Search for Tetraneutron by Pion Double Charge Exchange Reaction at J-PARC

Tetraneutron ($^4n$) has come back in the limelight, because of recent observation of a candidate resonant state at RIBF. We propose to investigate the pion double charge exchange (DCX) reaction, i.e. $^4\mathrm{He}({\pi}^- , {\pi}^+)$, as an alternative way to populate tetraneutron. An intense ${\pi}^-$ beam with the kinetic energy of ~850 MeV, much higher than that in past experiments at LAMPF and TRIUMF, will open up a possibility to improve the experimental sensitivity of the formation cross section, which will be much smaller than hitherto known DCX cross sections such as $^9\mathrm{Be}({\pi}^-, {\pi}^+)^9\mathrm{He}\ (g.s.)$.Comment: 4 pages, 1 figure; proceedings of the 14th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon (MENU2016), Kyoto, Japan, 25-30 July 201

Sensitivity of the deeply bound pionic atoms to the pion-nucleon sigma term σπN\sigma_{\pi N}

We discuss the sensitivity of the observables of the deeply bound pionic atoms to the pion-nucleon sigma term $\sigma_{\pi N}$ to investigate the possibility of the precise determination of the value of $\sigma_{\pi N}$ by the accurate data of the deeply bound pionic atoms expected to be obtained at RIBF/RIKEN. We evaluate that the 1 MeV variation of the $\sigma_{\pi N}$ value $\Delta \sigma_{\pi N} = 1$ MeV causes the shift of the binding energy $|\Delta B_\pi (1s)| = 5 \sim 7.5$ keV of the 1$s$ pionic atoms in Sn isotopes for the cases considered in this article. The width of the $1s$ state in the light Sn isotopes has good sensitivity to the $\sigma_{\pi N}$ value, too. We also study the sensitivity of the formation spectra of the deeply bound pionic atoms to the value of the $\sigma_{\pi N}$ term. The combined analyses of the observables of the deeply bound pionic atoms are found to be helpful to determine the $\sigma_{\pi N}$ term precisely. One of the interesting combination of the observables is the energy gap of the 1$s$ and $2p$ states ($B_{\pi}(1s) - B_\pi(2p)$) which experimental error is significantly smaller than that of the absolute value of the binding energy itself of each state. The expected experimental error of the energy gap is $10 \sim 15$ keV in Sn region which corresponds to the uncertainty of the $\sigma_{\pi N}$ value around 3 MeV in our evaluation.Comment: 9 pages, 8 figures, 3 table

Spectroscopy of eta'-nucleus bound states at GSI-SIS

The eta' meson mass may be reduced due to partial restoration of chiral symmetry. If this is the case, an eta'-nucleus system may form a nuclear bound state. We plan to carry out a missing-mass spectroscopy with the 12C(p,d) reaction at GSI-SIS. Peak structures corresponding to such a bound state may be observed even in an inclusive measurement, if the decay width is narrow enough.Comment: 4 pages, 2 figures, to appear in the proceedings of MESON2012 (12th International Workshop on Meson Production, Properties and Interaction), Krakow, Polan

Feasibility Study of Observing eta' Mesic Nuclei with (p,d) Reaction

A novel method is proposed to measure eta'(958) meson bound states in 11C nuclei by missing mass spectroscopy of the 12C(p,d) reaction near the eta' production threshold. It is shown that peak structures will be observed experimentally in an inclusive measurement in case that the in-medium eta' mass reduction is sufficiently large and that the decay width of eta' mesic states is narrow enough. Such a measurement will be feasible with the intense proton beam supplied by the SIS synchrotron at GSI combined with the good energy resolution of the fragment separator FRS.Comment: 12 pages, 6 figures, accepted for publication in Progress of Theoretical Physic

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