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1. Fast neutron background characterization of the future Ricochet experiment at the ILL research nuclear reactor

   https://doi.org/10.1140/epjc/s10052-022-11150-x  

   Augier, C. ; Baulieu, G. ; Belov, V. ; Berge, L. ; Billard, J. ; Bres, G. ; Bret, J-. L. ; Broniatowski, A. ; Calvo, M. ; Cazes, A. ; et al ( January 2023 , The European Physical Journal C)

   The futureRicochetexperiment aims at searching for new physics in the electroweak sector by providing a high precision measurement of the Coherent Elastic Neutrino-Nucleus Scattering (CENNS) process down to the sub-100 eV nuclear recoil energy range. The experiment will deploy a kg-scale low-energy-threshold detector array combining Ge and Zn target crystals 8.8 m away from the 58 MW research nuclear reactor core of the Institut Laue Langevin (ILL) in Grenoble, France. Currently, theRicochetCollaboration is characterizing the backgrounds at its future experimental site in order to optimize the experiment’s shielding design. The most threatening background component, which cannot be actively rejected by particle identification, consists of keV-scale neutron-induced nuclear recoils. These initial fast neutrons are generated by the reactor core and surrounding experiments (reactogenics), and by the cosmic rays producing primary neutrons and muon-induced neutrons in the surrounding materials. In this paper, we present theRicochetneutron background characterization using$$^3$$${}^3$He proportional counters which exhibit a high sensitivity to thermal, epithermal and fast neutrons. We compare these measurements to theRicochetGeant4 simulations to validate our reactogenic and cosmogenic neutron background estimations. Eventually, we present our estimated neutron background for the futureRicochetexperiment and the resulting CENNS detection significance. Our results show that depending on the effectiveness ofmore »the muon veto, we expect a total nuclear recoil background rate between 44 ± 3 and 9 ± 2 events/day/kg in the CENNS region of interest, i.e. between 50 eV and 1 keV. We therefore found that theRicochetexperiment should reach a statistical significance of 4.6 to 13.6 $$\sigma $$$\sigma$for the detection of CENNS after one reactor cycle, when only the limiting neutron background is considered.

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2. New high statistics results from the MINERvA experiment Medium Energy run

   https://doi.org/10.22323/1.390.0178  

   Schellman, Heidi Marie ( January 2021 , Proceedings of 40th International Conference on High Energy physics)

   Dolezal, Zdenek (Ed.)

   The MINERvA experiment has completed its physics run using the 6 GeV, on-axis NuMI ME beam at Fermilab. The experiment received a total of 12 x 10^20 protons on target in both neutrino and antineutrino mode running. This allows MINERvA a new level of statistics in neutrino interaction measurements with the ability to measure multi-dimensional differential cross sections. In addition, in order to make the most of this jump in statistics, a new level of precision in fluxprediction has been achieved. We present results from MINERvA's Medium Energy (ME) physics program, including the new kinematic regimes that are now accessible.
3. Measurement of the axial vector form factor from antineutrino–proton scattering

   https://doi.org/10.1038/s41586-022-05478-3  

   Cai, T. ; Moore, M. L. ; Olivier, A. ; Akhter, S. ; Dar, Z. Ahmad ; Ansari, V. ; Ascencio, M. V. ; Bashyal, A. ; Bercellie, A. ; Betancourt, M. ; et al ( February 2023 , Nature)

   Abstract Scattering of high energy particles from nucleons probes their structure, as was done in the experiments that established the non-zero size of the proton using electron beams 1 . The use of charged leptons as scattering probes enables measuring the distribution of electric charges, which is encoded in the vector form factors of the nucleon 2 . Scattering weakly interacting neutrinos gives the opportunity to measure both vector and axial vector form factors of the nucleon, providing an additional, complementary probe of their structure. The nucleon transition axial form factor, F A , can be measured from neutrino scattering from free nucleons, ν μ n  →  μ − p and $${\bar{\nu }}_{\mu }p\to {\mu }^{+}n$$ ν ¯ μ p → μ + n , as a function of the negative four-momentum transfer squared ( Q 2 ). Up to now, F A ( Q 2 ) has been extracted from the bound nucleons in neutrino–deuterium scattering 3–9 , which requires uncertain nuclear corrections 10 . Here we report the first high-statistics measurement, to our knowledge, of the $${\bar{\nu }}_{\mu }\,p\to {\mu }^{+}n$$ ν ¯ μ p → μ + n cross-section from the hydrogen atom, using the plastic scintillatormore »target of the MINERvA 11 experiment, extracting F A from free proton targets and measuring the nucleon axial charge radius, r A , to be 0.73 ± 0.17 fm. The antineutrino–hydrogen scattering presented here can access the axial form factor without the need for nuclear theory corrections, and enables direct comparisons with the increasingly precise lattice quantum chromodynamics computations 12–15 . Finally, the tools developed for this analysis and the result presented are substantial advancements in our capabilities to understand the nucleon structure in the weak sector, and also help the current and future neutrino oscillation experiments 16–20 to better constrain neutrino interaction models.« less
4. Measurement of final-state correlations in neutrino muon-proton mesonless production on hydrocarbon at $langle E_nurangle=3$ GeV

   Lu, X. G. ( July 2019 , Physical review letters)

   Final-state kinematic imbalances are measured in mesonless production of νμ+A→μ−+p+X in the MINERvA tracker. Initial- and final-state nuclear effects are probed using the direction of the μ−−p transverse momentum imbalance and the initial-state momentum of the struck neutron. Differential cross sections are compared to predictions based on current approaches to medium modeling. These models underpredict the cross section at intermediate intranuclear momentum transfers that generally exceed the Fermi momenta. As neutrino interaction models need to correctly incorporate the effect of the nucleus in order to predict neutrino energy resolution in oscillation experiments, this result points to a region of phase space where additional cross section strength is needed in current models, and demonstrates a new technique that would be suitable for use in fine-grained liquid argon detectors where the effect of the nucleus may be even larger.
5. Transition Edge Sensor Chip Design of a Modular CEvNs Detector for the Ricochet Experiment

   https://doi.org/10.1007/s10909-022-02927-1  

   Chen, Ran ; Pinckney, H. Douglas ; Figueroa-Feliciano, Enectali ; Hong, Ziqing ; Schmidt, Benjamin ( December 2022 , Journal of Low Temperature Physics)

   Coherent elastic neutrino-nucleus scattering (CEνNS) offers a valuable approach in searching for physics beyond the Standard Model. The Ricochet experiment aims to perform a precision measurement of the CEνNS spectrum at the Institut Laue-Langevin nuclear reactor with cryogenic solid-state detectors. The experiment will employ an array of cryogenic thermal detectors, each with a mass of around 30 g and an energy threshold of 50 eV. One section of this array will contain 9 Transition Edge Sensor (TES)-based calorimeters. The design will not only fulfill requirements for Ricochet, but also act as a demonstrator for future neutrino experiments that will require thousands of macroscopic detectors. In this article, we present an updated TES chip design, as well as performance predictions based on a numerical modeling.