GPPU Seminar

Date

15:00—17:00, January 20, 2026

Place

(hybrid) Room 745, Science Complex B (H-03), Zoom registration map

Abstract

1) The excited hyperon states Λ(1405) and Λ(1520) are regarded as spin partners originating from an L=1 configuration in the constituent quark model. While the mass of Λ(1520) is well reproduced within this framework, the Λ(1405) appears about 80~MeV lower than the predicted value, indicating a serious discrepancy. This anomaly has motivated theoretical interpretations in which the Λ(1405) is not a simple three-quark state but a dynamically generated hadronic system, characterized by a two-pole structure associated with the \Sigma\pi and \bar{K}N channels. Recent experiments have provided hints supporting this two-pole nature; however, the detailed internal structure and production mechanism of the Λ(1405) remain unresolved, and further experimental information is required. To address this issue, the CLAS Collaboration has been conducting comprehensive studies of hyperon electroproduction at Jefferson Lab using the CLAS12 detector. This experiment provides access to a wide kinematic range in Q^2 and W, offering a unique opportunity to investigate the excitation mechanisms of Λ(1405) and Λ(1520) in electroproduction. In this seminar, I will present an overview of the research background and the current status of my CLAS12 analysis, including event selection, background subtraction, and preliminary results.

2) The triple-alpha reaction is a key process in nucleosynthesis, so we have to understand the reaction rate in various environment. Recently, it is suggested that the reaction rate in a hot and dense environment such as supernovae can be enhanced by neutron induced deexcitation instead of by radiative decay. In order to determine the enhancement factor, we aim to measure neutron inelastic scattering on 12C, which is the inverse process of the deexcitaion by neutrons. For the 12C(n,n') measurements at astrophysical energy, a new 10MeV monoenergetic neutron source with a cryogenic hydrogen gas target has been developed. In addition, we installed a new collimator to reduce a background event originated from direct detection of neutron beam. We conducted a neutron scattering experiment with new experimental setup last November. In this talk, I will introduce the research overview and talk about the result from last experiment and future prospects.

3) The J-PARC E96 experiment is a carbon Xi-atomic X-ray spectroscopy experiment conducted at the K1.8 beamline of J-PARC. In this experiment, particles are produced via the (K-,K+) reaction and subsequently captured by carbon atoms to form Xi atoms. X-rays emitted from Xi-atoms are measured using Ge detectors surrounding an Active Fiber Target (AFT). In this presentation, I report the results of an antiprotonic atomic X-ray measurement performed as a test experiment.

Point

GSP 1