MINOS Experiment Research Articles

Measurement of the off-axis NuMI Neutrinos

An analysis of the off-axis beam is discussed. Fermi National Accelerator Laboratory has two beam lines that produce neutrinos: the Booster Neutrino Beam (BNB) and the NuMI beam line. The BNB beam is designed for use by the MiniBooNE experiment. The NuMI beam produces neutrinos for the MINOS experiment and it will be supplying the NOνA experiment with neutrinos. The MiniBooNE detector also observes neutrinos from the NuMI beamline, at an off-axis angle of 6.3 degrees. Samples of charged current quasi-elastic (CCQE) νμ and νe interactions were analyzed.

Quark-lepton complementarity revisited

We reexamine the quark-lepton complementarity (QLC) in nine angle-phase parametrizations with the latest result of a large lepton mixing angle $\vartheta_{13}$ from the T2K, MINOS and Double Chooz experiments. We find that there are still two QLC relations satisfied in P1, P4 and P6 parametrizations, whereas only one QLC relation holds in P2, P3, P5 and P9 parametrizations separately. We also work out the corresponding reparametrization-invariant forms of the QLC relations and check the resulting expressions with the experimental data. The results can be viewed as a check of the validity of the QLC relations, as well as a new perspective into the issue of seeking for the connection between quarks and leptons.

Combining accelerator and reactor measurements of θ 13: the first result

Abstract The lepton mixing angle θ 13, the only unknown angle in the standard three-flavor neutrino mixing scheme, is finally measured by the recent reactor and accelerator neutrino experiments. We perform a combined analysis of the data coming from T2K, MINOS, Double Chooz, Daya Bay and RENO experiments and find sin2 2θ 13 = 0.096 ± 0.013(±0.040) at 1 σ (3 σ) CL and that the hypothesis θ 13 = 0 is now rejected at a significance level of 7.7 σ. We also discuss the near future expectation on the precision of the θ 13 determination by using expected data from these ongoing experiments.

OPERA SUPERLUMINAL NEUTRINOS AND KINEMATICS IN FINSLER SPACETIME

The OPERA collaboration recently reported that the muon neutrinos could be superluminal. More recently, Cohen and Glashow pointed that such superluminal neutrinos would be suppressed since they lose their energies rapidly via bremsstrahlung. Here, we propose that the Finslerian nature of the spacetime could account for the superluminal phenomena of particles. The Finsler spacetime permits the existence of the superluminal behavior of particles while the causality still holds. A new dispersion relation is obtained in a class of Finsler spacetimes. It is shown that the superluminal speed is linearly dependent on the energy per unit mass of the particle. We find that such a superluminal speed formula is consistent with the data of the OPERA, MINOS and Fermilab-1979 neutrino experiments as well as the observations on the neutrinos from the SN1987A.

On self-complementarity relations of neutrino mixing

With the latest results of a large mixing angle θ13 for neutrinos by the T2K, MINOS and Double Chooz experiments, we find that the self-complementarity (SC) relations agree with the data in some angle-phase parametrizations of the lepton mixing matrix. There are three kinds of self-complementarity relations: (1) ϑi+ϑj=ϑk=45°; (2) ϑi+ϑj=ϑk; (3) ϑi+ϑj=45° (where i, j, k denote the mixing angles in the angle-phase parametrizations). We present a detailed study on the self-complementarity relations in nine different angle-phase parametrizations, and also examine the explicit expressions in reparametrization-invariant form, as well as their deviations from global fit. These self-complementarity relations may lead to new perspective on the mixing pattern of neutrinos.

THE PHANTOM OF THE OPERA: SUPERLUMINAL NEUTRINOS

This is a brief review on the experimental measurements of the muon neutrino velocities from the OPERA, Fermilab and MINOS experiments and that of the (anti)-electron neutrino velocities from the supernova SN1987A, and consequently on the theoretical attempts to attribute the data as signals for superluminality of neutrinos. Different scenarios on how to understand and treat the background fields in the effective field theory frameworks are pointed out. Challenges on interpreting the OPERA result as a signal of neutrino superluminality are briefly reviewed and discussed. It is also pointed out that a covariant picture of Lorentz violation can avoid the refutation on the OPERA experiment.

Some Recent Secondary Production Measurements for Neutrino Flux Determination

Recent measurements of meson production in proton-nucleus interactions have made possible reliable neutrino flux determinations at modern neutrino experiments. This article discusses preliminary results from the HARP, MIP, and E910 are discussed along with some of their implications for the MINOS, K2K, and MiniBooNE neutrino experiments.

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.

