Muon Neutrino Beam Research Articles

New results from T2K

The T2K experiment is a 295-km long-baseline neutrino experiment in Japan employing an off-axis muon neutrino beam with a ~ 0.6 GeV peak energy. The beam, produced from 30-GeV protons at the J-PARC complex on the Pacific coast, is directed to the Super-Kamiokande detector. T2K released the first long-baseline measurement of a nonzero value for the θ 13 mixing parameter through the observation of electron neutrino appearance (vµ → ve ) and produced the most precise measurement of θ 23 through the observation of muon neutrino disappearance (vµ → vµ ). T2K data, in combination with reactor experiments, also excludes at 90% C.L. a significant region of the Dirac CP phase: δ CP CP > -0.49(-0.98) for the normal (inverted) hierarchy. A full joint appearance and disappearance fit including both neutrino (7×1020 protons on target, PoT) and anti-neutrino (4 × 1020 PoT) data and, for the first time, a constraint from water target data in the near detector, is presented yielding improved sensitivity on δ CP and improved precision on sin2 2θ 23 and the atmospheric mass splitting.

Neutrinos from STORed Muons, nuSTORM

Neutrino beams produced from the decay of muons in a racetrack-like decay ring (the so called Neutrino Factory) provide a powerful way to study neutrino oscillation physics and, in addition, provide unique beams for neutrino interaction studies.The Neutrinos from STORed Muons (nuSTORM) facility is a neutrino factory-like facility designed for short baseline neutrino oscillation and neutrino interaction studies. However, due to the particular nature of nuSTORM, it can also provide an intense, very pure, muon neutrino beam from pion decay, which is possibly suitable for long-baseline neutrino oscillation searches as well. This so-called “Neo-conventional” muon neutrino beam from nuSTORM makes nuSTORM a hybrid neutrino factory.In this paper, the facility is described and a description of the neutrino beams and the precision to which they can be determined is given. Sensitivity plots are presented that indicate how well the facility can perform for short-baseline oscillation searches and show its potential for a neutrino interaction physics program. Finally, the concept of the “Neo-conventional” muon neutrino beam available at the nuSTORM facility is briefly discussed.

Short-lived particle search procedure in the OPERA experiment. Application to charm decays

The OPERA experiment has recently provided evidence of νμ→ντ neutrino oscillations in appearance mode through the detection of tau leptons produced in ντ Charged Current interactions. The OPERA detector collected data from 2008 to 2012, when it was exposed to the CNGS muon neutrino beam from CERN to Gran Sasso, 730 km away from the source. We report on the search procedure for short-lived particles and on its validation with charmed hadron decays. The latter, produced in about 4% of the neutrino interactions in OPERA, are an important background to the νμ→ντ channel and an ideal control sample as their decay exhibits topological and kinematical features strongly resembling the tau's decay.

T2K and Beyond

This paper presents thestate of the artof the T2K experiment and the measurements prospects for the incoming years. After a brief description of the experiment, the most recent results will be illustrated. The observation of the electron neutrino appearance in a muon neutrino beam and the new high-precision measurements of the mixing angleθ13by the reactor experiments have led to a reevaluation of the expected sensitivity to the oscillation parameters, relative to what was given in the original T2K proposal. For this reason the new physics potential of T2K for7.8×1021p.o.t. and for data exposure 3 times larger than that expected to be reachable with accelerator and beam line upgrades in 2026 before the start of operation of the next generation of long-baseline neutrino oscillation experiments will also be described in the text. In particular the last challenging scenario opens the door to the possibility of obtaining, under some conditions, a 3σmeasurement excludingsin⁡(δCP)=0.

Highlights from T2K

T2K is a long-baseline neutrino experiment designed to measure neutrino oscillations parameters. A high-intensity beam of muon neutrinos produced at the J-PARC accelerator complex is sent towards the near detector facility (the ND280 and INGRID detectors, located 280 m away from the neutrino source) and the far detector, Super-Kamiokande (295 km away). The change in the measured intensity and the composition of the neutrino beam between the near and far detectors are used to provide information on the oscillation parameters. T2K has delivered the world’s best measurement of the θ23 angle by observing muon neutrino disappearance. It was also the first experiment to observe electron neutrino appearance (2013) with a significance of 7.3 σ, to measure the associated θ13 mixing angle, and to provide the first hint of a non-zero δCP phase. The first running of anti-neutrinos in the T2K experiment shows a clear dip below 1 GeV, as expected for an oscillation signal. The T2K experiment is also capable of providing information on neutrino-nucleon cross sections at energies around 1 GeV, thanks to a large amount of target material present in the near detector facility.

