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DOE OSTI2016

Neutrino physics with JUNO

The Jiangmen Underground Neutrino Observatory (JUNO), a 20 kton multi-purpose underground liquid scintillator detector, was proposed with the determination of the neutrino mass hierarchy (MH) as a primary physics goal. The excellent energy resolution and the large fiducial volume anticipated for the JUNO detector offer exciting opportunities for addressing many important topics in neutrino and astro-particle physics. In this document, we present the physics motivations and the anticipated performance of the JUNO detector for various proposed measurements. Following an introduction summarizing the current status and open issues in neutrino physics, we discuss how the detection of antineutrinos generated by a cluster of nuclear power plants allows the determination of the neutrino MH at a 3–4σ significance with six years of running of JUNO. The measurement of antineutrino spectrum with excellent energy resolution will also lead to the precise determination of the neutrino oscillation parameters ${\mathrm{sin}}^{2}{\theta }_{12}$, ${\rm{\Delta }}{m}_{21}^{2}$, and $| {\rm{\Delta }}{m}_{{ee}}^{2}| $ to an accuracy of better than 1%, which will play a crucial role in the future unitarity test of the MNSP matrix. The JUNO detector is capable of observing not only antineutrinos from the power plants, but also neutrinos/antineutrinos from terrestrial and extra-terrestrial sources, including supernova burst neutrinos, diffuse supernova neutrino background, geoneutrinos, atmospheric neutrinos, and solar neutrinos. As a result of JUNO's large size, excellent energy resolution, and vertex reconstruction capability, interesting new data on these topics can be collected. For example, a neutrino burst from a typical core-collapse supernova at a distance of 10 kpc would lead to ~5000 inverse-beta-decay events and ~2000 all-flavor neutrino–proton ES events in JUNO, which are of crucial importance for understanding the mechanism of supernova explosion and for exploring novel phenomena such as collective neutrino oscillations. Detection of neutrinos from all past core-collapse supernova explosions in the visible universe with JUNO would further provide valuable information on the cosmic star-formation rate and the average core-collapse neutrino energy spectrum. Antineutrinos originating from the radioactive decay of uranium and thorium in the Earth can be detected in JUNO with a rate of ~400 events per year, significantly improving the statistics of existing geoneutrino event samples. Atmospheric neutrino events collected in JUNO can provide independent inputs for determining the MH and the octant of the ${\theta }_{23}$ mixing angle. Detection of the 7Be and 8B solar neutrino events at JUNO would shed new light on the solar metallicity problem and examine the transition region between the vacuum and matter dominated neutrino oscillations. Regarding light sterile neutrino topics, sterile neutrinos with ${10}^{-5}\;{{\rm{eV}}}^{2}\lt {\rm{\Delta }}{m}_{41}^{2}\lt {10}^{-2}\;{{\rm{eV}}}^{2}$ and a sufficiently large mixing angle ${\theta }_{14}$ could be identified through a precise measurement of the reactor antineutrino energy spectrum. Meanwhile, JUNO can also provide us excellent opportunities to test the eV-scale sterile neutrino hypothesis, using either the radioactive neutrino sources or a cyclotron-produced neutrino beam. The JUNO detector is also sensitive to several other beyondthe-standard-model physics. Examples include the search for proton decay via the $p\to {K}^{+}+\bar{\nu }$ decay channel, search for neutrinos resulting from dark-matter annihilation in the Sun, search for violation of Lorentz invariance via the sidereal modulation of the reactor neutrino event rate, and search for the effects of non-standard interactions. The proposed construction of the JUNO detector will provide a unique facility to address many outstanding crucial questions in particle and astrophysics in a timely and cost-effective fashion. Furthermore, it holds the great potential for further advancing our quest to understanding the fundamental properties of neutrinos, one of the building blocks of our Universe.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Initial report from the ICFA Neutrino Panel

