Search for coherent elastic neutrino-nucleus scattering with the NUCLEUS Experiment

Mattia Atzori Corona, on behalf of the NUCLEUS Collaboration [email protected] Search for coherent elastic neutrino-nucleus scattering with the NUCLEUS Experiment September 29-03/10/2025 Mattia Atzori Corona –INFN Tor Vergata Neutrino Telescopes –01/10/2025 2 In 1974, Freedman predicted that a neutrino could interact coherently with an entire nucleus. 𝜈 + 𝑍 𝐴N→ 𝜈 + 𝑍 𝐴NCOHERENCY: the scattering amplitude is the sum of the amplitudes over all the nucleons The single outcome of the interaction is a very small nuclear recoil energy (𝑇𝑛𝑟) Coherent Elastic 𝝂-Nucleus Scattering (CE𝝂NS) Mattia Atzori Corona –INFN Tor Vergata Neutrino Telescopes –01/10/2025 3 𝑑𝜎𝜈ℓ−𝑁 CE𝜈NS 𝑑𝑇nr =𝑮𝑭 𝟐𝒎𝑵 𝜋𝟏 − 𝒎𝑵𝑻𝐧𝐫 𝟐𝑬𝝂 𝟐𝒈𝑽 𝒑𝝂ℓ𝑍𝑭𝒑ഥ 𝒒𝟐+𝒈𝑽 𝒏𝑁𝑭𝒏ഥ 𝒒𝟐𝟐 Constants Kinematics CE𝝂NS Cross Section Nuclear Form Factor Neutrino couplings with protons and neutrons 𝑸ℓ,𝐒𝐌 𝑽 Nuclear Weak Charge CE𝝂NS couplings with radiative corrections (RC) 𝑔𝑉 𝑝ത 𝜈𝑒∼ 0.0382 𝑔𝑉 𝑛= −0.5117 MAC et al. JHEP 05 (2024) 271 The experiment is performed at 𝑞2≠ 0, and should be taken into account. A precise measurement of the CE𝝂NS cross section allows to study: •SM electroweak parameters (weak mixing angle) •𝛎-Telescopes to 𝛎-Microscopes: Nuclear physics (𝑹𝒏) •Neutrino electromagnetic properties (neutrino charge radius): N. Cargioli’s talk! •New mediators (heavy or light mediators) Visit my poster to know more! Poster Session: The CE𝝂NS Frontier Mattia Atzori Corona –INFN Tor Vergata Neutrino Telescopes –01/10/2025 4 The Faintest Signal from the Strongest 𝝂Interaction CE𝝂NS searches: low-threshold experiment required! CE𝝂NS Cross Section ∝ 𝑵𝟐 𝑇max =2𝐸𝜈 2 𝑚𝑡𝑎𝑟𝑔𝑒𝑡 Mattia Atzori Corona –INFN Tor Vergata Neutrino Telescopes –01/10/2025 5 2509.03559 The experimental site is the very near site (VNS) is located at 102 m and 72 m from the 2 reactors of the Chooz B plant ∼ 3 m.w.e. depth @ VNS → backgrounds need to be under control (see the NUCLEUS background prediction 2509.03559) Neutrinos expected at the detectors ≃ 𝟏. 𝟕 ⋅ 𝟏𝟎𝟏𝟐 𝝂/𝐜𝐦𝟐/𝒔 @ VNS assuming 0.8 duty cycle Reactor nominal thermal power: 2 ⋅ 4.25 GWth Collaboration Meeting @Chooz, March 2025 The NUCLEUS Experiment NEW NUCLEUS Collaboration Eur.Phys.J.C 79 (2019) 12, 1018 Mattia Atzori Corona –INFN Tor Vergata Neutrino Telescopes –01/10/2025 6 The NUCLEUS Experiment Target detectors: ∼10 g of CaWO4 and Al2O3with instrumented holders (inner veto) Internal shielding: cryogenic shielding of active germanium (COV) , 𝐵4C, borated polyethylene, lead and muon veto. Dry dilution refrigerator at ∼10 mK External shielding: borated polyethylene, lead and muon veto. The setup will be placed at the VNS, a 24 𝑚2 basement room. Mattia Atzori Corona –INFN Tor Vergata Neutrino Telescopes –01/10/2025 7 The NUCLEUS Experiment (a) Detector module (b) Inner veto (c) Detector holder Different materials can be used •CaWO4 •Al2O3 •Germanium; Silicon Transition edge sensor (TES) Particle Interaction Phonon production TES Signal and Resistance Change Signal recorded Mattia Atzori Corona –INFN Tor Vergata Neutrino Telescopes –01/10/2025 8 NUCLEUS Event Rate •The excellent energy resolution enables to reach an energy threshold as low as ∼20 eVnr •This allows to have a gram-scale detector, where hundreds of events are expected in one year Expected background budget in the NUCLEUS target detectors at the VNS, compared to the signal. The event rates are expressed in milli count per day (mcpd). NUCLEUS Collaboration, 2509.03559, accepted in PRD Mattia Atzori Corona –INFN Tor Vergata Neutrino Telescopes –01/10/2025 9 •Commissioning of an essential version of the experiment concluded in summer 2024 at the shallow Underground Laboratory (UGL) at TUM. •Two months of stable operation of target