The new experiment WAGASCI for water to hydrocarbon neutrino cross section measurement using the J-PARC beam

The T2K (Tokai-to-Kamioka) is a long baseline neutrino experiment designed to study various parameters that rule neutrino oscillations, with an intense beam of muon neutrinos. A near detector complex (ND280) is used to constrain non-oscillated flux and hence to predict the expected number of events in the far detector (Super-Kamiokande). The difference in the target material between the far (water) and near (scintillator, hydrocarbon) detectors leads to the main non-canceling systematic uncertainty for the oscillation analysis. In order to reduce this uncertainty a new water grid and scintillator detector, WAGASCI, has been proposed. The detector will be operated at the J-PARC neutrino beam line with the main physics goal to measure the charged current neutrino cross section ratio between water and hydrocarbon with a few percent accuracy. Further physics program may include high-precision measurements of different charged current neutrino interaction channels. The concept of the new detector will be covered together with the actual construction plan.

Event Reconstruction Techniques in NOvA

The NOvA experiment is a long-baseline neutrino oscillation experiment utilizing the NuMI beam generated at Fermilab. The experiment will measure the oscillations within a muon neutrino beam in a 300 ton Near Detector located underground at Fermilab and a functionally-identical 14 kiloton Far Detector placed 810 km away. The detectors are liquid scintillator tracking calorimeters with a fine-grained cellular structure that provides a wealth of information for separating the different particle track and shower topologies. Each detector has its own challenges with the Near Detector seeing multiple overlapping neutrino interactions in each event and the Far Detector having a large background of cosmic rays due to being located on the surface. A series of pattern recognition techniques have been developed to go from event records, to spatially and temporally separating individual interactions, to vertexing and tracking, and particle identification. This combination of methods to achieve the full event reconstruction will be discussed.

Implementation of an upward-going muon trigger for indirect dark matter searches at the NOvA far detector

The NOvA collaboration has constructed a 14,000 ton, fine-grained, low-Z, total absorption tracking calorimeter at an off-axis angle to an upgraded NuMI neutrino beam. This detector, with its excellent granularity and energy resolution and relatively low-energy neutrino thresholds, was designed to observe electron neutrino appearance in a muon neutrino beam, but it also has unique capabilities suitable for more exotic efforts. In fact, if an efficient upward- going muon trigger with sufficient cosmic ray background rejection can be demonstrated, NOvA will be capable of a competitive indirect dark matter search for low-mass WIMPs. The cosmic ray muon rate at the NOvA far detector is about 100 kHz and provides the primary challenge for triggering and optimizing such a search analysis. The status of the NOvA upward-going muon trigger is presented.

The NOvA simulation chain

The NOνA experiment is a two-detector, long-baseline neutrino experiment operating in the recently upgraded NuMI muon neutrino beam. Simulating neutrino interactions and backgrounds requires many steps including: the simulation of the neutrino beam flux using FLUKA and the FLUGG interface; cosmic ray generation using CRY; neutrino interaction modeling using GENIE; and a simulation of the energy deposited in the detector using GEANT4. To shorten generation time, the modeling of detector-specific aspects, such as photon transport, detector and electronics noise, and readout electronics, employs custom, parameterized simulation applications. We will describe the NOνA simulation chain, and present details on the techniques used in modeling photon transport near the ends of cells, and in developing a novel data-driven noise simulation. Due to the high intensity of the NuMI beam, the Near Detector samples a high rate of muons originating in the surrounding rock. In addition, due to its location on the surface at Ash River, MN, the Far Detector collects a large rate (˜ 140 kHz) of cosmic muons. We will discuss the methods used in NOνA for overlaying rock muons and cosmic ray muons with simulated neutrino interactions and show how realistically the final simulation reproduces the preliminary NOνA data.

ICARUS T600 - a large Liquid Argon Time Projection Chamber

The Liquid Argon Time Projection Chamber (LAr TPC) is a detection technique very well suited for the investigation of rare signals, including neutrino interactions. The ICARUS T600 is the largest LAr TPC ever built. It has recorded events both, from the CERN to Gran Sasso (CNGS) muon neutrino beam and cosmic rays interactions. Several important results have been achieved thanks to the three-dimensional event imaging and very good detector resolutions both, calorimetric and spatial. Two of them, namely the observation of a free electron lifetime exceeding 15 ms, and the search of LSND related anomalies in the νe appearance from the νμ CNGS beam will be shortly summarized.

