The CEνNS Frontier: Precision Probes of the Standard Model and Beyond

The 𝐂𝐄𝝂𝐍𝐒 process is sensitive to the weak mixing angle and to the neutron nuclear radius. The two quantities are intrinsically correlated within the cross section. The CE𝝂NS Frontier Precision probe of the Standard Model and beyond Mattia Atzori Corona ([email protected]n.it), INFN Tor Vergata The results presented are in collaboration with: M. Cadeddu, N.Cargioli, F. Dordei, C. Giunti & R. Pavarani Spallation Neutron Source (SNS) 𝜋decay-at-rest (~ 30 MeV) Pulsed neutrino source Reactor Neutrinos Produced at nuclear power plant (∼ 1 − 12 MeV) Only ҧ𝜈𝑒 Cesium Iodine Phys.Rev.Lett. 129 (2022) 8, 081801 11.6 𝝈 significance 14.6 kg crystal, 19.3 m ∼ 7 keVnr threshold ∼320 events observed Reactor CE𝝂NS on Germanium CONUS+ Observation @ Leibstadt (Switzerland), Nature 643, 1229–1233 (2025) 3.7 𝝈Observation (≃𝟑𝟗𝟓 𝐞𝐯𝐞𝐧𝐭𝐬)! ∼ 1 keVnr threshold, 3.73 kg Reactor details: 𝑃 = 3.6 GWth, L=20.7 m Additional measurements: 𝝂GeN Chinese Phys. C 49 053004 (2025) TEXONO Phys.Rev.Lett. 134 (2025) 12, 121802 Coherent Elastic Neutrino-Nucleus Scattering Freedman, PRD 9, 1389 (1974) 𝜈 + 𝑍 𝐴N→ 𝜈 + 𝑍 𝐴N The de Broglie wavelength of the exchanged 𝑍0 is of the order of the radius of the nucleus. •All the nucleons respond coherently (recoils as a whole) •Relatively large cross section ∝ 𝑁2 compared to other low energy neutrino interactions. CE𝜈NS is a very useful probe to explore extension of the Standard Model featuring new mediators. 𝑟𝜈ℓ 2 SM → 𝑟𝜈𝑒 2 𝑆𝑀 = −8.2 × 10−33𝑐𝑚2 𝑟 𝜈𝜇 2 𝑆𝑀 = −4.8 × 10−33𝑐𝑚2 𝑟𝜈𝜏 2 𝑆𝑀 = −3.0 × 10−33𝑐𝑚2 CE𝝂NS Cross Section 𝒅𝝈 𝒅𝑻𝐧𝐫 ≅𝑮𝑭 𝟐𝒎𝑵 𝝅𝟏 − 𝒎𝑵𝑻𝐧𝐫 𝟐𝑬𝝂 𝟐𝒈𝑽 𝒑𝒁𝑭𝒁𝒒𝟐+𝒈𝑽 𝒏𝑵𝑭𝑵𝒒𝟐𝟐 CE𝝂NS regime (𝑬𝝂≲𝟏𝟎 MeV) From EPL 143 (2023) 3, 34001 MAC, PhD Thesis Electroweak couplings with protons and neutrons Nuclear Form Factors (FF): the finite size of the nucleus matters With radiative corrections 𝑔𝑉 𝑝𝜈𝑒∼ 0.0382 𝑔𝑉 𝑝𝜈𝜇∼ 0.0299 𝑔𝑉 𝑝𝜈𝜏∼ 0.0255 𝑔𝑉 𝑛= −0.5117 Flavor dependent! Tree level: Flavor independent couplings 𝑔𝑉 𝑝=1 2− 2𝐬𝐢𝐧𝟐𝜽𝑾≃ 0.02274 𝑔𝑉 𝑛= −0.5 MAC et al. JHEP 05 (2024) 271 The experiment is performed at 𝑞2≠ 0 → flavor dependent radiative correction Protons •Nuclear distribution well known Atom. Data Nucl. Data Tabl. 60, 177–285 (1995)) Neutrons •Nuclear distribution poorly known •Neutrinos can be used a microscope to probe the neutron distribution 𝑍=55 N=78Cs Symmetrized Fermi /𝜌0 Form Factor: 𝐹 𝑞 = ׬𝑑3𝑥 𝜌 𝑥 𝑒𝑖𝑞⋅𝑥 < 𝟏 Suppression of the cross section *Other low-energy sources could be considered, but are not included in this poster. Reactor Flux PRC 108 (2023) 5, 055501 ⟨𝑬𝝂⟩ ≃ 𝟐 MeV 𝝂𝝁 Proton (1 GeV) Hg ഥ 𝝂𝝁+ 𝝂𝒆 ഥ 𝝂𝒆 ഥ 𝝂𝒆 ഥ 𝝂𝒆ഥ 𝝂𝒆 CsI 2022 MAC et al. EPJ.C 83 (2023)7,683 At SNS (𝐸𝜈<50 MeV) the nuclear structure plays a major role. CsI 2022 data show ∼ 6 𝜎 evidence for the suppression of the full coherence!