Search For Sterile Neutrinos Research Articles

DAEδALUS: A Path to [formula omitted] Using Cyclotron Decay-at-Rest Neutrino Sources

DAEδALUS is a proposed phased neutrino experiment to search for evidence of CP violation in the neutrino sector, which also provides a rich physics program at each stage of development. The final experiment will comprise several cyclotron-based accelerator units located at three different distances from a single, large underground detector such as LENA, MEMPHYS, or Hyper-K and search for evidence of CP violation in the oscillation probability of muon antineutrinos to electron antineutrinos over baselines of ∼ 20 km. This novel type of search will complement and extend the reach of conventional experiments designed to search for CP violation in neutrino oscillations such as the Long Baseline Neutrino Experiment (LBNE). IsoDAR is a separate proposed experiment possible at an early stage in the development of DAEδALUS. It is a definitive search for sterile neutrinos, capable of ruling out the parameter space allowed by global fits to the Reactor, SAGE, and GALLEX anomalies at 20σ(5σ) in 5 years (4 months).

IceCube Neutrinos: from Oscillations to PeV-Energy Events

With IceCube and its low-energy extension DeepCore, a neutrino detector with an energy reach from tens of gigaelectronvolt to exaelectronvolt has been commissioned. It measures the atmospheric neutrino spectrum from the lower energies where neutrinos oscillate to energies as large as 100 TeV with a statistic of more than 100,000 events per year. The initial results suggest that IceCube can measure the oscillation parameters in an energy range that exceeds existing observations by 1 order of magnitude, thus opening a new window on neutrino physics. We emphasize the search for sterile neutrinos particularly relevant to cosmology. We also discuss the first observation of (PEV) petaelectronvolt-Energy events that cannot be accommodated by the flux anticipated by extrapolation of the present atmospheric neutrino measurements.

NESSiE: An experimental search for sterile neutrinos with the CERN-SPS beam

NESSiE (Neutrino Experiment with SpectrometerS in Europe) is an experiment dedicated to the search for sterile neutrinos beyond the Standard Model with the CERN-SPS neutrino beam. The experiment is based on two identical LAr-TPC's followed by magnetized spectrometers, observing the electron and muon neutrino events at the “Near” (600m) and “Far” (1300m) positions from the proton target. The main characteristics of the spectrometers are described here. Spectrometers will exploit a classical dipole magnetic field with iron slabs, and a new concept air-core magnet will perform charge identification and muon momentum measurements in the energy range from ∼100MeV to few GeV over a large transverse area (>50m2).

A proposed search for sterile neutrinos with the ICARUS detector at the CERN-PS

An experiment to search for sterile neutrinos beyond the Standard Model with the CERN-PS 19.2 GeV beam and the technology of imaging in ultra-pure cryogenic liquid Argon is proposed. The superior quality of the LAr-TPC, now widely demonstrated experimentally and in particular its unique e/π0 discrimination allows a full rejection of backgrounds, offers the possibility to explore the neutrino conversion into sterile components as recently suggested by the analysis of different observed neutrino anomalies.The experiment is based on two identical LAr-TPC detectors observing the electron-neutrino signal in the Near and Far positions, the first of about 150 tons at 127 m from the proton target, the second one of about 600 tons placed 850 m away. This project will exploit the largest LAr-TPC ever built, ICARUS T600 now running underground at LNGS exposed to CNGS neutrino beam, by moving it from Gran Sasso to the CERN Far position. An additional 150 t detector will be constructed in the Near position. The intrinsic νE beam spectra are expected practically identical in the two positions; in addition all cross-sections and experimental biases cancel out in the comparison of the two detector signals allowing to perform a sensitive search for neutrino oscillations in the presence of sterile neutrinos.

Recent results and future development of Borexino

This paper summarizes the main recent results of the Borexino experiment, a liquid scintillator neutrino detector of unprecedented radiopurity currently running at the Laboratori Nazionali del Gran Sasso in Italy. Particularly, the paper is focused on the precision measurement of the 7Be solar neutrino flux, on the search of its day–night modulation, and on the first detection of pep neutrinos. The paper also covers a recent measurement of the CNGS neutrinos speed made in May 2012. A short discussion about the forthcoming scientific program on solar neutrinos, geoneutrinos, and sterile neutrino searches is included at the end.

