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Expected 95% C.L. exclusion contours from sterile neutrino searches. The black solid contour represents an expected limit on ¯ ν e disappearance using RENO's 2200 days of data. The red solid (dotted) contour represents an exclusion sensitivity originating from a relatively long (short) baseline search. The blue solid (dotted) contour represents an exclusion sensitivity coming from a search in the 1.2-3.0 MeV (3.0-8.0 MeV) region.
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We report a search result for a light sterile neutrino oscillation with roughly 2200 live days of data in the RENO experiment. The search is performed by electron antineutrino (ν¯e) disappearance taking place between six 2.8 GWth reactors and two identical detectors located at 294 m (near) and 1383 m (far) from the center of the reactor array. A sp...
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... sample is generated without statistical or systematic fluctuations assuming the three-neutrino hypothesis. Figure 1 shows an Asimov expected exclusion contour obtained from a search for a sterile neutrino oscillation by a far-to-near ratio method, which is described later. In the 10 −4 < jΔm 2 41 j < 0.5 eV 2 region, a relative spectral distortion between the two detectors occurs and provides search sensitivity. ...
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... The Daya Bay collaboration has published an experimental lower limit on the effective flux-averaged neutrino wave packet width [23], though it does not exclude the currently predicted value. Fig. 1 shows the red lines indicating the baselines of each of the reactor experiments described in [57] plus Daya Bay [60], RENO [61], and Double Chooz [62] experiments, alongside the approximate energy spread of the reactor antineutrino spectra. (3) Short baseline experiments: Short baseline neutrino oscillation experiments such as MiniBooNE [63], MicroBooNE [64], SBND [65], and ICARUS [66] (shown as orange lines in Fig. 1) detect neutrinos produced in beams of magnetically focused hadrons created by proton collisions on solid targets. ...
Models of spontaneous wave function collapse have been postulated to address the measurement problem in quantum mechanics. Their primary function is to convert coherent quantum superpositions into incoherent ones, with the result that macroscopic objects cannot be placed into widely separated superpositions for observably prolonged times. Many of these processes will also lead to loss of coherence in neutrino oscillations, producing observable signatures in the flavor profile of neutrinos at long travel distances. The majority of studies of neutrino oscillation coherence to date have focused on variants of the continuous state localization model, whereby an effective decoherence strength parameter is used to model the rate of coherence loss with an assumed energy dependence. Another class of collapse models that have been proposed posit connections to the configuration of gravitational field accompanying the mass distribution associated with each wave function that is in the superposition. A particularly interesting and prescriptive model is Penrose’s description of gravitational collapse which proposes a decoherence time τ determined through E g τ ∼ ℏ , where E g is a calculable function of the Newtonian gravitational potential. Here we explore application of the Penrose collapse model to neutrino oscillations, reinterpreting previous experimental limits on neutrino decoherence in terms of this model. We identify effects associated with both spatial collapse and momentum diffusion, finding that the latter is ruled out in data from the IceCube South Pole Neutrino Observatory so long as the neutrino wave packet width at production is σ ν , x ≤ 2 × 10 − 12 m .
Published by the American Physical Society 2024
... This is evident in figure 1-13, which shows the regions in sin 2 2 ee -∆m 2 parameter space preferred by the RAA and gallium anomalies, as well as global constraints from other experiments. These constraints come from short-to-medium-baseline reactor experiments, including NEOS [94], RENO [95], and Daya Bay [96], as well as very-short-baseline reactor experiments, including STEREO [97], DANSS [98], and PROSPECT [99]. Each of these experiments searches for e disappearance in a reactor-flux-agnostic way: the former though comparisons of the reactor e spectra measured by different detectors [100], and the latter through the use of modular or movable detectors capable of comparing e interaction rates across different baselines. ...
