MINOS Detectors Research Articles

Use of neutrino scattering events with low hadronic recoil to inform neutrino flux and detector energy scale

Charged-current neutrino interactions with low hadronic recoil (“low-ν”) have a cross-section that is approximately constant versus neutrino energy. These interactions have been used to measure the shape of neutrino fluxes as a function of neutrino energy at accelerator-based neutrino experiments such as CCFR, NuTeV, MINOS and MINERνA. In this paper, we demonstrate that low-ν events can be used to measure parameters of neutrino flux and detector models and that utilizationof event distributions over the upstream detector face can discriminate among parametersthat affect the neutrino flux model. From fitting a large sample of low-ν events obtained by exposing MINERνAto the NuMI medium-energy beam, we find that the best-fit flux parameters are within their a priori uncertainties, but the energy scale of muons reconstructed in the MINOS detector is shifted by 3.6% (or 1.8 times the a priori uncertainty on that parameter). These fit results are now used in all MINERνA cross-section measurements, and this technique can be applied by other experiments operating at MINERνA energies, such as DUNE.

The Results of MINOS and the Future with MINOS+

The MINOS experiment took data from 2005 up until 2012. The MINOS experiment took data from 2005 up until 2012, continuing beyond that as the MINOS+ experiment. The experiment is a two-detector, on-axis, long-baseline experiment, sending neutrinos from Fermilab to the Soudan Underground Laboratory in northern Minnesota. By searching for the deficit of muon neutrinos at the Far Detector, MINOS/MINOS+ is sensitive to the atmospheric neutrino oscillation parametersΔm322andθ23. By using the full MINOS data set looking at bothνμdisappearance andνeappearance in both neutrino and antineutrino configurations at the NuMI beam along with atmospheric neutrino data recorded at the FD, MINOS has made the most precise measurement ofΔm322. Using a full three-flavour framework and searching forνeappearance, MINOS/MINOS+ gains sensitivity toθ13, the mass hierarchy, and the octant ofθ23. Exotic phenomenon is also explored with the MINOS detectors looking for nonstandard interactions and sterile neutrinos. The current MINOS+ era goals are to build on the previous MINOS results improving the precision on the three-flavour oscillation parameter measurements and strengthening the constraints placed on the sterile neutrino parameter space.

Timing in the NOvA detectors with atomic clock based time transfers between Fermilab, the Soudan mine and the NOvA Far detector

The NOvA experiment uses a GPS based timing system both to internally synchronize the readout of the DAQ components and to establish an absolute wall clock reference which can be used to link the Fermilab accelerator complex with the neutrino flux that crosses the NOvA detectors. We describe the methods that were used during the commissioning of the NOvA DAQ and Timing systems to establish the synchronization between the Fermilab beam and the NOvA far detector. We present how high precision atomic clocks were trained and transported between the MINOS and NOvA detectors during a Northern Minnesota blizzard to validate the absolute time offsets of the experiments and make the first observation of beam neutrinos in the NOvA far detector.

Precision measurement of the speed of propagation of neutrinos using the MINOS detectors

We report a two-detector measurement of the propagation speed of neutrinos over a baseline of 734 km. The measurement was made with the NuMI beam at Fermilab between the near and far MINOS detectors. The fractional difference between the neutrino speed and the speed of light is determined to be (v/c-1) = (1.0±1.1) × 10^−6, consistent with relativistic neutrinos.

Long term performance of the MINOS calibration procedure and stability of the MINOS detectors

The MINOS detectors are steel-scintillator sampling tracking calorimeters and are calibrated using an in-situ light-injection system and cosmic ray muons. The MINOS Near and Far Detectors have been operating almost continuously since 2003 and 2005, providing opportunity to quantify the behavior of the various detector components, many of which are used in the next generation neutrino oscillation experiments, under long-term experimental operation. We report on the calibration procedure and its stability, as well as the time and temperature dependencies of the scintillator, wavelength-shifting fibers and photo-multiplier tubes.

