새소식

Department of Physics & Astronomy

[유종희 교수/양정열 박사] 수퍼카미오칸데 태양중성미자 주기성 탐색 결과 Physical Review Letters에 출간

2024-06-17l 조회수 562

중성미자는 약한상호작용을 하는 입자로서 그 검출이 극도로 어려운 것으로 악명이 높다.  태양은 중성미자의 강력한 발생원으로서 중심의 핵융합반응을 통해 지금 이순간에도 매초 평방 센티미터당 1천억개 이상의 태양중성미자가 지구표면에 쏟아지고 있다. 물질과의 상호작용이 매우 약한 중성미자를 검출하기 위해서는 거대한 검출기를 필요로 하는데, 일본의 카미오카에 위치한 수퍼카미오칸데는 약 5만톤의 물과 14,000여개의 광증폭센서를 이용한 지름40m x 높이 40규모의 초거대 중성미자 검출설비로서 1995년부터 운용되고 있으며, 하루 평균 약 15개의 태양중성미자를 검출하므로써, 태양의 중심부를 투명하게 관측하고 있다. 

우리 학과의 유종희 교수와 양정열 박사 (현 IBS 연구원, 2024년 2월 서울대 박사학위 논문주제) 는 약22년간 (1995~2018) 수집된  태양중성미자 데이터의 주기성을 중성미자 진동지수를 보정하여 정밀 분석했다. 그 결과, 세계최고의 정밀도로 태양중성미자의 연간 주기성을 측정했으며, 약10일 이상의 태양중성미자 주기성에 대해서도 5% 미만의 뛰어난 정밀도로 탐색이 가능함을 증명했다. 이는 중성미자 천문학이 정밀 탐색 시대로 진입했음을 알리는 중요한 결과이며, 현재 건설중인 Hyper-Kamiokande 실험(물 25만톤 규모)은 물론 한국의 중성미자 연구진들이 추진중인 한국중성미자관측소 (Korea Neutrino Observatory, 50만톤 규모)가 미래에 밝혀줄 투명한 우주의 기대를 높여주고 있다.   

We report a search for time variations of the solar 8B neutrino flux using 5804 live days of Super-Kamiokande data collected between May 31, 1996, and May 30, 2018. Super-Kamiokande measured the precise time of each solar neutrino interaction over 22 calendar years to search for solar neutrino flux modulations with unprecedented precision. Periodic modulations are searched for in a dataset comprising five-day interval solar neutrino flux measurements with a maximum likelihood method. We also applied the Lomb-Scargle method to this dataset to compare it with previous reports. The only significant modulation found is due to the elliptic orbit of the Earth around the Sun. The observed modulation is consistent with astronomical data: we measured an eccentricity of (1.53±0.35)%, and a perihelion shift of (−1.5±13.5) days.

 
이 연구 결과는 Physical Revew Letters지에 2024년 6월 14일 발표 되었다.

PRL 132241803 (2024)  https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.132.241803