Exotic hadron study is key role to investigate the hadron structure and dynamics of the low energy QCD. In 2003, the evidence of the pentaquark Θ + , a light baryon with strangeness S=+1, was reported as the first candidate for the multi-quark system by LEPS group [1]. After the first report, there have been many both theoretical and experimental works. However, since the existence of Θ + is not yet established, an experiment with higher sensitivity is required. The J-PARC E19 experiment was performed to search for pentaquark Θ + in the π p→K X reaction at the K1.8 beam line as the first experiment in the J-PARC Hadron Experimental Facility. The unique features of E19 are as follows;  Less ambiguity: A meson induced reaction is desirable to understand the production mechanism of Θ + . In addition, a liquid hydrogen target was used in E19 to reduce the background contribution.  High statistics and high resolution: High intensity π beam is available at J-PARC K1.8 beam line. The spectrometer for the beam and the scattered particle provided a mass resolution better than 2 MeV/c 2 (FWHM), which is useful to determine the narrow width. Physics runs were carried out in 2010 and 2012. In the first (second) run, 7.8×10 10 (8.7×10 10 ) π beam with the momentum of 1.92 (2.0) GeV/c was irradiated on the liquid hydrogen target. No peak structure was observed in the missing mass spectra of both data. The 90% confidence level upper limit of the production cross section was estimated to be 0.26 μb/sr [2] for the first run, which are averaged over 2-15 deg. in the laboratory frame. With a theoretical calculation using the effective Lagrangian approarch [3], the upper limit of the Θ + decay width was estimated to be 0.72 and 3.1 MeV/c 2 for J P =1/2 + and 1/2 for the first run. The analysis on the second run is ongoing. The contribution will review the result of E19 experiment including analysis update.

We have carried out an experiment to search for a neutron-rich hypernucleus, $^6_{\Lambda}$H, by the $^6$Li($\pi^-,K^+$) reaction at $p_{\pi^-}$ =1.2 GeV/$c$. The obtained missing mass spectrum with an estimated energy resolution of 3.2 MeV (FWHM) showed no peak structure corresponding to the $^6_{\Lambda}$H hypernucleus neither below nor above the $^4_{\Lambda}$H$+2n$ particle decay threshold. An upper limit of the production cross section for the bound $^6_{\Lambda}$H hypernucleus was estimated to be 1.2 nb/sr at 90% confidence level.

This Letter is concerned with the study of the Kstop−A→π±Σ∓A′ reaction in p-shell nuclei, i.e., 6,7Li, 9Be, 13C and 16O. The π±Σ∓/Kstop− emission rates are reported as a function of A. These rates are discussed in comparison with previous findings. The ratio π−Σ+/π+Σ− in p-shell nuclei is found to depart largely from that on hydrogen, which provides support for large in-medium effects possibly generated by the sub-threshold Λ(1405). The continuum momentum spectra of prompt pions and free sigmas are also discussed as well as the π±Σ∓ missing mass behavior and the link with the reaction mechanism. The apparatus used for the investigation is the FINUDA spectrometer operating at the DAΦNE ϕ-factory (LNF-INFN, Italy).

We analyse in detail a recently proposed technique for producing high rates of Ξ− hyperons from p¯ beams and for their slowing down until rest, as planned for the Double-Hypernuclei experiment at the future HESR-GSI facility. We describe the Monte Carlo event generator that we developed for this purpose, and discuss the numerical results obtained within our model, in connection with the expected performances and operation modes of the HESR ring.