Low energy kaon photoproduction from nuclei

Abstract

We study $K^+$-meson production in $\gamma{A}$ interaction at energies below the reaction threshold in free space. The Thomas-Fermi and spectral function approaches are used for the calculations of the production process. It is found that the measurement of the differential spectra may allow to reconstruct the production mechanism and to investigate the dispersion relations entering the production vertex. It is shown that the contribution from secondary pion induced reactions to the total kaon photoproduction is negligible for $E_\gamma{<}$1.2 GeV so that strangeness production at low energies is sensitive to the nuclear spectral function.Comment: 20 pages, espcrc1, including 12 figures, to appear in Nucl. Phys.

Analysis of Θproduction in K+- Xe collisions

“…However, as was shown in Ref. [18] calculations within the local Thomas-Fermi approximation are in reasonable agreement with the results obtained with realistic spectral functions evaluated within the orthogonal correlated basis approach [19,20] unless the calculations are performed for the production of particles at energies substantially below the threshold in free space.…”

“…We neglect the high momentum or correlated part of the spectral function, which contributes to subthreshold particle production [17,18], but does not affect the results of the present study. Indeed the maximum of the spectral function for high momenta, which is attributed to shortrange and tensor correlations, corresponds to a total en-ergy of the bound nucleon given as [17,16],…”

Influence of the nucleon spectral function in photon and electron induced reactions on nuclei

“…( 6), A 1/2 denotes the transverse helicity amplitude of the S 11 , which depends on Q 2 . In electroproduction, there is also a longitudinal contribution, which is negligible as well as the dependence of the cross section (7) on the polarization parameter ε [14]. Background processes for both reactions are negligible [23].…”

“…[6]). In [7,8] photon induced K + Λ production and proton induced production of heavy mesons K + , ρ, ω, φ on carbon has been studied within the framework of folding models showing also an influence in more exklusive reactions. In the energy regime where nucleon resonances play an important role there is another modification that should be taken into account: In the vacuum, it is known that the decay width of resonances into channels with unstable mesons (e.g.…”