Dark Matter Search Results from the PandaX-4T Commissioning Run (2107.13438v3)

Abstract: We report the first dark matter search results using the commissioning data from PandaX-4T. Using a time projection chamber with 3.7-tonne of liquid xenon target and an exposure of 0.63 tonne$\cdot$year, 1058 candidate events are identified within an approximate nuclear recoil energy window between 5 and 100 keV. No significant excess over background is observed. Our data set a stringent limit to the dark matter-nucleon spin-independent interactions, with a lowest excluded cross section (90% C.L.) of $3.8\times10^{-47} $cm$^2$ at a dark matter mass of 30 GeV/$c^2$.

• The paper reports no significant dark matter signal and sets a 90% CL upper limit of 3.8×10⁻⁴⁷ cm² for a 40 GeV/c² dark matter candidate.
• The experiment employs a dual-phase TPC with 3.7 tonnes of liquid xenon and rigorous calibration to achieve precise energy scale and background estimation.
• The refined analysis narrows the dark matter parameter space and paves the way for enhanced sensitivity in future extended data runs.

Overview of "Dark Matter Search Results from the PandaX-4T Commissioning Run"

This paper presents the initial findings of the PandaX-4T dark matter search experiment, conducted at the China Jinping Underground Laboratory. Utilizing a time projection chamber with a liquid xenon target mass of 3.7 tonnes and an exposure of 0.63 tonne-year, the researchers identify 1058 candidate events across a nuclear recoil energy window of 5 to 100 keV. Importantly, the experiment found no significant deviation from expected background levels, placing constraints on dark matter-nucleon spin-independent interactions.

Experiment Configuration and Calibration

The PandaX-4T experiment is an advanced direct detection endeavor aimed at uncovering dark matter interactions through nuclear recoils. Located in the Jinping Underground Laboratory, the setup employs a massive dual-phase time projection chamber, optimizing xenon as the detecting medium due to its desirable scintillation and ionization properties. The chamber is designed to minimize background interference, an essential requirement given the expected rarity of dark matter interactions.

Calibration of the detector's response is comprehensive, utilizing internal isotopes such as $^{83\rm m}$Kr and external neutron sources like $^{241}$Am-Be and D-D sources. These facilitate precise energy scale calibrations needed for distinguishing dark matter signals from background noise. Furthermore, the fidelity of event reconstruction within the chamber is assured through multiple calibration datasets, leading to an optimally refined understanding of both electron and nuclear recoil signals.

Data Analysis and Background Estimation

Data analysis begins with a rigorous categorization of observed events, applying a suite of noise-reduction and background discrimination techniques. The background model relies heavily on data-driven insights and simulations to account for sources such as radon, krypton, and tritium contamination. This careful accounting results in a total background estimation closely aligned with experimental results, showing no unexpected excess in detected events.

The research critically considers various sources of uncertainty—statistical and systematic—employing a profile likelihood ratio methodology. This facilitates the derivation of a new exclusion limit on dark matter-nucleon interaction cross-sections, notably setting an upper limit of $3.8\times10^{-47}$ cm$^2$ for a 40 GeV/c$^2$ dark matter particle with 90% confidence.

Implications and Future Directions

PandaX-4T represents a significant contributor to the ongoing quest to detect dark matter through direct interactions. While this commissioning phase revealed no positive dark matter signals, the results substantially tighten constraints on interaction cross-sections for spin-independent interactions. These constraints contribute to narrowing the parameter space for dark matter model theories, offering crucial benchmarks for both contemporary and future detection technologies.

Looking forward, the completion of the tritium removal campaign, coupled with extended data collection aiming for a 6-tonne-year exposure, promises improved sensitivity. The experiment's future stages could potentially achieve sensitivity gains by an order of magnitude, providing increasingly stringent tests of dark matter models, particularly in scenarios involving weak-scale particles.

Overall, through meticulous detector design and advanced analysis techniques, PandaX-4T propels the search for dark matter into more sensitive domains, conclusively guiding theoretical and experimental advancements in the field of particle astrophysics.