386 results found
Abud AA, Abi B, Acciarri R, et al., 2022, Separation of track- and shower-like energy deposits in ProtoDUNE-SP using a convolutional neural network, European Physical Journal C: Particles and Fields, Vol: 82, Pages: 1-19, ISSN: 1124-1861
Liquid argon time projection chamber detector technology provides high spatial and calorimetric resolutions on the charged particles traversing liquid argon. As a result, the technology has been used in a number of recent neutrino experiments, and is the technology of choice for the Deep Underground Neutrino Experiment (DUNE). In order to perform high precision measurements of neutrinos in the detector, final state particles need to be effectively identified, and their energy accurately reconstructed. This article proposes an algorithm based on a convolutional neural network to perform the classification of energy deposits and reconstructed particles as track-like or arising from electromagnetic cascades. Results from testing the algorithm on experimental data from ProtoDUNE-SP, a prototype of the DUNE far detector, are presented. The network identifies track- and shower-like particles, as well as Michel electrons, with high efficiency. The performance of the algorithm is consistent between experimental data and simulation.
Abe K, Akhlaq N, Akutsu R, et al., 2022, Scintillator ageing of the T2K near detectors fro 2010 to 2021, JOURNAL OF INSTRUMENTATION, Vol: 17, ISSN: 1748-0221
Abud AA, Abi B, Acciarri R, et al., 2022, Scintillation light detection in the 6-m drift-length ProtoDUNE Dual Phase liquid argon TPC, European Physical Journal C: Particles and Fields, Vol: 82, ISSN: 1124-1861
DUNE is a dual-site experiment for long-baseline neutrino oscillation studies, neutrino astrophysics and nucleon decay searches. ProtoDUNE Dual Phase (DP) is a 6 × 6 × 6 m3 liquid argon time-projection-chamber (LArTPC) that recorded cosmic-muon data at the CERN Neutrino Platform in 2019–2020 as a prototype of the DUNE Far Detector. Charged particles propagating through the LArTPC produce ionization and scintillation light. The scintillation light signal in these detectors can provide the trigger for non-beam events. In addition, it adds precise timing capabilities and improves the calorimetry measurements. In ProtoDUNE-DP, scintillation and electroluminescence light produced by cosmic muons in the LArTPC is collected by photomultiplier tubes placed up to 7 m away from the ionizing track. In this paper, the ProtoDUNE-DP photon detection system performance is evaluated with a particular focus on the different wavelength shifters, such as PEN and TPB, and the use of Xe-doped LAr, considering its future use in giant LArTPCs. The scintillation light production and propagation processes are analyzed and a comparison of simulation to data is performed, improving understanding of the liquid argon properties.
Abud AA, Abi B, Acciarri R, et al., 2022, Low exposure long-baseline neutrino oscillation sensitivity of the DUNE experiment, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 105, ISSN: 1550-2368
The Deep Underground Neutrino Experiment (DUNE) will produce world-leading neutrino oscillation measurements over the lifetime of the experiment. In this work, we explore DUNE’s sensitivity to observe charge-parity violation (CPV) in the neutrino sector, and to resolve the mass ordering, for exposures of up to 100 kiloton-megawatt-calendar years (kt-MW-CY), where calendar years include an assumption of 57% accelerator uptime based on past accelerator performance at Fermilab. The analysis includes detailed uncertainties on the flux prediction, the neutrino interaction model, and detector effects. We demonstrate that DUNE will be able to unambiguously resolve the neutrino mass ordering at a 4σ (5σ) level with a 66 (100) kt-MW-CY far detector exposure, and has the ability to make strong statements at significantly shorter exposures depending on the true value of other oscillation parameters, with a median sensitivity of 3σ for almost all true δCP values after only 24 kt-MW-CY. We also show that DUNE has the potential to make a robust measurement of CPV at a 3σ level with a 100 kt-MW-CY exposure for the maximally CP-violating values δCP=±π/2. Additionally, the dependence of DUNE’s sensitivity on the exposure taken in neutrino-enhanced and antineutrino-enhanced running is discussed. An equal fraction of exposure taken in each beam mode is found to be close to optimal when considered over the entire space of interest.
