Νμ Beam Research Articles

Neutrino Program at Fermilab - Enhancing proton beam power and accelerator infrastructure

The upcoming long baseline neutrino experiments aim to enhance proton beam power to multi-MW scale and utilize large-scale detectors to address the challenge of limited event statistics. The DUNE experiment at LBNF will test the three neutrino flavor paradigm and directly search for CP violation by studying oscillation signatures in the high intensity νµ (anti-νµ) beam to νe (anti-νe) measured over a long baseline. Higher beam power and improved accelerator up-time will enhance neutrino flux for the neutrino program by increasing the number of protons on target. LBNF/DUNE, as well as PIP-II upgrade and Accelerator Complex Evolution (ACE) plan, play a vital role in this effort. The scientific potential of ACE plan extends beyond neutrino physics, encompassing endeavors such as the Muon Collider, Charged Lepton Flavor Violation (CLFV), Dark Sectors, and exploration of neutrinos beyond DUNE. In the era of higher-power accelerator operation, research in target materials and beam instrumentation is crucial for optimizing design modifications. This abstract discusses Fermilab ACE, the science opportunities it provides, and how Fermilab is pushing the limits of proton beam power and accelerator infrastructure. By tackling neutrino beam challenges and exploring research and development ideas, we are advancing our understanding of fundamental particles and their interactions.

QED radiative corrections for accelerator neutrinos

Neutrino oscillation experiments at accelerator energies aim to establish charge-parity violation in the neutrino sector by measuring the energy-dependent rate of νe appearance and νμ disappearance in a νμ beam. These experiments can precisely measure νμ cross sections at near detectors, but νe cross sections are poorly constrained and require theoretical inputs. In particular, quantum electrodynamics radiative corrections are different for electrons and muons. These corrections are proportional to the small quantum electrodynamics coupling α ≈ 1/137; however, the large separation of scales between the neutrino energy and the proton mass (~GeV), and the electron mass and soft-photon detection thresholds (~MeV) introduces large logarithms in the perturbative expansion. The resulting flavor differences exceed the percent-level experimental precision and depend on nonperturbative hadronic structure. We establish a factorization theorem for exclusive charged-current (anti)neutrino scattering cross sections representing them as a product of two factors. The first factor is flavor universal; it depends on hadronic and nuclear structure and can be constrained by high-statistics νμ data. The second factor is non-universal and contains logarithmic enhancements, but can be calculated exactly in perturbation theory. For charged-current elastic scattering, we demonstrate the cancellation of uncertainties in the predicted ratio of νe and νμ cross sections. We point out the potential impact of non-collinear energetic photons and the distortion of the visible lepton spectra, and provide precise predictions for inclusive observables.

Annual modulation of the atmospheric muon flux measured by the OPERA experiment

The OPERA experiment, designed to search for νμ→ντ oscillations, reached its main goal by observing the appearance of ντ in the CNGS νμ beam. Thanks to its location in the underground Gran Sasso laboratory, under 3800 m.w.e., it has also been exploited as an observatory for TeV muons produced by cosmic rays in the atmosphere. In this paper the preliminary measurement of the annual modulation of the atmospheric muon flux with the OPERA detector is reported.

The nuSTORM experiment

The nuSTORM facility will provide νe and νµ beams from the decay of low energy muons confined within a storage ring. The instrumentation of the ring, combined with the excellent knowledge of muon decay, will make it possible to determine the neutrino flux at the %-level or better. The neutrino and anti-neutrino event rates are such that the nuSTORM facility serving a suite of near detectors will be able to measure νeN and νµN cross sections with the %-level precision required to allow the next generation of long-baseline neutrino-oscillation experiments to fulfil their potential. By delivering precise cross section measurements with a pure weak probe nuSTORM may have the potential to make measurements important to understanding the physics of nuclei. The precise knowledge of the initial neutrino flux also makes it possible to deliver uniquely sensitive sterile-neutrino searches. The concept for the nuSTORM facility will be presented together with an evaluation of its performance. The status of the planned consideration of nuSTORM at CERN in the context of the Physics Beyond Colliders workshop will be summarised.

