Value Of Neutrino Mass Research Articles

Testing the Origins of Neutrino Mass with Supernova-Neutrino Time Delay.

The origin of neutrino masses remains unknown. Both the vacuum mass and the dark mass generated by the neutrino interaction with dark matter (DM) particles or fields can fit the current oscillation data. The dark mass squared is proportional to the DM number density and, therefore, varies on the galactic scale with much larger values around the Galactic Center. This affects the group velocity and the arrival time delay of core-collapse supernovae (SN) neutrinos. This time delay, especially for the ν_{e} neutronization peak with a sharp time structure, can be used to distinguish the vacuum and dark neutrino masses. For illustration, we explore the potential of the Deep Underground Neutrino Experiment (DUNE), which is sensitive to ν_{e}. Our simulations show that DUNE can distinguish the two neutrino mass origins at more than 5σ C.L., depending on the observed local value of neutrino mass, the neutrino mass ordering, the DM density profile, and the SN location.

Deep learning based event reconstruction for cyclotron radiation emission spectroscopy

The objective of the cyclotron radiation emission spectroscopy (CRES) technology is to build precise particle energy spectra. This is achieved by identifying the start frequencies of charged particle trajectories which, when exposed to an external magnetic field, leave semi-linear profiles (called tracks) in the time–frequency plane. Due to the need for excellent instrumental energy resolution in application, highly efficient and accurate track reconstruction methods are desired. Deep learning convolutional neural networks (CNNs) - particularly suited to deal with information-sparse data and which offer precise foreground localization—may be utilized to extract track properties from measured CRES signals (called events) with relative computational ease. In this work, we develop a novel machine learning based model which operates a CNN and a support vector machine in tandem to perform this reconstruction. A primary application of our method is shown on simulated CRES signals which mimic those of the Project 8 experiment—a novel effort to extract the unknown absolute neutrino mass value from a precise measurement of tritium β −-decay energy spectrum. When compared to a point-clustering based technique used as a baseline, we show a relative gain of 24.1% in event reconstruction efficiency and comparable performance in accuracy of track parameter reconstruction.

A minimal inverse seesaw model with S4 flavour symmetry

We construct an S4 flavour symmetric minimal inverse seesaw model where the standard model is extended by adding two right-handed and two standard model gauge singlet neutrinos to explain the origin of tiny neutrino masses. The resulting model describes the lepton mass spectra and flavour mixing quite well for the case of the normal hierarchy of neutrino masses. The prediction of the model on the Dirac CP-violating phase is centered around 370.087°. Furthermore, using the allowed region for the model parameters, we have calculated the value of the effective Majorana neutrino mass, |〈mee〉|, which characterizes neutrinoless double beta decay.

Toward the discovery of matter creation with neutrinoless ββ decay

Observation of neutrino oscillations implies that neutrinos have mass, but one does not know whether they are described by Dirac or Majorana mass terms. The discovery of a Majorana mass would provide a test of the global symmetries of the standard model, and would have implications for the origin of the number of baryons in the Universe. To achieve this one can search for neutrinoless double-beta decay, a rare nuclear decay where two new electrons are created with no antimatter. The next generation of experiments will explore large Majorana neutrino mass values, also testing alternative theoretical models. In this review, devoted to neutrinoless double-beta decay, the particle and nuclear physics aspects involved in predicting the decay rate and the experimental search methods are discussed.

Analyzing the Time Spectrum of Supernova Neutrinos to Constrain Their Effective Mass or Lorentz Invariance Violation

