Neutrino Beam Research Articles

History of accelerator neutrino beams

Neutrino beams obtained from proton accelerators were first operated in 1962. Since then, neutrino beams have been intensively used in particle physics and evolved in many different ways. We describe the characteristics of various neutrino beams, relating them to the historical development of the physics studies and discoveries. We also discuss some of the ideas still under consideration for future neutrino beams.

First Measurement of Inclusive Muon Neutrino Charged Current Differential Cross Sections on Argon at E_{ν}∼0.8 GeV with the MicroBooNE Detector.

We report the first measurement of the double-differential and total muon neutrino charged current inclusive cross sections on argon at a mean neutrino energy of 0.8GeV. Data were collected using the MicroBooNE liquid argon time projection chamber located in the Fermilab Booster neutrino beam and correspond to 1.6×10^{20} protons on target of exposure. The measured differential cross sections are presented as a function of muon momentum, using multiple Coulomb scattering as a momentum measurement technique, and the muon angle with respect to the beam direction. We compare the measured cross sections to multiple neutrino event generators and find better agreement with those containing more complete treatment of quasielastic scattering processes at low Q^{2}. The total flux integrated cross section is measured to be 0.693±0.010(stat)±0.165(syst)×10^{-38} cm^{2}.

Results on Neutrino and Antineutrino Oscillations from the NOvA Experiment

NOvA is a two-detector long-baseline neutrino oscillation experiment using Fermilab’s 700 kW NuMI muon neutrino beam. With a total exposure of 8.85×1020 +12.33×1020 protons on target delivered to NuMI in the neutrino + antineutrino beam mode (78% more antineutrino data than in 2018), the experiment has made a 4.4q-significant observation of the ve appearance in a vм beam, measured oscillation parameters |Δm232|, sin2O23, and excluded most values near бCP = п/2 for the inverted neutrino mass hierarchy by more than 3q.

Search for heavy neutrinos with the T2K near detector ND280

This paper reports on the search for heavy neutrinos with masses in the range $140 < M_N < 493$ MeV/c$^2$ using the off-axis near detector ND280 of the T2K experiment. These particles can be produced from kaon decays in the standard neutrino beam and then subsequently decay in ND280. The decay modes under consideration are $N \to \ell^{\pm}_{\alpha} \pi^{\mp}$ and $N \to \ell^+_{\alpha} \ell^-_{\beta} \nu (\bar\nu)$ ($\alpha,\beta=e,\mu$). A search for such events has been made using the Time Projection Chambers of ND280, where the background has been reduced to less than two events in the current dataset in all channels. No excess has been observed in the signal region. A combined Bayesian statistical approach has been applied to extract upper limits on the mixing elements of heavy neutrinos to electron-, muon- and tau- flavoured currents ($U_e^2$, $U_{\mu}^2$, $U_{\tau}^2$) as a function of the heavy neutrino mass, e.g. $U_e^2 < 10^{-9}$ at $90\%$ C.L. for a mass of $390$ MeV/c$^2$. These constraints are competitive with previous experiments.

Letter of interest for a neutrino beam from Protvino to KM3NeT/ORCA

The Protvino accelerator facility located in the Moscow region, Russia, is in a good position to offer a rich experimental research program in the field of neutrino physics. Of particular interest is the possibility to direct a neutrino beam from Protvino towards the KM3NeT/ORCA detector, which is currently under construction in the Mediterranean Sea 40 km offshore Toulon, France. This proposal is known as P2O. Thanks to its baseline of 2595 km, this experiment would yield an unparalleled sensitivity to matter effects in the Earth, allowing for the determination of the neutrino mass ordering with a high level of certainty after only a few years of running at a modest beam intensity of approx ~90~hbox {kW}. With a prolonged exposure (approx 1500hbox { kW},,hbox {year}), a 2sigma sensitivity to the leptonic CP-violating Dirac phase can be achieved. A second stage of the experiment, comprising a further intensity upgrade of the accelerator complex and a densified version of the ORCA detector (Super-ORCA), would allow for up to a 6sigma sensitivity to CP violation and a 10^circ {-}17^circ resolution on the CP phase after 10 years of running with a 450 kW beam, competitive with other planned experiments. The initial composition and energy spectrum of the neutrino beam would need to be monitored by a near detector, to be constructed several hundred meters downstream from the proton beam target. The same neutrino beam and near detector set-up would also allow for neutrino-nucleus cross section measurements to be performed. A short-baseline sterile neutrino search experiment would also be possible.

