E27 and E15

Whether a Kaonic bound system, $K^-pp$, exists or not is one of important issues in Strangeness nuclear physics at J-PARC. Based on low-energy $KN$ scattering data and kaonic-atom X-ray data, it is well known that the $KN$ interaction near threshold has a strong attraction in the isospin 0 channel. It can be a driving force to form the Kaonic bound state, $K^-pp$. The FINUDA and DISTO collaborations reported possible signatures of the $K^-pp$ decaying into a $\Lambda p$ pair. In order to establish the existence, it would be crucial to confirm it in different reactions. At J-PARC, there are two experiments searching for the $K^-pp$: E27 and E15. In E27, the $d(\pi^+,K^+)X$ reaction at 1.7 GeV/c is used to produce the $K^-pp$. The inclusive $(\pi^+,K^+)$ spectrum is measured with the SKS spectrometer in a good energy resolution. To suppress large backgrounds coming from quasi-free hyperon(Ys and Y*s) productions, coincidence of high-momentum protons emitted in the target area (39 – 122 degrees) is further required. A pilot data taking was already performed in 2012, and the analysis results on the inclusive and coincidence spectra will be presented in the conference. In E15, the $^3\textrm{He}(K^-,n)X$ reaction at 1.0 GeV/c is used to produce the $K^-pp$. The forward neutron is detected by a neutron hodoscope with ~15-m time-of-flight. The $(K^-,p)$ spectrum can be also obtained. At the same time, the decay products from the $K^-pp$ are detected with a cylindrical detector system with an acceptance coverage of 66% of $4\pi$ surrounding the $^3$He target. A commissioning physics data taking was carried out in a short period in May, 2013. Some preliminary results will be reported.