We analyze the expected arrival time spectrum of supernova neutrinos using simulated luminosity and compute the expected number of events in future detectors such as the DUNE Far Detector and Hyper-Kamiokande. We develop a general method using minimum square statistics that can compute the sensitivity to any variable affecting neutrino time of flight. We apply this method in two different situations: First, we compare the time spectrum changes due to different neutrino mass values to put limits on electron (anti)neutrino effective mass. Second, we constrain Lorentz invariance violation through the mass scale, MQG, at which it would occur. We consider two main neutrino detection techniques: 1. DUNE-like liquid argon TPC, for which the main detection channel is νe+40Ar→e−+40K∗, related to the supernova neutronization burst; and 2. HyperK-like water Cherenkov detector, for which ν¯e+p→e++n is the main detection channel. We consider a fixed supernova distance of 10 kpc and two different masses of the progenitor star: (i) 15 M⊙ with neutrino emission time up to 0.3 s and (ii) 11.2 M⊙ with neutrino emission time up to 10 s. The best mass limits at 3σ are for O(1) eV. For νe, the best limit comes from a DUNE-like detector if the mass ordering happens to be inverted. For ν¯e, the best limit comes from a HyperK-like detector. The best limit for the Lorentz invariance violation mass scale at the 3σ level considering a superluminal or subluminal effect is MQG≳1013 GeV (MQG≳5×105 GeV) for linear (quadratic) energy dependence.

Signature of Massive Neutrinos from the Clustering of Critical Points. I. Density-threshold-based Analysis in Configuration Space

Critical points represent a subset of special points tracing cosmological structures, carrying remarkable topological properties. They thus offer a richer high-level description of the multiscale cosmic web, being more robust to systematic effects. For the first time, we characterize here their clustering statistics in massive neutrino cosmologies, including cross-correlations, and quantify their simultaneous imprints on the corresponding web constituents—i.e., halos, filaments, walls, and voids—for a series of rarity levels. Our first analysis is centered on a density-threshold-based approach in configuration space. In particular, we show that the presence of massive neutrinos does affect the baryon acoustic oscillation peak amplitudes of all of the critical point correlation functions above/below the rarity threshold, as well as the positions of their correspondent inflection points at large scales: departures from analogous measurements carried out in the baseline massless neutrino scenario can reach up to ∼7% in autocorrelations and ∼9% in cross-correlations at z = 0 when M ν = 0.1 eV and are more pronounced for higher neutrino mass values. In turn, these combined multiscale effects can be used as a novel technique to set upper limits on the summed neutrino mass and infer the type of hierarchy. Our study is particularly relevant for ongoing and future large-volume redshift surveys such as the Dark Energy Spectroscopic Instrument and the Rubin Observatory Legacy Survey of Space and Time, which will provide unique data sets suitable for establishing competitive neutrino mass constraints.

Speeds of Wave Propagation in Ideal Gaseous Molecular and Neutrino Media.

The neutrino mass values extracted from the pioneering Nobel Prize winning measurements of Kajita and co-workers at Superkamiokande were used in the classical Newton-Laplace equation for computing the speed of propagation of acoustic waves in gases comprising neutrinos. It is found that, surprisingly, acoustic waves in the lightest neutrino environments proceed with the speed of light in vacuum, c. This allows for the computation of c in terms of the lightest neutrino mass within 1% and is consistent with the fact that gravitational waves have been recently found to propagate with the speed of light. It is also found that the rest energy, m1c2, of the lightest neutrinos coincides with the photon energy at the cosmic background radiation temperature (CMBR). These findings are discussed in terms of the dual nature of photons and its possible interrelation with the omnipresent neutrinos. The present results also confirm that neutrino gases behave as ideal gases with only one-half of a translational degree of freedom, consistent with their one-dimensional, and practically one-directional, degree of freedom.

New limits from lepton flavour violating processes on the Littlest Higgs model with T-parity

