arXiv subjects

Emilio Ciuffoli

Publications and source records attributed to Emilio Ciuffoli.

At least 19 recordsLinked to original sources

arXiv2026

Precise Measurement of $\delta$ at LBL Experiments Using Only The Neutrino Sector

Currently, the CP-violating phase $\delta$ is the least precisely known among the neutrino mixing parameters. In the coming years, accelerator neutrino experiments such as DUNE and Hyper-K will measure $\delta$, significantly increasing the precision. Such a measurement is usually performed by comparing the oscillation probabilities in the neutrino and antineutrino sectors, thereby directly observing the CP violation. This approach, however, has some downsides: in particular, it is more challenging to obtain good statistics in the antineutrino sector, leading to increased statistical errors. In principle, however, it is possible to determine $\delta$ by looking only at the neutrino sector, studying the energy dependence of the oscillation probability. We investigate this possibility in detail; we find that, if this approach is used, the main issue would be the degeneracies with other mixing parameters, which affect the sensitivity to $\delta$. Those parameters, however, have already been measured with great precision, which will increase even more in the next few years; if those constraints are taken into account by introducing Gaussian penalty terms in the $\chi^2$, it is possible to achieve better results focusing only on the neutrino sector, rather than using the standard approach. Those degeneracies could also be broken by exploring a wider range of $L/E$: this can be achieved, for instance, by increasing the neutrino energy. In this way, the total beam intensity could also increase due to the relativistic boost (however, the conversion efficiency could decrease, affecting the total luminosity). We find that if the relativistic boost increases the number of events in the high-energy configuration, the best performance would be achieved in such a set-up; otherwise, the optimal approach would be to focus only on the neutrino mode without changing the beam energy.

hep-ph↗

arXiv2025

Testing the Gallium anomaly using Electron-Neutrino Scattering

The Gallium anomaly is an unexplained deficit in the neutrinos observed during the calibration of GALLEX and SAGE using a $^{51}$Cr radioactive source and recently confirmed by BEST. The possible explanations for this deficit include an overestimation of the neutrino absorption cross section in Ga, an incorrect measurement of the source activity or the existence of sterile neutrinos. However, as this deficit has only been observed in Ga detectors, it has not been possible to distinguish among various proposals. Therefore, we propose an experiment using the same radioactive source but with a different detection method, electron-neutrino scattering. We discuss potential locations for such an experiment, estimating the main backgrounds and expected event rates, considering various target masses and source positions. Even if the anomaly does not result from the detection method, such an experiment can provide an independent determination of the branching ratio of the $^{51}$Cr decay by using the spectral information or observing the scattering angle. It is also sensitive to an eventual baseline dependence of the anomaly, as is predicted in sterile neutrino models.

hep-ph↗

arXiv2024

Finite Energy Resolution, Correlations Between Bins and Non-Nested Hypotheses

We show that whenever independent events are binned, there is no correlation between bins. In particular, neither the uncertainty in the energy resolution nor a systematic error in the energy response of a detector will lead to a correlation between bins. This is in contrast with a result that recently appeared in the literature, where it was claimed that the finite energy resolution could induce correlation between bins, changing the distribution of $\Delta\chi^2$ when attempting to determine the neutrino mass ordering using reactor neutrinos. We will compute the expression for the variance of $\Delta\chi^2$ in the case of non-nested hypotheses if correlations between bins are present, showing that they could indeed affect the distribution. We will also show, however, that the detector response cannot introduce statistical correlations between bins unless these are already present in the original spectrum. Both of these results are valid in general: the absence of correlation is true for any detector response and the distribution of $\Delta\chi^2$ in the presence of (intrinsic) correlations, while obtained having the mass ordering in mind, it is true for any non-nested hypotheses.

