Exploring New Physics with PandaX-4T Low Energy Electronic Recoil Data Xinning Zeng PhD Student on behalf of PandaX xinningzeng@sjtu.edu.cn Dual Phase Liquid Xenon TPC Why LXe TPC? 1. Large A: large cross section & self-shielding; 2. 3D reconstruction and fiducialization; 3. Scalable; 4. Discrimination power. Detector Response 1. The detector response of low energy electronic recoil events is modelled by NEST ( Noble Element Simulation Technique); 2. Detector parameters (e.g. recombination rate, photon detection efficiency) are fit to Rn calibration data using unbinned likelihood fitting with emcee; 3. Calibrated NEST also fits well with sliced calibration data. The PandaX-4T experiment operates a dual-phase liquid xenon time projection chamber (LXe TPC) that is located in China Jinping Underground Laboratory. Energy release in xenon will produce prompt scintillation photon signals (S1) and ionized electrons. Electrons drift up under the inﬂuence of a downward electric field in the SV, and the delayed electroluminescence signals (S2) are generated in the gaseous xenon region with a much stronger electric field. Background Level Sensitivity to New Physics • Tritium spectrum identified in the data, which is likely originated from the tritium calibration at the end of PandaX-II; Tritium estimation comes from pre-fit of S1 spectrum, since no extra experimental constraints; • Beta events from 214Pb/212Pb is monitored by (5.5/8.8 MeV) 𝜶of 222Rn/220Rn. The activity of 214Pb is estimated to be 4.50 ± 0.20 µBq/kg (Run 0) and 5.52 ± 0.25 µBq/kg(Run 1), and 212Pb is estimated to be 0.28 ± 0.08 µBq/kg; • Beta events from 85Kr based on the delayed 𝛽−𝛾coincidence events of meta-stable state 85mRb, the activity of 85Kr is estimated to be 0.52 ± 0.27 ± 0.01 ppt and 0.94 ± 0.28 ± 0.02 ppt for Run 0 and Run 1; • Radioactivity of materials of the detector are estimated from high- purity Germanium counting-station and detailed fit of 0.44 - 2.6 MeV spectrum. • Long lived xenon isotopes, including 136Xe and 124Xe are calculated based on the measured half-life; L-captures (5.2 keV) of cosmogenically activated 127Xe in Run 0 is fitted from K-capture (408 keV); • Solar neutrinos are calculated using Standard solar models and the standard model anomalous magnetic moment; • Accidental backgrounds, resulting from the random pairing of S1 and S2 signals are estimated to be 7.6 ± 2.4 (Run 0) and 7.1 ± 2.3 (Run 1). Axions and Neutrinos from Sun 1. Axion production in the sun: Atomic recombination and deexcitation (ARD), Bremsstrahlung, and Compton (ABC); Primakoff effect; M1 nuclear transition of 57Fe (14.4 keV). 2. Neutrinos may have abnormally large magnetic moment due to the Majorana nature or exotic new physics beyond the Standard Model. Detection in PandaX-4T: 1. axio-electric effect; 2. inverse Primakoff effect; 3. neutrino-electron scattering. XXXI International Conference on Neutrino Physics and Astrophysics June 16-22, 2024 Milan, Italy Data and Bestfit A background-only fit is applied to check the consistency of data and background model. 1. Region of interest: qS1 > 2PE, E < 30 keV and above the ER 99.5% quantile; 2. 1D binned likelihood fit is used based on HistFitter; 3. Systematics including error of detection efficiencies and light/charge yield are added to fit; 4. The data are consistent with the background-only hypothesis: 𝜒!/NDF = 32.0/24. Based on CLs+b technique, model-independent sensitivities with 90% confidence level (C.L.) of axion couplings (gAe,gAegAN,gAγ), and neutrino magnetic moment µν are derived. 182 preliminary preliminary Details can be found in https://doi.org/10.48550/arXiv.2403.04239 Acknowledgement: Thanks for the mentioned theoretical works and the photographer Shibo Zhang preliminary preliminary preliminary preliminary