The ICARUS Experiment

The 760 ton ICARUS T600 detector performed a successful three-year physics run at the underground LNGS laboratories, studying neutrino oscillations with the CNGS neutrino beam from CERN, and searching for atmospheric neutrino interactions. ICARUS performed a sensitive search for LSND like anomalous νe appearance contributing to constrain the allowed parameters to a narrow region around Δm2≈eV2, where all the experimental results can be coherently accommodated at 90% C.L. The T600 detector underwent a significant overhauling at CERN and has now been moved to Fermilab, to be soon exposed to the Booster Neutrino Beam to search for sterile neutrino within the SBN program, devoted to definitively clarify the open questions of the presently observed neutrino anomalies. We address ICARUS achievements, its status and plans for the new run and the ongoing analyses also finalized to the next physics run at Fermilab.

Energy and flavor discrimination using precision time structure in on-axis neutrino beams

We propose to use a higher-frequency RF bunch structure for the primary proton beam on target and precision timing to select different energy and flavor spectra from a wide-band neutrino beam, based on the relative arrival times of the neutrinos with respect to the RF bunch structure. This `stroboscopic' approach is complementary to techniques that select different neutrino energy spectra based on the angle with respect to the beam axis. A timing-based approach allows for the selection of varying energy spectra from the same on-axis detector, and applies equally to both the near and far detectors in an oscillation experiment. Energy and flavor discrimination of neutrinos produced by hadrons in-flight will require proton bunch lengths on the order of 100 ps and commensurate time resolution in the detector. Correlating neutrino events with the parent proton interaction is currently limited by the nanosecond-scale width of the proton bunches impinging on the target. We show that these limitations can be addressed by using a superconducting RF cavity to rebunch the present 53.1 MHz RF bunch structure with a factor of 10 higher RF frequency, thus attaining the required shorter bunch length.

Stability of three neutrino flavor conversion in supernovae

Neutrino-neutrino interactions can lead to collective flavor conversion in the dense parts of a core collapse supernova. Growing instabilities that lead to collective conversions have been studied intensely in the limit of two-neutrino species and occur for inverted mass ordering in the case of a perfectly spherical supernova. We examine two simple models of colliding and intersecting neutrino beams and show, that for three neutrino species instabilities exist also for normal mass ordering even in the case of a fully symmetric system. Whereas the instability for inverted mass ordering is associated with Δ m312, the new instability we find for normal mass ordering is associated with Δ m212. As a consequence, the growth rate of these new instabilities for normal ordering is smaller by about an order of magnitude compared to the rates of the well studied case of inverted ordering.

Physicists dig deep to seek the origin of matter

“Here’s to low-grade ore and plenty of it,” mining magnate George Hearst reportedly said after he bought the Homestake Gold Mine in Lead, SD, in June 1877. Although the mine contained less than an ounce of the precious metal per ton, the sheer quantity of ore meant that the operation was profitable (1). From 1876 to 2001, miners dug thousands of feet in search of gold, making Homestake the largest and deepest gold mine in North America. Now, physicists and engineers are excavating gigantic caverns inside the defunct mine to look for something even more elusive: neutrinos. New caverns being excavated inside the defunct Homestake Gold Mine in Lead, SD, will house DUNE. The world’s largest such detector, DUNE will start running in 2026. Image credit: Shutterstock/Tom Grundy. The new caverns will house the Deep Underground Neutrino Experiment (DUNE), the world’s largest such detector. DUNE will start running in 2026, studying an intense beam of neutrinos coming from Fermilab, near Batavia, IL, about 1,300 kilometers away. The experiment will focus on a profound question: what is the origin of matter? In the early universe, matter and antimatter should have formed in equal amounts and then annihilated each other to leave only radiation. But the observable universe with its galaxies, stars, and planets is made of matter, so clearly, not all of it was annihilated. “How did we get from a universe that was equal amounts of matter and antimatter to a universe where there’s a bit of matter left over?” asks neutrino physicist Deborah Harris of Fermilab. Neutrinos could be key to answering that question. Because of their special ability to transform from one type into another, they may reveal fundamental differences between matter and antimatter. Homestake has history with the neutrino, offering up the first signs of this particle’s …

Sensitivity study of Protvino to ORCA (P2O) experiment: effect of antineutrino run, background and systematics

There is a proposal to send a neutrino beam from the Protvino accelerator complex located in Russia to the detector facility called ‘Oscillation Research with Cosmics in the Abyss’ (ORCA) in the Mediterranean sea to study neutrino oscillation. This is called the P2O experiment which will have a baseline of 2588 km. In this paper we carry out an sensitivity study to extract the best possible physics sensitivity of the P2O experiment. In particular, we study the effect of antineutrino runs, the role of background as well as the impact of controlling the systematic uncertainties vis-a-vis the statistics.