This thesis covers a range of experimental and theoretical efforts to elucidate the origin of the MiniBooNE low energy excess (LEE). We begin with the follow-up MicroBooNE experiment, which took data along the BNB from 2016 to 2021. This thesis specifically presents MicroBooNE's search for charged-current quasi-elastic (CCQE) interactions consistent with two-body scattering. The two-body CCQE analysis uses a novel reconstruction process, including a number of deep-learning-based algorithms, to isolate a sample of CCQE interaction candidates with purity. The analysis rules out an entirely -based explanation of the MiniBooNE excess at the confidence level. We next perform a combined fit of MicroBooNE and MiniBooNE data to the popular 3+1 model; even after the MicroBooNE results, allowed regions in - parameter space exist at the confidence level. This thesis also demonstrates that the MicroBooNE data are consistent with a -based explanation of the MiniBooNE LEE at the confidence level. Next, we investigate a phenomenological explanation of the MiniBooNE excess combining the 3+1 model with a dipole-coupled heavy neutral lepton (HNL). It is shown that a 500 MeV HNL can accommodate the energy and angular distributions of the LEE at the confidence level while avoiding stringent constraints derived from MINERA elastic scattering data. Finally, we discuss the Coherent CAPTAIN-Mills experiment--a 10-ton light-based liquid argon detector at Los Alamos National Laboratory. The background rejection achieved from a novel Cherenkov-based reconstruction algorithm will enable world-leading sensitivity to a number of beyond-the-Standard Model physics scenarios, including dipole-coupled HNLs.
... A number of other experiments have produced results impacting the sterile neutrino interpretations of the Ga anomaly: DANSS [84], Prospect [85], Stéréo [86], RENO & NEOS [87,88] and KATRIN [89] all quote limits and provide exclusion regions. As a collective they exclude most, but not all, of the BEST allowed space. ...
In order to test the end-to-end operations of gallium solar neutrino experiments, intense electron-capture sources were fabricated to measure the responses of the radiochemical SAGE and GALLEX/GNO detectors to known fluxes of low-energy neutrinos. Such tests were viewed at the time as a cross-check, given the many tests of 71Ge recovery and counting that had been routinely performed, with excellent results. However, the four 51Cr and 37Ar source experiments yielded rates below expectations, a result commonly known as the Ga anomaly. As the intensity of the electron-capture sources can be measured to high precision, the neutrino lines they produce are fixed by known atomic and nuclear rates, and the neutrino absorption cross section on 71Ga is tightly constrained by the lifetime of 71Ge, no simple explanation for the anomaly has been found. To check these calibration experiments, a dedicated experiment BEST was performed, utilizing a neutrino source of unprecedented intensity and a detector optimized to increase statistics while providing some information on counting rate as a function of distance from the source. The results BEST obtained are consistent with the earlier solar neutrino calibration experiments, and when combined with those measurements, yield a Ga anomaly with a significance of approximately 4sigma, under conservative assumptions. But BEST found no evidence of distance dependence and thus no explicit indication of new physics. In this review we describe the extensive campaigns carried out by SAGE, GALLEX/GNO, and BEST to demonstrate the reliability and precision of their experimental procedures, including 71Ge recovery, counting, and analysis. We also describe efforts to define uncertainties in the neutrino capture cross section. With the results from BEST, an anomaly remains.
... The measurement of nonstandard interaction (NSI) in the neutrino sector is an attractive approach to probe beyond-SM physics [2,3]. Current experimental efforts on neutrino NSI are conducted with different neutrino sources, such as reactor neutrinos [4][5][6][7][8][9][10][11][12], accelerator neutrinos [13][14][15][16], and radioactive sources [17][18][19][20][21]. In addition to these terrestrial sources, NSI can also be probed with neutrinos from astrophysical sources, such as stars [22], supernovae [23,24], terrestrial atmosphere [25], and others [26]. ...