New results from the OPERA experiment

The OPERA experiment reached its main goal by proving the appearance of νη in the CNGS νμ beam. A total sample of 5 candidates fulfilling the analysis defined in the proposal was detected with a S/B ratio of about ten allowing to reject the null hypothesis at 5.1σ. The search has been extended to γη-like interactions failing the kinematical analysis defined in the experiment proposal to obtain a statistically enhanced, lower purity, signal sample. Based on the enlarged data sample the estimation of Δm223 in appearance mode is presented. The search for νe interactions has been extended over the full data set with a more than twofold increase in statistics with respect to published data. The analysis of the νμ μ νe channel is updated and the implications of the electron neutrino sample in the framework of the 3+1 sterile model is discussed. An analysis of νμ μ νπ interactions in the framework of the sterile neutrino model has also been performed. Moreover the results of the analysis of the annual modulation of the cosmic muon rate will be presented.

Electron neutrino appearance in the NOvA experiment

NOvA is an off-axis, two-detector experiment studying neutrino oscillations with the νµ beam from Fermilab. This paper describes the νe appearance analysis, including data-driven constraints from Near Detector measurements. The data set corresponds to an exposure equivalent to 6.05 × 1020 protons-on-target in the Far Detector. We observed 33 νe candidates with a predicted background of 8.2 ± 0.8 (syst.), for a significance of appearance higher than 8σ. Preliminary results for the allowed values of δCP and θ23 in both hierarchies are presented.

Performance study of the new light collection system for the ICARUS T600 detector

The ICARUS T600 detector is the largest liquid argon time projection chamber (LArTPC) to be built and operated [1]. This detector was in operation in the INFN Gran Sasso underground laboratory until 2012, exposed to the CERN Neutrino to Gran Sasso (CNGS) νµ beam, performing neutrino oscillation studies. The ICARUS T600 is presently under refurbishment in order to make it suitable for surface level operation, as it will serve as the far detector for the Short-Baseline Neutrino (SBN) Program at Fermilab [2]. A major upgrade of the ICARUS detector in order to allow it to cope with a high cosmic background is the upgrade of the light collection system. The study presented here shows a simulation to optimize the PMT layout to allow for the localization and identification of interaction within the T600. An excellent performance can be obtained, with an error on the localization smaller than 20 cm and of the order of a few percent in the identification of cosmic rays.

VALOR joint oscillation analysis using multiple LAr-TPCs in the Booster Neutrino Beam at Fermilab

Anomalies observed by different experiments, the most significant ones being the ∼3.8 sigma νe appearance in a ∼50 MeV νµ beam from muon decay at rest observed by the LSND experiment and the ∼3.8 sigma νe and appearance in a ∼1 GeV neutrino beam from pion decay in flight observed by MiniBooNE, suggest the existence of sterile neutrinos. The Short Baseline Neutrino (SBN) program at Fermilab aims to perform a sensitive search for sterile neutrinos by performing analyses of νe appearance and νµ disappearance employing three Liquid Argon Time Projection Chambers (LAr-TPCs) at different baselines.The VALOR neutrino fitting group was established within the T2K experiment and has led numerous flagship T2K oscillation analyses, and provided sensitivity and detector optimisation studies for DUNE and Hyper-K. The neutrino oscillation framework developed by this group is able to perform fits of several samples and systematic parameters within different neutrino models and experiments. Thus, VALOR is an ideal environment for the neutrino oscillation fits using multiple LAr-TPC detectors with proper treatment of correlated systematic uncertainties necessary for the SBN analyses.

Determination of the muon charge sign with the dipolar spectrometers of the OPERA experiment

The OPERA long-baseline neutrino-oscillation experiment has observed the direct appearance of ντ in the CNGS νμ beam. Two large muon magnetic spectrometers are used to identify muons produced in the τ leptonic decay and in νμ CC interactions by measuring their charge and momentum. Besides the kinematic analysis of the τ decays, background resulting from the decay of charmed particles produced in νμ CC interactions is reduced by efficiently identifying the muon track. A new method for the charge sign determination has been applied, via a weighted angular matching of the straight track-segments reconstructed in the different parts of the dipole magnets. Results obtained for Monte Carlo and real data are presented. Comparison with a method where no matching is used shows a significant reduction of up to 40% of the fraction of wrongly determined charges.