hep-ph↗

arXiv2023

Neutron Activation Background in the NvDEx Experiment

An extremely low-background environment is a crucial requirement for any neutrinoless double beta decay experiment. Neutrons are very difficult to stop, because they can pass through the shields and activate nuclei in the detector, even inside the fiducial volume itself. Using Geant4 simulations we have studied the neutron background for N$\nu$DEx-100 and the most efficient way to reduce it. Using a 60 cm thick external HDPE shield the neutron background can be reduced down to $0.24\pm 0.06$ events/year, lower than the background rate due to natural radioactivity (0.42 events/year), which was used as a benchmark for these calculations. The amount of shielding material needed can be significantly reduced by placing HDPE in the empty space between the lead shield and the steel vessel; in this way, it is sufficient to add 20 cm external HDPE shield to reduce the neutron background down to $0.15\pm0.05$ events/year.

physics.ins-det↗

arXiv2022

Where Neutrino Decoherence Lies

Recently, several studies of neutrino oscillations in the vacuum have not found the decoherence long expected from the separation of wave packets of neutrinos in different mass eigenstates. We show that such decoherence will, on the other hand, be present in a treatment including any mechanism which leads to a dependence of the final state on both the neutrino's emission and absorption time. Our demonstration is in the 3+1d $V-A$ model, however the details of this model lead to an overall factor which does not affect our conclusions. This allows us to consider a simpler model. There we show that if the positions of the final state particles are measured, or equivalently entangled with the environment, then decoherence will damp neutrino oscillations. We also show that wave packet spreading can cause the decoherence to eventually saturate, without completely suppressing the oscillations.

hep-ph↗

arXiv2020

Measuring Entangled Neutrino States in a Toy Model QFT

Localized wave packet treatments of neutrino oscillations by various groups lead to mutually inconsistent predictions. The neutrino wave packet description arises as an approximate substitute for the evolution of an entangled state which is not localized. The disagreements arise from qualitative differences in the framework which are not specific to electroweak interactions, and so have analogues in simpler models. Therefore in this note we introduce a toy model which allows one to explicitly test these predictions while consistently keeping track of the entanglement of the neutrinos and the source particles. Our study is robust as we use only the Schrodinger picture evolution equations on the entangled state, which are solved explicitly without recourse to the wave packet approximation.

hep-ph↗

arXiv2020

A Sterile Neutrino Search at compact materials irradiation facility

The compact material irradiation facility (CMIF) is a current project in China that will provide a compact deuteron-beryllium neutron source. The target of this facility will be an intense and compact Isotope Decay-At-Rest (IsoDAR) neutrino source. In this paper, we propose to test the sterile neutrino hypothesis using CMIF as the neutrino source. At CMIF platform, the electron antineutrino production rate can be up to $2.0\times 10^{19}$ per day. When paired with an 80 t liquid scintillator detector to study short baseline electron antineutrino disappearance, the inverse beta decay (IBD) event rate is large enough to investigate the parameter ranges of interest for neutrino anomalies. Our sensitivity analysis shows that a short baseline experiment at this platform will provide a very competitive sterile neutrino search, especially in the high-$Δm^2$ region ($Δm^2 >10\,\text{eV}^2$).

physics.ins-det↗

arXiv2020

Wave Packets Losing Their Covariance

In neutrino physics, it is sometimes assumed that all wave packets must transform covariantly as Lorentz vectors. We show in a simple example that even if the initial conditions of a wave packet are covariant, then evolution in a relativistic interacting theory followed by a measurement of entangled particles can lead to a wave packet which is no longer covariant.

hep-ph↗

arXiv2020

Approximate Neutrino Oscillations in the Vacuum

It is well known that neutrino oscillations may damp due to decoherence caused by the separation of mass eigenstate wave packets or by a baseline uncertainty of order the oscillation wave length. In this note we show that if the particles created together with the neutrino are not measured and do not interact with the environment, then the first source of decoherence is not present. This demonstration uses the saddle point approximation and also assumes that the experiment lasts longer than a certain threshold. We independently derive this result using the external wave packet model and also using a model in which the fields responsible for neutrino production and detection are treated dynamically. Intuitively this result is a consequence of the fact that the neutrino emission time does not affect the final state and so amplitudes corresponding to distinct emission times must be added coherently. This fact also implies that oscillations resulting from mass eigenstates which are detected simultaneously arise from neutrinos which were not created simultaneously but are nonetheless coherent, realizing the neutrino oscillation paradigm of Kobach, Manohar and McGreevy.

