Precise measurement of the neutrino mixing parameter θ23 from muon neutrino disappearance in an off-axis beam.
Physical review letters 112 (2014) 181801-
New data from the T2K neutrino oscillation experiment produce the most precise measurement of the neutrino mixing parameter θ23. Using an off-axis neutrino beam with a peak energy of 0.6 GeV and a data set corresponding to 6.57×10(20) protons on target, T2K has fit the energy-dependent νμ oscillation probability to determine oscillation parameters. The 68% confidence limit on sin(2)(θ23) is 0.514(-0.056)(+0.055) (0.511±0.055), assuming normal (inverted) mass hierarchy. The best-fit mass-squared splitting for normal hierarchy is Δm32(2)=(2.51±0.10)×10(-3) eV(2)/c(4) (inverted hierarchy: Δm13(2)=(2.48±0.10)×10(-3) eV(2)/c(4)). Adding a model of multinucleon interactions that affect neutrino energy reconstruction is found to produce only small biases in neutrino oscillation parameter extraction at current levels of statistical uncertainty.
Combined analysis of νμ disappearance and νμ→νe appearance in MINOS using accelerator and atmospheric neutrinos.
Physical review letters 112 (2014) 191801-
We report on a new analysis of neutrino oscillations in MINOS using the complete set of accelerator and atmospheric data. The analysis combines the ν(μ) disappearance and ν(e) appearance data using the three-flavor formalism. We measure |Δm(32)(2)| = [2.28-2.46] × 10(-3) eV(2) (68% C.L.) and sin(2)θ(23) = 0.35-0.65 (90% C.L.) in the normal hierarchy, and |Δm(32)(2)| = [2.32-2.53] × 10(-3) eV(2) (68% C.L.) and sin(2)θ(23) = 0.34-0.67 (90% C.L.) in the inverted hierarchy. The data also constrain δ(CP), the θ(23} octant degeneracy and the mass hierarchy; we disfavor 36% (11%) of this three-parameter space at 68% (90%) C.L.
Nuclear Physics B - Proceedings Supplements 246-247 (2014) 23-28
The Tokai to Kamioka (T2K) experiment studies neutrino oscillations using a beam of muon neutrinos produced by an accelerator. The neutrinos travel from J-PARC on the east coast of Japan and are detected 295 kilometers further away in the Super-Kamiokande detector. A complex of near detectors located 280 meters away from the neutrino production target is used to better characterize the neutrino beam and reduce systematic uncertainties. The experiment aims at measuring electronic neutrino appearance (νμ→νe oscillation) to measure the neutrino mixing angle θ13, and muon neutrino disappearance to measure the neutrino mixing angle θ23 and mass splitting |δm322|. We report here electron neutrino appearance results using three years of data, recorded until the 2012 summer, as well as muon neutrino disappearance results based on the data coming from the first two years of the experiment. © 2013 Elsevier B.V.
Measurement of the intrinsic electron neutrino component in the T2K neutrino beam with the ND280 detector
PHYSICAL REVIEW D 89 (2014) ARTN 092003
Phys Rev Lett 112 (2014) 061802-
The T2K experiment has observed electron neutrino appearance in a muon neutrino beam produced 295 km from the Super-Kamiokande detector with a peak energy of 0.6 GeV. A total of 28 electron neutrino events were detected with an energy distribution consistent with an appearance signal, corresponding to a significance of 7.3σ when compared to 4.92±0.55 expected background events. In the Pontecorvo-Maki-Nakagawa-Sakata mixing model, the electron neutrino appearance signal depends on several parameters including three mixing angles θ12, θ23, θ13, a mass difference Δm(32)(2) and a CP violating phase δ(CP). In this neutrino oscillation scenario, assuming |Δm(32)(2)|=2.4×10(-3) eV(2), sin(2)θ(23)=0.5, and Δm322>0 (Δm(32)(2)<0), a best-fit value of sin(2)2θ(13)=0.140(-0.032)(+0.038) (0.170(-0.037)(+0.045)) is obtained at δ(CP)=0. When combining the result with the current best knowledge of oscillation parameters including the world average value of θ(13) from reactor experiments, some values of δ(CP) are disfavored at the 90% C.L.
