way, without any specific assumption about the $2\gamma$-exchange mechanism. Both these combinations have a general character and do not depend on the choice of the spin structure for the $2\gamma$-exchange. We show the inconsistency of other approximations recently used in the literature.Comment: Eight pages, no figure

Radiative corrections to polarization observables for elastic e+Ae+A-scattering. Part I: Virtual Compton Scattering

We calculate polarization phenomena for virtual Compton scattering on protons, at relatively large momentum transfer 1 GeV$^2$ $\le -q^2\le$ 5 GeV$^2$ on the basis of a model for $\gamma^*+ p\to \gamma+p$ with two main contributions: $\pi^0$-exchange in $t-$channel and $\Delta$-excitation in $s$-channel. This model applies from threshold to $\Delta$ region. The parameters entering in this model, such as coupling constants and electromagnetic form factors are well known. The analyzing powers for $\gamma^*+\vec p\to \gamma+ p$ and the components of the final proton polarization in $\gamma^*+ p\to \gamma+ \vec p$ are large in absolute value and show strong sensitivity to $\pi\bigotimes\Delta$ interference. These results can be applied to the calculation of radiative corrections to polarization phenomena in elastic $ep$-scattering.Comment: 18 pages, 9 figure

Polarization Phenomena in Hadronic and Nuclear Processes in Threshold Regime

The threshold region for processes of hadronic and nuclear interactions is very interesting for a theoretical as well as an experimental point of view. In this region one can apply different physical methods, starting from classical current algebra methods - for processes invloving soft pions, through effective Lagrangian approaches - or perturbative chiral symmetry theory (ChPT). The essential simplification of the spin structure of matrix elements for threshold regime results in better understanding of the underlying mechanisms and allows the analysis of polarization phenomena. A dedicated formalism is developed here for a wide class of processes including even such complicated processes as production of pseudoscalar and vector mesons in nucleon-nucleon collisions. Many interesting physical problems are discussed: hidden strangeness of nucleons and OZI-violation, $\eta N$ -and $\omega N$ interactions in S-state, the determination of P-parity of strange particles. Special attention is devoted to the analysis of the spin structure and polarization phenomena for nuclear processes with light nuclei which have important applications in fundamental astrophysics and in nuclear fusion.Comment: Review article, 83 pages 9 fig

Recent results on hadron form factors

We discuss the recent data on the electric proton form factor, obtained at JLab, which show a spectacular deviation from the commonly assumed dipole behavior. We discuss the implication of these results on the deuteron structure and on the neutron electric form factor: at relatively large $Q^2$ a revision of the deuteron models may be required, and the neutron electric form factor might become even larger than the proton electric form factor.Comment: 17 pages 4 figures Contribution to the Int. Workshop on Relativistic Nuclear Physics from hundreds of MeV to TeV, Varna, Bulgaria, 10-16 September 2001. Replacement of Fig. 1 and relative tex