hep-ph↗

arXiv2019

Uncertainty in the Reactor Neutrino Spectrum and Mass Hierarchy Determination

One of the challenges that must be overcome in order to determine the neutrino mass hierarchy using reactor neutrinos is the theoretical uncertainty in the unoscillated reactor neutrino spectrum: this is one of the reasons why, recently, it was proposed to add a near detector to the JUNO experiment. A model-independent treatment of the spectrum uncertainty will be discussed, as well as the effect that it will have on the final result. Moreover, since the neutrino spectrum depends on the chemical composition of the fuel, the spectra at the near and far detectors will be different, because they will receive neutrinos from different cores. Taking into account the time evolution of the chemical composition of the fuel in the reactor core, it is possible to reconstruct the far detector spectrum from the near detector data. We will show that the method used to reconstruct the spectrum can affect sensitivity to the mass hierarchy, however if the near detector is large enough the difference will be negligible.

hep-ph↗

arXiv2019

Entangled Neutrino States in a Toy Model QFT

It has been claimed that wave packets must be covariant and also that decohered neutrino oscillations are always revived during measurement. These conjectures are supported by general arguments which are not specific to the electroweak theory, and so if they are true for neutrinos they will also be true for simplified models. In this paper we produce such a simplified model in which the neutrino wave function, including its entanglement with the source particle and the environment, can be calculated explicitly in quantum field theory. It exhibits neutrino oscillation, which is reduced at late times by decoherence due to interactions of the source with the environment. One simple lesson from this model is that only the difference between the environmental interactions before and after neutrino emission can reduce the amplitude of neutrino oscillations. The model will be used to test the conjectures in a companion paper.

hep-ph↗

arXiv2018

Extracting nuclear form factors with coherent neutrino scattering

Coherent elastic neutrino-nucleus scattering (CEvNS) can be used to determine the neutron part of nuclear form factors, unlocking intrinsic properties of nuclear structure. In contrast with other such methods, CEvNS is free from both strong interaction effects and Coulomb distortions. We propose precision measurements of CEvNS with an upcoming accelerator facility and determine the corresponding requirements for such a neutrino detector. We find that most significant backgrounds come from fast neutrons, induced by cosmogenic muons or from the pion decays at rest in the target station. With ton-scale liquid noble gas detectors, we will not only achieve percent level precision in the measurement of neutron radii but also clarify contributions of higher-order moments to nuclear form factors.

physics.ins-det↗

arXiv2018

Getting the Most Neutrinos out of IsoDAR

Several experimental collaborations worldwide intend to test sterile neutrino models by measuring the disappearance of antineutrinos produced via isotope decay at rest (IsoDAR). The most advanced of these proposals have very similar setups, in which a proton beam strikes a target yielding neutrons which are absorbed by a high isotopic purity 7Li converter, yielding 8Li whose resulting decay yields the antineutrinos. In this note, we use FLUKA and GEANT4 simulations to investigate three proposed modifications of this standard proposal. In the first, the 7Li is replaced with 7Li compounds including a deuterium moderator. In the second, a gap is placed between the target and the converter to reduce the neutron bounce-back. Finally, we consider cooling the converter with liquid nitrogen. We find that these modifications can increase the antineutrino yield by as much as 50 percent. The first also substantially reduces the quantity of high purity 7Li which is needed.