JOURNAL OF HIGH ENERGY PHYSICS (2014) ARTN 094
PHYSICAL REVIEW D 90 (2014) ARTN 012010
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 698 (2013) 135-146
The T2K experiment is a long baseline neutrino oscillation experiment aiming to observe the appearance of νe in a νμ beam. The νμ beam is produced at the Japan Proton Accelerator Research Complex (J-PARC), observed with the 295 km distant Super-Kamiokande Detector and monitored by a suite of near detectors at 280 m from the proton target. The near detectors include a magnetized off-axis detector (ND280) which measures the unoscillated neutrino flux and neutrino cross-sections. The present paper describes the outermost component of ND280 which is a Side Muon Range Detector (SMRD) composed of scintillation counters with embedded wavelength shifting fibers and Multi-Pixel Photon Counter readout. The components, performance and response of the SMRD are presented. © 2012 Elsevier B.V.
PHYSICAL REVIEW D 88 (2013) ARTN 032002
Physical Review D - Particles, Fields, Gravitation and Cosmology 88 (2013)
We report new constraints on flavor-changing non-standard neutrino interactions from the MINOS experiment, in which neutrino versus antineutrino interactions can be distinguished on an event-by-event basis. We analyzed a combined set of beam neutrino and antineutrino data from the well-understood NuMI beam, and found no evidence for deviations from standard neutrino mixing. The observed energy spectra constrain the non-standard neutrino interactions parameter to the range -0.20<εμτ<0.07(90%C.L.). © 2013 American Physical Society.
Physical Review Letters 110 (2013)
We report measurements of oscillation parameters from νμ and ν̄μ disappearance using beam and atmospheric data from MINOS. The data comprise exposures of 10.71×1020 protons on target in the νμ-dominated beam, 3.36×1020 protons on target in the ν̄μ-enhanced beam, and 37.88 kton yr of atmospheric neutrinos. Assuming identical ν and ν̄ oscillation parameters, we measure |Δm2|=(2.41-0.10+0.09)×10-3 eV2 and sinâ¡2(2θ)=0.950-0.036+0.035. Allowing independent ν and ν̄ oscillations, we measure antineutrino parameters of |Δm̄2|=(2.50-0.25+0.23)×10-3 eV2 and sinâ¡2(2θ̄)=0.97-0.08+0.03, with minimal change to the neutrino parameters. © 2013 American Physical Society.
IEEE Nuclear Science Symposium Conference Record Institute of Electrical and Electronics Engineers Inc. (2013)
Systems based on 6LiF:ZnS(Ag) are good alternatives to 3He neutron detectors. Whilst the neutron absorption is well characterized in 6LiF:ZnS(Ag) layers, the detector efficiency is more likely to depend upon the light collection efficiency and light attenuation or uniformity across the active area - which can be large. We developed a segmented large area system (2 × 0.3 × 0.12) m comprising 16 neutron sensitive strips (1.6 m long) with embedded wavelength shifting fibers read out by MPPCs. The detector design is flexible and scalable and can be adapted to various applications. The active volume segmentation gives additional position sensitivity not possible with more monolithic designs. It also adds robustness to large fluxes of gamma-rays by triggering on smaller area ensuring a good operation in a mixed field of neutrons and other radiation. We report here the development and test of the prototype with calibrated sources of neutrons and gamma-rays. Measurements made at the Physical National Laboratory (UK) demonstrated a neutron detection rate of 3.05 n/s/ng at 2 m and a GARRn of 1.01. Studies of the uniformity of the efficiency and a drive by test were also conducted. © 2013 IEEE.
Inclusive production of protons, anti-protons, neutrons, deuterons and tritons in p+C collisions at 158 GeV/c beam momentum
European Physical Journal C 73 (2013) 1-66
The production of protons, anti-protons, neutrons, deuterons and tritons in minimum bias p+C interactions is studied using a sample of 385 734 inelastic events obtained with the NA49 detector at the CERN SPS at 158 GeV/c beam momentum. The data cover a phase space area ranging from 0 to 1.9 GeV/c in transverse momentum and in Feynman x from -0.8 to 0.95 for protons, from -0.2 to 0.3 for anti-protons and from 0.1 to 0.95 for neutrons. Existing data in the far backward hemisphere are used to extend the coverage for protons and light nuclear fragments into the region of intra-nuclear cascading. The use of corresponding data sets obtained in hadron-proton collisions with the same detector allows for the detailed analysis and model-independent separation of the three principle components of hadronization in p+C interactions, namely projectile fragmentation, target fragmentation of participant nucleons and intra-nuclear cascading. © 2013 The Author(s).