The discovery of neutrino oscillations implies that neutrinos have mass and that the flavour eigenstates mix. Non-zero neutrino masses require new physics beyond the Standard Model. Revealing the physics behind neutrino masses and mixing is among the highest priorities for particle physics in the twenty-first century. Measurements of the parameters that govern neutrino oscillations will have a profound impact on our understanding of particle physics, astrophysics and cosmology. Such a breadth of impact justifies a far-reaching experimental programme by which the properties of the neutrino that are presently unknown are determined, the three-neutrino-mixing picture is tested and the properties of the neutrino are measured with a precision sufficient to allow the physics that explains these properties to be understood. Accelerator-based neutrino-oscillation experiments are an essential component of this programme as they are the only way in which oscillations between all known flavours can be studied precisely. The accelerator-based neutrino-oscillation programme is international in both scope and engagement. The approved programme will improve our knowledge of the mixing angles and the mass-squared differences and may be able to determine the neutrino mass hierarchy. In the medium term, the Long-baseline Neutrino Experiment (LBNE) and the Tokai (J-PARC) to Hyper-Kamiokande experiment offer complementary approaches to searching for the violation of the matter-anti-matter symmetry in neutrino oscillations. For these experiments to realise their full potential coordinated programmes of hadro-production and neutrino-nucleus cross-section measurements are essential. A design study of an alternative wide-hand beam facility is underway: the Long-baseline Neutrino Observatory (LBNO) study will report by the end of 2014. New concepts such as the implementation of a neutrino beam on the European Spallation Source (ESSnuSB) and the use of muon decay-at-rest to search for the matter-anti-matter asymmetry (Daedalus) are also being studied. The Neutrino Factory, in which electron- and muon-neutrino beams are produced from the decay of muons confined within a storage ring, has been shown to offer the ultimate sensitivity and precision. The staged implementation of the facility has been studied. The attractive hrst stage, “nuSTORM”, has the potential to make detailed and precise studies of electron- and muon-neutrino-nucleus scattering and to make exquisitely sensitive searches for sterile neutrinos. A small number of measurements do not fit the elegant three-neutrino-mixing model. These measurements can be interpreted as evidence for new “sterile neutrino” states. If confirmed, these measurements will revolutionise the held. An experimental programme is underway to investigate these anomalies. It is important that these anomalies are addressed. Short-baseline contributions to this programme should have clear synergy with the long-baseline programme. This report presents the conclusions drawn by the Panel from three regional “Town Meetings” that took place between November 2013 and February 2014. The Panel recognises that to maximise the discovery potential of the accelerator-based neutrino-oscillation programme it will be essential to exploit the infrastructures that exist at CERN, FNAL and J-PARC and the expertise and resources that reside in laboratories and institutes around the world.

Cao, J.↗
DOE OSTI2011

A New Neutrino Oscillation

Starting in the late 1960s, neutrino detectors began to see signs that neutrinos, now known to come in the flavors electron ({nu}{sub e}), muon ({nu}{sub {mu}}), and tau ({nu}{sub {tau}}), could transform from one flavor to another. The findings implied that neutrinos must have mass, since massless particles travel at the speed of light and their clocks, so to speak, don't tick, thus they cannot change. What has since been discovered is that neutrinos oscillate at two distinct scales, 500 km/GeV and 15,000 km/GeV, which are defined by the baseline (L) of the experiment (the distance the neutrino travels) divided by the neutrino energy (E). Neutrinos of one flavor can oscillate into neutrinos of another flavor at both L/E scales, but the amplitude of these oscillations is different for the two scales and depends on the initial and final flavor of the neutrinos. The neutrino states that propogate unchanged in time, the mass eigenstates {nu}1, {nu}2, {nu}3, are quantum mechanical mixtures of the electron, muon, and tau neutrino flavors, and the fraction of each flavor in a given mass eigenstate is controlled by three mixing angles and a complex phase. Two of these mixing angles are known with reasonable precision. An upper bound exists for the third angle, called {theta}{sub 13}, which controls the size of the muon neutrino to electron neutrino oscillation at an L/E of 500 km/GeV. The phase is completely unknown. The existence of this phase has important implications for the asymmetry between matter and antimatter we observe in the universe today. Experiments around the world have steadily assembled this picture of neutrino oscillation, but evidence of muon neutrino to electron neutrino oscillation at 500 km/GeV has remained elusive. Now, a paper from the T2K (Tokai to Kamioka) experiment in Japan, reports the first possible observation of muon neutrinos oscillating into electron neutrinos at 500 km/GeV. They see 6 candidate signal events, above an expected background of 1.5 events. The probability that the 6 events are all background is only about 0.7%. Stated differently, this is a 2.7{sigma} indication that the parameter that controls the oscillation, the neutrino mixing angle {theta}{sub 13}, is nonzero, just shy of the 3{sigma} requirement to claim 'evidence for.' Nevertheless, this experiment provides the strongest indication to date that this oscillation actually occurs in nature.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