Search for Sterile Neutrino Mixing in the MINOS Experiment

In this poster, we present a search for disappearance of active neutrinos over a baseline of 735 km using the NuMI neutrino beam and the MINOS detectors. The data analyzed correspond to an exposure of 7.1×1020 protons-on-target. MINOS utilizes the most powerful neutrino beam currently in operation measured in two locations: a near detector at Fermilab, 1 km downstream of beam production, and a far detector, 734 km further away, in northern Minnesota. The poster characterizes the MINOS ability to measure neutral-current neutrino interactions, outlines the event selection methods employed and describes results obtained for three-flavour and four-flavour neutrino oscillation models.

Measuring Neutrino Cross Sections Using an In Situ Measurement of the NuMI Neutrino Flux

A measurement of the νμ inclusive charged current cross section on iron using the MINOS Detector is presented.

Improved Measurement of Muon Antineutrino Disappearance in MINOS

We report an improved measurement of ν(μ) disappearance over a distance of 735 km using the MINOS detectors and the Fermilab Main Injector neutrino beam in a ν(μ)-enhanced configuration. From a total exposure of 2.95×10(20) protons on target, of which 42% have not been previously analyzed, we make the most precise measurement of Δm2=[2.62(-0.28)(+0.31)(stat)±0.09(syst)]×10(-3) eV2 and constrain the ν(μ) mixing angle sin2(2θ)>0.75 (90% C.L.). These values are in agreement with Δm2 and sin2(2θ) measured for ν(μ), removing the tension reported in [P. Adamson et al. (MINOS), Phys. Rev. Lett. 107, 021801 (2011).].

Search for the disappearance of muon antineutrinos in the NuMI neutrino beam

We report constraints on antineutrino oscillation parameters that were obtained by using the two MINOS detectors to measure the 7% muon antineutrino component of the NuMI neutrino beam. In the Far Detector, we select 130 events in the charged-current muon antineutrino sample, compared to a prediction of 136.4 +/- 11.7(stat) ^{+10.2}_{-8.9}(syst) events under the assumption |dm2bar|=2.32x10^-3 eV^2, snthetabar=1.0. Assuming no oscillations occur at the Near Detector baseline, a fit to the two-flavor oscillation approximation constrains |dm2bar|<3.37x10^-3 eV^2 at the 90% confidence level with snthetabar=1.0.

MINOS neutrino oscillation results

Neutrinos interact only weakly with other matter and had been thought to be massless. However, if their mass is non-zero, they could change flavors as they propagate. Recent results from observations of atmospheric, solar, and reactor neutrinos indicate that they do change flavor and these observations have provided measurements of two of the three possible mixings. The MINOS experiment is now making precise measurements of the ν μ ↔ ν τ oscillations seen in atmospheric neutrinos, and extends our reach towards the so far unseen angle θ 1 3 by looking for ν e appearance from the ν μ beam. It does so by using the intense, well-understood NuMI neutrino beam created at Fermilab and observing it 735 km away at the Soudan Mine in Northeast Minnesota. This combination also allows investigation of the oscillation properties of anti-neutrinos, as the NuMI beam can focus opposite-charged pions to produce the anti-neutrinos, and the MINOS detectors are magnetized, allowing event-by-event discrimination of the resulting muon charge-sign.

Measurement of the Neutrino Mass Splitting and Flavor Mixing by MINOS

Measurements of neutrino oscillations using the disappearance of muon neutrinos from the Fermilab NuMI neutrino beam as observed by the two MINOS detectors are reported. New analysis methods have been applied to an enlarged data sample from an exposure of 7.25×10(20) protons on target. A fit to neutrino oscillations yields values of |Δm(2)|=(2.32(-0.08)(+0.12))×10(-3) eV(2) for the atmospheric mass splitting and sin(2)(2θ)>0.90 (90% C.L.) for the mixing angle. Pure neutrino decay and quantum decoherence hypotheses are excluded at 7 and 9 standard deviations, respectively.

