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  • Open Access

Resolving the gallium anomaly using an opaque liquid scintillator detector

Garv Chauhan1,2 and Patrick Huber2

  • 1Department of Physics, Arizona State University, 450 E. Tyler Mall, Tempe, Arizona 85287-1504 USA
  • 2Center for Neutrino Physics, Department of Physics, Virginia Tech, Blacksburg, Virginia 24061, USA

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Phys. Rev. D 113, 115058 – Published 23 June, 2026

DOI: https://doi.org/10.1103/hlrw-rby4

Abstract

The gallium anomaly has a global significance of greater than 5σ. While SM solutions are not strongly favored, most viable BSM solutions likewise run into strong tensions with reactor and solar neutrino data. In this work, we first emphasize that elastic scattering alone is insufficient to test and resolve the GA. Therefore, we require a detector with a calibrated neutrino source to precisely determine the incoming neutrino energy, avoid radiochemical extraction biases, and isolate oscillation-based effects. We propose to use charged-current neutrino capture on indium (In115) as a target as it offers a low threshold (114 keV) and reasonably high cross section. The triple coincidence provided by In115 neutrino capture can be fully exploited by an opaque scintillation detector that also provides energy and position information. Recent successful research and development by the LiquidO Collaboration makes our proposal realistic and timely. We show that a 100 ton indium target combined with two source runs of a 3.4 MCi Cr51 source can probe the complete parameter space of the gallium anomaly, both in the context of a vanilla sterile neutrino as well as more involved BSM scenarios.

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References (45)

