HKS acceptance

Figure 9 shows the momentum dependence of the HKS solid angle. The solid angle is more than 16 msr over the momentum region of 1.2 GeV/$c$ $\pm$ 12.5%. No decay factor is included in this solid angle.

Figure 10 shows beam profile at the Q1 entrance and exit, Q2 entrance and exit, and dipole entrance. The solid angle is limited vertically by the target chamber and the Q1 pole shape, and it is limited horizontally by the Q2 width. The dipole gap also limits the acceptance of the higher momentum side as seen in positive $x$ side of figure 8. It is due to the weaker vertical focusing power in the higher momentum region. Figure 11 shows two dimensional presentation of the HKS angular acceptance at a given momentum. The thick curve corresponds to 7$^\circ$ scattered particle and the others correspond to 6$^\circ$ (right one), 8$^\circ$ (left one) and so on. The detector packages of the HKS are placed to cover the scattering angle from 2$^\circ$ to 13$^\circ$, 160 mr horizontally and 150 mr vertically.