DUNE-PRISM – A New Method to Measure Neutrino Oscillations

The Deep Underground Neutrino Experiment (DUNE) is a next-generation long baseline neutrino oscillation experiment designed to make precision measurements in a 1.2 2.4 MW neutrino beam, which is directed 1285 km from the Fermi National Accelerator Laboratory (Fermilab) to the Sandford Underground Research Facility (SURF) in South Dakota. Neutrinos are measured at two detector facilities: a near detector located at Fermilab close where the beam is produced and a far detector at SURF. The neutrino beam can be configured to be composed primarily of either muon or anti-muon neutrinos. DUNE measures the disappearance of muon and anti-muon neutrinos and appearance electron and anti-electron neutrinos in the neutrino beam. Measuring these neutrino flavour transitions provides DUNE with sensitivity to the neutrino mass ordering, $\delta_{CP}$, $\theta_{13}$, $\theta_{23}$ and the magnitude of $\Delta m^2_{23}$. The DUNE Precision Reaction Independent Spectrum Measurement (DUNE-PRISM) concept presents a novel way to perform a neutrino oscillation analysis, which has the potential to significantly reduce the impact of large systematic uncertainties in the neutrino interaction model. The PRISM method linearly combines measurements of off-axis neutrino interactions at the DUNE near detector to produce data-driven predictions of the oscillated neutrino event rate spectrum at the far detector. By building an oscillated far detector prediction directly from data, any unknown or poorly modelled neutrino interaction effects will be naturally incorporated into the measurement of the parameters of the neutrino oscillation model. This thesis presents the first complete neutrino oscillation analysis for DUNE using the PRISM method. Details of the methodology are fully explained and the prospects for further improvements to the techniques described are highlighted. The expected impact and relative importance of the neutrino flux, cross section and detector systematic uncertainties are described in detail. Finally, this thesis demonstrates that the PRISM method is capable of performing a measurement of the oscillation parameters that is robust against neutrino interaction modelling errors.

Hasnip, Ciaran↗
DOE OSTI2016

Measurement of the Charged-Current Quasi-Elastic Cross-Section for Electron Neutrinos on a Hydrocarbon Target

