Basic design of the spectrometer

Basic specification of the HKS spectrometer was already given in Table 1. The HKS consists of two quadrupole magnets (Q1 and Q2) and one dipole magnet (D). Due to two degrees of freedom of the quadrupole doublet, the horizontal and vertical focusing can be simultaneously adjusted. The HKS is designed to achieve both 2 $\times$ 10$^{-4}$ (FWHM) momentum resolution and 20 msr solid angle acceptance at the same time when it is used with the splitter. The HKS is positioned at an angle of 7$^\circ$ with respect to 1.2 GeV/$c$ zero degree scattered particle to avoid scattered positively charged particles at 0 degrees, mostly positrons. The momentum acceptance was designed to be $\pm$12.5%, matching to that of the electron arm, as shown in Figure 7.