Millicharged particles in liquid argon neutrino experiments

We investigate the potential of Liquid Argon (LAr) neutrino detectors to search for millicharged particles, a well-motivated extension of the standard model. Detectors located downstream of an intense proton beam that is striking a target may be exposed to a large flux of millicharged particles. Millicharged particles interact primarily through low momentum exchange producing electron recoil events near detector threshold. Recently, sub-MeV detection capabilities were demonstrated by the Fermilab ArgoNeuT detector, a small LAr detector which was exposed to the NuMI neutrino beam. Despite high background rates and its small size, we show that ArgoNeuT is capable of probing unexplored parameter space with its existing dataset. In particular, we show that the excellent spatial resolution in LAr detectors allows rejecting backgrounds by requiring two soft hits that are aligned with the upstream target. We further discuss the prospects of these types of searches in future larger LAr neutrino detectors such as the DUNE near detector.

Neutrino oscillations and instabilities in degenerate relativistic astrophysical plasmas.

We set up a proposal to extend significantly recent works on neutrino-plasma interaction, allowing the possibility of deep degenerate and relativistic electrons, which are often present in compact stars such as high-density white dwarfs. The methodology involves the covariant hydrodynamic formulation of ultradense plasmas. We propose the generalization of previous studies, on the interaction between ion-acoustic waves and resonant neutrino flavor oscillations in a mixed neutrino beam, admitting degenerate and relativistic electron populations. Destabilization of the ion acoustic wave has higher growth rates, thanks to the very high densities present in plasmas under these extreme conditions. We take into account applications to white dwarf stars in the process of collapsing, producing type II supernovas.

Classical neutral point particle in linearly polarized EM plane wave field

We study a covariant classical model of neutral point particles with magnetic moment interacting with external electromagnetic fields. Classical dynamical equations which reproduce a correct behavior in the non-relativistic limit are introduced. We also discuss the non-uniqueness of the covariant torque equation. The focus of this work is on Dirac neutrino beam control. We present a full analytical solution of the dynamical equations for a neutral point particle motion in the presence of an external linearly polarized EM plane wave (laser) fields. Neutrino beam control using extremely intense laser fields could possibly demonstrate Dirac nature of the neutrino. However, for linearly polarized ideal laser waves we show cancellation of all leading beam control effects.

Search for neutral-current induced single photon production at the ND280 near detector in T2K

Neutrino neutral-current (NC) induced single photon production is a sub-leading order process for accelerator-based neutrino beam experiments including T2K. It is, however, an important process to understand because it is a background for electron (anti)neutrino appearance oscillation experiments. Here, we performed the first search of this process below 1 GeV using the fine-grained detector at the T2K ND280 off-axis near detector. By reconstructing single photon kinematics from electron–positron pairs, we achieved 95% pure gamma ray sample from protons-on-targets neutrino mode data. We do not find positive evidence of NC induced single photon production in this sample. We set the model-dependent upper limit on the cross-section for this process, at cm2 (90% C.L.) per nucleon, using the J-PARC off-axis neutrino beam with an average energy of GeV. This is the first limit on this process below 1 GeV which is important for current and future oscillation experiments looking for electron neutrino appearance oscillation signals.

The ENUBET ERC project for an instrumented decay tunnel for future neutrino beams

The ENUBET ERC project (2016–2021) is studying a narrow band neutrino beam where lepton production can be monitored at single particle level. For this purpose, the decay tunnel is instrumented with longitudinally segmented calorimeters. Three different specialized calorimeters have been designed and tested, two of which based on the shashlik calorimetric concept with a compact readout while the third is a less compact version with a lateral readout. All of the prototypes are composed of thick steel absorbers coupled to plastic scintillators. Regarding the shashlik modules, a matrix of 3 × 3 fibers runs transversely with a density of one fiber/cm2. The fibers are coupled individually to silicon photomultipliers mounted on a custom PCB allowing to reduce the dead zones between adjacent modules to an extremely small level compared to the “fiber bundling” configurations. This setup allows a very effective longitudinal segmentation and hence e/π separation. The second shashlik module is based on polysiloxane scintillators which come in liquid form, are poured around the fiber arrays and finally made solid with a thermal treatment. Finally, the lateral readout module, light is collected from both sides of each scintillator tile and the 10 fibers from the same UCM are bundled to a single SiPM. Here are discussed the results of test beams performed in 2016–2018 at the CERN-PS East Area and the characterization of SiPMs of different cell size (12μm and 15μm) before and after being exposed to neutron fluxes up to 1012/cm2 at the INFN-LNL CN accelerator facility.

