Beam and SKS spectrometers at the K1.8 beam line

High-resolution spectrometers for both incident beams and scattered particles have been constructed at the K1.8 beam line of the Hadron Experimental Facility at J-PARC. A point-to-point optics is realized between the entrance and exit of QQDQQ magnets for the beam spectrometer. Fine-pitch wire chamber trackers and hodoscope counters are installed in the beam spectrometer to accept a high rate beam up to 107 Hz. The superconducting kaon spectrometer for scattered particles was transferred from KEK with modifications to the cryogenic system and detectors. A missing-mass resolution of 1.9 ± 0.1 MeV/c2 (FWHM) was achieved for the ∑ peaks of (π±, K+) reactions on a proton target in the first physics run of E19 in 2010

J-PARC E27 Experiment to Search for a K−pp Bound State

We have carried out an experimental search for the simplest kaonic nucleus, $K^{ - }pp$, by using the $d(\pi ^{ + },K^{ + })$ reaction at $p_{\pi ^{ + }}$ = 1.69 GeV/$c$. The differential cross section of this reaction with covering a wide missing-mass range from the $\Lambda$ production threshold to the $\Lambda (1405)/\Sigma (1385)$ region has been measured for the first time. The inclusive missing-mass shape of the $\Lambda$ and $\Sigma$ production region was understood with a simple quasi-free picture except for an enhancement at 2.13 GeV/$c^{2}$ due to a $\Sigma N$ cusp. An obtained peak attributed to $Y^{*}$ production was significantly shifted to the low mass side compared with the simulation by $- 22.4$ MeV/$c^{2}$

A Σp\Sigma p scattering Experiment at J-PARC and the Analysis Status

International audienceJ-PARC E40 aims to measure the differential cross sections of the Σ^±p elastic scatterings and the Σ^−p → Λn conversion. A clear peak of Σ^− was observed in a missing mass spectrum of the π^−p → K^+X reaction and recoil protons from the πp elastic scattering were successfully observed in the data taken in the summer 2018. The rest of data taking is coming in the spring 2019

Strangeness physics programs by S-2S at J-PARC

In the K1.8 beam-line at Hadron Experimental Facility of J-PARC, a new magnetic spectrometer S-2S is being installed. S-2S was designed to achieve a high momentum resolution of Δp/p = 6 × 10−4 in FWHM. Several strangeness-physics programs which require the high resolution will be realized by S-2S. The present article introduces J-PARC E70 (missing-mass spectroscopy of Ξ12Be) and E94 (missing-mass spectroscopy of Λ7Li, Λ10B, and Λ12C) experiments

J-PARC E19 Experiment: Pentaquark Θ+ Search in Hadronic Reaction at J-PARC

A search for the Θ^+ pentaquark in the $\pi ^{ - }p \to K^{ - }X$ reaction was performed at the J-PARC Hadron Facility. Two data samples were collected in 2010 and 2012 at π beam momenta of 1.92 and 2.0 GeV/c, respectively. No peak structure was observed in the missing mass spectra obtained from either data set. The upper limit for the production cross section averaged over the scattering-angle range of 2° to 15° in the laboratory frame was found to be 0.28 µb/sr. The decay width of the Θ^+ can be directly connected to the production cross section through a theoretical calculation using an effective Lagrangian. The estimated upper limits of the width were 0.41 and 2.8 MeV for the spin-parities of 1/2^+ and 1/2^−, respectively