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| NEOS (experiment) | |
|---|---|
| Name | NEOS |
| Caption | NEOS detector schematic |
| Established | 2015 |
| Location | Hanbit Nuclear Power Plant, Gyeongju |
| Type | Reactor neutrino experiment |
| Leaders | Korea University, Sejong University, Kyungpook National University |
| Affiliation | Korea Atomic Energy Research Institute |
NEOS (experiment) NEOS was a short-baseline reactor neutrino experiment designed to study anomalies in reactor antineutrino fluxes and spectra near a commercial pressurized water reactor. The collaboration aimed to test sterile neutrino hypotheses and precision spectral measurements using a liquid scintillator detector deployed at a shallow depth. NEOS interfaced with international efforts on oscillation anomalies involving reactor, accelerator, and gallium results.
NEOS operated at the Hanbit Nuclear Power Plant near Yeonggwang County in the Republic of Korea with ties to institutions such as Korea University, Sejong University, and Kyungpook National University. Motivations included tensions between predictions from the Huber–Mueller model and measurements from experiments like Daya Bay, Double Chooz, RENO, and Bugey-3. The experiment addressed anomalies connected to findings from LSND, MiniBooNE, SAGE, and GALLEX and compared results to global fits from groups associated with Kopp et al., Gariazzo et al., and the Particle Data Group.
The NEOS detector was positioned approximately 24 m from a reactor core at a commercial pressurized water reactor unit, leveraging infrastructure at Hanbit Nuclear Power Plant and coordination with the Korea Hydro & Nuclear Power operator. The layout allowed studies of inverse beta decay signals comparable to those in Bugey-3 and complementary to long-baseline programs like T2K and NOvA. Shielding and overburden were adapted to local site constraints, with comparisons drawn to shallow sites used by PROSPECT and SoLid. The collaboration followed safety and access practices resembling protocols by International Atomic Energy Agency and national regulators.
NEOS employed a 1-ton gadolinium-doped liquid scintillator target contained within acrylic vessels instrumented with photomultiplier tubes similar to devices used by KamLAND, Borexino, and Daya Bay. The detector design included passive shielding layers using materials analogous to those in GERDA and active muon veto systems inspired by implementations at Super-Kamiokande and SNO+. Calibration used deployed radioactive sources comparable to those utilized by SNO and referenced to standards from National Institute of Standards and Technology. Electronics and high-voltage systems were procured from vendors with histories supporting experiments such as MINOS and IceCube.
The NEOS data acquisition system recorded prompt–delayed coincidence signatures of inverse beta decay with timing and energy resolutions benchmarked against analyses from Daya Bay, RENO, and Double Chooz. Event reconstruction pipelines adapted algorithms from collaborations like KamLAND and Borexino for pulse-shape discrimination and background rejection similar to methods used by PROSPECT and SoLid. Statistical analyses incorporated techniques from global oscillation fits by groups including Mention et al. and Giunti & Laveder, employing covariance methods related to treatments by Feldman–Cousins and likelihood frameworks akin to those used in IceCube sterile searches.
NEOS reported measurements of the reactor antineutrino energy spectrum and rate that probed parameter space suggested by sterile neutrino interpretations consistent with prior anomalies from LSND and MiniBooNE. The spectrum exhibited features comparable to the 5 MeV "bump" seen by Daya Bay and RENO, prompting comparisons to theoretical revisions like those from Hayes & Vogel and flux reevaluations by Huber and Mueller et al.. Constraints from NEOS were combined with data sets from Bugey-3, PROSPECT, and STEREO to limit mixing parameters referenced in analyses by Gariazzo et al. and the Particle Data Group.
NEOS quantified systematics associated with reactor fuel composition accounting for isotopes such as 235U, 238U, 239Pu, and 241Pu analogous to treatments by Daya Bay and the Huber–Mueller model. Detector-related uncertainties included energy scale and nonlinearity comparable to calibrations in KamLAND and Borexino, while background systematics accounted for cosmogenic isotopes like 9Li and 8He with veto strategies inspired by Super-Kamiokande and SNO. Cross-section uncertainties referenced inverse beta decay inputs from theoretical work by Vogel & Beacom and reactor modeling practices used in NEA and IAEA assessments.
NEOS influenced the short-baseline reactor neutrino program by contributing high-statistics spectral data relevant to the global sterile neutrino question alongside experiments such as PROSPECT, STEREO, and SoLid. Its findings informed reactor flux modeling efforts by groups led by Hayes, Mueller, and Huber and fed into combined fits by consortia working with the Particle Data Group. The experiment’s techniques for shallow deployment, calibration, and background suppression offer lessons applied to upcoming initiatives connected to JUNO, DUNE, and continued short-baseline searches coordinated with institutions like CERN and national laboratories including Oak Ridge National Laboratory.
Category:Neutrino experiments