Abud AA, Abi B, Acciarri R, et al., 2022, Design, construction and operation of the ProtoDUNE-SP liquid argon TPC, Journal of Instrumentation, Vol: 17, ISSN: 1748-0221
The ProtoDUNE-SP detector is a single-phase liquid argon time projection chamber (LArTPC) that was constructed and operated in the CERN North Area at the end of the H4 beamline. This detector is a prototype for the first far detector module of the Deep Underground Neutrino Experiment (DUNE), which will be constructed at the Sandford Underground Research Facility (SURF) in Lead, South Dakota, U.S.A. The ProtoDUNE-SP detector incorporates full-size components as designed for DUNE and has an active volume of 7 × 6 × 7.2 m3. The H4 beam delivers incident particles with well-measured momenta and high-purity particle identification. ProtoDUNE-SP's successful operation between 2018 and 2020 demonstrates the effectiveness of the single-phase far detector design. This paper describes the design, construction, assembly and operation of the detector components.
Abud AA, Abi B, Acciarri R, et al., 2021, Searching for solar KDAR with DUNE, Journal of Cosmology and Astroparticle Physics, Vol: 2021, ISSN: 1475-7516
The observation of 236 MeV muon neutrinos from kaon-decay-at-rest (KDAR) originating in the core of the Sun would provide a unique signature of dark matter annihilation. Since excellent angle and energy reconstruction are necessary to detect this monoenergetic, directional neutrino flux, DUNE with its vast volume and reconstruction capabilities, is a promising candidate for a KDAR neutrino search. In this work, we evaluate the proposed KDAR neutrino search strategies by realistically modeling both neutrino-nucleus interactions and the response of DUNE. We find that, although reconstruction of the neutrino energy and direction is difficult with current techniques in the relevant energy range, the superb energy resolution, angular resolution, and particle identification offered by DUNE can still permit great signal/background discrimination. Moreover, there are non-standard scenarios in which searches at DUNE for KDAR in the Sun can probe dark matter interactions.
Manly S, Kordosky M, On behalf of the DUNE Collaboration, 2021, Deep Underground Neutrino Experiment (DUNE) near detector conceptual design report, Instruments, Vol: 5, Pages: 1-250, ISSN: 2410-390X
The Deep Underground Neutrino Experiment (DUNE) is an international, world-class experiment aimed at exploring fundamental questions about the universe that are at the forefront of astrophysics and particle physics research. DUNE will study questions pertaining to the preponderance of matter over antimatter in the early universe, the dynamics of supernovae, the subtleties of neutrino interaction physics, and a number of beyond the Standard Model topics accessible in a powerful neutrino beam. A critical component of the DUNE physics program involves the study of changes in a powerful beam of neutrinos, i.e., neutrino oscillations, as the neutrinos propagate a long distance. The experiment consists of a near detector, sited close to the source of the beam, and a far detector, sited along the beam at a large distance. This document, the DUNE Near Detector Conceptual Design Report (CDR), describes the design of the DUNE near detector and the science program that drives the design and technology choices. The goals and requirements underlying the design, along with projected performance are given. It serves as a starting point for a more detailed design that will be described in future documents.
Abe K, Adrich P, Aihara H, et al., 2021, Supernova Model Discrimination with Hyper-Kamiokande, ASTROPHYSICAL JOURNAL, Vol: 916, ISSN: 0004-637X
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Abe K, Akhlaq N, Akutsu R, et al., 2021, First T2K measurement of transverse kinematic imbalance in the muon-neutrino charged-current single-π+ production channel containing at least one proton, Physical Review D, Vol: 103, Pages: 1-27, ISSN: 2470-0010
This paper reports the first T2K measurement of the transverse kinematic imbalance in the single-π+ production channel of neutrino interactions. We measure the differential cross sections in the muon-neutrino charged-current interaction on hydrocarbon with a single π+ and at least one proton in the final state, at the ND280 off axis near detector of the T2K experiment. The extracted cross sections are compared to the predictions from different neutrino-nucleus interaction event generators. Overall, the results show a preference for models that have a more realistic treatment of nuclear medium effects including the initial nuclear state and final-state interactions.