Appearance-type neutrino oscillation experiments, which observe the transition from muon neutrinos to electron neutrinos, promise to help answer some of the fundamental questions surrounding physics in the post-Standard-Model era. Because they wish to observe the interactions of electron neutrinos in their detectors, and because the power of current results is typically limited by their systematic uncertainties, these experiments require precise estimates of the cross-section for electron neutrino interactions. Of particular interest is the charged-current quasi-elastic (CCQE) process, which gures signi cantly in the composition of the reactions observed at the far detector. However, no experimental measurements of this crosssection currently exist for electron neutrinos; instead, current experiments typically work from the abundance of muon neutrino CCQE cross-section data and apply corrections from theoretical arguments to obtain a prediction for electron neutrinos. Veri cation of these predictions is challenging due to the di culty of constructing an electron neutrino beam, but the advent of modern high-intensity muon neutrino beams|together with the percent-level electron neutrino impurity inherent in these beams| nally presents the opportunity to make such a measurement. We report herein the rst-ever measurement of a cross-section for an exclusive state in electron neutrino scattering, which was made using the MINER A detector in the NuMI neutrino beam at Fermilab. We present the electron neutrino CCQE di erential cross-sections, which are averaged over neutrinos of energies 1-10 GeV (with mean energy of about 3 GeV), in terms of various kinematic variables: nal-state electron angle, nal-state electron energy, and the square of the fourmomentum transferred to the nucleus by the neutrino , Q 2 . We also provide a total cross-section vs. neutrino energy. While our measurement of this process is found to be in agreement with the predictions of the GENIE event generator, we also report on an unpredicted photon-like process we observe in a similar kinematic regime. The absence of this process from models for neutrino interactions is a potential stumbling block for future on-axis neutrino oscillation experiments. We include kinematic and particle species identi cation characterizations which can be used in building models to help address this shortcoming.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Identifying Muons for Neutrino Oscillation and Cross Section Experiments

Neutrinos ($\nu$) are interesting for many reasons; they are the only fundamental fermions which are electrically neutral; their mass is orders of magnitude smaller than the lightest charged lepton, the electron; and their solely weak interactions make them an excellent probe of the weak nuclear force. However, one of the most interesting aspects of neutrinos is that, unlike their charged lepton partners, neutrino mass and flavor eigenstates are not the same. All leptons possess 'lepton flavor', a property which is conserved in neutrino interactions. However, because of the difference in the mass and weak eigenstates of neutrinos, a quantum-interference effect is seen in the time evolution of neutrinos. This results in energy and distance dependent oscillations of the neutrino's lepton flavor called 'neutrino oscillations'. The MINOS experiment (Main Injector Neutrino Oscillation Search) was designed to measure the neutrino oscillation parameters, $\Delta m^2_{32}$ and $sin^2(2\theta_{32})$. MINOS is composed of two detectors located on a 'beam' of v[subscript mu]s. The MINOS Near Detector is located at Fermilab, and the Far Detector is located at the Soudan Mine in Minnesota, 734 km after the Near Detector. The MINER$\nu$A experiment (Main Injector Neutrino Experiment for $\nu$ - A) is a neutrino experiment placed directly in front of the MINOS Near Detector. MINER$\nu$s goal is to make precision measurements of neutrino cross sections. This will help with uncertainties in oscillation measurements, such as MINOS' at low energy. Although lepton flavor is conserved in neutrino interactions, the final state lepton can be a charged lepton ('charged current' interactions) or a neutrino ('neutral current' interactions) of a particular flavor. The identification of charged current $\nu_\mu$ interactions through the identification of a muon in the final state is a critical component to both neutrino oscillation and cross section measurements; neutral current events are a background to the oscillation signal bec! ause the properties of the incoming neutrino cannot be determined. Such identification is particularly difficult and important for low-energy neutrino events. In this thesis, we will discuss improvements to the MINOS charged current identification at low energies, studies to estimate the effect of the neutral current background on the measurement of the oscillation parameters, and the aspects of muon identification which are similar for the MINOS and MINER$\nu$A experiments. In 2010, the MINOS experiment released a measurement of the oscillation parameters based on $7.32x10^{20}$ POT. The results were $\Delta m^2_{32} = 2.32^{+.012}_{-0.08} x 10^3 eV^2$, and $sin^2(2\theta_{32}) > 0.90(90%,C.L.)$. This is the best measurement of the oscillation parameter, $\Delta m^2_{32}$, and a competitive measurement of $sin^2(2\theta_{32})$. The improvements to the charged current event selection helped MINOS observe a complete oscillation in neutrino energy.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Long-baseline Sterile Neutrino Searches in the NOvA Experiment

