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Coherent Collaboration

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The Coherent Collaboration (stylized as COHERENT Collaboration) is a multi-institutional effort to measure Coherent Elastic Neutrino-Nucleus Scattering (CEvNS) using the Spallation Neutron Source (SNS) at Oak Ridge National Lab in Oak Ridge, Tennessee.[1][2] The Coherent collaboration has deployed a suite of detectors with different detector technologies and target nuclei with the goal of directly measuring CEvNS, and this was accomplished in 2017 with a CsI[Na] scintillator crystal detector, making them the first in the world to do so.[3][4][5] By taking measurements of the CEvNS cross section for various target nuclei, the Coherent collaboration is able to provide a strong test of the predictions of the standard model. There are also opportunities to study various Beyond the Standard Model (BSM) effects, such as dark matter and sterile neutrinos.[2][6]

Physics

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Diagram of coherent elastic neutrino-nucleus scattering

The main goal of the Coherent collaboration was to observe Coherent Elastic Neutrino-Nucleus Scattering (CEvNS, pronounced /ˈsɛvəns/ like "seven-s"), which is a nuclear reaction involving low energy neutrinos scattering off nuclei. These nuclei experience a nuclear recoil and will then deposit some of its energy into the detector medium through ionization or excitation. This process was predicted by Daniel Z. Freedman in 1974, and was only directly observed for the first time by the Coherent collaboration in 2017.[7][4] CEvNS has since been observed (to 3.7σ) from a nuclear reactor source with the CONUS experiment.[8]

CEvNS is well defined in the Standard Model, allowing theoretical predictions to be compared directly with experimental measurements to test the model's validity.[7] The differential cross section predicted from the Standard Model shows a dominant dependence on the number of neutrons in the target nucleus, so by measuring cross sections for a range of target materials (such as argon, germanium, sodium, cesium, and iodine) and comparing them with the corresponding theoretical calculations for that nucleus, any significant deviation from the predicted behavior would indicate the presence of physics beyond the Standard Model.[2]

The Coherent collaboration is sensitive to various BSM effects, and exploring these theories is another primary goal. Dark matter is one such effect being studied, including accelerator-produced dark matter, sub-GeV leptophobic dark matter models, and weakly interacting massive particles, which are expected to coherently scatter with nuclei like a CEvNS event.[3][9][10] The Liquid Scinitillator Neutrino Detector and MiniBooNE experiments reported results that hinted at a fourth non-interacting neutrino called the sterile neutrino, and the Coherent collaboration would be sensitive to such a particle.[6] The inelastic neutrino-nucleus interactions of various nuclei are also of special interest to several causes. For example, the HALO experiment monitors the neutrino flux of supernovae by measuring neutrino-induced neutrons emitted in lead, so the Coherent collaboration has deployed a detector for measuring the cross section of this effect.[11][12] Measuring the inelastic neutrino interactions of the nucleus is also of special interest to neutrinoless double beta decay (0νββ) experiments for background reduction.[13] The Coherent collaboration has also deployed several liquid argon detectors to provide measurements of inelastic neutrino interactions of the argon nucleus, which is of special interest for studying solar-neutrino oscillations as well as the low-energy physics program for the Deep Underground Neutrino Experiment.[14][15][13]

Design

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Unlike a typical experiment which revolves around a single detector, the Coherent collaboration utilizes a series of smaller detector subsystems that rely on different target nuclei and different detector technologies, all working to observe and measure CEvNS. These detectors are located in what is known as "neutrino alley" at the SNS, which is a pion-decay-at-rest neutrino source providing a steady flux of neutrinos in the tens-of-MeV range.[2][5]

Below is a table outlining the various detector subsystems used for measurements of CEvNS, including details such as target nuclei, detector technology, target mass, distance from source, and deployment period (either includes range of operation or start date if still active):

Target Nuclei Detector Technology Target Mass

(kg)

Deployment

Period

CsI[Na] Doped scintillating crystal with PMT light readout 15 2015-2019[5]
Ar Single-phase liquid argon with PMT light readout 24 2016-2021[16]
Ge HPGe p-type point-contact 18 2022[17]
NaI[Tl] Doped scintillating crystal with PMT light readout 3500 2022[13]
Ar Single-phase liquid argon with PMT light readout 750 2025[18]
Ge HPGe p-type point-contact 50 2025[13]
CsI Undoped Scintillating crystal with SiPM light readout 10-15 2025[19]

Along with studying CEvNS, the Coherent collaboration has deployed a series of other detectors with physics goals besides studying CEvNS. Below is a table outlining these various detector subsystems and details describing their operation, such as detector name, detector technology, primary physics goal, and deployment period (either includes range of operation or start date if still active):