Joint νμ Disappearance and νe Appearance Analysis at the T2K Experiment Using a Frequentist Approach

The T2K long-baseline neutrino oscillation experiment has observed the disappearance of νμ and the appearance of νe from its νμ beam. Since 2010, it has accumulated 6.57×1020 protons on target and observed 120νμ and 28νe event candidates. With this dataset, corresponding to only ∼8% of its goal POT, T2K has achieved world leading results: the best precision in θ23, the strongest evidence of νe appearance in a νμ beam and the first hint on δCP. Its first joint 3-flavour oscillation analysis, combining the νμ disappearance and νe appearance channels, is presented in this paper using a Frequentist approach. The results of this analysis, combined with the measurements from reactor experiments, indicate that δCP is consistent with −π/2. Furthermore, the data excluded values of δCP in the interval [0.146,0.825]π([−0.080,1.091]π) at the 90% CL for normal (inverted) mass hierarchy.

Initial Probe of δCP by the T2K Experiment with νμ Disappearance and νe Appearance

The T2K long-baseline neutrino oscillation experiment has observed the disappearance of νμ and the appearance of νe from its νμ beam and it has accumulated 6.57×1020 protons on target, ∼ 8% of its goal POT. Combining its νμ disappearance and νe appearance measurements with the results from reactor experiments, T2K has obtained the first constraint to date on the CP-violating phase δCP. Two kind of joint 3-flavour oscillation analyses have been performed, based on either Frequentist or Bayesian methods, and the results from both analyses indicate that δCP is consistent with −π/2. Furthermore, the data excluded values for δCP: the excluded regions found at the 90% CL with the Frequentist analysis are [0.146,0.825]π ([-0.080,1.091]π) for normal (inverted) mass hierarchy; and the Bayesian 90% CI obtained, marginalizing over the mass hierarchy and assuming flat priors, is [-1.13,0.14]π. Although more T2K neutrino (and possibly anti-neutrino) data is necessary to confirm this result, whose sensitivity could be enhanced in combination with results from a new generation of long-baseline neutrino oscillation experiments and the latest reactor measurements, this first hint on CP violation opens exciting possibilities.

Search for νμ → νe oscillations with the OPERA experiment in the CNGS beam

The OPERA hybrid detector, designed to prove neutrino oscillations in the νμ→ντ channel, was exposed to the CNGS νμ beam at a distance of 730 km from the neutrino source. Profiting of the tracking capabilities of its Emulsion Cloud Chamber system, OPERA can perform also a search for νμ→νe oscillations. Current results are compatible with the non-oscillation hypothesis in the three flavour mixing model. The same data allow to constrain the non-standard oscillation parameters θnew and Δmnew2 indicated by the LSND and MiniBooNE experiments.

Recent results from the T2K experiment

T2K is a long-baseline neutrino oscillation experiment based in Japan. It was the first experiment to observe ν e appearance in a νμ beam, and has more recently produced the highest precision measurement of the oscillation parameter θ 23 and has begun to probe the charge-parity violation phase δ . Using a νμ beam disappearance sample, T2K measures sin2 θ 23 = 0.514+0.055 -0.056 and Δm 2 32 = (2.51 ± 0.10)×10−3 eV2 /c4 assuming the normal mass hierarchy, and sin2 θ 23 = 0.511±0.055 and Δm 2 13 = (2.48 ± 0.10)×10−3 eV2 /c4 assuming the inverted mass hierarchy. A joint fit between νμ beam appearance and disappearance samples produces consistent results for sin2 θ 23 and Δm 2 32 whilst also excluding at 90% confidence level the regions δ = [0.15,0.83]π for the normal hierarchy and δ = [− 0.08,1.09]π . Using a beam disappearance sample, and , consistent with previous measurements and the T2K ν μ sample.