Abe K, Akhlaq N, Akutsu R, et al., 2021, Improved constraints on neutrino mixing from the T2K experiment with 3.13×1021 protons on target, Physical Review D, Vol: 103, Pages: 1-59, ISSN: 2470-0010
The T2K experiment reports updated measurements of neutrino and antineutrino oscillations using both appearance and disappearance channels. This result comes from an exposure of 14.9(16.4)×1020 protons on target in neutrino (antineutrino) mode. Significant improvements have been made to the neutrino interaction model and far detector reconstruction. An extensive set of simulated data studies have also been performed to quantify the effect interaction model uncertainties have on the T2K oscillation parameter sensitivity. T2K performs multiple oscillation analyses that present both frequentist and Bayesian intervals for the Pontecorvo-Maki-Nakagawa-Sakata parameters. For fits including a constraint on sin2θ13 from reactor data and assuming normal mass ordering T2K measures sin2θ23=0.53+0.03−0.04 and Δm232=(2.45±0.07)×10−3 eV2 c−4. The Bayesian analyses show a weak preference for normal mass ordering (89% posterior probability) and the upper sin2θ23 octant (80% posterior probability), with a uniform prior probability assumed in both cases. The T2K data exclude CP conservation in neutrino oscillations at the 2σ level.
Deisting A, Waldron A, Atkin E, et al., 2021, Commissioning of a high pressure time projection chamber with optical readout, Instruments, Vol: 5, ISSN: 2410-390X
The measurements of proton–nucleus scattering and high resolution neutrino–nucleus interaction imaging are key in reducing neutrino oscillation systematic uncertainties in future experiments. A High Pressure Time Projection Chamber (HPTPC) prototype has been constructed and operated at the Royal Holloway University of London and CERN as a first step in the development of a HPTPC that is capable of performing these measurements as part of a future long-baseline neutrino oscillation experiment, such as the Deep Underground Neutrino Experiment. In this paper, we describe the design and operation of the prototype HPTPC with an argon based gas mixture. We report on the successful hybrid charge and optical readout using four CCD cameras of signals from 241Am sources.
Abi B, Acciarri R, Acero MA, et al., 2021, Supernova neutrino burst detection with the Deep Underground Neutrino Experiment, European Physical Journal C: Particles and Fields, Vol: 81, Pages: 1-26, ISSN: 1124-1861
The Deep Underground Neutrino Experiment (DUNE), a 40-kton underground liquid argon time projection chamber experiment, will be sensitive to the electron-neutrino flavor component of the burst of neutrinos expected from the next Galactic core-collapse supernova. Such an observation will bring unique insight into the astrophysics of core collapse as well as into the properties of neutrinos. The general capabilities of DUNE for neutrino detection in the relevant few- to few-tens-of-MeV neutrino energy range will be described. As an example, DUNE’s ability to constrain the νe spectral parameters of the neutrino burst will be considered.
Abi B, Acciarri R, Acero MA, et al., 2021, Prospects for beyond the standard model physics searches at the deep underground neutrino experiment DUNE collaboration, European Physical Journal C: Particles and Fields, Vol: 81, Pages: 1-51, ISSN: 1124-1861
The Deep Underground Neutrino Experiment (DUNE) will be a powerful tool for a variety of physics topics. The high-intensity proton beams provide a large neutrino flux, sampled by a near detector system consisting of a combination of capable precision detectors, and by the massive far detector system located deep underground. This configuration sets up DUNE as a machine for discovery, as it enables opportunities not only to perform precision neutrino measurements that may uncover deviations from the present three-flavor mixing paradigm, but also to discover new particles and unveil new interactions and symmetries beyond those predicted in the Standard Model (SM). Of the many potential beyond the Standard Model (BSM) topics DUNE will probe, this paper presents a selection of studies quantifying DUNE’s sensitivities to sterile neutrino mixing, heavy neutral leptons, non-standard interactions, CPT symmetry violation, Lorentz invariance violation, neutrino trident production, dark matter from both beam induced and cosmogenic sources, baryon number violation, and other new physics topics that complement those at high-energy colliders and significantly extend the present reach.
