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Dark Matter

     It has now been proven that the major matter component of the Universe is dark matter. The Standard Model does not accommodate a suitable dark matter candidate. Therefore the existence of dark matter is a crucial phenomenological evidence for physics Beyond the Standard Model. The pressing goal of current and future dark matter experiments is to answer the question of whether dark matter interacts with normal matter other than gravity; i.e. if dark matter is detectable. We are developing experiment to directly detect those dark matters.


     One of the strong candidate of the dark matter is the hypothetical particle called axions. The axion has been postulated to solve the strong-CP problem in quantum chromodynamics. The strong-CP problem is manifested by the null observation of the neutron’s electric dipole moment. The Peccei-Quinn U(1) symmetry breaking mechanism was suggested as a solution to the problem. The mechanism leaves a pseudo-Goldstone boson field, interpreted as the axion. Moreover, the non-thermal axion production mechanism in the early Universe suggests the axion as a cold dark matter candidate. Especially a light axion is an ideal dark matter candidate which would have been produced during the Big Bang. The ultimate goal of the axion experiments at our lab is to discover the axion dark matters. The discovery of the axion will resolve the strong-CP problem, and the discovery of dark matter will revolutionize our understanding of the Universe.
   • Design, construction, and operation of an 18 T 70 mm no-insulation REBCO magnet for an axion haloscope experiment (RSI 91, 023314) 2020-02-06 [EP]
   • Magnetoresistance in cooper at high frequency and high magnetic fields (JINST 12 P10023) 2017-10-31


     Neutrinos are one of the least understood fundamental particles. Studying neutrinos provide insight into undiscovered principles of nature. The Coherent Elastic Neutrino-Nucleus Scattering process, or CENNS, has been observed in 2017. The coherence conditions requires a sufficiently small momentum transfer to the target nucleus so that the waves of the off-scattered nucleons in the nucleus are all in phase and add up coherently. The CENNS is one of the most important step towards approaching the vast unexplored low energy neutrino physics --- a vital process leading to supernova explosion, r-process nucleosynthesis of the elements and fundamental tests of the Standard Model, that includes measurements of weak mixing angles and the search for exotic new physics such as a neutrino magnetic moment, sterile neutrinos, background of dark matter searches, and non-standard neutrino interactions.
   • Observation of coherent elastic neutrino-nucleus scattering in argon (Fermilab JETP Seminar) 2020-01-10 [slide][mp4]
   • First constraint on coherent elastic neutrino-nucleus scattering in argon (PRD 100, 115020) 2019-12-09
   • Observation of coherent elastic neutrino-nucleus scattering (Science 357, 6356) 2017-08-03

     In the Standard Model, neutrinos are assumed to have zero mass. However, experimental observations during the last two decades showed that this assumption is incorrect. Neutrino flavor oscillation is a quantum mechanical flavor mixing phenomena where a neutrino created with a lepton flavor can be transformed into a different flavor. Neutrino oscillation through flavor mixing implies that neutrinos have non-zero mass. The detailed study of the neutrino flavor mixing matrix may also provide solutions to understand the matter dominant Universe.
   • Observation of reactor antineutrino disapperance using delayed neutron capture on hydrogen at RENO (JHEP 04 029) 2020-04-06
   • Fuel-composition dependent reactor neutrinos from RENO experiment (PRL 122, 232501) 2019-06-12
   • Neutrino oscillation study from RENO experiment (PRL 121, 201801) 2018-11-15


Particle Physics Laboratory