detectors with active and passive shielding! Commissioning Run @ TUM Setup: •One 𝐂𝐚𝐖𝐎𝟒 crystal with TES and one 𝐀𝐥𝟐𝐎𝟑 double TES readout •One Outer Veto Crystal •Full passive shielding without B4C •Full muon veto system NUCLEUS Collaboration, 2508.02488, accepted in PRD NEW Mattia Atzori Corona –INFN Tor Vergata Neutrino Telescopes –01/10/2025 16 1 MeV 10 MeV 100 MeV 1 GeV 10 GeV 100 GeV M.Cadeddu et al EPL 143 (2023) 3, 34001 𝐸𝜈≃100 GeV 𝜆𝑍0≪ 𝑅 Interaction with individual constituents: inelastic process 𝐸𝜈≃100 −1000 MeV 𝜆𝑍0< 𝑅 Scattering not totally coherent 𝐸𝜈≃10 MeV 𝜆𝑍0> 𝑅 Coherency condition Coherence occurs when the de Broglie wavelength of the 𝑍0 exceeds the nuclear size. ≃ 6 − 10 fm 𝝂 − N Interactions 𝝀𝒁𝟎≃𝟏 |𝒒| 𝑬𝝂 Mattia Atzori Corona –INFN Tor Vergata Neutrino Telescopes –01/10/2025 17 CE𝝂NS couplings with radiative corrections (RC) 𝑔𝑉 𝑝𝜈𝑒∼ 0.0382 𝑔𝑉 𝑝𝜈𝜇∼ 0.0299 𝑔𝑉 𝑝𝜈𝜏∼ 0.0255 𝑔𝑉 𝑛= −0.5117 Flavor dependence! Radiative corrections play a crucial role in the CE𝜈NS and 𝜈ES. MAC et al. JHEP 05 (2024) 271 The experiment is performed at 𝑞2≠ 0, and should be taken into account. Such diagrams describe SM photon-mediated neutrino interactions. The strength of this interaction is given by the neutrino charge radius. C.Giunti et al. Rev.Mod.Phys. 87 (2015) 531 Radiative Corrections: Neutrino Charge Radius CE𝝂NS: 𝑔𝑉 𝑝≃1 2− 2 sin2𝜃𝑊−2𝜋𝛼𝐸𝑀 3𝐺𝐹𝒓𝝂ℓ 𝟐 𝐞𝐟𝐟 +RC 𝝂𝐄S: 𝑔𝑉 𝜈ℓ≃ − 1 2+ 2 sin2𝜃𝑊+2𝜋𝛼𝐸𝑀 3𝐺𝐹𝒓𝝂ℓ 𝟐 𝐞𝐟𝐟 +𝛿ℓ,𝑒 +RC NCR Mattia Atzori Corona –INFN Tor Vergata Neutrino Telescopes –01/10/2025 18 The neutrino charge radius is a vertex correction to the CE𝜈NS process. The experiment is performed at 𝒒𝟐≠ 𝟎: 𝑔𝑉 𝑝≃1 2− 2 sin2𝜃𝑊−2𝜋𝛼𝐸𝑀 3𝐺𝐹𝒓𝝂ℓ 𝟐 𝐞𝐟𝐟 +RC The Neutrino Charge Radius 𝑟 𝜈ℓ 2eff = − 𝐺𝐹 2 2𝜋23 − 12𝑅ℓ𝑞2 MAC et al. JHEP 05 (2024) 271 One needs to account for this effect when extracting the neutrino charge radius from the data Electroweak Couplings (tree level) 𝑔𝑉 𝑝=1 2− 2 sin2𝜃𝑊≃ 0.02274 Mattia Atzori Corona –INFN Tor Vergata Neutrino Telescopes –01/10/2025 19 Reactors Neutrinos are produced through 𝜷-decay at a reactor plants. CE𝝂NS Searches @ Reactors Neutrinos are produced through the 𝛽 decay of fission fuels involving: 235U, 239Pu, 241Pu and 238U ഥ 𝝂𝒆ഥ 𝝂𝒆 ഥ 𝝂𝒆 ഥ 𝝂𝒆 ഥ 𝝂𝒆≃𝟏𝟎𝟏𝟑 𝝂/𝐜𝐦𝟐/𝒔 @ 20 m Reactor Flux PRC 108 (2023) 5, 055501 Pros ✓Lower neutrino energies: full coherency regime, complementarity with SNS ✓Lower momentum transfers ✓Different reactors available in the world Cons Limited background rejection power Very low threshold is required Uncertainties due to quenching factor Uncertainty on the neutrino flux (Theo ⊗Exp) ⟨𝑬𝝂⟩ ≃ 𝟐 MeV Mattia Atzori Corona –INFN Tor Vergata Neutrino Telescopes –01/10/2025 20 Light Vector Mediator Models MAC et al JHEP 05 (2022) 109 Mattia Atzori Corona –INFN Tor Vergata Neutrino Telescopes –01/10/2025 21 The Low-Energy Excess SciPost Phys. Proc. 9, 001 (2022) Mattia Atzori Corona –INFN Tor Vergata Neutrino Telescopes –01/10/2025 22 The procedure follows different steps: 1. From Poisson distribution with predicted mean value 𝐸𝑖(𝜂), produce the mock data 𝑂𝑖. 2. Evaluate for a big number of realizations (e.g. 104). 3. The number of times in which the value of 𝜒2 is smaller than the original value of 𝜒2 is counted, and the C.L. [%] is evaluated by CL =counts total number of trials Excluding models with Erickcek et al. (Phys.Rev.D 76 (2007) 042007) ➢For a given observed energy spectrum, it is possible to exclude physics model that predict an enhanced number of events; ➢The background is of unknown origin: one can only exclude models whose statistical realization predicts more event than in observed data Counts 𝑻𝒏𝒓 Theory 𝐸𝑖is the average number of events assuming a given signal hypothesis 𝑈𝑖 is the experimental realization, i.e. the observed number of events 𝑂𝑖𝑂𝑖 Statistical Methods with The Low-Energy Excess