Abe K, Akhlaq N, Akutsu R, et al., 2021, Measurements of (nu)over-bar(mu) and (nu)over-bar(mu) + nu(mu) charged-current cross-sections without detected pions or protons on water and hydrocarbon at a mean anti-neutrino energy of 0.86 GeV, Progress of Theoretical and Experimental Physics, Vol: 2021, ISSN: 0033-068X
We report measurements of the flux-integrated ν̅μ and ν̅μ + νμ charged-current cross-sections on water and hydrocarbon targets using the T2K anti-neutrino beam with a mean beam energy of 0.86 GeV. The signal is defined as the (anti-)neutrino charged-current interaction with one induced μ± and no detected charged pion or proton. These measurements are performed using a new WAGASCI module recently added to the T2K setup in combination with the INGRID Proton Module. The phase space of muons is restricted to the high-detection efficiency region, pμ>400 MeV/c and θμ<30∘, in the laboratory frame. An absence of pions and protons in the detectable phase spaces of pπ>200 MeV/c, θπ<70∘ and pp>600 MeV/c, θp<70∘ is required. In this paper, both the ν¯¯¯μ cross-sections and ν¯¯¯μ+νμ cross-sections on water and hydrocarbon targets and their ratios are provided by using the D’Agostini unfolding method. The results of the integrated ν¯¯¯μ cross-section measurements over this phase space are σH2O=(1.082±0.068(stat.)+0.145−0.128(syst.))×10−39cm2/nucleon, σCH=(1.096±0.054(stat.)+0.132−0.117(syst.))×10−39cm2/nucleon, and σH2O/σCH=0.987±0.078(stat.)+0.093−0.090(syst.). The ν¯¯¯μ+νμ cross-section is σH2O=(1.155±0.064(stat.)+0.148−0.129(syst.))×10−39cm2/nucleon, σCH=(1.159±0.049(stat.)+0.129−0.115(syst.))×10−39cm2/nucleon, and σH2O/σCH=0.996±0.069(stat.)+0.083−0.078(syst.).
Abe K, Akhlaq N, Akutsu R, et al., 2021, T2K measurements of muon neutrino and antineutrino disappearance using 3.13 x 10(21) protons on target, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 103, Pages: 1-9, ISSN: 1550-2368
We report measurements by the T2K experiment of the parameters θ23 and Δm232, which govern the disappearance of muon neutrinos and antineutrinos in the three-flavor PMNS neutrino oscillation model at T2K’s neutrino energy and propagation distance. Utilizing the ability of the experiment to run with either a mainly neutrino or a mainly antineutrino beam, muon-like events from each beam mode are used to measure these parameters separately for neutrino and antineutrino oscillations. Data taken from 1.49×1021 protons on target (POT) in neutrino mode and 1.64×1021 POT in antineutrino mode are used. The best-fit values obtained by T2K were sin2(θ23)=0.51+0.06−0.07(0.43+0.21−0.05) and Δm232=2.47+0.08−0.09(2.50+0.18−0.13)×10−3 eV2/c4 for neutrinos (antineutrinos). No significant differences between the values of the parameters describing the disappearance of muon neutrinos and antineutrinos were observed. An analysis using an effective two-flavor neutrino oscillation model where the sine of the mixing angle is allowed to take nonphysical values larger than 1 is also performed to check the consistency of our data with the three-flavor model. Our data were found to be consistent with a physical value for the mixing angle.
Abi B, Abud AA, Acciarri R, et al., 2020, First results on ProtoDUNE-SP liquid argon time projection chamber performance from a beam test at the CERN Neutrino Platform, Journal of Instrumentation, Vol: 15, Pages: 1-100, ISSN: 1748-0221
The ProtoDUNE-SP detector is a single-phase liquid argon time projection chamber with an active volume of 7.2× 6.1× 7.0 m3. It is installed at the CERN Neutrino Platform in a specially-constructed beam that delivers charged pions, kaons, protons, muons and electrons with momenta in the range 0.3 GeV/c to 7 GeV/c. Beam line instrumentation provides accurate momentum measurements and particle identification. The ProtoDUNE-SP detector is a prototype for the first far detector module of the Deep Underground Neutrino Experiment, and it incorporates full-size components as designed for that module. This paper describes the beam line, the time projection chamber, the photon detectors, the cosmic-ray tagger, the signal processing and particle reconstruction. It presents the first results on ProtoDUNE-SP's performance, including noise and gain measurements, dE/dx calibration for muons, protons, pions and electrons, drift electron lifetime measurements, and photon detector noise, signal sensitivity and time resolution measurements. The measured values meet or exceed the specifications for the DUNE far detector, in several cases by large margins. ProtoDUNE-SP's successful operation starting in 2018 and its production of large samples of high-quality data demonstrate the effectiveness of the single-phase far detector design.
