Toward new frontiers : Encounter and synergy of state-of-the-art astronomical detectors and exotic quantum beams

Core of a neutron star can be interpreted as a giant nucleus, and is a bridge between nuclear physics and astrophysics. In the neutron star, as the Fermi energy of neutron is sufficiently high to produce s quark, hyperon appearance is naturally expected. Thus, the nature of the existing neutron stars found by astronomical research should be explained by the ΛN interaction revealed by hypernuclear physics. Recently, the super heavy neutron stars were found [1-2]. However, the existence of such the neutron stars cannot be understood from the view point of hypernuclear physics because those neutron stars will be collapsed due to lack of the repulsive force. Therefore, the many body forces such as ΛNN is expected to be a source of extra repulsion to support the super heavy neutron star. Understanding of the ΛN many-body force through the precise hypernuclear experiment is one of motivation of the group A02.

However, a theoretical suggestion to this attempt is raised [3], that is, accuracy of the present two-body ΛN interaction models is not enough, i.e. the partial waves higher than the P wave are not well known, to discuss the many-body force via hypernuclear experiments. Thus, we aim to perform a high static Λp scattering experiment at the J-PARC high momentum (high-p) beam line to understand the two-body ΛN interaction precisely. Our project is complementary to hypernuclear experiments.

Production of a lot of Λ particles is essential for the high statistics. The property of the J-PARC high-p beam line, which can provide the 30 MHz secondary pion beam, satisfies our purpose. The high intensity beam results the high reaction rate. The performance of the DAQ system, especially, the trigger is a key to carry out experiments in the high-p beam line. Thus, by removing the hardware trigger system, the data streaming type DAQ system is required. In this DAQ system, all the front-end electronics digitizes all the detector hits and stream all the data to the computer. The CPU cluster system finds the event from the streamed data in real time. In this project, we aim to develop the data streaming type front-end electronics for the scintillating fiber detector in order to realize the Λp scattering experiment in the J-PARC high-p beam line. As the data taking efficiency of 99% under the 1 MHz/ch condition, this electronics has PETIROC2A ASIC for the analog signal amplification and has the 4 Gbps data link realized by multi-GbE.

J-PARC Hadron Hall and high-momentum (high-p) beam line

Schematic diagram of the Λp scattering experiment in the double-scattering scheme. Λ particles produced in the π^–p → K*⁰ Λ reaction are further scattered from a proton target. The scattered proton and decaying particles from K*⁰ are measured using a detector around the target and a forward spectrometer, respectively.

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