We investigate exotic neutrino interactions using the 205.4-kg · day dataset from the CDEX-10 experiment at the China Jinping Underground Laboratory. New constraints on the mass and couplings of new gauge bosons are presented. Two nonstandard neutrino interactions are considered: a U(1) B-L gauge-boson-induced interaction between an active neutrino and electron/nucleus, and a dark-photon-induced interaction between a sterile neutrino and electron/nucleus via kinetic mixing with a photon. This work probes an unexplored parameter space involving sterile neutrino coupling with a dark photon. New laboratory limits are derived on dark photon masses below 1 eV/c 2 at some benchmark values of Δm 2 41 and g 02 sin 2 2θ 14 .
... The measurement of nonstandard interaction (NSI) in the neutrino sector is an attractive approach to probe beyond-SM physics [2,3]. Current experimental efforts on neutrino NSI are conducted with different neutrino sources, such as reactor neutrinos [4][5][6][7][8][9][10][11][12], accelerator neutrinos [13][14][15][16], and radioactive sources [17][18][19][20][21]. In addition to these terrestrial sources, NSI can also be probed with neutrinos from astrophysical sources, such as stars [22], supernovae [23,24], terrestrial atmosphere [25], and others [26]. ...
We investigate exotic neutrino interactions using the 205.4−kg·day dataset from the CDEX-10 experiment at the China Jinping Underground Laboratory. New constraints on the mass and couplings of new gauge bosons are presented. Two nonstandard neutrino interactions are considered: a U(1)B–L gauge-boson-induced interaction between an active neutrino and electron/nucleus, and a dark-photon-induced interaction between a sterile neutrino and electron/nucleus via kinetic mixing with a photon. This work probes an unexplored parameter space involving sterile neutrino coupling with a dark photon. New laboratory limits are derived on dark photon masses below 1 eV/c2 at some benchmark values of Δm412 and g′2sin22θ14.
... In the lowest energy range, gallium experiments study the production rate of inverse beta decay on 71 Ga from an intense electron neutrino source [3][4][5][6][7][8]. Also at MeVenergies, reactor experiments have performed searches for the presence of electron antineutrino disappearance by comparing observations to theoretical predictions of the rates [9] or by searching for oscillatory patterns in measurements performed at different positions [10][11][12][13][14][15][16][17][18][19][20]. All these low-energy experiments have yielded confirmatory signals that range in significance from ∼2 to more than 5 sigma but at the same time have yielded constraints that contradict these observations, specially when taking into account solar neutrino analysis [21,22]. ...
... In this work, we focus on the low-energy region, where searches using electron antineutrinos from nuclear reactors and radioactive sources are performed [6,[10][11][12]16,17]. We will show how the plane wave approximation breaks for values of the wave packet size currently allowed [61] and how introducing this formalism produces observable effects. ...
Light sterile neutrinos have been motivated by anomalies observed in short-baseline neutrino experiments. Among them, radioactive-source and reactor experiments have provided evidence and constraints, respectively, for electron neutrino disappearance compatible with an eV-scale neutrino. The results from these observations are seemingly in conflict. This paper brings into focus the assumption that the neutrino wave packet can be approximated as a plane wave, which is adopted in all analyses of such experiments. We demonstrate that the damping of oscillation due to decoherence effects, e.g., a finite wave packet size, solves the tension between these electron-flavor observations and constraints.
... The measurement of non-standard interaction (NSI) in the neutrino sector provides an attractive approach to probe the new physics beyond the SM [2,3]. Current experimental efforts on neutrino measurements are being conducted with different neutrino sources, such as reactor neutrinos [4][5][6][7][8][9][10][11][12], accelerator neutrinos [13][14][15][16], and radioactive sources [17][18][19][20][21]. Besides these terrestrial sources, neutrinos can also be produced from astrophysical sources, such as stellar [22], Supernova [23,24], atmosphere [25], and others [26]. ...
We investigate the exotic neutrino interactions using the 205.4 kg day exposure dataset of the CDEX-10 experiment at the China Jinping Underground Laboratory. New constraints on the mass and couplings of extra gauge boson are presented. The results are interpreted in two physics scenarios including an U (1)B−L gauge boson induced interaction between active neutrinos and electron/nucleus, and a dark photon induced the interaction between sterile neutrino and electron/nucleus where the dark photon couples to the Standard Model particles through kinetic mixing with the photon. This work probes new parameter space involving sterile neutrino coupling with dark photon with masses below 1 eV/c 2 at some typical choice of ∆m 2 41 and g 2 sin 2 2θ14, which was previously unexplored by dark matter direct detection experiments and neutrino experiments.