Experimental high energy physics constitutes the experimental investigation of the fundamental building blocks of matter and radiation and their interactions. These fundamental building blocks are classified as bosons and fermions. Neutrinos are fermions that come under the lepton category. According to the Standard Model of particle physics, they are massless, neutral particles that interacts with matter only through weak force and comes in three different flavors. Neutrinos exhibit a characteristic property, known as the neutrino oscillation. Neutrino oscillation is the the change of neutrino from one flavor to another flavor as they propagates in space. This phenomenon is only possible if the neutrinos are massive. The reported anomalous result from LSND and MiniBooNE experiments demanded the existence of a fourth kind of neutrino, at the same time, LEP experimental result confirms that only three active neutrino can exist. So if they exists, this fourth kind of neutrino can’t interact through weak force or they can be called as sterile neutrino. Some of the experiments favored the existence of sterile neutrinos, at the same time, there are some other experiments that disfavors their existence. So the search for the sterile neutrinos is very active in the field of experimental neutrino physics. NOvA is a long-baseline experiment with two functionally identical detectors, a Near Detector (ND) at Fermilab and a Far Detector at Ash River, Minnesota which is 810 km far away from the ND. They are offaxis detectors that lie 14.6 mrad off from the beam axis. This enables the detector to receive a neutrino beam with energy peak at 2 GeV. The NOvA experiment is designed to run with both the neutrino beam and antineutrino beam and NOvA has the potential to search for the existence of sterile neutrinos. This thesis is based on the sterile neutrino search by looking at the depletion of the neutral-current (NC) energy spectrum of neutrinos at the FD. Since NC events are not sensitive to three flavor oscillation, any depletion of NC events at the FD indicates the existence of sterile neutrinos.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Three-Flavor Neutrino Oscillations with MINOS+

This dissertation presents the analysis of the last two years of data from the MINOS+ long-baseline neutrino oscillation experiment. The analysis explores the data above the first oscillation maximum for neutrinos in the standard three-flavor neutrino oscillation model, adding significantly more neutrino events and constraining the model with increased precision. The analysis of the high-energy region of the MINOS+ data set, where previously there has been limited study, can help constrain alternative models or possibly show evidence of new phenomena. The predecessor to MINOS+, the MINOS experiment, measured $\nu_\mu$ disappearance and $\nu_{e}$ appearance using Fermilab's NuMI $\nu_\mu$ beam from 2005 to 2012. During this period the neutrino beam's energy spectrum was focused to peak near the first oscillation maximum. In addition to measuring accelerator beam neutrinos, the MINOS Far Detector collected a sample of atmospheric neutrinos from 2003 to 2011. With the se two samples, MINOS measured the atmospheric mass splitting, $\Delta{m}^2_{32}$, at the 5\% level and the value of $\sin^2\theta_{23}$ at the 15\% level. The data also constrained the CP violating parameter $\delta_{\rm CP}$. The MINOS+ experiment exposed the MINOS detectors to a neutrino beam peaked at energies above the oscillation maximum from 2013 to 2016. With this higher energy neutrino beam, MINOS+ measures the shape of the $\nu_\mu$ survival probability away from the oscillation maximum with unprecedented precision. Measuring the shape of the oscillation probability as a function of neutrino energy is an essential test of the three-flavor oscillation model. At these higher energies where the standard oscillation probability decreases, the neutrino energy spectrum is sensitive to potential perturbations from mixing with additional sterile neutrinos or non-standard neutrino interactions. This analysis of the complete data set from MINOS+ finds no significant deviatio ns from the three-flavor oscillation probability in the ener! gy region of 4 to 10\,GeV covered by the neutrino beam. This provides increased confidence in the three-flavor model in this region and provides new constraints of the atmospheric oscillation parameters, $\Delta{m}^2_{32}$ and $\sin^2\theta_{23}$, by combining the MINOS and MINOS+ data sets. The hierarchy of the neutrino masses is related to the sign of $\Delta{m}^2_{32}$. When $\Delta{m}^2_{32} > 0$, the mass hierarchy is classified as normal. When $\Delta{m}^2_{32} < 0$, the mass hierarchy is classified as inverted. This analysis cannot rule out either of the mass hierarchies. For the normal mass hierarchy, the combined analysis measures $\lvert{\Delta{m}^2_{32}}\rvert = 2.41\pm 0.09 \times 10^{-3}\,{\mathrm{eV}^2}$ at 68\% C.L. and $\sin^2\theta_{23} = 0.42_{-0.06}^{+0.23}$ at 90\% C.L. For the inverted mass hierarchy, this analysis measures $\lvert{\Delta{m}^2_{32}}\rvert = 2.47_{-0.10}^{+0.08} \times 10^{-3}\,{\mathrm{eV}^2}$ at 68\% C.L. and $\sin^2\theta_{23} = 0.42_{ -0.06}^{+0.23}$ at 90\% C.L. In addition to the analysis and measurement of the atmospheric oscillation parameters using MINOS+, this work updates the constraint on $\delta_{\rm CP}$ from MINOS and performs an exploratory combination using $\nu_\mu$ disappearance data from the NOvA experiment. The NOvA experiment uses the NuMI beam in an off-axis strategy that results in a narrow flux of muon neutrinos at the first oscillation maximum and allows precision measurements of the three-flavor parameters. Since NOvA and MINOS+ shared the same neutrino beam, their data can be combined taking advantage of common beam related uncertainties. Combined, the data from the MINOS, MINOS+, and NOvA experiments precisely map $\nu_\mu$ oscillation probabilities using the same neutrino beam in a way that could not be attempted before.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Nuclear Effects in Neutrino Detection