Evidence and Search for Sterile Neutrinos at Accelerators

The LSND short-baseline neutrino experiment has published evidence for antineutrino oscillations at a mass scale of ~1 eV2. The MiniBooNE experiment, designed to test this evidence for oscillations at an order of magnitude higher neutrino energy and distance, observes excesses of events in both neutrino mode and antineutrino mode. While the MiniBooNE neutrino excess has a neutrino energy spectrum that is softer than expected from LSND, the MiniBooNE antineutrino excess is consistent with neutrino oscillations and with the LSND oscillation signal. When combined with oscillation measurements at the solar and atmospheric mass scales, assuming that the LSND and MiniBooNE signals are due to neutrino oscillations, these experiments imply the existence of more than three neutrino mass states and, therefore, one or more sterile neutrinos. Such sterile neutrinos, if proven to exist, would have a big impact on particle physics, nuclear physics, and astrophysics and would contribute to the dark matter of the universe. Future experiments under construction or proposed at Fermilab, ORNL, CERN, and in Japan will provide a definitive test of short-baseline neutrino oscillations and will have the capability of proving the existence of sterile neutrinos.

An Appraisal of Muon Neutrino Disappearance at Short Baseline

Neutrino physics is nowadays receiving more and more attention as a possible source of information for the long-standing problem of new physics beyond the Standard Model. The recent measurement of the third mixing angle <svg style="vertical-align:-3.39066pt;width:20.637501px;" id="M1" height="16.450001" version="1.1" viewBox="0 0 20.637501 16.450001" width="20.637501" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,12.162)"><path id="x1D703" d="M475 507q0 -83 -20 -172t-56 -167.5t-93.5 -129t-125.5 -50.5q-157 0 -157 227q0 78 21.5 164t59 161t96.5 123.5t126 48.5q79 0 114 -58t35 -147zM391 522q0 155 -81 155q-62 0 -111 -82.5t-73 -200.5h253q12 81 12 128zM373 346h-255q-12 -91 -12 -150q0 -72 20 -123&#xA;t63 -51q34 0 64 28.5t52.5 77t39 103t28.5 115.5z" /></g> <g transform="matrix(.012,-0,0,-.012,8.525,16.25)"><path id="x31" d="M384 0h-275v27q67 5 81.5 18.5t14.5 68.5v385q0 38 -7.5 47.5t-40.5 10.5l-48 2v24q85 15 178 52v-521q0 -55 14.5 -68.5t82.5 -18.5v-27z" /></g><g transform="matrix(.012,-0,0,-.012,14.236,16.25)"><path id="x33" d="M285 378v-2q65 -13 102 -54.5t37 -97.5q0 -57 -30.5 -104.5t-74 -75t-85.5 -42t-72 -14.5q-31 0 -59.5 11t-40.5 23q-19 18 -16 36q1 16 23 33q13 10 24 0q58 -51 124 -51q55 0 88 40t33 112q0 64 -39 96.5t-88 32.5q-29 0 -64 -11l-6 29q77 25 118 57.5t41 84.5&#xA;q0 45 -26.5 69.5t-68.5 24.5q-67 0 -120 -79l-20 20l43 63q51 56 127 56h1q66 0 107 -37t41 -95q0 -42 -31 -71q-22 -23 -68 -54z" /></g> </svg> in the standard mixing oscillation scenario encourages us to pursue the still missing results on leptonic CP violation and absolute neutrino masses. However, several puzzling measurements exist which deserve an exhaustive evaluation. We will illustrate the present status of the muon disappearance measurements at small <svg style="vertical-align:-2.22495pt;width:27.575001px;" id="M2" height="14.85" version="1.1" viewBox="0 0 27.575001 14.85" width="27.575001" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,12.012)"><path id="x1D43F" d="M559 163q-23 -66 -68 -163h-474l6 26q62 4 79.5 19.5t28.5 75.5l78 409q7 35 8.5 49t-8 25t-24 13t-51.5 5l5 28h266l-6 -28q-65 -5 -79.5 -18t-25.5 -74l-76 -406q-10 -57 14 -75q12 -13 96 -13q93 0 126 29q41 40 76 109z" /></g><g transform="matrix(.017,-0,0,-.017,9.769,12.012)"><path id="x2F" d="M368 703l-264 -866h-60l265 866h59z" /></g><g transform="matrix(.017,-0,0,-.017,16.772,12.012)"><path id="x1D438" d="M609 650l-19 -162l-30 -2q2 69 -14 94q-9 18 -28.5 26t-74.5 8h-88q-30 0 -37 -6.5t-12 -36.5l-41 -212h103q48 0 69 5.5t32 19t26 50.5h29l-40 -198h-30q2 58 -11.5 70.5t-85.5 12.5h-99l-30 -167q-17 -87 3 -101q18 -15 111 -15q59 0 89 7t54 27q8 7 15.5 16t16 21.5&#xA;l14 20.5t15 23.5t13.5 21.5l29 -10q-52 -129 -71 -163h-500l6 28q66 4 83 17.5t28 73.5l77 409q11 61 -0.5 75.5t-78.5 18.5l10 28h467z" /></g> </svg> and the current CERN project to revitalize the neutrino field in Europe with emphasis on the search for sterile neutrinos. We will then illustrate the achievements that a double muon spectrometer can make with regard to discovery of new neutrino states, using a newly developed analysis.

