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The neutrino mass hierarchy determination (ν MHD) is one of the main goals of the major current and future neutrino experiments. The statistical analysis usually proceeds from a standard method, a single-dimensional estimator 1D−Δχ2 that shows some drawbacks and concerns, together with a debatable strategy. The drawbacks and considerations of the standard method will be explained through the following three main issues. The first issue corresponds to the limited power of the standard method. The Δχ2 estimator provides us with different results when different simulation procedures were used. Regarding the second issue, when χminNH2 and χminIH2 are drawn in a 2D map, their strong positive correlation manifests χ2 as a bidimensional variable, instead of a single-dimensional estimator. The overlapping between the χ2 distributions of the two hypotheses leads to an experiment sensitivity reduction. The third issue corresponds to the robustness of the standard method. When the JUNO sensitivity is obtained using different procedures, either with Δχ2 as one-dimensional or χ2 as two-dimensional estimator, the experimental sensitivity varies with the different values of the atmospheric mass, the input parameter. We computed the oscillation of Δχ2¯ with the input parameter values, Δm2input. The MH significance using the standard method, Δχ2, strongly depends on the values of the parameter Δm2input. Consequently, the experiment sensitivity depends on the precision of the atmospheric mass. This evaluation of the standard method confirms the drawbacks.

A bstract The exclusive photoproduction reactions γp → J/ψ (1 S ) p and γp → ψ (2 S ) p have been measured at an ep centre-of-mass energy of 318 GeV with the ZEUS detector at HERA using an integrated luminosity of 373 pb − 1 . The measurement was made in the kinematic range 30 < W < 180 GeV, Q 2 < 1 GeV 2 and | t | < 1 GeV 2 , where W is the photon-proton centre-of-mass energy, Q 2 is the photon virtuality and t is the squared four-momentum transfer at the proton vertex. The decay channels used were J/ψ (1 S ) → μ + μ − , ψ (2 S ) → μ + μ − and ψ (2 S ) → J/ψ (1 S ) π + π − with subsequent decay J/ψ (1 S ) → μ + μ − . The ratio of the production cross sections, R = σ ψ (2 S ) /σ J/ψ (1 S ) , has been measured as a function of W and | t | and compared to previous data in photoproduction and deep inelastic scattering and with predictions of QCD-inspired models of exclusive vector-meson production, which are in reasonable agreement with the data.

The azimuthal correlation angle,$$\\Delta \\phi $$Δ ϕ , between the scattered lepton and the leading jet in deep inelastic$$e^{\\pm }p$$e ± p scattering at HERA has been studied using data collected with the ZEUS detector at a centre-of-mass energy of$$\\sqrt{s} = 318 {\\,\\text {Ge}\\hspace{-0.66666pt}\\text {V}}$$s = 318 Ge V , corresponding to an integrated luminosity of$$326 \\,\\text {pb}^{-1}$$326 pb - 1 . A measurement of jet cross sections in the laboratory frame was made in a fiducial region corresponding to photon virtuality$$10 {\\,\\text {Ge}\\hspace{-0.66666pt}\\text {V}}^2< Q^2 < 350 {\\,\\text {Ge}\\hspace{-0.66666pt}\\text {V}}^2$$10 Ge V 2 < Q 2 < 350 Ge V 2 , inelasticity$$0.04< y < 0.7$$0.04 < y < 0.7 , outgoing lepton energy$$E_e > 10 {\\,\\text {Ge}\\hspace{-0.66666pt}\\text {V}}$$E e > 10 Ge V , lepton polar angle$$140^\\circ< \\theta _e < 180^\\circ $$140 ∘ < θ e < 180 ∘ , jet transverse momentum$$2.5 {\\,\\text {Ge}\\hspace{-0.66666pt}\\text {V}}< p_\\textrm{T,jet} < 30 {\\,\\text {Ge}\\hspace{-0.66666pt}\\text {V}}$$2.5 Ge V < p T,jet < 30 Ge V , and jet pseudorapidity$$-1.5< \\eta _\\textrm{jet} < 1.8$$- 1.5 < η jet < 1.8 . Jets were reconstructed using the$$k_\\textrm{T}$$k T algorithm with the radius parameter$$R = 1$$R = 1 . The leading jet in an event is defined as the jet that carries the highest$$p_\\textrm{T,jet}$$p T,jet . Differential cross sections,$$d\\sigma /d\\Delta \\phi $$d σ / d Δ ϕ , were measured as a function of the azimuthal correlation angle in various ranges of leading-jet transverse momentum, photon virtuality and jet multiplicity. Perturbative calculations at$$\\mathcal {O}(\\alpha _{s}^2)$$O ( α s 2 ) accuracy successfully describe the data within the fiducial region, although a lower level of agreement is observed near$$\\Delta \\phi \\rightarrow \\pi $$Δ ϕ → π for events with high jet multiplicity, due to limitations of the perturbative approach in describing soft phenomena in QCD. The data are equally well described by Monte Carlo predictions that supplement leading-order matrix elements with parton showering.