A BRIEF REVIEW OF MINOS NEUTRINO OSCILLATION RESULTS

The MINOS long-baseline experiment is using the NuMI neutrino beam to make precise measurements of neutrino flavor oscillations in the "atmospheric" neutrino sector. MINOS observes the νμ disappearance oscillations seen in atmospheric neutrinos, tests possible disappearance to sterile ν by measuring the neutral current flux, and extends our reach towards the so far unseen θ13 by looking for νe appearance in this νμ beam. The magnetized MINOS detectors also allow tests of CPT conservation by discriminating between neutrinos and anti-neutrinos on an event-by-event basis. The intense, well-understood NuMI neutrino beam created at Fermilab is observed 735 km away at the Soudan Mine in Northeast Minnesota. High-statistics studies of the neutrino interactions themselves and the cosmic rays seen by the MINOS detectors have also been made. MINOS started taking beam data in May 2005 and is now nearing the end of its five-year run. This paper reviews results published based on the first several years of data.

Search for sterile neutrino mixing in the MINOS long-baseline experiment

A search for depletion of the combined flux of active neutrino species over a 735 km baseline is reported using neutral-current interaction data recorded by the MINOS detectors in the NuMI neutrino beam. Such a depletion is not expected according to conventional interpretations of neutrino oscillation data involving the three known neutrino flavors. A depletion would be a signature of oscillations or decay to postulated non-interacting "sterile" neutrinos, scenarios not ruled out by existing data. From an exposure of 3.18x10^{20} protons on target in which neutrinos of energies between ~500 MeV and 120 GeV are produced predominantly as nu_mu, the visible energy spectrum of candidate neutral-current reactions in the MINOS far detector is reconstructed. Comparison of this spectrum to that inferred from a similarly selected near detector sample shows that of the portion of the nu_mu flux observed to disappear in charged-current interaction data, the fraction that could be converting to a sterile state is less than 52% at 90% confidence level (C.L.). The hypothesis that active neutrinos mix with a single sterile neutrino via oscillations is tested by fitting the data to various models. In the particular four-neutrino models considered, the mixing angles theta_{24} and theta_{34} are constrained to be less than 11 degrees and 56 degrees at 90% C.L., respectively. The possibility that active neutrinos may decay to sterile neutrinos is also investigated. Pure neutrino decay without oscillations is ruled out at 5.4 standard deviations. For the scenario in which active neutrinos decay into sterile states concurrently with neutrino oscillations, a lower limit is established for the neutrino decay lifetime tau_3/m_3 > 2.1x10^{-12} s/eV at 90% C.L..

Current MINOS neutrino oscillation results

The MINOS experiment is now making precise measurements of the νμ disappearance oscillations seen in atmospheric neutrinos, tests possible disappearance to sterile ν by measuring the neutral current flux, and has extended our reach towards the so far unseen θ13 by looking for νe appearance in the νμ beam. It does so by using the intense, well-understood NuMI neutrino beam created at Fermilab and observing it 735km away at the Soudan Mine in Northeast Minnesota. High-statistics studies of the neutrino interactions themselves and the cosmic rays seen by the MINOS detectors have also been made. Results from MINOS' first three years of operations will be presented.

Cosmic ray studies with the MINOS detectors

The MINOS experiment uses two layered scintillator and steel detectors along with a muon neutrino beam to search for νμ disappearance, and thus neutrino oscillations. The Far Detector (‘FD’) is situated in a former iron mine in the Soudan Underground Mine State Park in Northeastern MN, 700 m (2070 mwe) below the surface. This 5.4 kt steel/scintillator calorimeter measures the neutrino flux after they have traveled the 735 km baseline. It also detects atmospheric neutrinos at a rate of several per week, and is the first magnetized atmospheric neutrino detector, able to discriminate between νμ and νμ on an event-by-event basis. The similar 1 kt Near Detector (‘ND’) is 100 m (220 mwe) underground at Fermilab. This poster discusses the science being done with the high energy cosmic ray muons which penetrate the rock overburden and are seen by the detectors. The typical surface energy of those seen at the FD are ∼1 TeV (coming from ∼8 TeV primary cosmic rays) and ∼110 GeV at the ND (∼900 GeV primaries).

