Production of hyperons by virtual photons

doi:10.1016/0550-3213(75)90481-2

Nuclear Physics B

Volume 95, Issue 1, 25 August 1975, Pages 77-97

https://doi.org/10.1016/0550-3213(75)90481-2 Get rights and content

Abstract

The electroproduction of K⁺Y on protons, $ep → ek^{+} Y, (Y ≡Λ; Σ^{0}; Σ′^{0} (1385); Λ′(1405); Λ′(1520))$ was investigated by measuring the scattered electron and the produced K⁺ meson in coincidence. The differential cross sections were determined as functions of W, q², t and ^φK_γ in the kinematical region: $1.9 ⩽ W ⩽ 2.8 GeV$ $−0.10 ⩾q^{2} ⩾−0.60 GeV^{2} /c^{2}$ $^{t} min^{⩾t}^{⩾t} min^{−0.33GeV^{2}/c^{2}}$ , $0 ⩽ φ_{Kγ} ⩽ 360°$ .

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Cited by (37)

Study of the Σ(1385) and Λ (1405) resonances in K + photoproduction processes
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The $γ p \to K^{+} π^{0} Λ$ and $γ p \to K^{+} π Σ$ reactions are studied in the kinematic region where the $π^{0} Λ (1116)$ and $π Σ (1192)$ pairs originate dominantly from the decay of the $Σ (1385)$ and $Λ (1405)$ resonances. We consider laboratory photon energies around 2 GeV, i.e. total center of mass energies above the known resonance region. We compute the t-channel kaon-exchange contribution to these reactions using $K^{-} p \to π^{0} Λ$ and $K^{-} p \to π Σ$ amplitudes calculated in the framework of a chiral coupled-channel effective field theory of meson–baryon scattering. We extract from the calculated cross section the gauge-invariant double kaon pole term. We find this term to be large and likely to drive significantly the $γ p \to K^{+} π^{0} Λ$ and $γ p \to K^{+} π Σ$ reactions in the kinematics under investigation. Accurate measurements of t-distributions for these processes, in progress or planned at ELSA and at SPring-8, are needed to confirm this expectation and assess the possibility of studying antikaon–nucleon dynamics just below threshold through these reactions.
The associated photoproduction of positive kaons and π0 Λ or π ∑ pairs in the region of the ∑(1385) and Λ(1405) resonances
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The $γ p \to K^{+} π^{0} Λ$ and $γ p \to K^{+} π Σ$ reactions are studied in the kinematic region where the $π^{0} Λ (1116)$ and $π Σ (1192)$ pairs originate dominantly from the decay of the $Σ (1385)$ and $Λ (1405)$ resonances. We consider laboratory photon energies around 2 GeV, significantly above the threshold for producing the $K^{+} Σ (1385)$ and $K^{+} Λ (1405)$ final states. We compute for both reactions the process in which the ingoing photon dissociates into a real $K^{+}$ and a virtual $K^{-}$ , the off-shell $K^{-}$ scattering subsequently off the proton target to produce the $π^{0} Λ$ or πΣ pair. The $K^{-} p \to π^{0} Λ$ and $K^{-} p \to π Σ$ amplitudes are calculated in the framework of a chiral coupled-channel effective field theory of meson–baryon scattering. The structure of the amplitudes reflects the dominance of the $Λ (1405)$ in the πΣ channel and of the $Σ (1385)$ in the πΛ channel. The full pion–hyperon final state interaction is included in these amplitudes. We extract from the calculated cross section the gauge-invariant double kaon pole term. We find this term to be large and leading to sizeable cross sections for both the $γ p \to K^{+} π^{0} Λ$ and $γ p \to K^{+} π Σ$ reactions, in qualitative agreement with the scarce data presently available. Accurate measurements of these cross sections should make it possible to extract the contribution of the double kaon pole and hence to assess the possibility of studying kaon–nucleon dynamics just below threshold through these reactions.
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1999, Nuclear Physics A
The result of a feasibility study to measure the Λ polarization in associated K⁺–Λ electro-production is presented. This measurement was performed in the experimental Hall C at Jefferson Lab. The scattered electron was detected in the HMS spectrometer, and the electro-produced kaon and the proton from the Λ→pπ⁻ decay were both detected in the SOS spectrometer. This quantity is very sensitive to the elementary p(e,e′K)Λ process and gives information on resonance production, and Regge exchange, among others. The result presented was measured at Q²=1.50 (GeV/c)² and cosθ_Kγ^CM=14°. The limits of the Λ polarization, with respect to the $p_{γ} × p_{K}$ axis, were found to be −0.21 and +0.89 with a confidence level of 68%. The result is compared to theoretical predictions based on an effective hadronic field Lagrangian model and a Regge framework model.
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Nuclear Physics B

Abstract

References (11)

Nucl. Phys.

Nucl. Phys.

Phys. Rev.

Phys. Rev.

Nuovo Cimento

Nuovo Cimento

Nucl. Phys.

Cited by (37)

Study of the Σ(1385) and Λ (1405) resonances in K <sup>+</sup> photoproduction processes

The associated photoproduction of positive kaons and π<sup>0</sup> Λ or π ∑ pairs in the region of the ∑(1385) and Λ(1405) resonances

Hyperon electroproduction with CLAS

Λ polarization in associated K<sup>+</sup> - Λ electro-production

Kaon electroproduction on deuterium

Associated strangeness electroproduction on the nucleon