In 1956 Reines & Cowan discovered the neutrino using a liquid scintillator detector. The neutrinos interacted with the scintillator, producing light that propagated across transparent volumes to surrounding photo-sensors. This approach has remained one of the most widespread and successful neutrino detection technologies used since. This article introduces a concept that breaks with the conventional paradigm of transparency by confining and collecting light near its creation point with an opaque scintillator and a dense array of optical fibres. This technique, called LiquidO, can provide high-resolution imaging to enable efficient identification of individual particles event-by-event. A natural affinity for adding dopants at high concentrations is provided by the use of an opaque medium. With these and other capabilities, the potential of our detector concept to unlock opportunities in neutrino physics is presented here, alongside the results of the first experimental validation. Liquid scintillator detectors have been used to study neutrinos ever since their discovery in 1956. The authors introduce an opaque scintillator detector concept for future neutrino experiments with increased capacity for particle identification and a natural affinity for doping.

Nuclear reactors are a source of electron antineutrinos due to the presence of unstable fission products that undergo β - decay. They will be exploited by the JUNO experiment to determine the neutrino mass ordering and to get very precise measurements of the neutrino oscillation parameters. This requires the reactor antineutrino spectrum to be characterized as precisely as possible both through high-resolution measurements, as foreseen by the TAO experiment, and detailed simulation models. In this paper, we present a benchmark analysis utilizing Serpent Monte Carlo simulations in comparison with real pressurized water reactor spent fuel data. Our objective is to study the accuracy of fission fraction predictions as a function of different reactor simulation approximations. Then, using the BetaShape software, we construct reactor antineutrino spectrum using the summation method, thereby assessing the influence of simulation uncertainties on it.

The neutrino mass hierarchy determination ( ν MHD) is one of the main goals of the major current and future neutrino experiments. The statistical analysis usually proceeds from a standard method, a single-dimensional estimator 1 D − Δ χ 2 that shows some drawbacks and concerns, together with a debatable strategy. The drawbacks and considerations of the standard method will be explained through the following three main issues. The first issue corresponds to the limited power of the standard method. The Δ χ 2 estimator provides us with different results when different simulation procedures were used. Regarding the second issue, when χ min NH 2 and χ min IH 2 are drawn in a 2D map, their strong positive correlation manifests χ 2 as a bidimensional variable, instead of a single-dimensional estimator. The overlapping between the χ 2 distributions of the two hypotheses leads to an experiment sensitivity reduction. The third issue corresponds to the robustness of the standard method. When the JUNO sensitivity is obtained using different procedures, either with Δ χ 2 as one-dimensional or χ 2 as two-dimensional estimator, the experimental sensitivity varies with the different values of the atmospheric mass, the input parameter. We computed the oscillation of Δ χ 2 ¯ with the input parameter values, Δ m 2 input . The MH significance using the standard method, Δ χ 2 , strongly depends on the values of the parameter Δ m 2 input . Consequently, the experiment sensitivity depends on the precision of the atmospheric mass. This evaluation of the standard method confirms the drawbacks.

