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.
Forward single π0 production by coherent neutral-current interactions, νA→νAπ0, is investigated using a 2.8×1020 protons-on-target exposure of the MINOS Near Detector. For single-shower topologies, ...the event distribution in production angle exhibits a clear excess above the estimated background at very forward angles for visible energy in the range 1–8 GeV. Cross sections are obtained for the detector medium comprised of 80% iron and 20% carbon nuclei with ⟨A⟩=48, the highest-⟨A⟩ target used to date in the study of this coherent reaction. The total cross section for coherent neutral-current single π0 production initiated by the νμ flux of the NuMI low-energy beam with mean (mode) Eν of 4.9 GeV (3.0 GeV), is 77.6±5.0(stat)−16.8+15.0(syst)×10−40 cm2 pernucleus. The results are in good agreement with predictions of the Berger-Sehgal model.
The transport of methane from the rhizosphere to the atmosphere takes place in the intercellular spaces and stomata of wetland plants, and foliar gas exchange is one of the critical steps of the ...transport process. The objectives of our research were to investigate: (i) variation in foliar gas exchange among four common wetland plant species (i.e.,
Peltandra virginica L.,
Orontium aquaticum L.,
Juncus effusus L., and
Taxodium distichum L.), (ii) the role of key environmental factors (i.e., light, temperature, and carbon dioxide concentration) in controlling foliar methane emission, and (iii) physiological mechanisms underlying the variation in methane emission due to species and the environment. Experiments were conducted in an instantaneous, flow-through gas-exchange system that operated on a mass balance approach and concurrently measured foliar fluxes of methane, water vapor, and carbon dioxide. The chamber system allowed for the control of light, temperature, humidity, and carbon dioxide concentration. Diel patterns of methane emission varied among species, with daylight emissions from
P. virginica and
O. aquaticum 2–4 times those of
J. effusus and
T. distichum in saturating light. Foliar methane emission from
P. virginica (1.80
μmol
m
−2
s
−1) under ambient daylight conditions was an order of magnitude higher than that of the other three species (∼0.20
μmol
m
−2
s
−1). As leaf temperature was increased by 10
°C, methane emission increased by a factor of 1.5–2.2, and the temperature effect was independent of stomatal conductance. When data were pooled among the four species, varying the light and carbon dioxide concentrations in a stepwise manner produced changes in foliar methane emission that were associated with stomatal conductance (
r
2
=
0.52). To scale our observations to other wetland plant species, a stepwise multiple regression model is offered that incorporates stomatal conductance and net carbon dioxide assimilation to estimate instantaneous methane emission from foliar surfaces. The model indicates that changes in stomatal conductance affect methane emission three times more than equivalent changes in net carbon dioxide assimilation.
The MINOS calibration detector Adamson, P.; Crone, G.; Jenner, L. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2006, 2006-1-00, Letnik:
556, Številka:
1
Journal Article
Recenzirano
This paper describes the MINOS calibration detector (CalDet) and the procedure used to calibrate it. The CalDet, a scaled-down but functionally equivalent model of the MINOS Far and Near detectors, ...was exposed to test beams in the CERN PS East Area during 2001–2003 to establish the response of the MINOS calorimeters to hadrons, electrons and muons in the range 0.2–10
GeV/
c
. The CalDet measurements are used to fix the energy scale and constrain Monte Carlo simulations of MINOS.
This Letter reports on a search for nu(mu) --> nu(e) transitions by the MINOS experiment based on a 3.14x10(20) protons-on-target exposure in the Fermilab NuMI beam. We observe 35 events in the Far ...Detector with a background of 27+/-5(stat)+/-2(syst) events predicted by the measurements in the Near Detector. If interpreted in terms of nu(mu) --> nu(e) oscillations, this 1.5sigma excess of events is consistent with sin2(2theta(13)) comparable to the CHOOZ limit when |Delta m2|=2.43x10(-3) eV2 and sin2(2theta(23))=1.0 are assumed.
We report the first detailed comparisons of the rates and spectra of neutral-current neutrino interactions at two widely separated locations. A depletion in the rate at the far site would indicate ...mixing between nu(mu) and a sterile particle. No anomalous depletion in the reconstructed energy spectrum is observed. Assuming oscillations occur at a single mass-squared splitting, a fit to the neutral- and charged-current energy spectra limits the fraction of nu(mu) oscillating to a sterile neutrino to be below 0.68 at 90% confidence level. A less stringent limit due to a possible contribution to the measured neutral-current event rate at the far site from nu(e) appearance at the current experimental limit is also presented.
The rate of high energy cosmic ray muons as measured underground is shown to be strongly correlated with upper‐air temperatures during short‐term atmospheric (10‐day) events. The effects are seen by ...correlating data from the MINOS underground detector and temperatures from the European Centre for Medium Range Weather Forecasts during the winter periods from 2003–2007. This effect provides an independent technique for the measurement of meteorological conditions and presents a unique opportunity to measure both short and long‐term changes in this important part of the atmosphere.
Abstract
We report a measurement of the flux-integrated $\nu_{\mu}$ charged-current cross sections on water, hydrocarbon, and iron in the T2K on-axis neutrino beam with a mean neutrino energy of 1.5 ...GeV. The measured cross sections on water, hydrocarbon, and iron are $\sigma^{\rm{H_{2}O}}_{\rm{CC}} = (0.840\pm 0.010(\mathrm{stat.})^{+0.10}_{-0.08}(\mathrm{syst.}))\times10^{-38}\,\mathrm{cm}^2$/nucleon, $\sigma^{\rm{CH}}_{\rm{CC}} = (0.817\pm 0.007(\mathrm{stat.})^{+0.11}_{-0.08}(\mathrm{syst.}))\times10^{-38}\,\mathrm{cm}^2$/nucleon, and $\sigma^{\rm{Fe}}_{\rm{CC}} = (0.859\pm 0.003(\mathrm{stat.})^{+0.12}_{-0.10}(\mathrm{syst.}))\times10^{-38}\,\mathrm{cm}^2$/nucleon, respectively, for a restricted phase space of induced muons: $\theta_{\mu}<45^{\circ}$ and $p_{\mu}>$0.4 GeV/$c$ in the laboratory frame. The measured cross section ratios are ${\sigma^{\rm{H_{2}O}}_{\rm{CC}}}/{\sigma^{\rm{CH}}_{\rm{CC}}} = 1.028\pm 0.016(\mathrm{stat.})\pm 0.053(\mathrm{syst.})$, ${\sigma^{\rm{Fe}}_{\rm{CC}}}/{\sigma^{\rm{H_{2}O}}_{\rm{CC}}} = 1.023\pm 0.012(\mathrm{stat.})\pm 0.058(\mathrm{syst.})$, and ${\sigma^{\rm{Fe}}_{\rm{CC}}}/{\sigma^{\rm{CH}}_{\rm{CC}}} = 1.049\pm 0.010(\mathrm{stat.})\pm 0.043(\mathrm{syst.})$. These results, with an unprecedented precision for the measurements of neutrino cross sections on water in the studied energy region, show good agreement with the current neutrino interaction models used in the T2K oscillation analyses.
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