Detector

Name

Detector Technology Primary Physics Goal Deployment

Period

NaI Neutrino Experiment (NaIνE) NaI[Tl] scintillator crystals with PMT light readout of target Measure the inclusive electron-neutrino charged-current cross section on 2016[20]
Multiplicity and Recoil Spectrometer (MARS) Plastic scintillator layers with interlinked gadolinium coated Mylar sheet and PMT light readout Monitor and characterize the beam-related neutron background 2017[21]
Neutrino-Induced-Neutron (NIN) Liquid scintillator detectors with PMT light readout inside lead target Study neutrino-induced-neutrons from lead 2015-2024[22]
Heavy water Cherenkov detector with PMT light readout Measure the absolute neutrino flux 2022[23]
LArTPC Liquid Argon Time Projection Chamber (LArTPC) Measure neutrino-argon inelastic cross section 2025[13]

Operations timeline

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The idea for the Coherent collaboration running at the SNS was first outlined in a white paper from 2012, eventually leading to funding first being approved in 2013.[24] The first detector was a 14.6 kg doped CsI[Na] scintillator crystal deployed in 2015, and was used for the first detection of CEvNS in 2017.[4] Since then, the Coherent collaboration has deployed various different and larger detectors, resulting in the first ever CEvNS detection in both argon and germanium nuclei.[16][17]

The SNS also has upgrade plans that will benefit the Coherent collaboration, including an upgrade to the SNS proton beam that will bring the power to 2 MW by 2025, and a second target station planned to be operational in the 2030s. This will bring the final power to 2.8 MW with protons divided between the two stations.[13]

