Neutrinos

229 pages229 pages229 pagesThe Proceedings of the 2011 workshop on Fundamental Physics at the Intensity Frontier. Science opportunities at the intensity frontier are identified and described in the areas of heavy quarks, charged leptons, neutrinos, proton decay, new light weakly-coupled particles, and nucleons, nuclei, and atoms

Nuclear binding energy and transverse momentum imbalance in neutrino-nucleus reaction

Observables based on the final state kinematic imbalances are measured in the mesonless production of $\nu_\mu+A\rightarrow\mu^-+p+X$ in the MINERvA tracker. Components of the muon-proton momentum imbalances parallel ($\delta p_{Ty}$) and perpendicular($\delta p_{Tx}$) to the momentum transfer in the transverse plane are found to be sensitive to the nuclear effects such as Fermi motion, binding energy and non-QE contributions. The QE peak location in $\delta p_{Ty}$ is particularly sensitive to the binding energy. Differential cross sections are compared to predictions from different neutrino interaction models. None of the Fermi gas models simultaneously describe every feature of the QE peak width, location, and non-QE contribution to the signal process. Correcting the GENIE's binding energy implementation according to theory causes better agreement with data. Hints of proton left-right asymmetry is observed in $\delta p_{Tx}$. Better modelling of the binding energy can reduce bias in neutrino energy reconstruction and these observables can be applied in current and future experiments to better constrain nuclear effects

Measurement of total and differential cross sections of neutrino and antineutrino coherent π± production on carbon

Neutrino induced coherent charged pion production on nuclei, $\overline{ u}_\mu A\to\mu^\pm\pi^\mp A$, is a rare inelastic interaction in which the four-momentum squared transfered to the nucleus is nearly zero, leaving it intact. We identify such events in the scintillator of MINERvA by reconstructing |t| from the final state pion and muon momenta and by removing events with evidence of energetic nuclear recoil or production of other final state particles. We measure the total neutrino and antineutrino cross sections as a function of neutrino energy between 2 and 20 GeV and measure flux integrated differential cross sections as a function of $Q^2$, $E_\pi$ and $\theta_\pi$. The $Q^2$ dependence and equality of the neutrino and anti-neutrino cross-sections at finite $Q^2$ provide a confirmation of Adler's PCAC hypothesis

Measurement of νμ charged-current single π0 production on hydrocarbon in the few-GeV region using MINERvA

The semiexclusive channel νμ+CH→μ-π0+nucleon(s) is analyzed using MINERvA exposed to the low-energy NuMI νμ beam with spectral peak at Eν≃3 GeV. Differential cross sections for muon momentum and production angle, π0 kinetic energy and production angle, and for squared four-momentum transfer are reported, and the cross section σ(Eν) is obtained over the range 1.5 GeV≤Eν<20 GeV. Results are compared to GENIE and NuWro predictions and to published MINERvA cross sections for charged-current π+(π0) production by νμ(νμ) neutrinos. Disagreements between data and simulation are observed at very low and relatively high values for muon angle and for Q2 that may reflect shortfalls in modeling of interactions on carbon. For π0 kinematic distributions, however, the data are consistent with the simulation and provide support for generator treatments of pion intranuclear scattering. Using signal-event subsamples that have reconstructed protons as well as π0 mesons, the pπ0 invariant mass distribution is obtained, and the decay polar and azimuthal angle distributions in the rest frame of the pπ0 system are measured in the region of Δ(1232)+ production, W<1.4 GeV

Neutrino flux predictions for the NuMI beam

Knowledge of the neutrino flux produced by the Neutrinos at the Main Injector (NuMI) beamline is essential to the neutrino oscillation and neutrino interaction measurements of the MINERvA, MINOS+, NOvA and MicroBooNE experiments at Fermi National Accelerator Laboratory. We have produced a flux prediction which uses all available and relevant hadron production data, incorporating measurements of particle production off of thin targets as well as measurements of particle yields from a spare NuMI target exposed to a 120 GeV proton beam. The result is the most precise flux prediction achieved for a neutrino beam in the one to tens of GeV energy region. We have also compared the prediction to in situ measurements of the neutrino flux and find good agreement

Evidence for Neutral-Current Diffractive π0 Production from Hydrogen in Neutrino Interactions on Hydrocarbon

The MINERvA experiment observes an excess of events containing electromagnetic showers relative to the expectation from Monte Carlo simulations in neutral-current neutrino interactions with mean beam energy of 4.5 GeV on a hydrocarbon target. The excess is characterized and found to be consistent with neutral-current π0 production with a broad energy distribution peaking at 7 GeV and a total cross section of 0.26±0.02(stat.)±0.08(sys.)×10-39 cm2. The angular distribution, electromagnetic shower energy, and spatial distribution of the energy depositions of the excess are consistent with expectations from neutrino neutral-current diffractive π0 production from hydrogen in the hydrocarbon target. These data comprise the first direct experimental observation and constraint for a reaction that poses an important background process in neutrino-oscillation experiments searching for νμ to νe oscillations

Measurement of the antineutrino to neutrino charged-current interaction cross section ratio in MINERvA

We present measurements of the neutrino and antineutrino total charged-current cross sections on carbon and their ratio using the MINERvA scintillator-tracker. The measurements span the energy range 2-22 GeV and were performed using forward and reversed horn focusing modes of the Fermilab low-energy NuMI beam to obtain large neutrino and antineutrino samples. The flux is obtained using a subsample of charged-current events at low hadronic energy transfer along with precise higher energy external neutrino cross section data overlapping with our energy range between 12-22 GeV. We also report on the antineutrino-neutrino cross section ratio, RCC, which does not rely on external normalization information. Our ratio measurement, obtained within the same experiment using the same technique, benefits from the cancellation of common sample systematic uncertainties and reaches a precision of ∼5% at low energy. Our results for the antineutrino-nucleus scattering cross section and for RCC are the most precise to date in the energy range Eν<6 GeV

Measurement of Neutral-Current K+ Production by Neutrinos using MINERvA

Neutral-current production of K+ by atmospheric neutrinos is a background in searches for the proton decay p→K+ν. Reactions such as νp→νK+Λ are indistinguishable from proton decays when the decay products of the Λ are below detection threshold. Events with K+ are identified in MINERvA by reconstructing the timing signature of a K+ decay at rest. A sample of 201 neutrino-induced neutral-current K+ events is used to measure differential cross sections with respect to the K+ kinetic energy, and the non-K+ hadronic visible energy. An excess of events at low hadronic visible energy is observed relative to the prediction of the neut event generator. Good agreement is observed with the cross section prediction of the genie generator. A search for photons from π0 decay, which would veto a neutral-current K+ event in a proton decay search, is performed, and a 2σ deficit of detached photons is observed relative to the genie prediction

Measurement of quasielastic-like neutrino scattering at (E-v) similar to ~3.5 GeV on a hydrocarbon target

MINERvA presents a new analysis of neutrino induced quasielastic-like interactions in a hydrocarbon tracking target. We report a double-differential cross section using the muon transverse and longitudinal momentum. In addition, differential cross sections as a function of the square of the four-momentum transferred and the neutrino energy are calculated using a quasielastic hypothesis. Finally, an analysis of energy deposited near the interaction vertex is presented. These results are compared to modified genie predictions as well as a NuWro prediction. All results use a data set produced by 3.34 × 10^20 protons on target creating a neutrino beam with a peak energy of approximately 3.5 GeV