Measurement of Neutrino Oscillations with the MINOS Detectors in the NuMI Beam

This Letter reports new results from the MINOS experiment based on a two-year exposure to muon neutrinos from the Fermilab NuMI beam. Our data are consistent with quantum-mechanical oscillations of neutrino flavor with mass splitting |Deltam2| = (2.43+/-0.13) x 10(-3) eV2 (68% C.L.) and mixing angle sin2(2theta) > 0.90 (90% C.L.). Our data disfavor two alternative explanations for the disappearance of neutrinos in flight: namely, neutrino decays into lighter particles and quantum decoherence of neutrinos, at the 3.7 and 5.7 standard-deviation levels, respectively.

Neutrino oscillation results from MINOS

We report an updated measurement of muon neutrino disappearance in the NuMI neutrino beam performed using the MINOS detectors. This preliminary result is based on an increased data set corresponding to 2.50 × 1020 protons on the NuMI target, and incorporates a number of improvements to our analysis. We observe 563 candidate vμ CC interactions in the far detector data, compared with an expectation of 738 ± 30 in the absence of oscillations. A maximum likelihood fit to the observed far detector energy spectrum assuming two-flavour vμ → vτ oscillations yields best fit oscillation parameters of Δm223 = 2.38+0.20−0.16 × 10−3eV2 and sin22θ23 = 1.00−0.08 with errors quoted at the 68% confidence level.

Measurement of neutrino velocity with the MINOS detectors and NuMI neutrino beam

The velocity of a similar to 3 GeV neutrino beam is measured by comparing detection times at the near and far detectors of the MINOS experiment, separated by 734 km. A total of 473 far detector neutrino events was used to measure (nu - c)/c=5.1 +/- 2.9 x 10(-5) (at 68% C.L.). By correlating the measured energies of 258 charged-current neutrino events to their arrival times at the far detector, a limit is imposed on the neutrino mass of m(nu)50 MeV/c(2) (99% C.L.).

Measurement of the atmospheric muon charge ratio at TeV energies with the MINOS detector

The 5.4 kton MINOS far detector has been taking charge-separated cosmic ray muon data since the beginning of August, 2003 at a depth of 2070 meters-water-equivalent in the Soudan Underground Laboratory, Minnesota, USA. The data with both forward and reversed magnetic field running configurations were combined to minimize systematic errors in the determination of the underground muon charge ratio. When averaged, two independent analyses find the charge ratio underground to be 1.374 +/- 0.004 (stat.) +0.012 -0.010(sys.). Using the map of the Soudan rock overburden, the muon momenta as measured underground were projected to the corresponding values at the surface in the energy range 1-7 TeV. Within this range of energies at the surface, the MINOS data are consistent with the charge ratio being energy independent at the two standard deviation level. When the MINOS results are compared with measurements at lower energies, a clear rise in the charge ratio in the energy range 0.3 -- 1.0 TeV is apparent. A qualitative model shows that the rise is consistent with an increasing contribution of kaon decays to the muon charge ratio.

First MINOS Results with the NuMI Beam

The results from the initial exposure of the MINOS detectors to neutrinos produced by the Fermilab NuMI beam are reported here. The exposure consisted of 1.27 × 10 20 120 GeV protons incident on the NuMI target. The data show the observation of 215 neutrinos with energies below 30 GeV while 336 ± 14.4 events were expected. The data are consistent with ν μ disappearance via neutrino oscillations with | Δ m 23 2 | = 2.74 −0.26 +0.44 × 10 −3 eV 2 / c 4 and sin 2 2 θ 23 > 0.87 (68% C.L.).