Session T11: Accelerator Neutrino Experiments

Status of the MiniBooNE combined appearance analysis

MiniBooNE experiment was designed to test if the anomalous LSND signal is due to neutrino oscillations. The LSND experiment observed an excess of $\bar{\nu}_e$ events in a $\bar{\nu}_{\mu}$ beam. This result cannot be explained by oscillations of 3 Standard Model neutrinos. A possible explanation is the existence of light sterile neutrinos. The MiniBooNE experiment collected data using both a $\nu_{\mu}$ beam and a $\bar{\nu}_{\mu}$ beam looking for signal at the same L/E as LSND. In neutrino mode an excess of events was observed at low energies, however the shape of the excess was not consistent with LSND within a simple model with 1 sterile neutrino. In anti-neutrino mode an excess of events was observed in both low and high energy region consistent with LSND type oscillations. The status of a combined analysis of neutrino and anti-neutrino mode will be presented.   

Neutral Pion Production in MINERvA

MINER$\nu$A is a neutrino-nucleus scattering experiment employing multiple nuclear targets. The experiment is searching for neutral pion production, both in charged current and neutral current, from coherent, resonant and deep-inelastic processes off these targets. Neutral pions are detected through the 2 photon decay that then produce electromagnetic showers. We will describe how we isolate and reconstruct the electromagnetic showers to calculate the invariant mass of the photon pair.   

Identifying NuE-CC and NuEbar-CC in the LBNE Water Cerenkov Detector

A 200 kt Water Cherenkov (WC) detector is one of the proposed LBNE far detectors which will be placed 1300 km from the neutrino source. We present a status of the identification of NuE Charged-Current (CC) and NuEbar-CC in the WC in the 0.5--8 GeV neutrino energy, a range pertinent to LBNE. The first and second oscillation maxima occur at ~2.5 and ~0.8 GeV, respectively. In the first maximum the majority of CC are composed of non quasi-elastic interactions. Neutral Current (NC) induced pions constitute the dominant background to the NuE and NuEbar appearance. This study relies upon a scan of Monte Carlo generated events including about 1,000 NuE-CC, 200 NuEbar-CC, and 10,000 NC. In a blind scan, where the signal NuE-CC and background NC events are mixed, events with one, two, and three rings are identified. The energy and angle of the selected events are smeared using the Super-Kamiokande's parametric resolution functions. Simple kinematic cuts were imposed to reduce the NC background while keeping the signal efficiency high. We present the CC identification efficiency as a function of visible neutrino energy as well as presenting a set of notable kinematic distributions.   

Fast Photon Monte Carlo for Water Cherenkov Detectors

We present \emph{Chroma}, a high performance optical photon simulation for large particle physics detectors, such as the water Cerenkov far detector option for LBNE. This software takes advantage of the CUDA parallel computing platform to propagate photons using modern graphics processing units. In a computer model of a 200 kiloton water Cerenkov detector with 29,000 photomultiplier tubes, Chroma can propagate 2.5 million photons per second, around 200 times faster than the same simulation with Geant4. Chroma uses a surface based approach to modeling geometry which offers many benefits over a solid based modelling approach which is used in other simulations like Geant4.   

Monte Carlo-based Reconstruction in Water Cherenkov Detectors using \emph{Chroma}

We demonstrate the feasibility of event reconstruction---including position, direction, energy and particle identification---in water Cherenkov detectors with a purely Monte Carlo-based method. Using a fast optical Monte Carlo package we have written, called \emph{Chroma}, in combination with several variance reduction techniques, we can estimate the value of a likelihood function for an arbitrary event hypothesis. The likelihood can then be maximized over the parameter space of interest using a form of gradient descent designed for stochastic functions. Although slower than more traditional reconstruction algorithms, this completely Monte Carlo-based technique is universal and can be applied to a detector of any size or shape, which is a major advantage during the design phase of an experiment. As a specific example, we focus on reconstruction results from a simulation of the 200 kiloton water Cherenkov far detector option for LBNE.   

Crosscheck of GLoBES Sensitivity Calculations For LBNE

The proposed Long Baseline Neutrino Experiment (LBNE) aims to precisely measure neutrino oscillation parameter $\theta_{13}$, determine neutrino mass hierarchy, and detect possible CP violation in the neutrino sector. We use GLoBES, a software package created to simulate long baseline neutrino experiments, to predict the sensitivity of the proposed 200 kiloton water Cherenkov detector to the above parameters. In particular, we are interested in quantifying the effects of the detector's energy resolution and energy bias on the sensitivity. We have performed an independent crosscheck of GLoBES's sensitivity calculations with an ensemble of toy Monte Carlo data sets to test GLoBES's treatment of systematic uncertainties such as energy resolution and bias.   

Study of Neutrino-Antineutrino Transitions in MINOS

MINOS is a long-baseline neutrino oscillation experiment composed of two detectors along Fermilab's high-intensity NuMI neutrino beam. In addition to studying oscillation between different flavors of neutrinos, MINOS is also capable of studying the possibility of transitions between neutrinos and antineutrinos. The observation of such a signal would indicate the violation of Lorentz and CPT symmetry in the neutrino sector. I present the analysis techniques being developed to study the muon neutrino to muon antineutrino transitions, including event selection and prediction of the Far Detector spectrum. The expected MINOS sensitivity to the transition of $\nu_{\mu}$'s to $\bar{\nu}_{\mu}$'s is also discussed.   

DAE$\delta$ALUS Target Design Optimization

DAE$\delta$ALUS, the Decay At-rest Experiment for $\delta_{CP}$ At the Laboratory for Underground Science will look for evidence of CP-violation in the neutrino sector, which may explain the matter/antimatter asymmetry in our universe. It will make precision measurements of oscillations of anti-muon neutrinos to anti-electron neutrinos using multiple neutrino sources created by low-cost compact cyclotrons. DAE$\delta$ALUS will utilize a decay-at-rest neutrino beam produced by 800 MeV protons impacting a graphite target. Two well-established Monte Carlo codes, MARS and GEANT4, have been used to optimize the design and the performance of the target. A benchmarking of the results obtained with these codes will also be presented.   

Methods to Determine Neutrino Flux at Low Energies: Investigation of the Low $\nu $ Method

We investigate the low $\nu $ method (developed by the CCFR/NuTeV collaborations) to determine the neutrino flux in a wide band neutrino beam at very low energies, a region of interest to neutrino oscillations experiments. Events with low hadronic final state energy $\nu $ $< \quad \nu _{cut}$ of 1, 2 and 5 GeV were used by the MINOS collaboration to determine the neutrino flux in their measurements of neutrino ( ) and antineutrino ( ) total cross sections. The lowest energy for which the method was applied is 3.5 GeV and the lowest energy was 6 GeV. At these energies, the cross sections are dominated by inelastic processes. We investigate the application of the method to determine the neutrino flux for and energies as low as 0.75 GeV, where the cross sections are dominated by quasielastic scattering and $\Delta $(1232) resonance production. We find that the method can be extended to low energies by using $\nu _{cut}$ values of 0.5 and 0.25 GeV, which are feasible in fully active neutrino detectors such as MINER$\nu $A.