We report the results of a search for νe appearance in a νµ beam in the MINOS long-baseline neutrino experiment. With an improved analysis and an increased exposure of 8.2 × 10 20 protons on the NuMI target at Fermilab, we find that 2 sin 2 (θ23) sin 2 (2θ13) < 0.12 (0.20) at 90% confidence level for δ=0 and the normal (inverted) neutrino mass hierarchy, with a best fit of 2 sin 2 (θ23) sin 2 (2θ13) = 0.041−0.031 (0.079−0.053 ). The θ13=0 hypothesis is disfavored by the MINOS data at the 89% confidence level.PACS numbers: 14.60. Pq, 14.60.Lm, arXiv:1108.0015v1 [hep-ex] 29 Jul 2011 2 It has been experimentally established that neutrinos undergo flavor change as they propagate [1][2][3][4][5][6][7]. This phenomenon is well-described by three-flavor neutrino oscillations, characterized by the spectrum of neutrino masses together with the elements of the PMNS mixing matrix [8]. This matrix is often parametrized by three Euler angles θ ij and a CP-violating phase δ. While θ 12 and θ 23 are known to be large [1,4,6], θ 13 appears to be relatively small [9][10][11][12][13], with the tightest limits so far coming from the CHOOZ [10] and MINOS [12] experiments. The T2K collaboration has recently reported indications of a nonzero value for θ 13 at the 2.5σ confidence level (C.L.) [14]. This letter reports new θ 13 constraints from the MINOS experiment, using an increased data set and significant improvements to the analysis.MINOS is a two-detector long-baseline neutrino oscillation experiment situated along the NuMI neutrino beamline [15]. The 0.98-kton Near Detector (ND) is located on-site at Fermilab, 1.04 km downstream of the NuMI target. The 5.4-kton Far Detector (FD) is located 735 km downstream in the Soudan Underground Laboratory. The two detectors have nearly identical designs, each consisting of alternating layers of steel (2.54 cm thick) and plastic scintillator (1 cm). The scintillator layers are constructed from optically isolated, 4.1 cm wide strips that serve as the active elements of the detectors. The strips are read out via optical fibers and multi-anode photomultiplier tubes. Details can be found in Ref. [16].The data used in this analysis come from an exposure of 8.2×1020 protons on the NuMI target. The corresponding neutrino events in the ND have an energy spectrum that peaks at 3 GeV and a flavor composition of 91.7% ν µ , 7.0% ν µ , and 1.3% ν e +ν e , as estimated by beamline and detector Monte Carlo (MC) simulations, with additional constraints from MINOS ND data and external measurements [6,17]. The two-detector arrangement and the relatively small intrinsic ν e component make this analysis rather insensitive to beam uncertainties. Neutrino-nucleus and final-state interactions are simulated using NEUGEN3 [18], and particle propagation and detector response are simulated with GEANT3 [19].MINOS is sensitive to θ 13 through ν µ → ν e oscillations. To leading order, the probability for this oscillation mode is given bywhere ∆m 2 32 (in units of eV 2 ) and θ 23 are the dominant atmospheric oscillation...

The Main Injector Neutrino Oscillation Search (MINOS) experiment uses an acceleratorproduced neutrino beam to perform precision measurements of the neutrino oscillation parameters in the "atmospheric neutrino" sector associated with muon neutrino disappearance. This long-baseline experiment measures neutrino interactions in Fermilab's NuMI neutrino beam with a near detector at Fermilab and again 735 km downstream with a far detector in the Soudan Underground Laboratory in northern Minnesota. The two detectors are magnetized steel-scintillator tracking calorimeters. They are designed to be as similar as possible in order to ensure that differences in detector response have minimal impact on the comparisons of event rates, energy spectra and topologies that are essential to MINOS measurements of oscillation parameters. The design, construction, calibration and performance of the far and near detectors are described in this paper.

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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.

The NOvA experiment has seen a 4.4σ signal ofν e appearance in a 2 GeVν μ beam at a distance of 810 km. Using 12.33 × 10 20 protons on target delivered to the Fermilab NuMI neutrino beamline, the experiment recorded 27ν μ →ν e candidates with a background of 10.3 and 102ν μ →ν μ candidates. This new antineutrino data are combined with neutrino data to measure the parameters jΔm 2 32 j ¼ 2.48 þ0.11 −0.06 × 10 −3 eV 2 =c 4 and sin 2 θ 23 in the ranges from (0.53-0.60) and (0.45-0.48) in the normal neutrino mass hierarchy. The data exclude most values near δ CP ¼ π=2 for the inverted mass hierarchy by more than 3σ and favor the normal neutrino mass hierarchy by 1.9σ and θ 23 values in the upper octant by 1.6σ.

2016-12-23T18:47:23

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We report on νe andνe appearance in νµ andνµ beams using the full MINOS data sample. The comparison of these νe andνe appearance data at a 735 km baseline with θ13 measurements by reactor experiments probes δ, the θ23 octant degeneracy, and the mass hierarchy. This analysis is the first use of this technique and includes the first accelerator long-baseline search forνµ →νe. Our data disfavor 31% (5%) of the three-parameter space defined by δ, the octant of the θ23, and the mass hierarchy at the 68% (90%) C.L. We measure a value of 2sin 2 (2θ13)sin 2 (θ23) that is consistent with reactor experiments. 2PACS numbers: 14.60. Pq, 14.60.Lm, The neutrino oscillation phenomenon is successfully modeled by a theory of massive neutrino eigenstates that are different from the neutrino flavor eigenstates. These sets of eigenstates are related by the PMNS matrix [1] which is commonly parameterized by three angles, θ ij , and a CP-violating phase, δ.The values of θ 12 and θ 23 have been measured [2-4] with indications that θ 23 is not maximal [5][6][7]. The final angle, θ 13 , is now known to have a nonzero value from measurements by reactor experiments [8][9][10], the measurement by the T2K [11] accelerator experiment, and from earlier MINOS results [12,13].Despite these accomplishments, the value of δ is still unknown, as is the ordering of the neutrino masses, which is referred to as the neutrino mass hierarchy. Much of the attention in the neutrino community is now focused on resolving these unknowns. The mass hierarchy is not only a fundamental property of neutrinos but also has a direct impact on the ability of neutrinoless double beta decay searches to state definitively whether the neutrino is its own antiparticle [14]. Reactor experiments make a pure measurement of θ 13 , whereas the ν µ → ν e and ν µ →ν e appearance probabilities measured by accelerator experiments such as MINOS depend on the value of δ and sin 2 (θ 23 ). In addition, the long-baseline of MI-NOS means that interactions between neutrinos and the matter of the Earth make the appearance probabilities dependent on the neutrino mass hierarchy [15,16].We report the result from the search for ν e (ν e ) appearance in a ν µ (ν µ ) beam using the full MINOS data sample. This result uses an exposure of 10.6 × 10 20 protons-ontarget taken with a ν beam and an exposure of 3.3 × 10 20 protons-on-target taken with aν beam. The neutrino sample is 30% larger than the sample used for the previous MINOS results on this topic [13]. This analysis represents the first long-baseline search forν µ →ν e appearance and places new constraints on θ 13 and on a combination of δ, θ 23 , and the neutrino mass hierarchy.In the MINOS experiment [17], neutrino oscillation is studied with the NuMI beamline [18] by measuring neutrino interactions in two detectors. The Near Detector (ND), which has a fiducial mass of 29 tons, is at a distance of 1.04 km from the production target and is used to determine the composition of the beam before the neutrinos have oscillated. The Far Detector...