Euclid is an ESA mission designed to understand why the expansion of the Universe is accelerating and what is the nature of the dark energy responsible for this acceleration. By measuring two cosmological probes simultaneously, the Weak Gravitational Lensing and the Galaxy Clustering (BAO and Redshift-Space distorsions), Euclid will constrain dark energy, general relativity, dark matter and the initial conditions of the Universe with unprecedented accuracy. Euclid will be equipped with a 1.2 m diameter SiC mirror telescope feeding 2 instruments: the visible imager and the Near-Infrared Spectro-Photometer. Here the Euclid's observation probes and main aims are recalled, and the NISP instrument and expected performances are presented.

The NESSiE Collaboration has been setup to undertake a conclusive experiment to clarify the muon-neutrino disappearance measurements at short baselines in order to put severe constraints to models with more than the three-standard neutrinos. To this aim the current FNAL-Booster neutrino beam for a Short-Baseline experiment was carefully evaluated by considering the use of magnetic spectrometers at two sites, near and far ones. The detector locations were studied, together with the achievable performances of two OPERA-like spectrometers. The study was constrained by the availability of existing hardware and a time-schedule compatible with the undergoing project of multi-site Liquid–Argon detectors at FNAL. The settled physics case and the kind of proposed experiment on the Booster neutrino beam would definitively clarify the existing tension between the ν μ disappearance and the ν e appearance/disappearance at the eV mass scale. In the context of neutrino oscillations the measurement of ν μ disappearance is a robust and fast approach to either reject or discover new neutrino states at the eV mass scale. We discuss an experimental program able to extend by more than one order of magnitude (for neutrino disappearance) and by almost one order of magnitude (for antineutrino disappearance) the present range of sensitivity for the mixing angle between standard and sterile neutrinos. These extensions are larger than those achieved in any other proposal presented so far.

Neutrino physics is nowadays receiving more and more attention as a possible source of information for the long-standing problem of new physics beyond the Standard Model. The recent measurement of the third mixing angle θ13 in the standard mixing oscillation scenario encourages us to pursue the still missing results on leptonic CP violation and absolute neutrino masses. However, several puzzling measurements exist which deserve an exhaustive evaluation. We will illustrate the present status of the muon disappearance measurements at small L/E and the current CERN project to revitalize the neutrino field in Europe with emphasis on the search for sterile neutrinos. We will then illustrate the achievements that a double muon spectrometer can make with regard to discovery of new neutrino states, using a newly developed analysis.

Many extensions of the Standard Model of particle physics explain the dominance of matter over antimatter in our Universe by neutrinos being their own antiparticles. This would imply the existence of neutrinoless double-β decay, which is an extremely rare lepton-number-violating radioactive decay process whose detection requires the utmost background suppression. Among the programmes that aim to detect this decay, the GERDA Collaboration is searching for neutrinoless double-β decay of Ge by operating bare detectors, made of germanium with an enriched Ge fraction, in liquid argon. After having completed Phase I of data taking, we have recently launched Phase II. Here we report that in GERDA Phase II we have achieved a background level of approximately 10 counts keV kg yr . This implies that the experiment is background-free, even when increasing the exposure up to design level. This is achieved by use of an active veto system, superior germanium detector energy resolution and improved background recognition of our new detectors. No signal of neutrinoless double-β decay was found when Phase I and Phase II data were combined, and we deduce a lower-limit half-life of 5.3 × 10 years at the 90 per cent confidence level. Our half-life sensitivity of 4.0 × 10 years is competitive with the best experiments that use a substantially larger isotope mass. The potential of an essentially background-free search for neutrinoless double-β decay will facilitate a larger germanium experiment with sensitivity levels that will bring us closer to clarifying whether neutrinos are their own antiparticles.