Abi B, Acciarri R, Acero MA, et al., 2020, Neutrino interaction classification with a convolutional neural network in the DUNE far detector, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 102, Pages: 092003 – 1-092003 – 20, ISSN: 1550-2368
The Deep Underground Neutrino Experiment is a next-generation neutrino oscillation experiment that aims to measure CP-violation in the neutrino sector as part of a wider physics program. A deep learning approach based on a convolutional neural network has been developed to provide highly efficient and pure selections of electron neutrino and muon neutrino charged-current interactions. The electron neutrino (antineutrino) selection efficiency peaks at 90% (94%) and exceeds 85% (90%) for reconstructed neutrino energies between 2–5 GeV. The muon neutrino (antineutrino) event selection is found to have a maximum efficiency of 96% (97%) and exceeds 90% (95%) efficiency for reconstructed neutrino energies above 2 GeV. When considering all electron neutrino and antineutrino interactions as signal, a selection purity of 90% is achieved. These event selections are critical to maximize the sensitivity of the experiment to CP-violating effects.
Abe K, Akhlaq N, Akutsu R, et al., 2020, Measurement of the charged-current electron (anti-)neutrino inclusive cross-sections at the T2K off-axis near detector ND280, The Journal of High Energy Physics, Vol: 2020, Pages: 1-43, ISSN: 1029-8479
The electron (anti-)neutrino component of the T2K neutrino beam constitutes the largest background in the measurement of electron (anti-)neutrino appearance at the far detector. The electron neutrino scattering is measured directly with the T2K off-axis near detector, ND280. The selection of the electron (anti-)neutrino events in the plastic scintillator target from both neutrino and anti-neutrino mode beams is discussed in this paper. The flux integrated single differential charged-current inclusive electron (anti-)neutrino cross-sections, dσ/dp and dσ/d cos(θ), and the total cross-sections in a limited phase-space in momentum and scattering angle (p > 300 MeV/c and θ ≤ 45°) are measured using a binned maximum likelihood fit and compared to the neutrino Monte Carlo generator predictions, resulting in good agreement.
Abi B, Acciarri R, Acero MA, et al., 2020, Long-baseline neutrino oscillation physics potential of the DUNE experiment, The European Physical Journal C, Vol: 80, Pages: 1-34, ISSN: 1434-6044
The sensitivity of the Deep Underground Neutrino Experiment (DUNE) to neutrino oscillation is determined, based on a full simulation, reconstruction, and event selection of the far detector and a full simulation and parameterized analysis of the near detector. Detailed uncertainties due to the flux prediction, neutrino interaction model, and detector effects are included. DUNE will resolve the neutrino mass ordering to a precision of 5σ, for all δCP values, after 2 years of running with the nominal detector design and beam configuration. It has the potential to observe charge-parity violation in the neutrino sector to a precision of 3σ (5σ) after an exposure of 5 (10) years, for 50% of all δCP values. It will also make precise measurements of other parameters governing long-baseline neutrino oscillation, and after an exposure of 15 years will achieve a similar sensitivity to sin22θ13 to current reactor experiments.
