[Paper Review] Kaon photo-production on the nucleon and deuteron

P. Bydžovský, M. Sotona+2 more|ArXiv.org|Dec 9, 2004

Quantum Chromodynamics and Particle Interactions3 citations

TL;DR

This study investigates kaon photo-production on the nucleon and deuteron using isobaric models to assess their impact on inclusive cross sections. It finds significant model dependence in K⁰ production on the deuteron, especially for forward angles, indicating that experimental data can discriminate between models despite similar fits to K⁺ data on the proton.

ABSTRACT

Isobaric models for the photo-production of K$^+$ are discussed and their predictions are shown in the K$^0$ photo-production. The models are further used in spectator model calculations of the K$^0$ photo-production on deuteron. Considerable dependence of the inclusive cross section on the elementary amplitude was found.

Motivation & Objective

• To evaluate the sensitivity of deuteron K⁰ photo-production cross sections to different isobaric models of elementary nucleon amplitudes.
• To assess whether experimental data from the deuteron reaction can distinguish between models that fit K⁺ production on the proton equally well.
• To investigate the role of the K₁ meson coupling ratio rKK₁ in determining predictions for K⁰ production on the neutron and deuteron.
• To demonstrate that the spectator model approximation is viable for inclusive d(γ,K⁰)Λp reactions despite missing ΛN final-state interactions.
• To provide a framework for reducing theoretical uncertainty in hypernuclear photo-production calculations through improved elementary amplitude constraints.

Proposed method

• Adopted isobaric models (K-MAID, SLA, M2, H2) with hadronic form factors and SU(3) symmetry constraints to describe p(γ,K⁺)Λ amplitudes.
• Used the same models to predict n(γ,K⁰)Λ amplitudes via isospin symmetry, with rKK₁ as a free parameter in most models.
• Applied the spectator model in impulse approximation to calculate d(γ,K⁰)Λp cross sections, assuming the proton remains unexcited.
• Employed non-relativistic Bonn wave functions for the deuteron to compute the final-state overlap integrals.
• Calculated differential and double-differential cross sections as functions of photon energy, kaon angle, and momentum, varying rKK₁.
• Compared model predictions across different kinematic regions, especially forward angles, to identify sensitivity to rKK₁ and resonance content.

Experimental results

Research questions

• RQ1 How do different isobaric models for p(γ,K⁺)Λ production translate into predictions for n(γ,K⁰)Λ production?
• RQ2 To what extent does the choice of the K₁ meson coupling ratio rKK₁ affect predictions for K⁰ photo-production on the deuteron?
• RQ3 Can experimental data from the d(γ,K⁰)Λp reaction discriminate between isobaric models that fit K⁺ data equally well?
• RQ4 How sensitive are inclusive deuteron cross sections to the inclusion of hadronic form factors and resonance content in the elementary amplitude?
• RQ5 What is the role of final-state interactions in the ΛN system, and does their omission in the spectator model significantly affect predictions?

Key findings

• Models with hadronic form factors (K-MAID, M2, H2) predict significantly lower forward-angle cross sections for K⁺ production than those without, especially at Eγ > 1.5 GeV.
• The SLA and K-MAID models show strong sensitivity to the rKK₁ parameter, with cross sections varying widely across the tested range of -1.6 to -3.4.
• In contrast, the M2 and H2 models are much less sensitive to rKK₁, producing stable predictions across the parameter space.
• The differential cross section for d(γ,K⁰)Λp exhibits strong model dependence, particularly at low kaon angles and photon energies around 1 GeV.
• The bump structure in the K⁰ cross section on the neutron at 1.1 GeV is driven by N*(1720) resonance exchange, with model dependence arising from resonance coupling and form factors.
• Double-differential cross sections in d(γ,K⁰)Λp show that experimental data at forward kaon angles and low energies can distinguish between models, especially SLA and K-MAID versus M2 and H2.