^{134}Xe is a candidate isotope for neutrinoless double beta decay (0νββ) search. In addition, the two-neutrino case (2νββ) allowed by the standard model of particle physics has not yet been ...observed. With the 656-kg natural xenon in the fiducial volume of the PandaX-4T detector, which contains 10.4% of ^{134}Xe, and its initial 94.9-day exposure, we have established the most stringent constraints on 2νββ and 0νββ of ^{134}Xe half-lives, with limits of 2.8×10^{22} yr and 3.0×10^{23} yr at 90% confidence level, respectively. The 2νββ (0νββ) limit surpasses the previously reported best result by a factor of 32 (2.7), highlighting the potential of large monolithic natural xenon detectors for double beta decay searches.
In this letter, we report the dark matter search results from the
commissioning run and the first science run of the PandaX-4T experiment. A
blind analysis is carried out on the entire data set. The ...data processing is
improved compared to previous work, unifying the low-level signal
reconstruction in a wide energy range up to 120 keV. With a total exposure of
1.54 tonne$\cdot$year, no significant excess of nuclear recoil events is found.
The lowest 90% confidence level exclusion on the spin-independent cross section
is $1.6 \times 10^{-47} \mathrm{cm}^2$ at a dark matter mass of 40 GeV$/c^2$.
Our results represent the most stringent constraint for a dark matter mass
above 100 GeV$/c^2$.
The PandaX-4T liquid xenon detector at the China Jinping Underground
Laboratory is used to measure the solar $^8$B 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
1.25 and 1.04 tonne$\cdot$year are collected for the paired and US2,
respectively. After unblinding, 3 and 332 events are observed with an
expectation of 2.8$\pm$0.5 and 251$\pm$32 background events, for the paired and
US2 data, respectively. A combined analysis yields a best-fit $^8$B neutrino
signal of 3.5 (75) events from the paired (US2) data sample, with $\sim$37\%
uncertainty, and the background-only hypothesis is disfavored at 2.64$\sigma$
significance. This gives a solar $^8$B neutrino flux of
($8.4\pm3.1$)$\times$10$^6$ cm$^{-2}$s$^{-1}$, consistent with the standard
solar model prediction. This is the first indication of solar $^8$B neutrino
``fog'' in a dark matter direct detection experiment.
\(^{134}\)Xe is a candidate isotope for neutrinoless double beta decay~(\(0\nu\beta\beta\)) search. In addition, the two-neutrino case (\(2\nu\beta\beta\)) allowed by the Standard Model of particle ...physics has not yet been observed. Utilizing the 10.4% of \(^{134}\)Xe in the natural xenon in the PandaX-4T detector and its first 94.9-day exposure, we have established the most stringent constraints on \(2\nu\beta\beta\) and \(0\nu\beta\beta\) of \(^{134}\)Xe half-lives, with limits of \(2.8\times10^{22}\) yr and \(3.0\times10^{23}\) yr at 90% confidence level, respectively. The \(2\nu\beta\beta\) (\(0\nu\beta\beta\)) limit surpasses the previously reported best result by a factor of 32 (2.7), highlighting the potential of large monolithic natural xenon detectors.
We report the first search for the elastic scatterings between cosmic-ray boosted sub-MeV dark matter and electrons in the PandaX-4T liquid xenon experiment. Sub-MeV dark matter particles can be ...accelerated by scattering with electrons in the cosmic rays and produce detectable electron recoil signals in the detector. Using the commissioning data from PandaX-4T of 0.63~tonne\(\cdot\)year exposure, we set new constraints on DM-electron scattering cross sections for DM masses ranging from 10~eV/\(c^2\) to 3~keV/\(c^2\).
Neutrinos from core-collapse supernovae are essential for the understanding of neutrino physics and stellar evolution. The dual-phase xenon dark matter detectors can provide a way to track explosions ...of galactic supernovae by detecting neutrinos through coherent elastic neutrino-nucleus scatterings. In this study, a variation of progenitor masses as well as explosion models are assumed to predict the neutrino fluxes and spectra, which result in the number of expected neutrino events ranging from 6.6 to 13.7 at a distance of 10 kpc over a 10-second duration with negligible backgrounds at PandaX-4T. Two specialized triggering alarms for monitoring supernova burst neutrinos are built. The efficiency of detecting supernova explosions at various distances in the Milky Way is estimated. These alarms will be implemented in the real-time supernova monitoring system at PandaX-4T in the near future, providing the astronomical communities with supernova early warnings.