Recent Evolution of the Offline Computing Model of the NOvA Experiment

The NOvA experiment at Fermilab is a long-baseline neutrino experiment designed to study νe appearance in a νμ beam. Over the last few years there has been intense work to streamline the computing infrastructure in preparation for data, which started to flow in from the far detector in Fall 2013. Major accomplishments for this effort include migration to the use of off-site resources through the use of the Open Science Grid and upgrading the file-handling framework from simple disk storage to a tiered system using a comprehensive data management and delivery system to find and access files on either disk or tape storage. NOvA has already produced more than 6.5 million files and more than 1 PB of raw data and Monte Carlo simulation files which are managed under this model. The current system has demonstrated sustained rates of up to 1 TB/hour of file transfer by the data handling system. NOvA pioneered the use of new tools and this paved the way for their use by other Intensity Frontier experiments at Fermilab. Most importantly, the new framework places the experiment's infrastructure on a firm foundation, and is ready to produce the files needed for first physics.

T2K results and perspectives

T2K is a long-baseline neutrino oscillation experiment using a νμ beam produced at the J-PARC facility. Neutrinos are detected at a Near Detector complex (ND280) and at the Far Detector (Super-Kamiokande). Details of the analyses at ND280 are given in these proceedings as well as the most recent oscillation results. With the data collected so far T2K has produced the first observation of νe appearance, the best measurement of θ23 through νμ disappearance and, in combination with reactor results, first hints of a non-zero value of δCP.

Locating the neutrino interaction vertex with the help of electronic detectors in the OPERA experiment

The OPERA experiment is designed for the direct observation of the appearance of ντ from νμ → ντ oscillation in a νμ beam. A description of the procedure of neutrino interaction vertex localization (Brick Finding) by electronic detectors of a hybrid OPERA setup is presented. The procedure includes muon track and hadronic shower axis reconstruction and a determination of the target bricks with the highest probability to contain the vertex.

The OPERA Experiment and Recent Results

OPERA (Oscillation Project with Emulsion tRacking Apparatus) is a long-baseline neutrino experiment, designed to perform the first direct detection of νμ → ντ oscillation in appearance mode. The OPERA detector is placed in the CNGS long baseline νμ beam, 732 km away from the neutrino source. The detector, consisting of a modular target made of lead - nuclear emulsion units complemented by electronic trackers and muon spectrometers, has been conceived to select ντ charged current interactions through the observation of the outcoming tau leptons and their subsequent decays. Runs with CNGS neutrinos were carried out from 2008 to 2012. In this paper results on νμ → ντ oscillations with background estimation and statistical significance are reported.

Experimental Prospect

This is the first conference of this series the three of the lepton mixing angles are known. The non-zero value of the third mixing angle (θ13) has been reported by νe appearance in accelerator νμ beam and by ν¯e disappearance in reactor experiments. The observation of the νe appearance in νμ beam is the first clear evidence of the flavor oscillations. The results also show that neutrino oscillations phenomena can be described by three-generation scheme to the first approximation, where mixing of neutrinos can be described by three angles and one complex phase. There are two main issues to be investigated by neutrino oscillation experiments. One is the study of CP violation in lepton secto. Namely, the measurement of CP violating complex phase δCP and the studies of the nature of CP violation phenomena in lepton sector. The other is search for neutrinos beyond three generations. There are indications of the existence of additional neutrinos, which should be tested by definitive experiments. The number of neutrino species has important implications not only in particle physics but also in physics of early Universe. Also many fundamental natures of neutrinos remain to be studied, such as absolute values of masses, nature of the particle (Majorana or Dirac particle). This article concentrates on the future experimental prospects on the study of neutrino physics by means of neutrino oscillation.

The T2K Side Muon Range Detector (SMRD)

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 295km distant Super-Kamiokande Detector and monitored by a suite of near detectors at 280m 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.

The T2K fine-grained detectors

T2K is a long-baseline neutrino oscillation experiment searching for νe appearance in a νμ beam. The beam is produced at the J-PARC accelerator complex in Tokai, Japan, and the neutrinos are detected by the Super-Kamiokande detector located 295km away in Kamioka. A suite of near detectors (ND280) located 280 m downstream of the production target is used to characterize the components of the beam before they have had a chance to oscillate and to better understand various neutrino interactions on several nuclei. This paper describes the design and construction of two massive fine-grained detectors (FGDs) that serve as active targets in the ND280 tracker. One FGD is composed solely of scintillator bars while the other is partly scintillator and partly water. Each element of the FGDs is described, including the wavelength shifting fiber and Multi-Pixel Photon Counter used to collect the light signals, the readout electronics, and the calibration system. Initial tests and in situ results of the FGDs' performance are also presented.