First Indication of Solar B8 Neutrinos through Coherent Elastic Neutrino-Nucleus Scattering in PandaX-4T

Collaboration
Jul 15, 2024
9 pages
Published in:
  • Phys.Rev.Lett. 133 (2024) 19, 191001
  • Published: Nov 7, 2024
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Abstract: (APS)
The PandaX-4T liquid xenon detector at the China Jinping Underground Laboratory is used to measure the solar B8 neutrino flux by detecting neutrinos through coherent scattering with xenon nuclei. Data samples requiring the coincidence of scintillation and ionization signals (paired), as well as unpaired ionization-only signals (US2), are selected with energy threshold of approximately 1.1 keV (0.33 keV) nuclear recoil energy. Combining the commissioning run and the first science run of PandaX-4T, a total exposure of 1.20 and 1.04tonne·year are collected for the paired and US2, respectively. After unblinding, 3 and 332 events are observed with an expectation of 2.8±0.5 and 251±32 background events, for the paired and US2 data, respectively. A combined analysis yields a best-fit B8 neutrino signal of 3.5 (75) events from the paired (US2) data sample, with 37% uncertainty, and the background-only hypothesis is disfavored at 2.64σ significance. This gives a solar B8 neutrino flux of (8.4±3.1)×106cm-2s-1, consistent with the standard solar model prediction. It is also the first indication of solar B8 neutrino “fog” in a dark matter direct detection experiment.
Note:
  • Accepted by Physical Review Letters