Abi B, Acciarri R, Acero MA, et al., 2020, Executive summary, JOURNAL OF INSTRUMENTATION, Vol: 15, Pages: 2-+, ISSN: 1748-0221
The preponderance of matter over antimatter in the early universe, the dynamics of the supernovae that produced the heavy elements necessary for life, and whether protons eventually decay—these mysteries at the forefront of particle physics and astrophysics are key to understanding the early evolution of our universe, its current state, and its eventual fate. The Deep Underground Neutrino Experiment (DUNE) is an international world-class experiment dedicated to addressing these questions as it searches for leptonic charge-parity symmetry violation, stands ready to capture supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. The DUNE far detector technical design report (TDR) describes the DUNE physics program and the technical designs of the single- and dual-phase DUNE liquid argon TPC far detector modules. This TDR is intended to justify the technical choices for the far detector that flow down from the high-level physics goals through requirements at all levels of the Project. Volume I contains an executive summary that introduces the DUNE science program, the far detector and the strategy for its modular designs, and the organization and management of the Project. The remainder of Volume I provides more detail on the science program that drives the choice of detector technologies and on the technologies themselves. It also introduces the designs for the DUNE near detector and the DUNE computing model, for which DUNE is planning design reports. Volume II of this TDR describes DUNE's physics program in detail. Volume III describes the technical coordination required for the far detector design, construction, installation, and integration, and its organizational structure. Volume IV describes the single-phase far detector technology. A planned Volume V will describe the dual-phase technology.
Abi B, Acciarri R, Acero MA, et al., 2020, Volume III DUNE far detector technical coordination, Journal of Instrumentation, Vol: 15, Pages: 1-193, ISSN: 1748-0221
The preponderance of matter over antimatter in the early universe, the dynamics of the supernovae that produced the heavy elements necessary for life, and whether protons eventually decay—these mysteries at the forefront of particle physics and astrophysics are key to understanding the early evolution of our universe, its current state, and its eventual fate. The Deep Underground Neutrino Experiment (DUNE) is an international world-class experiment dedicated to addressing these questions as it searches for leptonic charge-parity symmetry violation, stands ready to capture supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. The DUNE far detector technical design report (TDR) describes the DUNE physics program and the technical designs of the single- and dual-phase DUNE liquid argon TPC far detector modules. Volume III of this TDR describes how the activities required to design, construct, fabricate, install, and commission the DUNE far detector modules are organized and managed. This volume details the organizational structures that will carry out and/or oversee the planned far detector activities safely, successfully, on time, and on budget. It presents overviews of the facilities, supporting infrastructure, and detectors for context, and it outlines the project-related functions and methodologies used by the DUNE technical coordination organization, focusing on the areas of integration engineering, technical reviews, quality assurance and control, and safety oversight. Because of its more advanced stage of development, functional examples presented in this volume focus primarily on the single-phase (SP) detector module.
Abi B, Acciarri R, Acero MA, et al., 2020, Volume IV The DUNE far detector single-phase technology, Journal of Instrumentation, Vol: 15, Pages: 1-619, ISSN: 1748-0221
The preponderance of matter over antimatter in the early universe, the dynamics of the supernovae that produced the heavy elements necessary for life, and whether protons eventually decay—these mysteries at the forefront of particle physics and astrophysics are key to understanding the early evolution of our universe, its current state, and its eventual fate. DUNE is an international world-class experiment dedicated to addressing these questions as it searches for leptonic charge-parity symmetry violation, stands ready to capture supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. Central to achieving DUNE's physics program is a far detector that combines the many tens-of-kiloton fiducial mass necessary for rare event searches with sub-centimeter spatial resolution in its ability to image those events, allowing identification of the physics signatures among the numerous backgrounds. In the single-phase liquid argon time-projection chamber (LArTPC) technology, ionization charges drift horizontally in the liquid argon under the influence of an electric field towards a vertical anode, where they are read out with fine granularity. A photon detection system supplements the TPC, directly enhancing physics capabilities for all three DUNE physics drivers and opening up prospects for further physics explorations. The DUNE far detector technical design report (TDR) describes the DUNE physics program and the technical designs of the single- and dual-phase DUNE liquid argon TPC far detector modules. Volume IV presents an overview of the basic operating principles of a single-phase LArTPC, followed by a description of the DUNE implementation. Each of the subsystems is described in detail, connecting the high-level design requirements and decisions to the overriding physics goals of DUNE.
