GPPU Seminar

Date

13:00-15:30, February 17th, 2025

Place

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

Abstract

1) The CLAS collaboration conducts hadron mass spectroscopy via photo- and electroproduction at Jefferson Lab (JLab) in the United States. To date, we have measured the differential cross section of the Λ(1405) resonance by detecting its Σπ decay final states with high statistics, providing support for its hadron-molecular state. However, the available data on its Q2 dependence remains insufficient and we haven’t revealed its structural dynamics. To address it, I am analyzing the data from CLAS12 Run Group K (RG-K) experiments, conducted in 2018 and 2024, which focus on the electroproduction of hyperons with high statistics. In this seminar, I will provide an overview of hadron physics and the current understanding of Λ(1405), followed by an introduction to the CLAS12 RG-K experiment and a report on the current status of my analysis.

2) We investigate the level-crossing phenomenon in two-axion systems, where the mass eigenvalues intersect as the mass of one axion increases with the cooling of the universe. This phenomenon can significantly alter the abundance of axions in the early universe. Our study focuses on its impact on the QCD axion and an axion-like particle, identifying viable regions of axion mass and decay constant that explain the observed dark matter. Furthermore, we derive an improved expression for the adiabatic condition that overcomes limitations in earlier formulations and we numerically validate its effectiveness. Our analysis reveals specific relations between axion masses and axion-photon couplings within the viable region. These relations could potentially serve as a smoking gun signal for this scenario if confirmed experimentally. 

3) Cold atoms are atomic gases that are cooled at almost zero temperature by laser technology. In cold atom systems, by using the Feshbach resonance, it is possible to tune the strength of interaction between cold atoms, and various strongly correlated systems have been realized with cold atoms. One of the strongly correlated phenomena observed in cold atoms is the Efimov state. If you consider a strongly correlated 3-body system, this 3-body system exhibits 3-body bound states featuring discrete scale invariance. Efimov states appear in various 3-body systems, for example, cold atoms, magnon, and nuclear systems, and are called universal phenomena in 3-body systems. In 2022, an experimental group at Kyoto University realized the Feshbach resonance in Er-Li mixtures. This system is expected to exhibit fermionic Efimov states. However, Er has a large magnetic moment, and we have to take into account the effect of dipole interaction in addition to van der Waals interaction. Therefore, we investigated how the dipole interaction affects the universality of Efimov states.

Point

GSP 1