First measurement of νμ charged-current π0 production on argon with the MicroBooNE detector

We report the first measurement of the flux-integrated cross section of $\nu_{\mu}$ charged-current single $\pi^{0}$ production on argon. This measurement is performed with the MicroBooNE detector, an 85 ton active mass liquid argon time projection chamber exposed to the Booster Neutrino Beam at Fermilab. This result on argon is compared to past measurements on lighter nuclei to investigate the scaling assumptions used in models of the production and transport of pions in neutrino-nucleus scattering. The techniques used are an important demonstration of the successful reconstruction and analysis of neutrino interactions producing electromagnetic final states using a liquid argon time projection chamber operating at the earth's surface.

Commissioning and beam test of a high pressure time projection chamber

Due to their large active volume and low energy threshold for particle detection Time Projection Chambers (TPCs) are promising candidates to characterise neutrino beams at the next generation long baseline neutrino oscillation experiments such as DUNE and Hyper-K. The higher target density for the incoming neutrino beam of a TPC filled with gas at High Pressure (HPTPC) will potentially allow a better neutrino-nucleus interaction measurements as compared with TPCs at atmospheric pressure.The HPTPC we built has an active volume of about 0.5m3 which is embedded into a pressure vessel rated up to 6bar absolute pressure. A cascade of three meshes amplifies the primary ionisations. The induced charge on each mesh is read out. In addition the photons emitted during the gas amplification are read out by four CCD cameras focused on the readout plane, which thus image the 2D projection of a particle’s tracks on the transverse plane. The third coordinate is reconstructed from the charge signal.We tested the HPTPC’s performance during a four week beam test at the CERN PS, measuring low momentum proton (≤0.5GeV) interactions with the counting gas. Several mixtures with Argon predominance have been tested for their light yield and gas gain. The aim is to calculate the proton-Ar cross-section from the data sample, which will enter the calculations of final state interactions in neutrino Ar scattering.

Leggett-Garg inequality in the context of three flavor neutrino oscillation

The present work is devoted to the characterization of the Leggett-Garg inequality for three-flavoured neutrino oscillations in presence of both matter and Charge-Conjugation and Parity violating (CP) effects. This study complements and completes the recent one put forward in [17] by relaxing the stationary condition. At variance with the latter case, the LGI contains interference terms which cannot be expressed in terms of experimentally measurable quantities, thus drawing a clear-cut distinction between the two scenarios, as well as highlighting the role of the stationary assumption on such systems. We find that the additional terms are small for high energy neutrino beam compared to the maximum value attained by the Leggett-Garg parameter.

Final results of the OPERA experiment on ντ appearance and the OPERA “legacy”

OPERA (Oscillation Project with Emulsion tRacking Apparatus) was a long-baseline experiment at the INFN Gran Sasso laboratory (LNGS) designed to search for νμ → ντ oscillations in appearance mode. It took data from 2008 to 2012 with the CNGS neutrino beam from CERN. In 2015, after the detection of five ντ candidates with a signal-to-background ratio of ∼ 10, the discovery of ντ appearance in the CNGS beam was announced with 5.1σ significance. After having reached the experiment main goal, the selection of ντ candidates has been extended by loosening the selection criteria and applying a multivariate approach for events identification, in order to improve the statistical uncertainty in the measurement of the oscillation parameters and of ντ properties. Future experiments that will take advantage of the improvements done by OPERA in the use of nuclear emulsions will also be described.

Simulated Neutrino Signals of Low and Intermediate Energy Neutrinos on Cd Detectors

Neutrino-nucleus reactions cross sections, obtained for neutrino energies in the range $\varepsilon_{\nu}\leq 100-120$ MeV (low- and intermediate-energy range), which refer to promising neutrino detection targets of current terrestrial neutrino experiments, are presented and discussed. At first, we evaluated original cross sections for elastic scattering of neutrinos produced from various astrophysical and laboratory neutrino sources with the most abundant Cd isotopes $^{112}$Cd, $^{114}$Cd and $^{116}$Cd. These isotopes constitute the main material of the COBRA detector aiming to search for neutrinoless double beta decay events and neutrino-nucleus scattering events at the Gran Sasso laboratory (LNGS). The coherent $\nu$-nucleus reaction channel addressed with emphasis here, dominates the neutral current $\nu$-nucleus scattering, events of which have only recently been observed for a first time in the COHERENT experiment at Oak Ridge. Subsequently, simulated $\nu$-signals expected to be recorded at Cd detectors are derived through the application of modern simulation techniques and employment of reliable neutrino distributions of astrophysical $\nu$-sources (as the solar, supernova and Earth neutrinos), as well as laboratory neutrinos (like the reactor neutrinos, the neutrinos produced from pion-muon decay at rest and the $\beta$-beam neutrinos produced from the acceleration of radioactive isotopes at storage rings as e.g. at CERN).