Although the interactions of neutrinos with elementary particles are described with impressive precision by the Standard Model, neutrino-nucleus reactions remain less well understood. Improvements in our knowledge of neutrino-nucleus scattering will be an important requirement for the success of future experimental efforts involving neutrinos at both low ($\sim$\SI{10}{\MeV}) and medium ($\sim$\SI{1}{\GeV}) energies. In the low energy regime, the planned DUNE experiment will attempt to observe neutrinos from a nearby core-collapse supernova using liquid argon time projection chambers (LArTPCs). Unlike other large neutrino detectors, which are primarily sensitive to electron antineutrinos, DUNE will observe mostly charged current absorptions of electron neutrinos on \isotope[40]{Ar} in response to a supernova, providing a unique window into the physics of stellar collapse. Despite the importance of low-energy neutrino-nucleus reactions to DUNE's supernova physics goals, prior to the work presented in this thesis, no thorough consideration of the many possible final states generated by neutrino-argon scattering, including those involving the emission of nucleons or heavier nuclear fragments, had yet been attempted in the literature for the energy range of interest for supernova neutrinos. To aid DUNE's supernova physics program, this thesis presents a detailed theoretical model of low-energy neutrino-argon scattering. This model has been implemented within a new event generator called MARLEY (Model of Argon Reaction Low Energy Yields) which may be used to simulate realistic $\isotope[40]{Ar}(\nu_e,e^-)\isotope[40]{K}^*$ events for LArTPC supernova neutrino sensitivity studies. At medium energies, large theoretical uncertainties in predictions of neutrino-induced neutron production present a problem for precision neutrino oscillation experiments, attempts to discover the Diffuse Supernova Neutrino Background, and searches for proton decay. To const rain the widely-varying predictions of current nuclear model! s, the Accelerator Neutrino Neutron Interaction Experiment (ANNIE) collaboration plans to make a systematic measurement of neutron production by neutrino interactions in water. Because the ANNIE experimental hall is located only \SI{100}{\meter} away from the Fermilab Booster Neutrino Beam target, background neutrons correlated in time with the beam could potentially interfere with this proposed measurement. As a first step toward ANNIE's ultimate physics goals, this thesis presents an analysis of background neutron rates as a function of position within the ANNIE detector. These rates are found to be small enough for the neutron yield measurements to proceed as planned.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