Search for Sterile Neutrinos Including Recent Results from the ICARUS Detector in the CNGS Neutrino Beam

Search for Sterile Neutrinos Including Recent Results from the ICARUS Detector in the CNGS Neutrino Beam

Search for new physics with neutrinos at radioactive ion beam facilities

We propose applications of radioactive ion beam facilities to investigate physics beyond the Standard Model. In particular, we focus upon the search for sterile neutrinos and the possible measurement of coherent neutrino-nucleus scattering, by means of a low-energy beta beam with a Lorentz boost factor $\ensuremath{\gamma}\ensuremath{\approx}1$. In both cases, we consider $^{8}\mathrm{Li}$ and $^{8}\mathrm{B}$ ions as neutrino sources. In the considered setup, the collected radioactive ions are sent inside a $4\ensuremath{\pi}$ detector. For the first application, we provide the number of events associated with neutrino-nucleus coherent scattering, when the detector is filled with a noble liquid. For the sterile search, we consider that the spherical detector is filled with a liquid scintillator, and that the neutrino detection channel is inverse beta decay. We provide the exclusion curves for the sterile neutrino mixing parameters, based upon the $3+1$ formalism, depending upon the achievable ion intensity. Our results are obtained both from total rates, and by including spectral information with binning in energy and in distance. The proposed experiment represents a possible alternative to clarify the current anomalies observed in neutrino experiments.

Artificial neutrino source experiment in Borexino

An experiment with an artificial neutrino source in Borexino is presented. The neutrino source can be located outside the detector or eventually, at the end of the solar neutrino phase, could be deployed inside. The physics case for the source experiment includes the search for short-baseline neutrino oscillations, neutrino-electron scattering at sub-MeV range, neutrino magnetic moment. Preliminary predictions of the sensitivity are reported for the sterile neutrino search.

Experimental bounds on sterile neutrino mixing angles

Abstract We derive bounds on the mixing between the Standard Model (“active”) neutrinos and their right-chiral (“sterile”) counterparts in the see-saw models, by combining neutrino oscillation data and results of direct experimental searches. We demonstrate that the mixing of sterile neutrinos with any active flavour can be significantly suppressed for the values of the angle θ 13 measured recently by Daya Bay and RENO experiments. We reinterpret the results of searches for sterile neutrinos by the PS191 and CHARM experiments, considering not only charged current but also neutral current-mediated decays, as applicable in the case of see-saw models. The resulting lower bounds on sterile neutrino lifetime are up to an order of magnitude stronger than previously discussed in the literature. Combination of these results with the upper bound on the lifetime coming from primordial nucleosynthesis rule out the possibility that two sterile neutrinos with the masses between 10 MeV and the pion mass are solely responsible for neutrino flavour oscillations. We discuss the implications of our results for the Neutrino Minimal Standard Model (the νMSM).

