Annual Report 2018

Thanks to the high performance and high activities of RCNP users, RCNP has been selected as one of the six International Joint Usage / Research center in 2018 by MEXT. We report some of the highlights in this annual report.

First of all, the upgrade of AVF cyclotron has been started in full swing. The basic design of the new AVF cyclotron has been fixed and some of the elements has been constructed. We expect to improve the beam intensity by a factor of 5~10 by the upgrade. Please find the outlook of the upgrade project in this report.

From the activities at the Ring Cyclotron Facility, a pilot experiment has been carried out to study the gamma decay from Isovector giant dipole resonance by placing the Grand Raiden at 0 degree with a large-volume LaBr³ detector array. The data analysis is still preliminary, bit it shows that the gamma-decay coincidence measurement in the energy range of 10-20 MeV with a branching ratio of the order of 1% or smaller is feasible. Another topic with the Grand Raiden at 0 degree is the study of the tensor-force in high momentum neutron pickup reaction. To search for a direct evidence of the effect of the tensor forces, the ¹⁶O(p,d) reaction at relatively high- momentum transfers was performed. A strong enhancement of the ratio for the positive-parity state was observed.

Commissioning of the LEPS2 spectrometer has been started. The spectrometer consists of a large solenoid magnet, drift chambers, a time production chamber, aerogel Cherenkov counters, barrel electromagnet calorimeter, and barrel RPCs. The barrel RPC is a key counter for identification of kaons from pion background in high momentum regions. The performance of RPC is reported. Detector developments are also in progress for charmed baryon spectroscopy at the J-PARC high momentum beam line. In addition to the beam line construction, theoretical study on the production and decays of charmed baryons are carried out extensively. The study suggests the production and decays of charmed baryon may be related to their constituent nature such as a di-quark correlation.

This report covers many other actives such as study of double beta decay of ⁴⁸Ca and investigation of phase transition points from the canonical approach in lattice QCD. I hope you will find them interesting!

Sincerely yours,

Takashi Nakano
Director of Research Center for Nuclear Physics