  1. SAGE Collaboration, Measurement of the response of the Russian-American gallium experiment to neutrinos from a Cr-51 source, Phys. Rev. C 59, 2246 (1999).
  2. GALLEX Collaboration, Final results of the Cr-51 neutrino source experiments in GALLEX, Phys. Lett. B 420, 114 (1998).
  3. F. Kaether, W. Hampel, G. Heusser, J. Kiko, and T. Kirsten, Reanalysis of the GALLEX solar neutrino flux and source experiments, Phys. Lett. B 685, 47 (2010).
  4. V. V. Barinov et al., Search for electron-neutrino transitions to sterile states in the BEST experiment, Phys. Rev. C 105, 065502 (2022).
  5. J. M. Berryman, P. Coloma, P. Huber, T. Schwetz, and A. Zhou, Statistical significance of the sterile-neutrino hypothesis in the context of reactor and gallium data, J. High Energy Phys. 02 (2022) 055.
  6. S. R. Elliott, V. Gavrin, and W. Haxton, The gallium anomaly, Prog. Part. Nucl. Phys. 134, 104082 (2024).
  7. C. Giunti, Y. F. Li, C. A. Ternes, O. Tyagi, and Z. Xin, Gallium anomaly: Critical view from the global picture of νe and ν¯e disappearance, J. High Energy Phys. 10 (2022) 164.
  8. KATRIN Collaboration, Sterile-neutrino search based on 259 days of KATRIN data, arXiv:2503.18667.
  9. P. Huber, Testing the gallium anomaly, Phys. Rev. D 107, 096011 (2023).
  10. V. Brdar, J. Gehrlein, and J. Kopp, Towards resolving the gallium anomaly, J. High Energy Phys. 05 (2023) 143.
  11. V. Brdar, J. Kopp, J. Liu, P. Prass, and X.-P. Wang, Fuzzy dark matter and nonstandard neutrino interactions, Phys. Rev. D 97, 043001 (2018).
  12. C. Giunti and M. Laveder, Hint of CPT violation in short-baseline electron neutrino disappearance, Phys. Rev. D 82, 113009 (2010).
  13. H. Davoudiasl and P. B. Denton, Sterile neutrino shape shifting caused by dark matter, Phys. Rev. D 108, 035013 (2023).
  14. C. Grieb, J. Link, and R. S. Raghavan, Probing active to sterile neutrino oscillations in the LENS detector, Phys. Rev. D 75, 093006 (2007).
  15. R. S. Raghavan, Inverse β decay of In115→Sn*115: A new possibility for detecting solar neutrinos from the proton-proton reaction, Phys. Rev. Lett. 37, 259 (1976).
  16. LiquidO Collaboration, Neutrino physics with an opaque detector, Commun. Phys. 4, 273 (2021).
  17. LiquidO Collaboration, The stochastic light confinement of LiquidO, arXiv:2503.02541.
  18. LiquidO Collaboration, Muon tracking in a LiquidO opaque scintillator detector, J. Instrum. 21, P01010 (2026).
  19. A. Cabrera Serra, Cloud: A new generation of neutrino science at chooz, 10.5281/zenodo.10049846 (2023).
  20. A. Cabrera Serra, The superchooz experiment: Unveiling the opportunity, 10.5281/zenodo.7504162 (2022).
  21. G. Bellini et al., Precision measurement of the Be7 solar neutrino interaction rate in Borexino, Phys. Rev. Lett. 107, 141302 (2011).
  22. R. S. Raghavan, New prospects for real time spectroscopy of low-energy electron neutrinos from the Sun, Phys. Rev. Lett. 78, 3618 (1997).
  23. R. S. Raghavan, pp solar neutrino spectroscopy: Return of the indium detector, arXiv:hep-ex/0106054.
  24. L. Pfeiffer, A. P. Mills, R. S. Raghavan, and E. A. Chandross, Indium-loaded liquid scintillator for low-energy solar-neutrino spectroscopy, Phys. Rev. Lett. 41, 63 (1978).
  25. I. R. Barabanov, L. B. Bezrukov, V. I. Gurentsov, G. Y. Novikova, V. V. Sinev, and E. A. Yanovich, New possibilities for pp-cycle solar neutrino registration by use of indium detector, Phys. At. Nucl. 86, 1189 (2023).
  26. LiquidO Collaboration, Characterization of a radiation detector based on opaque water-based liquid scintillator, Nucl. Instrum. Methods Phys. Res., Sect. A 1071, 170075 (2025).
  27. V. N. Gavrin, T. V. Ibragimova, J. P. Kozlova, V. A. Tarasov, E. P. Veretenkin, and A. I. Zvir, Measurement of neutrino source activity in the experiment BEST by calorimetric method, J. Instrum. 16, P04012 (2021).
  28. M. A. Acero, C. Giunti, and M. Laveder, Limits on nu(e) and anti-nu(e) disappearance from Gallium and reactor experiments, Phys. Rev. D 78, 073009 (2008).
  29. A. B. McDonald, Dark matter detection with liquid argon, Nucl. Phys. B1003, 116436 (2024).
  30. J. Aalbers et al., A next-generation liquid xenon observatory for dark matter and neutrino physics, J. Phys. G 50, 013001 (2023).
  31. Y. Farzan and T. Schwetz, A decoherence explanation of the gallium neutrino anomaly, SciPost Phys. 15, 172 (2023).
  32. Borexino Collaboration, First simultaneous precision spectroscopy of pp, Be7, and pep solar neutrinos with Borexino Phase-II, Phys. Rev. D 100, 082004 (2019).
  33. BOREXINO Collaboration, Comprehensive measurement of pp-chain solar neutrinos, Nature (London) 562, 505 (2018).
  34. BOREXINO Collaboration, Improved measurement of solar neutrinos from the carbon-nitrogen-oxygen cycle by Borexino and its implications for the standard solar model, Phys. Rev. Lett. 129, 252701 (2022).
  35. BOREXINO Collaboration, Final results of Borexino on CNO solar neutrinos, Phys. Rev. D 108, 102005 (2023).
  36. Borexino open data archives, https://borex.lngs.infn.it/category/opendata/.
  37. Borexino Collaboration, Constraints on flavor-diagonal non-standard neutrino interactions from Borexino Phase-II, J. High Energy Phys. 02 (2020) 038.
  38. N. Vinyoles, A. M. Serenelli, F. L. Villante, S. Basu, J. Bergström, M. C. Gonzalez-Garcia, M. Maltoni, C. Peña-Garay, and N. Song, A new generation of standard solar models, Astrophys. J. 835, 202 (2017).
  39. E. J. Konopinski, The experimental clarification of the laws of beta-radioactivity, Annu. Rev. Nucl. Part. Sci. 9, 99 (1959).
  40. P. Coloma, P. Coloma, M. C. Gonzalez-Garcia, M. C. Gonzalez-Garcia, M. Maltoni, M. Maltoni, J. P. Pinheiro, and S. Urrea, Constraining new physics with Borexino Phase-II spectral data, J. High Energy Phys. 07 (2022) 138.
  41. E. P. Veretenkin, V. N. Gavrin, S. N. Danshin, T. V. Ibragimova, A. A. Kalashnikova, J. P. Kozlova, and A A Martynov, Calorimetric system for high-precision determination of activity of the Cr51 neutrino source in the BEST experiment, J. Phys. Conf. Ser. 798, 012140 (2017).
  42. S. A. Fisher and R. L. Hershberger, Branching ratios for EC decay of Be7 and Cr51, Nucl. Phys. A423, 121 (1984).
  43. A. Konstantinov, T. Sazonova, S. Sepman, A. Zanevsky, and N. Karmalitsyn, Determination of x-ray and gamma-ray emission probabilities of Cr51 and Y88, Nucl. Instrum. Methods Phys. Res., Sect. A 339, 200 (1994).
  44. P. Yalçin and Y. Kurucu, Emission probabilities of K X- and γ-rays following Cr51 and Ga67 decay, Appl. Radiat. Isot. 62, 63 (2005).
  45. D. S. Moreira, M. F. Koskinas, I. M. Yamazaki, and M. S. Dias, Determination of Cr51 and Am241 x-ray and gamma-ray emission probabilities per decay, Appl. Radiat. Isot. 68, 596 (2010).

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Phys. Rev. D 113, 115058– Published 23 June, 2026
  • Received 21 July 2025
  • Accepted 4 May 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.

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