Status of the XENONnT Dark Matter Experiment

Status of the XENONnT Dark matter Experiment Ananthakrishnan Ravindran On behalf of the XENON collaboration. XLZD-Oz Workshop | Sydney | Nov 25-27 Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 1 The XENON Collaboration 200+ Scientists 29 Institutions 12 Countries Main Motivation Discover Weakly Interacting Massive Particles (WIMPs). Other studies Coherent Elastic NeutrinoNucleus Scattering (CEvNS), 0𝑣𝛽𝛽, Solar Axions and ALPs, Supernovae, etc. How we do it: •Very low backgrounds: active and passive shielding, fiducialization, etc. •Robust tools to correct detector effects and look for very small signals. •Perform a “blind analysis”. Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 1 The XENON Collaboration 200+ Scientists 29 Institutions 12 Countries XENON program timeline 2006 58.6 livedays BG: 600 / (t.d.keV) XENON10 25 kg LXe XENON100 160 kg LXe 2008 477 livedays BG: 5.3 / (t.d.keV) XENON1T 3200 kg LXe 2015 279 livedays BG: 0.2 / (t.d.keV) XENONnT 8600 kg LXe 2020 300+ livedays (ongoing) BG: 0.04 / (t.d.keV) Lowest ER background level ever achieved in a LXe based experiment!! Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 2 XENONnT Experiment LNGS, Italy 3600 m.w.e shielding 3 Nested Detectors Sharing the same DAQ ➢LXe Dual Phase Time Projection Chamber (TPC) with 5.9t active volume. (Eur. Phys. J. C 84, 784 (2024), JCAP11(2020)031) ➢Gd-doped Water Cherenkov Neutron Veto (NV). ➢Gd-doped Water Cherenkov Muon Veto (MV) (2014 JINST 9 P11006) Hall B Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 3 XENONnT Time Projection Chamber 1.5m 1.3m Drift Field Edrift_XnT =23 V/cm Extraction Field Eextr_XnT = 2.9 𝑘𝑉/𝑐𝑚 Max drift time tdrift_max = 2.2 𝑚𝑠 Total LXe VLXe_cryo = 8.5 tonnes Active LXe VLXe_active = 5.9 tonnes PMT Array 494 3“ PMTs in total Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 4 Dual Phase TPC: Working Principle •Particle interaction in LXe create both prompt scintillation(S1) and delayed ionization signals. •Ionization electrons drifted upwards by drift field and extracted into gas phase by extraction field; leads to electroluminescent light(S2). •Signals collected in the top and bottom PMT arrays. 3D Position Reconstruction x, y : S2 hit pattern z: Drift time of eEnergy Reconstruction Combined S1 and S2 area; calibrated with known sources. Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 5 XENONnT Neutron Veto JCAP11(2020)031 See talk by Marco Selvi •33 m3 demineralized water, optically separated from outer MV. •120 8” high-QE PMTs. •(𝟓𝟑 ± 𝟑)% tagging efficiency with water. •With 500ppm GdSO doping, tagging efficiency increases to ~𝟕𝟕%. Credits: Marco Selvi Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 6 XENONnT Infrastructure Rn Column •Continuous online distillation. •222Rn conc (SR0): 𝟏. 𝟖 𝝁𝑩𝒒/𝒌𝒈 •222Rn conc (SR1): 𝟎. 𝟖 𝝁𝑩𝒒/𝒌𝒈 Eur. Phys. J. C (2022) 82: 1104 Kr Column •natKr/Xe concentration < 50 ppq Eur. Phys. J. C 77, 275 (2017) nT DAQ •Triggerless DAQ. Shared between three detectors. 2023 JINST 18 P07054 LXe Purification •Removes electronegative impurities. Eur. Phys. J. C (2022) 82: 860 ReStoX •Fast xenon recovery system through Xenon crystallization. Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 7 Online distillation for 222Rn Eur. Phys. J. C (2022) 82: 1104 Xe Rn •222Rn (𝑡Τ 12= 3.8𝑑)emanates from detector material. •Continuous online distillation utilizes the difference in vapour pressure. SR0: GXe only SR1: GXe + LXe •Purifies 1.8t (0.2t) of liquid (gas) xenon per day. 1T: ~13 𝜇𝐵𝑞/𝑘𝑔 nT SR0: 𝟏. 