The first experiment at the J-PARC K1.8 beam line using the SKS spectrometer

The Superconducting Kaon Spectrometer (SKS) system has been constructed at the J-PARC K1.8 beam line. With all detectors being operational since October, 2009, a series of commissioning data have been taken successfully such that the SKS system performance could be assessed. In particular, the (π⁻, p) elastic scattering and the P(π⁻, K⁺)Σ⁻ reaction were used for this purpose with the beam momentum of 0.5 GeV/c and 1.25 GeV/c, respectively. The measured resolution of Σ⁻ missing mass was 1.7 MeV/c²(FWHM) corresponding to 3.3 MeV/c (FWHM) momentum resolution of the SKS system. Overall, the SKS system showed an expected performance which proved the readiness for the first physics experiment at the K1.8 beam line.