ICARUS and Sterile Neutrinos

The ICARUS T600 detector is the largest operational liquid Argon Time Projection Chamber (LAr-TPC) ever built, and it successfully took data at the Gran Sasso laboratories (LNGS), with both the CNGS muon-neutrino beam and cosmic rays, from May 2010 to June 2013. During the data taking campaign, a dedicated search was performed for an excess of electron neutrino events, possibly related to non-standard oscillations into sterile states. No evidence of excess was found, and a new Short Baseline experiment is now being developed at Fermilab, in order to definitely prove or exclude the existence of such sterile neutrinos.

Summary of the Latest Results and Future Prospects from the T2K Experiment

The T2K long-baseline experiment is located in Japan and is designed to study oscillations of muon neutrinos. T2K obtains a beam of muon neutrinos peaked at 0.6 GeV that are produced at J-PARC accelerator complex by converting a beam of 30-GeV protons hitting a graphite target. Upon traveling 295 km, neutrinos are detected by the Super-Kamiokande (SK) water Cherenkov detector. Located at 280 m from the target, the near detector complex (ND280) provides information about un-oscillated neutrino flux, beam stability and interaction cross-sections. The T2K experiment observed electron neutrino appearance at SK with the significance of 7.3σ and measured the associated oscillation parameter θ13 for both normal and inverted mass hierarchies. In addition, by looking at muon neutrino disappearance T2K provided improved measurements of the θ23 and Δm232 parameters. The results of these measurements are presented as well as a brief summary of the selected neutrino cross-section measurements. Future prospects of the T2K experiment are discussed.

Measurement of the muon beam direction and muon flux for the T2K neutrino experiment

The Tokai-to-Kamioka (T2K) neutrino experiment measures neutrino oscillations by using an almost pure muon neutrino beam produced at the J-PARC accelerator facility. The T2K muon monitor was installed to measure the direction and stability of the muon beam which is produced together with the muon neutrino beam. The systematic error in the muon beam direction measurement was estimated, using data and MC simulation, to be 0.28 mrad. During beam operation, the proton beam has been controlled using measurements from the muon monitor and the direction of the neutrino beam has been tuned to within 0.3 mrad with respect to the designed beam-axis. In order to understand the muon beam properties,measurement of the absolute muon yield at the muon monitor was conducted with an emulsion detector. The number of muon tracks was measured to be $(4.06\pm0.05)\times10^4$ cm$^{-2}$ normalized with $4\times10^{11}$ protons on target with 250 kA horn operation. The result is in agreement with the prediction which is corrected based on hadron production data.

Neutrino oscillation physics potential of the T2K experiment

The observation of the recent electron neutrino appearance in a muon neutrino beam and the high-precision measurement of the mixing angle $\theta_{13}$ have led to a re-evaluation of the physics potential of the T2K long-baseline neutrino oscillation experiment. Sensitivities are explored for CP violation in neutrinos, non-maximal $\sin^22\theta_{23}$, the octant of $\theta_{23}$, and the mass hierarchy, in addition to the measurements of $\delta_{CP}$, $\sin^2\theta_{23}$, and $\Delta m^2_{32}$, for various combinations of $\nu$-mode and \(\bar{\nu}\)-mode data-taking. With an exposure of $7.8\times10^{21}$~protons-on-target, T2K can achieve 1-$\sigma$ resolution of 0.050(0.054) on $\sin^2\theta_{23}$ and $0.040(0.045)\times10^{-3}~\rm{eV}^2$ on $\Delta m^2_{32}$ for 100\%(50\%) neutrino beam mode running assuming $\sin^2\theta_{23}=0.5$ and $\Delta m^2_{32} = 2.4\times10^{-3}$ eV$^2$. T2K will have sensitivity to the CP-violating phase $\delta_{\rm{CP}}$ at 90\% C.L. or better over a significant range. For example, if $\sin^22\theta_{23}$ is maximal (i.e $\theta_{23}$=$45^\circ$) the range is $-115^\circ<\delta_{\rm{CP}}<-60^\circ$ for normal hierarchy and $+50^\circ<\delta_{\rm{CP}}<+130^\circ$ for inverted hierarchy. When T2K data is combined with data from the NO$\nu$A experiment, the region of oscillation parameter space where there is sensitivity to observe a non-zero $\delta_{CP}$ is substantially increased compared to if each experiment is analyzed alone.