Jones SB, Nonnenmacher TS, Atkin E, et al., 2020, Off-axis characterisation of the CERN T10 beam for low momentum proton measurements with a high pressure gas time projection chamber, Instruments, Vol: 4, Pages: 21-21, ISSN: 2410-390X
We present studies of proton fluxes in the T10 beamline at CERN. A prototype high pressure gas time projection chamber (TPC) was exposed to the beam of protons and other particles, using the 0.8 GeV/c momentum setting in T10, in order to make cross section measurements of low energy protons in argon. To explore the energy region comparable to hadrons produced by GeV-scale neutrino interactions at oscillation experiments, i.e., near 0.1 GeV of kinetic energy, methods of moderating the T10 beam were employed: the dual technique of moderating the beam with acrylic blocks and measuring scattered protons off the beam axis was used to decrease the kinetic energy of incident protons, as well as change the proton/minimum ionising particle (MIP) composition of the incident flux. Measurements of the beam properties were made using time of flight systems upstream and downstream of the TPC. The kinetic energy of protons reaching the TPC was successfully changed from ∼0.3 GeV without moderator blocks to less than 0.1 GeV with four moderator blocks (40 cm path length). The flux of both protons and MIPs off the beam axis was increased. The ratio of protons to MIPs vary as a function of the off-axis angle allowing for possible optimisation of the detector to select the type of required particles. Simulation informed by the time of flight measurements show that with four moderator blocks placed in the beamline, (5.6 ± 0.1) protons with energies below 0.1 GeV per spill traversed the active TPC region. Measurements of the beam composition and energy are presented.
Abe K, Akutsu R, Ali A, et al., 2020, First measurement of the charged current (nu)over-bar(mu) double differential cross section on a water target without( )pions in the final state, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 102, Pages: 1-16, ISSN: 1550-2368
This paper reports the first differential measurement of the charged-current ¯νμ interaction cross section on water with no pions in the final state. The unfolded flux-averaged measurement using the T2K off-axis near detector is given in double-differential bins of μ+ momentum and angle. The integrated cross section in a restricted phase space is σ=(1.11±0.18)×10−38 cm2 per water molecule. Comparisons with several nuclear models are also presented.
Abe K, Akhlaq N, Akutsu R, et al., 2020, Simultaneous measurement of the muon neutrino charged-current cross section on oxygen and carbon without pions in the final state at T2K, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 101, Pages: 112004 – 1-112004 – 32, ISSN: 1550-2368
This paper reports the first simultaneous measurement of the double differential muon neutrino charged-current cross section on oxygen and carbon without pions in the final state as a function of the outgoing muon kinematics, made at the ND280 off-axis near detector of the T2K experiment. The ratio of the oxygen and carbon cross sections is also provided to help validate various models’ ability to extrapolate between carbon and oxygen nuclear targets, as is required in T2K oscillation analyses. The data are taken using a neutrino beam with an energy spectrum peaked at 0.6 GeV. The extracted measurement is compared with the prediction from different Monte Carlo neutrino-nucleus interaction event generators, showing particular model separation for very forward-going muons. Overall, of the models tested, the result is best described using local Fermi gas descriptions of the nuclear ground state with RPA suppression.
Abe K, Akhlaq N, Akutsu R, et al., 2020, First combined measurement of the muon neutrino and antineutrino charged-current cross section without pions in the final state at T2K, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 101, Pages: 112001 – 1-112001 – 44, ISSN: 1550-2368
This paper presents the first combined measurement of the double-differential muon neutrino and antineutrino charged-current cross sections with no pions in the final state on hydrocarbon at the off-axis near detector of the T2K experiment. The data analyzed in this work comprise 5.8×1020 and 6.3×1020 protons on target in neutrino and antineutrino mode respectively, at a beam energy peak of 0.6 GeV. Using the two measured cross sections, the sum, difference, and asymmetry were calculated with the aim of better understanding the nuclear effects involved in such interactions. The extracted measurements have been compared with the prediction from different Monte Carlo generators and theoretical models showing that the difference between the two cross sections have interesting sensitivity to nuclear effects.