𝟖 𝝁𝑩𝒒/𝒌𝒈 nT SR1: 𝟎. 𝟖 𝝁𝑩𝒒/𝒌𝒈 222 Rn activity Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 14 SR0 Results: LowER Contour for an 1T-like excess. Blinding for ER Search 𝐸𝐸𝑅 < 20𝑘𝑒𝑉 𝑅 < 63𝑐𝑚 Exposure: 1.16ty •Detection efficiency dominated by 3-fold S1 requirement. Bump due to still blinded NR region. •Selection: S2>500 PE, vetoes, S1/S2 quality cuts and fiducial volume = 4.37 ± 0.14 𝑡𝑜𝑛. •Average cut acceptance efficiency ~ 86%. Efficiencies Phys. Rev. Lett. 129, 161805 Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 15 SR0 Results: LowER Contour for an 1T-like excess. Blinding for ER Search 𝐸𝐸𝑅 < 20𝑘𝑒𝑉 𝑅 < 63𝑐𝑚 Blinded region Exposure: 1.16ty Backgrounds •At low energies dominated by 214Pb decays. •Data driven AC background model. •E>40keV dominated by two weak processes: ➢2𝑣𝛽𝛽 (136Xe), 2𝑣𝐸𝐶𝐸𝐶 (124Xe) Phys. Rev. Lett. 129, 161805 Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 16 SR0 Results: LowER Exposure: 1.16ty Fit to unblinded data Phys. Rev. Lett. 129, 161805 Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 17 SR0 Results: LowER Excluded LowER Excess observed in XENON1T at 4𝜎; 1T excess probably from 3H World leading laboratory results for ‘Beyond Standard Model’ Signals. Lowest level of ER background in any Lxe experiment: 15.8 𝑒𝑣𝑒𝑛𝑡𝑠/(𝑡. 𝑦. 𝑘𝑒𝑉) Phys. Rev. Lett. 129, 161805 Solar axions Neutrino Magnetic Moment ALPs DM Dark Photons Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 18 SR0 Results: WIMPs Exposure: 1.09ty Blinding for WIMP Search 𝐸𝐸𝑅 < 10𝑘𝑒𝑉 𝑅 < 61.5𝑐𝑚 Efficiencies •Selection: S1/S2 consistent with signal-like, S2 consistent with ediffusion, S1/S2 quality cuts and fiducial volume = 4.18 ± 0.13 𝑡𝑜𝑛. Phys. Rev. Lett. 131, 041003 Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 19 SR0 Results: WIMPs Exposure: 1.09ty Blinding for WIMP Search 𝐸𝐸𝑅 < 10𝑘𝑒𝑉 𝑅 < 61.5𝑐𝑚 Backgrounds 210Pb plate out from PTFE walls; constrained by choice of FV 214Pb 𝛽-decays; constrained by ER/NR discrimination Accidental coincidences: Random pairing of S1s and S2s. Modelled by a data-driven method, constrained by analysis cuts. NR background: Radiogenic neutrons (constrained by veto tagging) and CEvNS events in RoI. Phys. Rev. Lett. 131, 041003 Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 20 SR0 Results: WIMPs Exposure: 1.09ty Fit to unblinded data Phys. Rev. Lett. 131, 041003 Total events: 152. In blinded region: 16 Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 21 SR0 Results: WIMPs No significant excess observed. Best exclusion limit of 𝟐. 𝟔 × 𝟏𝟎−𝟒𝟕 𝒄𝒎𝟐 at 28 𝐺𝑒𝑉/𝑐2. PCL to median sensitivity to avoid spurious limits *to be updated with latest results from LZ and PandaX-4T Phys. Rev. Lett. 131, 041003 Fit to unblinded data Spin-independent Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 22 SR0+1 Results: CEvNS See talk by Fei Gao Measured 8B flux: 4.7−2.7 +3.6 ×106 𝑐𝑚−2𝑠−1. In agreement with other measurements. Flux weighted CEvNS crosssection in agreement with Standard Model. First measurement of CEvNS cross section in Xe. First DM experiment to enter the neutrino fog. Smallest solar neutrino detector. arXiv:2408.02877 [nucl-ex] Observed 𝟏𝟎. 𝟕−𝟒.𝟐 +𝟑.𝟕 8B CEvNS events at 𝟐. 𝟕𝟑𝝈 significance. Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 23 SR0+1 Results: Low-Mass WIMPs •Same dataset and analysis framework for CEvNS search is used. •Here, 8B CEvNS becomes a background. •No excess over background observed. ➢New parameter space excluded. Best 90% limit of 2.5 × 10−45 𝑐𝑚2 for WIMP mass of 6 GeV. ➢First search into the neutrino fog. arXiv:2409.17868 [hep-ex] See talk by Fei Gao Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 27 XENONnT Muon Veto 2014 JINST 9 P11006 •Water Cherenkov detector. •700t demineralized water. •High reflectivity inner coating. •84 Hamamatsu 8” PMTs. •Active veto against muon induced neutrons. •Acts as passive shield against gamma rays and neutrons from the surrounding. 9.6 m 10.2 m Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 28 85Kr Distillation Eur. Phys. J. C 77, 275 (2017) PTEP 5, 053H01 (2022) •natKr traces (natKr/Xe > 1ppb) exist in xenon extracted from the air, and is an ER background. •Mitigated through cryogenic distillation of Xenon with a dedicated column before collecting science data. •Online distillation can also remove radioactive Ar-37. •Kr (more volatile) goes up and Kr-depleted Xe is collected from the bottom. •natKr/Xe concentration <50 ppq achieved in nT. Xe Kr Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 29 Spin Dependent WIMPs WIMP neutron-only coupling WIMP proton-only coupling WIMP results reinterpreted as a purely spin-dependent coupling to 131Xe and 129Xe Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 30 NR and ER Response calibration (SR0) •AmBe calibration data fitted to emission model. In good agreement with NEST v1. •AmBe source placed close to the TPC wall using the U-tubes. •Fit using a Markov Chain Monte-Carlo method (MCMC) [Both ER and NR responses]. Nuclear Recoil Response Electronic Recoil Response arXiv:2406.13638 [physics.data-an] •220Rn and 37Ar calibration data fitted to emission model. In good agreement with NEST in RoI. •Internal calibration sources used. Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 31 88YBe Calibration: Low Energy NR response •152 keV neutrons produced by photodisintegration of 9Be due to 𝜸 from 88Y show similar recoil energy spectrum in TPC as 8B CEvNS. •Excellent matching with model. Light and charge yield are constrained by fit of 88YBe data on NEST model at 23 V/cm. Dedicated publication in preparation. Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 32 Corrections to Detector Effects Calibrations using 83mKr S1 Light collection efficiency S2 Light collection efficiency Field Distortion Correction SR0 SR1 SR1 •Perform regular (~biweekly) calibration using internal calibration source. •83mKr uniformly distributed in the TPC 83mKr 83Kr 𝐸 = 32.1𝑘𝑒𝑉 𝑇1/2 = 1.83ℎ 𝐸 = 9.4𝑘𝑒𝑉 𝑇1/2 =154.4𝑛𝑠 Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 33 Accidental Coincidences(AC) Time → Not Detected Isolated S2 Time → Not Detected Isolated S1 Time → Accidentally paired Reconstructed as AC event Event 2 Event 1 •ACs are accidental pairings of Isolated S1 and Isolated S2 signals. •AC rate before mitigation: ➢Isolated S1 rate: ~15 Hz ➢Isolated S2 rate: ~150 mHz ➢Raw AC rate: ~400 events/day •Modelled by a Data-Driven method. •Major background for the CEvNS search. •Removed by analysis cuts on the ‘time-shadow’, boosted decision tree (BDT) scores for S1 and S2 signals. [More details in CEvNS talk by Fei Gao] Ananthakrishnan Ravindran | ravi[email protected].fr| XLZD-Oz Workshop, Sydney | 25-27 Nov 34 Choice of Fiducial Volume 2023 WIMP analysis; FV chosen to give the best signal-background discrimination ratio. 2024 CEvNS analysis; FV chosen to exclude regions with limited detector modelling and higher background rates. CEvNS: Regions near the perpendicular wire are also excluded from analysis as effects from the wire are not sufficiently well simulated, and thus may bias the S2 BDT score (trained on simulations).