Sizeable θ 13 from the charged lepton sector in SU(5), (tri-)bimaximal neutrino mixing and Dirac CP violation

The recent results from T2K and MINOS experiments point towards a relatively large value of the reactor angle \theta_13 in the lepton sector. In this paper we show how a large \theta_13 can arise from the charged lepton sector alone in the context of an SU(5) GUT. In such a scenario (tri-)bimaximal mixing in the neutrino sector is still a viable possibility. We also analyse the general implications of the considered scenario for the searches of CP violation in neutrino oscillations.

Where we are on θ13: addendum to ‘Global neutrino data and recent reactor fluxes: status of three-flavor oscillation parameters’

In this addendum to Schwetz et al (2011 New J. Phys.13 063004), we consider the recent results from long-baseline νμ → νe searches at the Tokai to Kamioka (T2K) and Main Injector Neutrino Oscillation Search (MINOS) experiments and investigate their implications for the mixing angle θ13 and the leptonic Dirac CP phase δ. By combining the 2.5σ indication for a nonzero value of θ13 coming from the T2K data with global neutrino oscillation data, we obtain a significance for θ13 > 0 of about 3σ with best fit points sin2 θ13 = 0.013 (0.016) for normal (inverted) neutrino mass ordering. These results depend somewhat on assumptions concerning the analysis of reactor neutrino data.

Results for CCQE scattering with the MINOS near detector

The MINOS experiment has the world's largest data set of neutrino interactions in the 1-10 GeV range. In addition, this data set is for neutrino interactions on iron, allowing us to explore the nuclear effects on neutrino scattering. We present preliminary results from a low hadronic energy, quasielastic enhanced sample of neutrino-iron interactions observed by the MINOS Near Detector in the NuMI neutrino beam at Fermilab. From a shape fit to the Q2 distribution for these events, we extract a value for the effective axial-vector mass MA which best describes that distribution. We discuss the very low Q2 behavior of this sample and the most important systematic effects for this measurement. Then we explore how we can increase our sensitivity to MA by adding exclusive final state selections to the Q2 shape fit.

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.

Physics at the NuMI Beam

This contribution to the proceedings of the 2010 NOW Workshop summarises the latest results from the MINOS experiment and talks about the future prospects for the MINER ν A and NO ν A experiments. Descriptions of the Fermilab NuMI neutrino beam, its performance and future potential as well as that of the associated accelerator complex are also given.

First Direct Observation of Muon Antineutrino Disappearance

This Letter reports the first direct observation of muon antineutrino disappearance. The MINOS experiment has taken data with an accelerator beam optimized for ν(μ) production, accumulating an exposure of 1.71 × 10²⁰ protons on target. In the Far Detector, 97 charged current ν(μ) events are observed. The no-oscillation hypothesis predicts 156 events and is excluded at 6.3σ. The best fit to oscillation yields |Δm²| = [3.36(-0.40)(+0.46)(stat) ± 0.06(syst)] × 10⁻³ eV², sin²(2θ) = 0.86(-0.12)(+0.11)(stat) ± 0.01(syst). The MINOS ν(μ) and ν(μ) measurements are consistent at the 2.0% confidence level, assuming identical underlying oscillation parameters.

Gauged Lμ–Lτ and different muon neutrino and anti-neutrino oscillations: MINOS and beyond

If a Z′ gauge boson of a gauged Lμ–Lτ symmetry is very light, it is associated with a long-range leptonic force. In this case, the particles in the Sun create via mixing of Z′ with the standard model Z a flavor-dependent potential for muon neutrinos in terrestrial long-baseline experiments. The potential changes sign for anti-neutrinos and hence can lead to apparent differences in neutrino and anti-neutrino oscillations without introducing CP or CPT violation. This can for instance explain the recently found discrepancy in the survival probabilities of muon neutrinos and anti-neutrinos in the MINOS experiment. We obtain the associated parameters of gauged Lμ–Lτ required to explain this anomaly, and compare our scenario to usually considered non-standard interactions. When applied to MINOS, both approaches have difficulties with existing limits. The consequences for future long-baseline experiments and for the anomalous magnetic moment of the muon are discussed. The main feature is that atmospheric neutrino mixing has to be non-maximal in order to have an effect. Neutrino masses tend to have a mild hierarchy.

Testing matter effects in propagation of atmospheric and long-baseline neutrinos

We quantify our current knowledge of the size and flavor structure of the matter effects in the evolution of atmospheric and long-baseline neutrinos based solely on the analysis of the corresponding neutrino data. To this aim we generalize the matter potential of the Standard Model by rescaling its strength, rotating it away from the e-e sector, and rephasing it with respect to the vacuum term. This phenomenological parametrization can be easily translated in terms of non-standard neutrino interactions in matter. We show that in the most general case, the strength of the potential cannot be determined solely by atmospheric and long-baseline data. However its flavor composition is very much constrained and the present determination of the neutrino masses and mixing is robust under its presence. We also present an update of the constraints arising from this analysis in the particular case in which no potential is present in the e-mu and e-tau sectors. Finally we quantify to what degree in this scenario it is possible to alleviate the tension between the oscillation results for neutrinos and antineutrinos in the MINOS experiment and show the relevance of the high energy part of the spectrum measured at MINOS.

