Angular distribution and azimuthal asymmetry for pentaquark production in proton-proton collisions

Angular distributions for production of the ${\Theta }^{+}$ pentaquark are calculated for the collisions of polarized protons with polarized target protons. We compare calculations based on different assumptions concerning spin and parity ($J=1/2^{\pm },3/2^{\pm }$) of the ${\Theta }^{+}$ state. For a wide class of interactions the spin correlation parameters describing the asymmetric angular distributions are calculated up to 250 MeV above production threshold. The deviations from the near-threshold behavior are investigated.

Figure 1

Calculated diagrams for ${\Theta }^{+}$ production in a pp collision.

Figure 2

Calculated angular distributions in the center-of-mass system for unpolarized beam and target for different spin-parity assignments of the ${\Theta }^{+}$ states at an energy of 0.13 GeV above threshold.

Figure 3

Calculated correlation parameters as a function of the polar angle Θ for different assumptions on the spin-parity assignments of the ${\Theta }^{+}$ particle at an excess energy of 0.13 GeV.

Figure 4

Spin correlation parameters at 90${}^{°}$ in the center-of-mass system calculated for K exchange as a function of the excess energy $\sqrt{s}-\sqrt{s_{\text{thr}}}$ for different assumptions on the spin-parity assignments of the ${\Theta }^{+}$ particle.

Figure 5

Spin correlation parameters at 90${}^{°}$ as a function of the excess energy for a combination of K and $K^{*}$ exchange. The thick (thin) lines present calculations with positive (negative) coupling strengths of the $K^{*}$ exchange given in Table .

Figure 6

Excess energy dependence of the combination $(1+A_{\mathit{xx}}){\sigma }_0$ for various spin and parity states of ${\Theta }^{+}$. The plot on the left (right) shows results for positive (negative) coupling strengths of the $K^{*}$ exchange given in Table .