... The measurement of nonstandard interaction (NSI) in the neutrino sector is an attractive approach to probe beyond-SM physics [2,3]. Current experimental efforts on neutrino NSI are conducted with different neutrino sources, such as reactor neutrinos [4][5][6][7][8][9][10][11][12], accelerator neutrinos [13][14][15][16], and radioactive sources [17][18][19][20][21]. In addition to these terrestrial sources, NSI can also be probed with neutrinos from astrophysical sources, such as stars [22], supernovae [23,24], terrestrial atmosphere [25], and others [26]. ...
We investigate the exotic neutrino interactions using the 205.4 kg day exposure dataset of the CDEX-10 experiment at the China Jinping Underground Laboratory. New constraints on the mass and couplings of extra gauge boson are presented. The results are interpreted in two physics scenarios including an gauge boson induced interaction between active neutrinos and electron/nucleus, and a dark photon induced the interaction between sterile neutrino and electron/nucleus where the dark photon couples to the Standard Model particles through kinetic mixing with the photon. This work probes new parameter space involving sterile neutrino coupling with dark photon with masses below 1 eV at some typical choice of and , which was previously unexplored by dark matter direct detection experiments and neutrino experiments.
... The best fit parameter (black point) is found at | = . For the comparison, shown are the NEOS+Daya Bay[40] 90% C.L. (gray shaded) and RENO far/near[85] 95% C.L. (blue dotted) limits on the disappearance. Also shown is a 95% C.L. allowed region of RAA[20] (black dotted) with the best fit[86] (star). ...
Search for New Physics beyond the Standard Model is the main direction in particle physics nowadays. There are several experimental hints of New Physics. The most statistically significant (5-6 standard deviations) are the hints of eV mass scale sterile neutrinos. They come from electron antineutrino disappearance in reactor experiments, electron neutrino disappearance in experiments with very powerful radioactive sources, and electron (anti)neutrino appearance in the muon (anti)neutrino beams. Very important results in this field were obtained in 2021 by the BEST, MicroBooNE, and Neutrino-4 collaborations as well as by several other experiments. However, the situation is still or maybe even more controversial. We review these indications of New Physics and prospects for the next few years with the emphasis on reactor experiments.
... Such detectors are used for the measurement of the antineutrino flux coming from nuclear reactors. Experiments such as STEREO [7][8][9], Daya Bay [10,11] and RENO [12] have employed Gd-loaded liquid scintillators for their measurements. In these cases, the detection of an electron antineutrino ν e is registered through the Inverse-Beta-Decay process (IBD) on the protons of the liquid: ...
The precise modeling of the de-excitation of Gd isotopes is of great interest for experimental studies of neutrinos using Gd-loaded organic liquid scintillators. The FIFRELIN code was recently used within the purposes of the STEREO experiment for the modeling of the Gd de-excitation after neutron capture in order to achieve a good control of the detection efficiency. In this work, we report on the recent additions in the FIFRELIN de-excitation model with the purpose of enhancing further the de-excitation description. Experimental transition intensities from EGAF database are now included in the FIFRELIN cascades, in order to improve the description of the higher energy part of the spectrum. Furthermore, the angular correlations between {\gamma} rays are now implemented in FIFRELIN, to account for the relative anisotropies between them. In addition, conversion electrons are now treated more precisely in the whole spectrum range, while the subsequent emission of X rays is also accounted for. The impact of the aforementioned improvements in FIFRELIN is tested by simulating neutron captures in various positions inside the STEREO detector. A repository of up-to-date FIFRELIN simulations of the Gd isotopes is made available for the community, with the possibility of expanding for other isotopes which can be suitable for different applications.