Deep Core muon neutrino rate and anisotropy by mixing and CPT violation

Neutrinos are allowed to mix and to oscillate among their flavor. Muon and tau in particular oscillate at largest values. Last Minos experiment claimed MINOS Collaboration [12] possible difference among their matter and anti-matter masses, leading to a first violation of the most believed CPT symmetry. Isotropically born atmospheric muon neutrino at E ν μ ≃ 20 – 80 GeV , while upgoing, they might be partially suppressed by mixing in analogy to historical SuperKamiokande muon neutrino disappearance into tau, leading to large-scale anisotropy signals. Here, we show an independent muon rate foreseen in Deep Core based on observed SK signals extrapolated to Deep Core mass and its surrounding. Our rate prediction partially differ from previous ones. The ν μ , ν ̄ μ disappearance into ν τ , ν ̄ τ is leading to a μ , μ ̄ anisotropy in vertical upgoing muon track: in particular along channel 3–5 we expect a huge rate (nearly ten thousand of events) of neutral current events, charged current electron and inclined crossing muons. Moreover, at channel 6–9 we expect a severe suppression of the rate due to muon disappearance (in CPT conserved frame). A CPT violation may induce a suppression of vertical upgoing tracks because of larger ν ̄ μ reduction for E ν ̄ μ ≥ 35 GeV , corresponding to channel 9–10, and an amplified rate of events between channels 4–5–6.

SEARCH FOR νμ→νe OSCILLATIONS IN THE MINOS EXPERIMENT

The MINOS experiment uses the NuMI νμ beam to make precise measurements of neutrino flavor oscillations in the "atmospheric" neutrino sector. MINOS can also probe the yet-unknown neutrino mixing angle θ13 by searching for a νe appearance signal in the νμ beam. This paper reviews the techniques developed for the first νe appearance analysis in MINOS.

Apparent multipleΔm322inν¯μandνμsurvival oscillations from nonstandard interaction matter effect

Neutrinos propagating through matter may participate in forward coherent neutral-current--like scattering arising from nonstandard interactions as well as from the Mikheyev-Smirnov-Wolfenstein matter potential ${V}_{e}$. We show that at fixed long baselines through matter of constant density, the nonstandard interaction potential ${ϵ}_{\ensuremath{\mu}\ensuremath{\tau}}{V}_{e}$ can contribute an additional term to the oscillation phase whose sign differs for ${\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}}$ versus ${\ensuremath{\nu}}_{\ensuremath{\mu}}$ propagation in matter. Its presence can cause different apparent $\ensuremath{\Delta}{m}^{2}$ to be erroneously inferred on the basis of oscillations in vacuum, with values lying above (for ${\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}}$) or below (for ${\ensuremath{\nu}}_{\ensuremath{\mu}}$) the actual $\ensuremath{\Delta}{m}_{32}^{2}$ for the case where ${ϵ}_{\ensuremath{\mu}\ensuremath{\tau}}$ is predominantly real-valued and of sign opposite to $\ensuremath{\Delta}{m}_{32}^{2}$. A nonstandard interaction scenario invoking only $\ensuremath{\mathfrak{R}}({ϵ}_{\ensuremath{\mu}\ensuremath{\tau}})$ is shown to be capable of accounting for a disparity recently reported between oscillation survival for ${\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}}$ and ${\ensuremath{\nu}}_{\ensuremath{\mu}}$ fluxes measured at 735 km by the MINOS experiment. Implications for mantle traversal by atmospheric neutrinos are examined. The nonstandard interaction matter potential with nonmaximal mixing could evade conventional atmospheric neutrino analyses which do not distinguish ${\ensuremath{\nu}}_{\ensuremath{\mu}}$ from ${\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}}$ on an event-by-event basis.

Interpretation of MINOS data in terms of nonstandard neutrino interactions

The MINOS experiment at Fermilab has recently reported a tension between the oscillation results for neutrinos and anti-neutrinos. We show that this tension, if it persists, can be understood in the framework of non-standard neutrino interactions (NSI). While neutral current NSI (non-standard matter effects) are disfavored by atmospheric neutrinos, a new charged current coupling between tau neutrinos and nucleons can fit the MINOS data without violating other constraints. In particular, we show that loop-level contributions to flavor-violating tau decays are sufficiently suppressed. However, conflicts with existing bounds could arise once the effective theory considered here is embedded into a complete renormalizable model. We predict the future sensitivity of the T2K and NOvA experiments to the NSI parameter region favored by the MINOS fit, and show that both experiments are excellent tools to test the NSI interpretation of the MINOS data.