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Herry Kwee

College of William and Mary
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Theta+ Photoproduction in a Regge Model

Narrow pentaquark states may arise in constituent quark models and such
states may be studied precisely at electron accelerators. The
photoproduction of the $\Theta^+(1540)$ resonance on the nucleon, through $K$
and $K^*$ Regge exchanges is analyzed. The size of the cross sections for
the $\gamma n \to K^- \Theta^+$ and $\gamma p \to \bar K^0 \Theta^+$
reactions are compared. The model allows us to estimate the cross sections
corresponding to a given upper bound on the width of the $\Theta^+$.
Furthermore, the cross sections sensitivity to the spin-parity assignments
$J^P = \frac{1}{2}^\pm$ and $\frac{3}{2}^\pm$ for the $\Theta^+$ resonance is
investigated. The photon asymmetry is found to display a pronounced
sensitivity to the parity of the $\Theta^+$, making it a very promising
observable for determining the quantum numbers of the $\Theta^+$ resonance.
This analysis is relevant to a planned Hall A experiment at JLab that will
provide the most definitive statement to date on the existence of the
$\Theta^+$.

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