Active to sterile neutrino oscillations: Coherence and MINOS results

We study the νμ–νs oscillation effects in the near detector of the MINOS experiment. Conceptually, the MINOS search for sterile neutrinos with mass ∼1 eV realizes an interesting situation of partial decoherence of the neutrino state at the production. This corresponds to a difference of energies of the two mass eigenstates that is comparable with or bigger than the width of the initial state (pion). We show that these effects modify the MINOS bound on mixing of sterile neutrino for Δm412≳0.5 eV2 and make the experiment insensitive to oscillations with Δm412≳15 eV2. Oscillations with Δm412=(1–3) eV2 could explain some deficit of events observed in the low energy bins in the near detector and correspondingly the excess of events in the far detector.

Search for sterile neutrinos at reactors

The sensitivity to the sterile neutrino mixing at very short baseline reactor neutrino experiments is investigated. In the case of conventional (thermal neutron) reactors it is found that the sensitivity is lost for $\Delta m^2 \gtrsim$ 1 eV$^2$ due to smearing of the reactor core size. On the other hand, in the case of an experimental fast neutron reactor Joyo, because of its small size, sensitivity to $\sin^22\theta_{14}$ can be as good as 0.03 for $\Delta m^2 \sim$ several eV$^2$ with the Bugey-like detector setup.

The T2K experiment

The T2K experiment is a long-baseline neutrino oscillation experiment. Its main goal is to measure the last unknown lepton sector mixing angle {\theta}_{13} by observing {\nu}_e appearance in a {\nu}_{\mu} beam. It also aims to make a precision measurement of the known oscillation parameters, {\Delta}m^{2}_{23} and sin^{2} 2{\theta}_{23}, via {\nu}_{\mu} disappearance studies. Other goals of the experiment include various neutrino cross section measurements and sterile neutrino searches. The experiment uses an intense proton beam generated by the J-PARC accelerator in Tokai, Japan, and is composed of a neutrino beamline, a near detector complex (ND280), and a far detector (Super-Kamiokande) located 295 km away from J-PARC. This paper provides a comprehensive review of the instrumentation aspect of the T2K experiment and a summary of the vital information for each subsystem.

Swift observation of Segue 1: constraints on sterile neutrino parameters in the darkest galaxy

Abstract Some extensions of standard particle physics postulate that dark matter may be partially composed of weakly interacting sterile neutrino particles that have so far eluded detection. We use a short (∼5 ks) archival X-ray observation of Segue 1 obtained with the X-ray Telescope (XRT) onboard the Swift satellite to exclude the presence of sterile neutrinos in the 1.6–14 keV mass range down to a flux limit of 6 × 10−12 erg cm−2 s−1 within 67 pc of its centre. With an estimated mass-to-light ratio of ∼3400 M⊙/L⊙, Segue 1 is the darkest ultrafaint dwarf galaxy currently measured. Spectral analysis of the Swift XRT data fails to find any non-instrumental spectral feature possibly connected with the radiative decay of a dark matter particle. Accordingly, we establish upper bounds on the sterile neutrino parameter space based on the non-detection of emission lines in the spectrum. The present work provides the most sensitive X-ray search for sterile neutrinos in a region with the highest dark matter density yet measured.

Kinematic reconstruction of atmospheric neutrino events in a large water Cherenkov detector with proton identification