References

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  1. ^ "COHERENT | ORNL". coherent.ornl.gov. Retrieved 2025-11-22.
  2. ^ a b c d Dunietz, Jesse. "Ever-Elusive Neutrinos Spotted Bouncing Off Nuclei for the First Time". Scientific American. Retrieved 2025-11-30.
  3. ^ a b Chen, Sophia. "Physicists Capture the Elusive Neutrino Smacking Into an Atom's Core". Wired. ISSN 1059-1028. Retrieved 2025-12-07.
  4. ^ a b c "Milk jug–sized detector captures neutrinos in a whole new way". www.science.org. Retrieved 2025-11-24.
  5. ^ a b c Akimov, D.; Albert, J. B.; An, P.; Awe, C.; Barbeau, P. S.; Becker, B.; Belov, V.; Brown, A.; Bolozdynya, A. (2017-08-03), Observation of Coherent Elastic Neutrino-Nucleus Scattering, arXiv, arXiv:1708.01294, doi:10.48550/arXiv.1708.01294, retrieved 2025-11-23
  6. ^ a b Bisset, Iain A.; Dutta, Bhaskar; Huang, Wei-Chih; Strigari, Louis E. (2024-10-01). "Short baseline neutrino anomalies at stopped pion experiments". Journal of High Energy Physics. 2024 (10): 3. doi:10.1007/JHEP10(2024)003. ISSN 1029-8479.
  7. ^ a b Freedman, Daniel Z. (1974-03-01). "Coherent effects of a weak neutral current". Physical Review D. 9 (5): 1389–1392. doi:10.1103/PhysRevD.9.1389. ISSN 0556-2821.
  8. ^ Ackermann, N.; Bonet, H.; Bonhomme, A.; Buck, C.; Fülber, K.; Hakenmüller, J.; Hempfling, J.; Heusser, G.; Lindner, M. (2025-07-31), Direct observation of coherent elastic antineutrino-nucleus scattering, arXiv, doi:10.48550/arXiv.2501.05206, arXiv:2501.05206, retrieved 2025-11-24
  9. ^ Collaboration, COHERENT; Akimov, D.; An, P.; Awe, C.; Barbeau, P. S.; Becker, B.; Belov, V.; Bernardi, I.; Blackston, M. A. (2022-05-26), A COHERENT constraint on leptophobic dark matter using CsI data, arXiv, arXiv:2205.12414, doi:10.48550/arXiv.2205.12414, retrieved 2025-11-24
  10. ^ Collaboration, COHERENT; Akimov, D.; An, P.; Awe, C.; Barbeau, P. S.; Becker, B.; Belov, V.; Blackston, M. A.; Bolozdynya, A. (2019-11-15), Sensitivity of the Coherent Experiment to Accelerator-Produced Dark Matter, arXiv, arXiv:1911.06422, doi:10.48550/arXiv.1911.06422, retrieved 2025-11-24
  11. ^ Duba, C A; Duncan, F; Farine, J; Habig, A; Hime, A; Robertson, R G H; Scholberg, K; Shantz, T; Virtue, C J; Wilkerson, J F; Yen, S (2008-11-01). "HALO – the helium and lead observatory for supernova neutrinos". Journal of Physics: Conference Series. 136 (4) 042077. doi:10.1088/1742-6596/136/4/042077. ISSN 1742-6596.
  12. ^ Engel, J.; McLaughlin, G. C.; Volpe, C. (2003-01-23). "What can be learned with a lead-based supernova-neutrino detector?". Physical Review D. 67 (1). doi:10.1103/PhysRevD.67.013005. ISSN 0556-2821.
  13. ^ a b c d e f Akimov, D.; Alawabdeh, S.; An, P.; Arteaga, A.; Awe, C.; Barbeau, P. S.; Barry, C.; Becker, B.; Belov, V. (2022-04-10), The Coherent Experimental Program, arXiv, arXiv:2204.04575, doi:10.48550/arXiv.2204.04575, retrieved 2025-11-22
  14. ^ Asai, Shoji; Ballarino, Amalia; Bose, Tulika; Cranmer, Kyle; Cyr-Racine, Francis-Yan; Demers, Sarah; Geddes, Cameron; Gershtein, Yuri; Heeger, Karsten (2024-07-27), Exploring the Quantum Universe: Pathways to Innovation and Discovery in Particle Physics - Report of the 2023 Particle Physics Project Prioritization Panel, arXiv, arXiv:2407.19176, doi:10.48550/arXiv.2407.19176, retrieved 2025-11-30
  15. ^ Jachowicz, Natalie; Dessel, Nils Van; Nikolakopoulos, Alexis (2019-06-19), Low-energy neutrino scattering in experiment and astrophysics, arXiv, arXiv:1906.08191, doi:10.48550/arXiv.1906.08191, retrieved 2025-12-07
  16. ^ a b Collaboration, COHERENT; Akimov, D.; Albert, J. B.; An, P.; Awe, C.; Barbeau, P. S.; Becker, B.; Belov, V.; Blackston, M. A. (2021-02-15), First Measurement of Coherent Elastic Neutrino-Nucleus Scattering on Argon, arXiv, doi:10.48550/arXiv.2003.10630, arXiv:2003.10630, retrieved 2025-11-23
  17. ^ a b Adamski, S.; Ahn, M.; Barbeau, P. S.; Belov, V.; Bernardi, I.; Bock, C.; Bolozdynya, A.; Bouabid, R.; Browning, J. (2024-06-19), First detection of coherent elastic neutrino-nucleus scattering on germanium, arXiv, doi:10.48550/arXiv.2406.13806, arXiv:2406.13806, retrieved 2025-11-23
  18. ^ "Detector Subsystems – COHERENT at the SNS". Retrieved 2025-12-05.
  19. ^ Barbeau, P. S.; Belov, V.; Bernardi, I.; Bock, C.; Bolozdynya, A.; Bouabid, R.; Browning, J.; Cabrera-Palmer, B.; Conley, E. (2023-11-21), Accessing new physics with an undoped, cryogenic CsI CEvNS detector for COHERENT at the SNS, arXiv, doi:10.48550/arXiv.2311.13032, arXiv:2311.13032, retrieved 2025-12-05
  20. ^ An, P.; Awe, C.; Barbeau, P. S.; Becker, B.; Belov, V.; Bernardi, I.; Bock, C.; Bolozdynya, A.; Bouabid, R. (2024-03-07), Measurement of the Electron-Neutrino Charged-Current Cross Sections on ^{127}I with the COHERENT NaIνE detector, arXiv, arXiv:2305.19594, doi:10.48550/arXiv.2305.19594, retrieved 2025-11-23
  21. ^ Collaboration, COHERENT; Akimov, D.; An, P.; Awe, C.; Barbeau, P. S.; Becker, B.; Belov, V.; Bernardi, I.; Blackston, M. A. (2022-04-14), Monitoring the SNS basement neutron background with the MARS detector, arXiv, arXiv:2112.02768, doi:10.48550/arXiv.2112.02768, retrieved 2025-11-23
  22. ^ Collaboration, COHERENT; An, P.; Awe, C.; Barbeau, P. S.; Becker, B.; Belling, S. W.; Belov, V.; Bernardi, I.; Bock, C. (2023-10-30), Measurement of {}^{nat}Pb(ν_e,Xn) production with a stopped-pion neutrino source, arXiv, arXiv:2212.11295, doi:10.48550/arXiv.2212.11295, retrieved 2025-11-23
  23. ^ Collaboration, COHERENT; Akimov, D.; An, P.; Awe, C.; Barbeau, P. S.; Becker, B.; Belov, V.; Bernardi, I.; Blackston, M. A. (2021-08-25), A D_{2}O detector for flux normalization of a pion decay-at-rest neutrino source, arXiv, arXiv:2104.09605, doi:10.48550/arXiv.2104.09605, retrieved 2025-11-23
  24. ^ Bolozdynya, A.; Cavanna, F.; Efremenko, Y.; Garvey, G. T.; Gudkov, V.; Hatzikoutelis, A.; Hix, W. R.; Louis, W. C.; Link, J. M. (2012-11-22), Opportunities for Neutrino Physics at the Spallation Neutron Source: A White Paper, arXiv, arXiv:1211.5199, doi:10.48550/arXiv.1211.5199, retrieved 2025-11-23
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