Deeply virtual and exclusive electroproduction of ω-mesons

Christopher Newport University 23606 Newport News VA USA
European Physical Journal A (Impact Factor: 2.42). 01/2005; 24(3):445-458. DOI: 10.1140/epja/i2005-10032-4
Source: arXiv

ABSTRACT The exclusive ω electroproduction off the proton was studied in a large kinematical domain above the nucleon resonance region and for the highest possible photon virtuality (Q2) with the 5.75 GeV beam at CEBAF and the CLAS spectrometer. Cross-sections were measured up to large values of the four-momentum transfer (- t < 2.7="">2) to the proton. The contributions of the interference terms σ{TT} and σ{TL} to the cross-sections, as well as an analysis of the ω spin density matrix, indicate that helicity is not conserved in this process. The t-channel π0 exchange, or more generally the exchange of the associated Regge trajectory, seems to dominate the reaction γ*p↦ωp, even for Q2 as large as 5 GeV2. Contributions of handbag diagrams, related to Generalized Parton Distributions in the nucleon, are therefore difficult to extract for this process. Remarkably, the high-t behaviour of the cross-sections is nearly Q2-independent, which may be interpreted as a coupling of the photon to a point-like object in this kinematical limit.


Available from: W. J. Briscoe, Jun 03, 2015
1 Follower
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Based on the collinear factorization approach, we present a comprehensive perturbative next-to-leading (NLO) analysis of deeply virtual meson production (DVMP). Our representation in conformal Mellin space can serve as basis for a global fitting procedure to access generalized parton distributions from experimental measurements of DVMP and deeply virtual Compton scattering (DVCS). We introduce a rather general formalism for the evaluation of conformal moments that can be developed further beyond the considered order. We also confirm previous diagrammatical findings in the pure singlet quark channel. Finally, we use the analytic properties of the hard scattering amplitudes to estimate qualitatively the size of radiative corrections and illustrate these considerations with some numerical examples. The results suggest that global NLO GPD fits, including both DVMP and DVCS data, could be more stable than often feared.
    Nuclear Physics B 07/2014; 884. DOI:10.1016/j.nuclphysb.2014.04.012 · 3.95 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We review very briefly a few recent highlight results from Jefferson Lab concerning nucleon Form Factors and Generalized Parton Distributions for which data with unprecedented precision and phase space coverage have be obtained these past few years. Along with new theoretical developements, these data allow to make some nucleon imaging in terms of partonic degrees of freedom in both momentum and space dimensions.
    International Journal of Modern Physics E 01/2012; 18(10). DOI:10.1142/S0218301309014524 · 0.84 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Exploiting a set of generalized parton distributions (GPDs) derived from analyses of hard exclusive leptoproduction of rho0, phi and pi+ mesons, we investigate the omega spin density matrix elements (SDMEs) recently measured by the HERMES collaboration. It turns out from our study that the pion pole is an important contribution to omega production. It will be treated as a one-particle exchange since its evaluation from the GPD E-tilde considerably underestimates its contribution. As an intermediate step of our analysis we extract the pi-omega transition form factor for photon virtualities less than 4 GeV^2. From our approach we achieve results for the omega SDMEs in good agreement with the HERMES data. The role of the pion pole in exclusive rho0 and phi leptoproduction is discussed too.
    European Physical Journal A 07/2014; 50(9). DOI:10.1140/epja/i2014-14146-2 · 2.42 Impact Factor