Baseline optimization for the measurement ofCPviolation, mass hierarchy, andθ23octant in a long-baseline neutrino oscillation experiment

Next-generation long-baseline electron neutrino appearance experiments will seek to discover CP violation, determine the mass hierarchy and resolve the $\theta_{23}$ octant. In light of the recent precision measurements of $\theta_{13}$, we consider the sensitivity of these measurements in a study to determine the optimal baseline, including practical considerations regarding beam and detector performance. We conclude that a detector at a baseline of at least 1000 km in a wide-band muon neutrino beam is the optimal configuration.

Muon neutrino disappearance at T2K

The T2K experiment has observed the disappearance of muon neutrinos from the J-PARC muon-neutrino beam. Using data corresponding to 3.01 × 1020 protons on target, 58 muon neutrino event candidates were observed; 205 ± 17 (syst.) events are expected under the no-oscillation hypothesis. A fit to the observed rate and energy spectrum in a neutrino oscillation framework with three active neutrino flavours in constant density matter, assuming the normal mass hierarchy, yields a best fit mixing angle sin2 θ23 = 0.514 ± 0.082 and best fit mass squared splitting |Δm232| = 2.44+0.17−0.15 × 10-3 eV2/c4, which corresponds to the maximal disappearance probability.

T2K on-axis detector results: cross section measurements

The T2K experiment brings the world leading constraints on the atmospheric parameters, sin2 θ 23 = 0.514 ± 0.082 and |Δm 32 2 | = (2.44−0.15 +0.17 ) × 10−3 eV2 .c−4 , along with first observation of the electron neutrino appearance in the muon neutrino beam. In the upcoming years, a higher precision measurement of the PMNS matrix parameters with possible evidence of a non zero CP violation phase requires a reduction in the main systematics which come from the cross section model. The INGRID detector is the onaxis detector of the long-baseline T2K experiment. Though its main goal is to monitor the neutrino flux intensity and off-axis angle, this proceeding presents the νμ cross section measurements that have been performed to reduce the uncertainty on the neutrino cross section models.

T2K on-axis detector results: cross section measurements

The T2K experiment brings the world leading constraints on the atmospheric parameters, sin2θ23 = 0.514 ± 0.082 and |Δm322| = (2.44−0.15+0.17) × 10−3eV2.c−4, along with first observation of the electron neutrino appearance in the muon neutrino beam. In the upcoming years, a higher precision measurement of the PMNS matrix parameters with possible evidence of a non zero CP violation phase requires a reduction in the main systematics which come from the cross section model. The INGRID detector is the onaxis detector of the long-baseline T2K experiment. Though its main goal is to monitor the neutrino flux intensity and off-axis angle, this proceeding presents the νμ cross section measurements that have been performed to reduce the uncertainty on the neutrino cross section models.

Recent Results from the OPERA Experiment

The OPERA experiment has been designed to perform the first detection of neutrino oscillations in the νμ → ντ channel in direct appearance mode, through the event by event detection of the tau lepton produced in ντ charged current interactions. OPERA is a hybrid detector, made of emulsion/lead target elements and of electronic detectors, placed in the CNGS muon neutrino beam from CERN to Gran Sasso, 730km away from the source. Neutrino interactions from the CNGS neutrino runs were recorded from 2008 until the end of 2012. We report on the data sample analysed so far and give the latest OPERA results on νμ → ντ and νμ → νe oscillation searches.

New results from the T2K experiment

Since its discovery, neutrino oscillation has been the subject of intense research. The θ13 parameter of the neutrino mixing matrix is of particular importance. A non-zero θ13 opens the possibility to study CP violation in the neutrino sector which could help explain the matter anti-matter asymmetry in the Universe. The Tokai-To-Kamioka (T2K) experiment was designed to measure electron neutrino appearance and muon neutrino disappearance using a muon neutrino beam produced at the J-PARC facility in Tokai, Japan. The Super-Kamiokande detector, located 295 km from the neutrino source, acts as the far detector. An improved analysis and all the data taken through June 9, 2012 provide 11 electron neutrino candidates in the far detector corresponding to 3.1 standard deviations from the θ13=0 hypothesis. This excess is currently the strongest indication of electron neutrino appearance and it yields for normal hierarchy and δCP=0, 0.053<sin2⁡2θ13<0.141 at 68% confidence level.