Measurement of neutrino oscillation parameters from muon neutrino disappearance with an off-axis beam
Phys Rev Lett 110 (2013) 171801-
We report on ν(e) and ν(e) appearance in ν(μ) and ν(μ) beams using the full MINOS data sample. The comparison of these ν(e) and ν(e) appearance data at a 735 km baseline with θ13 measurements by reactor experiments probes δ, the θ23 octant degeneracy, and the mass hierarchy. This analysis is the first use of this technique and includes the first accelerator long-baseline search for ν(μ) → ν(e). Our data disfavor 31% (5%) of the three-parameter space defined by δ, the octant of the θ23, and the mass hierarchy at the 68% (90%) C.L. We measure a value of 2sin(2)(2θ13)sin(2)(θ23) that is consistent with reactor experiments.
Measurement of the inclusive nu(mu) charged current cross section on carbon in the near detector of the T2K experiment
PHYSICAL REVIEW D 87 (2013) ARTN 092003
Physical Review D - Particles, Fields, Gravitation and Cosmology 87 (2013)
The CoGeNT Collaboration has recently published results from a fifteen month data set which indicate an annual modulation in the event rate similar to what is expected from weakly interacting massive particle interactions. It has been suggested that the CoGeNT modulation may actually be caused by other annually modulating phenomena, specifically the flux of atmospheric muons underground or the radon level in the laboratory. We have compared the phase of the CoGeNT data modulation to that of the concurrent atmospheric muon and radon data collected by the MINOS experiment which occupies an adjacent experimental hall in the Soudan Underground Laboratory. The results presented are obtained by performing a shape-free χ2 data-to-data comparison and from a simultaneous fit of the MINOS and CoGeNT data to phase-shifted sinusoidal functions. Both tests indicate that the phase of the CoGeNT modulation is inconsistent with the phases of the MINOS muon and radon modulations at the 3.0σ level. © 2013 American Physical Society.
Journal of Instrumentation 8 (2013)
The T2K experiment studies oscillations of an off-axis muon neutrino beam between the J-PARC accelerator complex and the Super-Kamiokande detector. Special emphasis is placed on measuring the mixing angle θ 13 by observing νe appearance via the sub-dominant νμ νe oscillation and searching for CP violation in the lepton sector. The experiment includes a sophisticated, off-axis, near detector, the ND280, situated 280 m downstream of the neutrino production target in order to measure the properties of the neutrino beam and to understand better neutrino interactions at the energy scale below a few GeV. The data collected with the ND280 are used to study charged- and neutral-current neutrino interaction rates and kinematics prior to oscillation, in order to reduce uncertainties in the oscillation measurements by the far detector. A key element of the near detector is the ND280 electromagnetic calorimeter (ECal), consisting of active scintillator bars sandwiched between lead sheets and read out with multi-pixel photon counters (MPPCs). The ECal is vital to the reconstruction of neutral particles, and the identification of charged particle species. The ECal surrounds the Pi-0 detector (PØD) and the tracking region of the ND280, and is enclosed in the former UA1/NOMAD dipole magnet. This paper describes the design, construction and assembly of the ECal, as well as the materials from which it is composed. The electronic and data acquisition (DAQ) systems are discussed, and performance of the ECal modules, as deduced from measurements with particle beams, cosmic rays, the calibration system, and T2K data, is described.© 2013 IOP Publishing Ltd and Sissa Medialab srl.
IEEE Nuclear Science Symposium Conference Record Institute of Electrical and Electronics Engineers Inc. (2013)
The detection of anti-neutrinos from nuclear reactors at close stand-off is a challenging measurement. The requirements for a remote monitoring device that could be used for close stand-off reactor core monitoring is difficult to meet with standard liquid scintillator technologies. Due to the low rate of anti-neutrinos detectable within 10 m from research reactors the detection efficiency has to be as high as possible with a relatively compact and safe design. The more practical aspects of the system are usually difficult to meet because these systems have to be deployed at low overburden where reactor gamma-ray and neutron backgrounds are a few orders of magnitude higher than the anti-neutrino rate. Large and costly passive shielding is usually needed to reduce these backgrounds closer to the anti-neutrino rate (typically 10 -4 Hz/tonne). A novel approach to measuring reactor anti-neutrinos was developed based on composite Polyvynil-Toluene and 6LiF:ZnS(Ag) scintillators. The system is highly segmented and read out by a network of wavelength shifting fibers and MPPCs which enables accurate localization of the outgoing positron and neutron. This more precise imaging of the interaction help with discriminating backgrounds and thus limits the required passive shielding around the detector. We report the expected performance from a Geant4 Monte-Carlo simulation of the system and the test of a 8 kg active mass prototype deployed at the BR2 reactor in Mol, Belgium. Measurements of the reactor on and off backgrounds rates and energy spectrum of signal candidates are presented using data collected at BR2 during summer 2013. © 2013 IEEE.