We report the development of a proton identification method for the Super-Kamiokande (SK) detector. This new tool is applied to the search for events with a single proton track, a high purity neutral current sample of interest for sterile neutrino searches. After selection using a neural network, we observe 38 events in the combined SK-I and SK-II data corresponding to 22 85.1 days of exposure, with an estimated signal-to-background ratio of 1.6 to 1. Proton identification was also applied to a direct search for charged-current quasielastic (CCQE) events, obtaining a high precision sample of fully kinematically reconstructed atmospheric neutrinos, which has not been previously reported in water Cherenkov detectors. The CCQE fraction of this sample is 55%, and its neutrino (as opposed to antineutrino) fraction is 91.7{+-}3%. We selected 78{mu}-like and 47 e-like events in the SK-I and SK-II data set. With this data, a clear zenith angle distortion of the neutrino direction itself is reported in a sub-GeV sample of {mu} neutrinos where the lepton angular correlation to the incoming neutrino is weak. Our fit to {nu}{sub {mu}}{yields}{nu}{sub {tau}} oscillations using the neutrino (L/E) distribution of the CCQE sample alone yields a wide acceptance region compatible with our previousmore » results and excludes the no-oscillation hypothesis at 3-sigma.« less

Sterile neutrinos at future long baseline experiments

We review the current status of sterile neutrino searches and discuss the potential of future long baseline experiments to study their properties.

Neutral current interactions in MINOS: A search for sterile neutrinos

The Main Injector Neutrino Oscillation Search (MINOS) long baseline experiment has been taking beam data since 2005, having accumulated 4.2 x 10^20 protons-on-target to date. MINOS utilizes the most powerful neutrino beam currently in operation, measuring it in two locations: a Near detector at Fermilab, close to beam production, and a Far detector, 735 km downstream, in Northern Minnesota. Although the measurement of oscillations between active neutrino flavours is the primary goal of MINOS, important contributions can be extracted from studies of neutral current neutrino interactions in the detectors. The several million neutrinos per year observed at the Near detector may improve the existing body of knowledge of neutrino cross sections and the Near-Far comparison of the observed energy spectrum for neutral current events constrains exotic models such as oscillations into sterile neutrinos. This poster outlines the MINOS capabilities of observing neutral current neutrino interactions, describes the employed methodology for event selection and shows preliminary results obtained with an exposure of 2.46 x 10^20 protons-on-target. Comparisons with 3-flavour and 4-flavour neutrino oscillation models are shown. An outlook on the expected improvements as MINOS accumulates more data is also presented.

Recoilless resonant emission and detection of electron antineutrinos

Recoilless resonant capture of monoenergetic electron antineutrinos (Mössbauer antineutrinos) emitted in bound-state β-decay in the system 3H – 3He is discussed. The recoilfree fraction including a possible phonon excitation due to local lattice expansion and contraction at the time of the nuclear transition, homogeneous and inhomogeneous line broadening, and the relativistic second-order Doppler effect are considered. It is demonstrated that homogeneous line broadening is essential due to stochastic magnetic relaxation processes in a metallic lattice. Inhomogeneous line broadening plays an equally important role. An essential issue which has been overlooked up to now, is an energy shift of the resonance line due to the direct influence of the binding energies of the 3H and 3He atoms in the lattice on the energy of the electron antineutrinos. This energy shift as well as the second-order Doppler shift exhibit variations in a non-perfect (inhomogeneous) lattice and may seriously jeopardize the observation of Mössbauer antineutrinos. If successful in spite of these enormous difficulties, Mössbauer antineutrino experiments could be used to gain new and deep insights into the nature of neutrino oscillations, determine the neutrino mass hierarchy as well as up to now unknown oscillation parameters, search for sterile neutrinos, and measure the gravitational redshift of electron antineutrinos in the field of the Earth.

OscSNS: Precision neutrino measurements at the Spallation Neutron Source

The Spallation Neutron Source (SNS), located at Oak Ridge Laboratory [1] in the United States, will be coming online over the next few years. In addition to producing fluxes of high-intensity neutrons, the interaction of the proton beam with the liquid mercury target produces copious pions. The π+ and subsequent μ+ decay at rest, providing a neutrino beam comprising νμ, νe, and anti-νμ components. This neutrino beam is ideal for high-precision neutrino experiments. OscSNS [2] is a proposed multi-purpose experiment that will perform a search for light sterile neutrinos, search for beyond the Standard Model interactions using neutrino oscillations, and provide tests of Standard Model predictions through world-record precision neutrino cross section measurements. OscSNS plans to submit a full proposal for funding in 2009.