# Publications

## Measurement of double beta decay half-life of 136Xe with the PandaX-4T detector

(2022)

Precise measurement of two-neutrino double beta decay~(DBD) half-life is an important step for the searches of Majorana neutrinos with neutrinoless double-beta decay. We report the measurement of DBD half-life of ${}^{136}Xe$ using the PandaX-4T dual-phase Time Projection Chamber~(TPC) with 3.7-tonne natural xenon and the first 94.9-day physics data release. The background model in the fiducial volume is well constrained in situ by events in the outer active region. With a ${}^{136}Xe$ exposure of 15.5 kg-year, we establish the half-life as 2.27±0.03(stat.)±0.09(syst.) $\times$ 10^{21} year. This is the first DBD half-life measurement with natural xenon and demonstrates the physics capability of a large-scale liquid xenon TPC in the field of rare event searches.

## Search for light fermionic dark matter absorption on electrons in PandaX-4T

PHYSICAL REVIEW LETTERS, Vol.129, 161804(2022)

We report a search on sub-MeV fermionic dark matter absorbed by electrons with an outgoing active neutrino using the $0.63$ tonne year exposure collected by the PandaX-4T liquid xenon experiment. No significant signals are observed over the expected background. The data are interpreted into limits to the effective couplings between such dark matter and the electron. For axial-vector or vector interactions, our sensitivity is competitive in comparison to existing astrophysical bounds on the decay of such a dark matter candidate into photon final states. In particular, we present the first direct detection limits for a vector (axial-vector) interaction which are the strongest in the mass range from $35$ to $55$ ($25$ to $45$) $keV/c^2$ in comparison to other astrophysical and cosmological constraints.

## First search for the absorption of fermionic dark matter with the PandaX-4T experiment

Physical Review Letters, Vol.129, 161803(2022)

Compared to the signature of dark matter elastic scattering off nuclei, absorption of fermionic dark matter by nuclei opens up a new searching channel for light dark matter with a characteristic mono-energetic signal. In this letter, we explore the 95.0-day data from PandaX-4T commissioning run and report the first dedicated searching results of the fermionic dark matter absorption signal through neutral current process. No significant signal was found and the lowest limit on the dark matter-nucleon interaction cross section is set to be $1.5 \times 10^{-50} cm^{2}$ for a fermionic dark matter mass of $40 MeV / c^{2}$ with 90% confidence level.

## Constraints on the axial-vector and pseudo-scalar mediated WIMP-nucleus interactions from PandaX-4T experiment

Physics Letters B(2022)

We present the constraints on the axial-vector and pseudo-scalar mediated WIMP-nucleus interactions from the PandaX-4T experiment, using the data set corresponding to a total exposure of 0.63 tonne⋅year. No significant signal excess is observed, and the most stringent upper limits to date on the spin-dependent WIMP-neutron scattering cross section are set at 90% confidence level with the minimum WIMP-neutron scattering cross section of $5.8\times 10^{-42}cm^{2}$ for WIMP mass of 40 $GeV/c^{2}$. Exclusion limits on the axial-vector and pseudo-scalar simplified models are also derived.

## A search for two-component Majorana dark matter in a simplified model using the full exposure data of PandaX-II experiment

Physics Letters B, Vol.832, 137254(2022)

In the two-component Majorana dark matter model, one dark matter particle can scatter off the target nuclei, and turn into a slightly heavier component. In the framework of a simplified model with a vector boson mediator, both the tree-level and loop-level processes contribute to the signal in direct detection experiment. In this paper, we report the search results for such dark matter from PandaX-II experiment, using total data of the full 100.7 tonne⋅day exposure. No significant excess is observed, so strong constraints on the combined parameter space of mediator mass and dark matter mass are derived. With the complementary search results from collider experiments, a large range of parameter space can be excluded.

## Study of background from accidental coincidence signals in the PandaX-II experiment

Chinese Physics C, Vol.46, 103001(2022)

Study of background from accidental coincidence signals in the PandaX-II experiment

## Neutron-induced nuclear recoil background in the PandaX-4T experiment

Chinese Physics C(2022)

Neutron-induced nuclear recoil background is critical to the dark matter searches in the PandaX-4T liquid xenon experiment. This paper studies the feature of neutron background in liquid xenon and evaluates their contribution in the single scattering nuclear recoil events through three methods. The first method is fully Monte Carlo simulation based. The last two are data-driven methods that also use the multiple scattering signals and high energy signals in the data, respectively. In the PandaX-4T commissioning data with an exposure of 0.63 tonne⋅year, all these methods give a consistent result that there are 1.15±0.57 neutron-induced background in dark matter signal region within an approximated nuclear recoil energy window between 5 and 100 keV.

## Low radioactive material screening and background control for the PandaX-4T experiment

Journal of High Energy Physics, Vol.06, 147(2022)