The "SeaBell Project" pathfinder project has made important progress to verify the feasibility of selecting the site of China's first deep-sea neutrino telescope

The "Hailing Project" pathfinder project team led by Shanghai Jiao Tong University completed various scheduled sea trials this month and arrived safely in Shanghai. Photo by Xu Jing

On September 17, Shanghai Jiao Tong University announced on the 17th that the "Hailing Plan" pathfinder project team led by the school has completed various scheduled sea trial tasks and arrived in Shanghai safely this month. After preliminary analysis, the feasibility of pre-selected sea area as a candidate site for neutrino telescopes is verified. This scientific expedition also laid a solid foundation for the follow-up promotion of the "Hailing Project".

The voyage was led by Xu Donglian, a scholar of Li Zhengdao of Shanghai Jiaotong University, and Tian Xinliang, a scholar of ocean engineering, as the leader, and more than 30 researchers and technicians from Shanghai Jiao Tong University, Peking University, Tsinghua University, University of Science and Technology of China, and the Second Institute of Oceanography of the Ministry of Natural Resources participated.

Since November 2018, after careful demonstration and the development of related instruments and equipment, as a pre-research demonstration project of the "Sea Bell Project", the "Sea Bell Pathfinder" sea test team has recently successfully deployed several sets of self-developed experimental instruments in the predetermined sea area, not only collecting in situ precious data of more than 1TB of sea depth of 3500 meters, but also scanning and testing the relevant properties of full water deep seawater.

In addition, the team also successfully deployed a set of submarine markers that can monitor the submarine flow field, biological activity, sediment and test telescope components for a long time, providing a basis for the design and long-term operation and maintenance of subsequent telescope arrays.

"We look forward to participating in international cooperation when it is completed." Xu Donglian said that the Neutrino observation project of the "Hailing Project" will be completed by 2030, and after completion, it will form an array of about 4km *4km grid points, monitoring more than 1 million Beijing water cubes and 1,000 West Lakes. This deep-sea telescope project can monitor a wider area of the south China Sea as the Earth rotates, adding new support for multi-messenger astronomy research. After the progress of neutrino research, further tomography of the Earth's interior can be carried out to understand the mysteries of the Earth's interior.

The "Hailing Project" is led by the Li Zhengdao Research Institute of Shanghai Jiao Tong University, the project team leader is Jing Yipeng, academician of the Chinese Academy of Sciences, and the chief scientist is Xu Donglian, aiming to explore the construction of China's first high-energy neutrino telescope project in the deep sea area below 3 kilometers, explore the extreme universe by capturing high-energy celestial neutrinos, and build China's complete multi-messenger astronomical network, which will be a large scientific device that can lead the cutting-edge cross-research of particle physics, astrophysics, geophysics, marine geography, marine biology and so on. It has significant potential to nurture a number of original scientific discoveries.

Neutrinos are one of the basic units that make up the universe and the most numerous particles in the universe. It is not charged and interacts with matter extremely weakly, like a ghost, and extremely difficult to catch. Neutrinos were first predicted theoretically in 1930, but were not experimentally observed until 1956. There are many sources of neutrinos in the universe, such as the Big Bang, supernova explosions, binary neutron star mergers, black hole explosions and other extreme astrophysical processes; if dark matter is elementary particles, neutrinos may also be produced through mutual annihilation or spontaneous decay. Because of its ghostly nature, neutrinos have strong penetration, can easily escape the extreme, dense celestial environment, carrying the information of the violent physical processes in it, and are the ideal for studying the extreme universe.

The idea of neutrino astronomy originated in 1960 Markov's proposal to build a Cherenkov light detection element array in the deep sea or lake; the Antares/KM3NeT project in the Mediterranean Sea and the Baikal/GVD project in Lake Baikal are both planned, but it is more difficult to build a neutrino telescope in seawater, and the most well-known neutrino telescope Ice Cube (Ice Cube) has chosen to build the detector array in the Antarctic ice layer at a depth of 2500 meters.

Built in 2010, IceCube is currently the world's largest neutrino detector. In 2013, Ice Cube first detected a diffuse stream of high-energy neutrinos from beyond the earth, knocking on the door to high-energy neutrino astronomy; however, this neutrino stream showed no signs of agglomeration or explicitly pointed back to any known celestial source, suggesting that there is no celestial source of intense radiation of high-energy neutrinos in the universe near Earth. To effectively find celestial sources of high-energy neutrinos, it is still necessary to improve the detection sensitivity of the next generation of neutrino telescopes.

At present, Europe and the United States are actively preparing to build a second-generation neutrino telescope with greatly optimized performance, which is expected to be completed around 2030; when a major breakthrough may be achieved in the field of neutrino astronomy.

Xu Donglian has studied and worked in the Ice Cube Cooperation Group for many years, and is a young scholar active in the field of neutrino astronomy in recent years. Through the accumulation of time in the international cooperation group, she gradually germinated a "dream" - china-led construction of neutrino telescopes in the waters of the South China Sea. In September 2018, Xu Donglian returned to China to join the Lee Zheng Dao Research Institute. In August 2020, Xu Donglian, on behalf of the "Hailing Project" team, made an invited report at the National High-Energy Physics Development Strategy Seminar (Qingdao), and formally proposed the construction plan and action plan of the South China Sea Neutrino Telescope - "Hailing Project". (End)

Source: China News Network