The $\\gamma p \\rightarrow K^+ \\pi^0 \\Lambda$ and $\\gamma p \\rightarrow K^+ \\pi \\Sigma $
reactions are studied in the kinematic region where the $\\pi^0 \\Lambda$(1116) and $\\pi\\Sigma$(1192) pairs
originate dominantly from the decay of the $\\Sigma$(1385) and $\\Lambda$(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
$K^- p \\rightarrow \\pi^0 \\Lambda$ and $K^- p \\rightarrow \\pi \\Sigma$
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 $\\gamma p \\rightarrow K^+ \\pi^0 \\Lambda$
and $\\gamma p \\rightarrow K^+ \\pi \\Sigma $
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. |