Sirunyan AM, Tumasyan A, Adam W, et al., 2020, Study of dijet events with a large rapidity gap between the two leading jets in pp collisions at root s = 7TeV (vol 78, 242, 2018), European Physical Journal C: Particles and Fields, Vol: 80, Pages: 1-15, ISSN: 1124-1861
Events with no charged particles produced between the two leading jets are studied in proton–proton collisions at s√=7 TeV. The jets were required to have transverse momentum pjetT>40 GeV and pseudorapidity 1.5<|ηjet|<4.7, and to have values of ηjet with opposite signs. The data used for this study were collected with the CMS detector during low-luminosity running at the LHC, and correspond to an integrated luminosity of 8pb−1. Events with no charged particles with pT>0.2 GeV in the interval −1<η<1 between the jets are observed in excess of calculations that assume no color-singlet exchange. The fraction of events with such a rapidity gap, amounting to 0.5–1% of the selected dijet sample, is measured as a function of the pT of the second-leading jet and of the rapidity separation between the jets. The data are compared to previous measurements at the Tevatron, and to perturbative quantum chromodynamics calculations based on the Balitsky–Fadin–Kuraev–Lipatov evolution equations, including different models of the non-perturbative gap survival probability.
Abe K, Akutsu R, Ali A, et al., 2020, Search for electron antineutrino appearance in a long-baseline muon antineutrino beam, Physical Review Letters, Vol: 124, Pages: 161802-1-161802-8, ISSN: 0031-9007
Electron antineutrino appearance is measured by the T2K experiment in an accelerator-produced antineutrino beam, using additional neutrino beam operation to constrain parameters of the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) mixing matrix. T2K observes 15 candidate electron antineutrino events with a background expectation of 9.3 events. Including information from the kinematic distribution of observed events, the hypothesis of no electron antineutrino appearance is disfavored with a significance of 2.40σ and no discrepancy between data and PMNS predictions is found. A complementary analysis that introduces an additional free parameter which allows non-PMNS values of electron neutrino and antineutrino appearance also finds no discrepancy between data and PMNS predictions.
Abe K, Akutsu R, Ali A, et al., 2020, Constraint on the matter-antimatter symmetry-violating phase in neutrino oscillations, Nature, Vol: 580, Pages: 339-344, ISSN: 0028-0836
The charge-conjugation and parity-reversal (CP) symmetry of fundamental particles is a symmetry between matter and antimatter. Violation of this CP symmetry was first observed in 19641, and CP violation in the weak interactions of quarks was soon established2. Sakharov proposed3 that CP violation is necessary to explain the observed imbalance of matter and antimatter abundance in the Universe. However, CP violation in quarks is too small to support this explanation. So far, CP violation has not been observed in non-quark elementary particle systems. It has been shown that CP violation in leptons could generate the matter–antimatter disparity through a process called leptogenesis4. Leptonic mixing, which appears in the standard model’s charged current interactions5,6, provides a potential source of CP violation through a complex phase δCP, which is required by some theoretical models of leptogenesis7,8,9. This CP violation can be measured in muon neutrino to electron neutrino oscillations and the corresponding antineutrino oscillations, which are experimentally accessible using accelerator-produced beams as established by the Tokai-to-Kamioka (T2K) and NOvA experiments10,11. Until now, the value of δCP has not been substantially constrained by neutrino oscillation experiments. Here we report a measurement using long-baseline neutrino and antineutrino oscillations observed by the T2K experiment that shows a large increase in the neutrino oscillation probability, excluding values of δCP that result in a large increase in the observed antineutrino oscillation probability at three standard deviations (3σ). The 3σ confidence interval for δCP, which is cyclic and repeats every 2π, is [−3.41, −0.03] for the so-called normal mass ordering and [−2.54, −0.32] for the inverted mass ordering. Our results indicate CP violation in leptons and our method enables sensitive searches for matter–antimatter
Abe K, Akutsu R, Ali A, et al., 2020, Measurement of the muon neutrino charged-current single pi(+) production on hydrocarbon using the T2K off-axis near detector ND280, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 101, ISSN: 1550-2368
We report the measurements of the single and double differential cross section of muon neutrino charged-current interactions on carbon with a single positively charged pion in the final state at the T2K off-axis near detector using 5.56×1020 protons on target. The analysis uses data control samples for the background subtraction and the cross section signal, defined as a single negatively charged muon and a single positively charged pion exiting from the target nucleus, is extracted using an unfolding method. The model-dependent cross section, integrated over the T2K off-axis neutrino beam spectrum peaking at 0.6 GeV, is measured to be σ=(11.76±0.44(stat)±2.39(syst))×10−40 cm2 nucleon−1. Various differential cross sections are measured, including the first measurement of the Adler angles for single charged pion production in neutrino interactions with heavy nuclei target.
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