Comparison of the near-threshold production of η- and K-mesons in proton-proton collisions

Fäldt, Göran; Wilkin, C.

doi:10.1007/s002180050239

Cited by 56 publications

(115 citation statements)

References 15 publications

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“…We note that pion exchange graphs dominate the production process for all angles in each case. This result is similar to the observation made in the case of associated kaon production in elementary pp collisions [21,56] …”

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confidence: 90%

A relativistic two-nucleon model for reaction

2006

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We investigate the A(p, K + ) Λ B reaction within a covariant two nucleon model. We focus on amplitudes which are described by creation, propagation and decay into relevant channel of N * (1650), N * (1710), and N * (1720) intermediate baryonic resonance states in the initial collision of the projectile nucleon with one of its target counterparts This collision is modeled by the exchange of π as well as ρ and ω mesons. The bound state nucleon and hyperon wave functions are obtained by solving the Dirac equation with appropriate scalar and vector potentials. Expressions for the reaction amplitudes are derived taking continuum particle wave functions in both distorted wave and plane wave approximations. Detailed numerical results are presented in the plane wave approximation; estimates of the effects of the initial and final state interactions are given in the eikonal approximation. Cross sections of 1 -2 nb/sr at the peak positions, are obtained for favored transitions in case of heavier targets. PACS numbers: 25.40.V e, 13.75. − n,, 13.75.Jz

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confidence: 90%

A relativistic two-nucleon model for reaction

2006

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“…Furthermore, it is difficult to decide what kind of meson exchange mechanism is dominant for the reaction as was questioned in Ref. [5].In the lower part of Fig. 1, we show the separate contribution from π, η and ρ-meson exchanges to the energy dependence of the total cross sections.…”

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confidence: 92%

“…Moreover, it was found [2,3] that the dominant contribution to the pp → pΛK + reaction comes from the K-exchange mechanism. Alternatively, the study of Fäldt and Wilkin [5] which was made analogous to the pp → ppη reaction with a nonrelativistic treatment including the final state interaction, suggests that the total cross sections for the pp → pΛK + reactions at energies only slightly above threshold can possibly be explained by one pion-exchange followed by N ⋆ (1650) resonance excitation. Furthermore, they claim that these two ingredients alone are almost enough to describe the data.…”

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confidence: 99%

A clue to the mechanism of ΛK+ production in pp-reactions

1998

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We analyse the pp → pΛK + total cross section data which were recently measured by the COSY-11 collaboration at an energy 2 MeV above the reaction threshold. Our analysis suggests that the measurement of the invariant mass spectrum for the ΛK + at energies around 100 MeV above the threshold can provide a new constraint on the theoretical calculations for this reaction. In particular, the measurement can give a clue as to whether the reaction is dominated by resonance excitation or not. Thus, it should contribute to further understanding of the strangeness production mechanism. We show the invariant mass spectra for the ΛK + system in these optimal kinematic conditions calculated by several approaches, and demonstrate that our suggestion is experimentally feasible. : 13.75, 25.40, 14.20.G, 24.10 Keywords: Kaon production, Proton proton collision, Baryon resonance, One boson exchange, ΛK + invariant mass spectrum * Supported in part by the Forschungszentrum Jülich, and the Australian Research Council † sibirt@theorie.physik.uni-giessen.de ‡ ktsushim@physics.adelaide.edu.au § athomas@physics.adelaide.edu.au 0 Recently the COSY-11 Collaboration [1] measured the total cross section for the reaction, pp → pΛK + , at energy 2 MeV above the reaction threshold. The data were compared with the theoretical models which are presently available for this reaction [2,3,4,5]. Among them, both the predictions of Sibirtsev [2] and Li and Ko [3] could reproduce the experimental data at this energy well only with the inclusion of pion and kaon exchanges, but without the inclusion of any resonances which are observed to decay to the ΛK + channel. Moreover, it was found [2,3] that the dominant contribution to the pp → pΛK + reaction comes from the K-exchange mechanism. Alternatively, the study of Fäldt and Wilkin [5] which was made analogous to the pp → ppη reaction with a nonrelativistic treatment including the final state interaction, suggests that the total cross sections for the pp → pΛK + reactions at energies only slightly above threshold can possibly be explained by one pion-exchange followed by N ⋆ (1650) resonance excitation. Furthermore, they claim that these two ingredients alone are almost enough to describe the data. One of their motivations was to study whether the same type of meson exchange model could be capable of explaining simultaneously the near-threshold η and K production data -one pion exchange followed by N ⋆ (1650) resonance excitation for the present case. PACSIn Ref.[4], within the resonance model, we performed the most detailed study of kaon production in proton-proton collisions with a full relativistic treatment. This included the mechanism adopted by Fäldt and Wilkin [5] as just one of the processes in evaluating the total cross sections. However, it has turned out that our calculation underestimates the data [1] at energy 2 MeV above the threshold -as shown in Fig. 1. It underestimates the experimental data from COSY by about a factor of 2, although it reproduces the existing data fairly wel...

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“…The existing theoretical studies of this reaction are based either on a single boson (π or K meson) exchange mechanism [17][18][19][20] or a resonance model [22][23][24]. In the first method, the K + production is assumed to take place essentially through the exchange of one intermediate pion or K-meson; the excitation of any intermediate nucleon resonance is not considered.…”

Section: Introductionmentioning

confidence: 99%

pp→pK+Λreaction in an effective Lagrangian model

Shyam

1999

Phys. Rev. C

128

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We investigate the pp → pK + Λ reaction within an effective Lagrangian model where the contributions to the amplitudes are taken into account within the tree level. The initial interaction between the two nucleons is modeled by the exchange of π, ρ, ω and σ mesons and the ΛK + production proceeds via the excitation of the N * (1650), N * (1710), N * (1720) baryonic resonances. The parameters of the model at the nucleon-nucleon-meson vertices are determined by fitting the elastic nucleon-nucleon scattering with an effective interaction based on the exchange of these four mesons, while those at the resonance vertices are calculated from the known decay widths of the resonances as well as the vector meson dominance model. Available experimental data is described well by this approach. The one-pion-exchange diagram dominates the production process at both higher and lower beam energies. The ρ and ω meson exchanges make negligible contributions. However, the σ-exchange processes contribute substantially to the total cross sections at lower beam energies. The excitation of the N * (1710) and N * (1650) resonances dominate this reaction at beam momenta above and below 3 GeV/c respectively. The interference among the amplitudes of various resonance excitation processes is significant. For beam energies very close to the K + production threshold the hyperon-proton final state interaction effects are quite important. The data is selective about the model used to describe the low energy scattering of the two final state baryons.

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Comparison of the near-threshold production of η- and K-mesons in proton-proton collisions

Cited by 56 publications

References 15 publications

A relativistic two-nucleon model for reaction

A relativistic two-nucleon model for reaction

A clue to the mechanism of ΛK+ production in pp-reactions

pp→pK+Λreaction in an effective Lagrangian model

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