physics.ins-det↗

arXiv2017

Statistical Methods for the Neutrino Mass Hierarchy

In the next decade several experiments will attempt to determine the neutrino mass hierarchy, i.e. the sign of $Δm_{31}^2$. In the last years it was noticed that the two hierarchies are disjoint hypotheses and, for this reason, Wilks' theorem cannot be applied: this means that $Δχ^2=χ^2_{IH}-χ^2_{NH}$ does not follow a one-degree-of-freedom chi-square distribution. It was proven that, under certain assumptions, it follows instead a Gaussian distribution with $σ=2\sqrtμ$. I will present several possible definition of sensitivity and review the approaches proposed in the literature, both within the Bayesian and the frequentist framework, examining advantages and disadvantages and discussing how they should be modified if the conditions for Gaussianity are not fulfilled. I will also discuss the possibility of introducing a new pull parameter in order to avoid the issue related to the non-nested hypotheses and the differences between marginalization and minimization, showing under which conditions the two procedures yield the same $Δχ^2$.

hep-ph↗

arXiv2016

Sensitivity to the Neutrino Mass Hierarchy

In the next decade, a number of experiments will attempt to determine the neutrino mass hierarchy. Feasibility studies for such experiments generally determine the expected value of Delta chi^2. As the hierarchy is a discrete choice, Delta chi^2 does not obey a one degree of freedom chi^2 distribution and so the number of sigmas of confidence of the hierarchy determination is not the square root of the expected Delta chi^2. We present a simple formula for the sensitivity to the hierarchy that can be expected from the median experiment as a function of the expected Delta chi^2.

hep-ph↗

arXiv2015

Neutrino Physics with Accelerator Driven Subcritical Reactors

Accelerator driven system (ADS) subcritical nuclear reactors are under development around the world. They will be intense sources of free, 30-50 MeV antimuon decay at rest antimuon neutrinos. These ADS reactor neutrinos can provide a robust test of the LSND anomaly and a precise measurement of the leptonic CP-violating phase delta, including sign(cos(delta)). The first phase of many ADS programs includes the construction of a low energy, high intensity proton or deuteron accelerator, which can yield competitive bounds on sterile neutrinos.

hep-ph↗

arXiv2015

Measuring theta12 Despite an Uncertain Reactor Neutrino Spectrum

The recently discovered 5 MeV bump highlights that the uncertainty in the reactor neutrino spectrum is far greater than some theoretical estimates. Medium baseline reactor neutrino experiments will deliver by far the most precise ever measurements of theta12. However, as a result of the bump, such a determination of theta12 using the theoretical spectrum would yield a value of sin^2(2theta12) which is more than 1% higher than the true value. We show that by using recent measurements of the reactor neutrino spectrum the precision of a measurement of theta12 at a medium baseline reactor neutrino experiment can be improved appreciably. We estimate this precision as a function of the 9Li spallation background veto efficiency and dead time.

hep-ph↗

arXiv2015

Vetoing Cosmogenic Muons in A Large Liquid Scintillator

At upcoming medium baseline reactor neutrino experiments the spallation 9Li background will be somewhat larger than the inverse beta decay reactor neutrino signal. We use new FLUKA simulations of spallation backgrounds to optimize a class of veto strategies and find that surprisingly the optimal veto for the mass hierarchy determination has a rejection efficiency below 90%. The unrejected background has only a modest effect on the physics goals. For example $Δχ^2$ for the hierarchy determination falls by 1.4 to 3 points depending on the muon tracking ability. The optimal veto strategy is essentially insensitive to the tracking ability, consisting of 2 meter radius, 1.1 second cylindrical vetoes of well tracked muons with showering energies above 3 to 4 GeV and 0.7 second full detector vetoes for poorly tracked muons above 15 to 18 GeV. On the other hand, as the uncertainty in theta12 will be dominated by the uncertainty in the reactor neutrino spectrum and not statistical fluctuations, the optimal rejection efficiency for the measurement of theta12 is 93% in the case of perfect tracking.

physics.ins-det↗