* 𝑹𝒏𝟏𝟑𝟑𝐂𝐬 ≃ 𝑹𝒏(𝟏𝟐𝟕𝐈) = 𝟓. 𝟒𝟕 ± 𝟎. 𝟑𝟖 fm *Obtained with fixed value of the weak mixing angle a low-energies. At reactors (𝐸𝜈<10 MeV) the FF are ∼1. The extraction on the weak mixing angle is not dependent on the nuclear neutron radius CsI+Ar+Ge+Reactors 𝐬𝐢𝐧𝟐𝜽𝑾𝒒𝟐→ 𝟎 ≃ 𝟎. 𝟐𝟐𝟗−𝟎.𝟎𝟏𝟗 +𝟎.𝟎𝟐𝟎 Electroweak combined 𝐬𝐢𝐧𝟐𝜽𝑾𝒒𝟐→ 𝟎 ≃ 𝟎. 𝟐𝟑𝟗𝟔 ± 𝟎. 𝟎𝟎𝟏𝟕 MAC et al. 2506.13555 & Phys.Rev.D 112 (2025) 1, 015007 MAC et al. PRD 110 (2024) 3, 033005 Rev.Mod.Phys. 87 (2015) 531 The neutrino charge radius is the only neutrino electromagnetic properties different from zero in the standard model. Neutrinos are neutral particles, therefore, they can not couple directly with photons → 𝟏 loop diagrams are needed The NCR modifies the neutrino-proton coupling through: 𝑔𝑉 𝑝≃1 2− 2 sin2𝜃𝑊−2𝜋𝛼𝐸𝑀 3𝐺𝐹 𝒓𝝂ℓ 𝟐 𝐞𝐟𝐟 + flavor independent radiative correction •CE𝜈NS data provides a very powerful and innovative method to study the details of the 𝜈nucleon interaction vertex •At 1 𝜎 we find 𝒆 − flavor 𝝁 − flavor 𝑟 𝜈𝑒 2= 3.2 ± 4.7 × 10−32cm2 𝑟 𝜈𝜇 2= −3.9−2.7 +2.8 ×10−32cm2 MAC et al, JHEP 05 (2024) 271 Assuming such non standard neutrino interaction (NSI), the Lagrangian is In this framework, the mediator mass is ≫than the momentum transfer → high mediator mass limit L=−2 2𝐺𝐹σℓ=𝑒,𝜇 𝜈ℓ𝐿𝛾𝜌𝜈ℓL σ𝑓=𝑢,𝑑 𝜖ℓℓ 𝑓𝑉(ҧ 𝑓𝛾𝜌𝑓) Flavor preserving NSI The weak charge is modified according to 𝑄ℓ,NSI 𝑉= (𝑔𝑉 𝑝𝜈ℓ+ 2𝜖ℓℓ 𝑢𝑉 + 𝜖ℓℓ 𝑑𝑉)𝑍𝐹𝑍𝑞2+ (𝑔𝑉 𝑛+ 𝜖ℓℓ 𝑢𝑉 + 2𝜖ℓℓ 𝑑𝑉) 𝑁 𝐹𝑁𝑞2 𝜖ℓℓ 𝑓𝑉 =𝑔𝑍′ 2 2𝐺𝐹Ԧ𝑞 2+ 𝑚𝑍′ 2 In term of the mass (𝑚𝑍′) & coupling (𝑔𝑍′): light mediators! CE𝝂NS Low-Energy 𝝂∗CE𝝂NS Measurements Liquid Argon Phys.Rev.Lett. 126 (2021) 1, 01200213 3.5 𝝈 significance 24.4 kg, 27.5 m ∼20 keVnr threshold ∼120 events observed Germanium Phys.Rev.Lett. 134 (2025) 23, 231801 3.9 𝝈 significance, 10.66 kg ∼ 7 keVnr threshold ∼2 𝝈 tension with the SM Agreement among the different CEνNS data, separating the contribution from the different flavors. 90% CL MAC et al., Phys.Lett.B 869 (2025) 139856 Electroweak and Nuclear Physics Searches for new mediators Neutrino Charge Radius Toward precision physics with CE𝝂NS MAC et al., Phys.Lett.B 869 (2025) 139856 Universal model 𝑍′ In the Universal model, the new charges are all equal to one. COHERENT Cryo-CsI Cryo-CsI I (II): 10 700 kg of undoped CsI ∼ 0.5 keVnr threshold ∼1000 events/SNS-year with Cryo-CsI I @ 19 m from SNS COHERENT is developing an intense experimental program to enable precision physics tests with CE𝜈NS. SNS upgrades are foreseen, as well as a dedicated campaign to precisely determine the neutrino flux (COH-Collaboration: Phys.Rev.D 109 (2024) 9, 092005). Liquid Argon - 750 750(610) kg of active (fiducial) mass ∼20 keVnr threshold ∼5000 events/SNS-year Two scenarios: systematic uncertainty 8% and 5%. To learn more, check out our website! See MAC et al., arXiv: 2509.04205 See MAC et al., arXiv: 2509.04205