We study lepton flavor violation (LFV) within the Littlest Higgs Model with T parity (LHT) realizing an inverse seesaw (ISS) mechanism of type I. In this scenario there appear new $\mathcal{O}$(TeV) Majorana neutrinos, driving LFV. We are analyzing the heavy Majorana neutrinos effects on LFV processes: $\ell \to \ell' \gamma$, $Z \to \bar{\ell}\ell'$, $L \to 3 \ell$ decays and $\mu \to e$ conversion in nuclei but we emphasize Type III decay channel of $L \to 3 \ell$ which are known as "wrong-sign": $\ell \rightarrow \ell' \ell'' \Bar{\ell}'''$ satisfying $\ell \neq \ell' = \ell'' \neq \ell'''$, since these processes vanish in the traditional LHT. First, we get values to $| \theta_{ej} \theta^{\dagger}_{\mu j}|$, $| \theta_{ej} \theta^{\dagger}_{\tau j}|$, and $| \theta_{\mu j} \theta^{\dagger}_{\tau j}|$ through $\ell \to \ell' \gamma$. With aid of these limits for mixing matrices, we can demonstrate that results for branching ratios of wrong sign processes yield within one order of magnitude below present bounds. We do not expect large correlations among the two wrong-sign decay modes. Also, we see that the mean values of heavy Majorana neutrino masses for all LFV processes are quasi-degenerate around 4 TeV.

Determining the Neutrino Mass Eigenstates and the Effective Majorana Mass

This paper aims at solving several open questions in current neutrino physics: the neutrino mass hierarchy, the Dirac CP violating phase, the absolute mass of neutrinos, the nature of neutrinos (Dirac or Majorana), the Majorana matrix and the absolute value of the effective Majorana neutrino mass. In the research presented in this paper, we have shown that the precise definition of the mass splittings between neutrino mass eigenstates, done in the latest analysis of experimental data, can be of crucial importance for defining the nature of neutrino mass hierarchy. The Standard Model has three generations of fundamental matter particles. Three generations of the charged lepton mass show a hierarchical structure: mτ > mμ > me. Owing to that, there is a belief and it is considered that neutrinos may follow such hierarchical structure. In our calculations, we have also included the latest data obtained, based on the processing of measurement results, which showed that even with such data, obtained results favor the normal neutrino mass hierarchy. As for the individual neutrino mass calculated in this paper, in today’s neutrino physics it is only known that neutrino mass scale is bounded only from above, and both the Dirac and the Majorana character of neutrinos are compatible with all observations. Among some of the questions resolved in this paper, which are related to the properties of neutrinos, a positive answer was also given to the question of whether light neutrinos are self-conjugate particles or not.

Aspects of gravitational decoherence in neutrino lensing

We study decoherence effects in neutrino flavour oscillations in curved spacetime with particular emphasis on the lensing in a Schwarzschild geometry. Assuming Gaussian wave packets for neutrinos, we argue that the decoherence length derived from the exponential suppression of the flavour transition amplitude depends on the proper time of the geodesic connecting the events of the production and detection in general gravitational setting. In the weak gravity limit, the proper time between two events of given proper distance is smaller than that in the flat spacetime. Therefore, in presence of a Schwarzschild object, the neutrino wave packets have to travel relatively more physical distance in space to lapse the same amount of proper time before they decoher. For non-radial propagation applicable to the lensing phenomena, we show that the decoherence, in general, is sensitive to the absolute values of neutrino masses as well as the classical trajectories taken by neutrinos between the source and detector along with the spatial widths of neutrino wave packets. At distances beyond the decoherence length, the probability of neutrino flavour transition due to lensing attains a value which depends only on the leptonic mixing parameters. Hence, the observability of neutrino lensing significantly depends on these parameters and in-turn the lensing can provide useful information about them.

Search for a heavy neutral Higgs boson in a left-right model with an inverse seesaw mechanism at the LHC

We develop a low scale left-right symmetric model based on $SU(3)_C\times SU(2)_L\times SU(2)_R\times U(1)_{B-L}\times Z_2$ with a simplified Higgs sector consisting of only one bidoublet and one $SU(2)_R$ doublet. In this model, the tiny values of light neutrino masses are generated through an inverse-seesaw mechanism. We emphasize that in this setup, the tree-level flavor changing neutral current can be strongly suppressed, consistent with the current experimental constraints. We show that the lightest $CP$-even Higgs boson, which is like the standard model Higgs boson, and the next lightest Higgs boson, $h'$, are generated from the neutral components of the bidoublet. We show that the mass of the next lightest Higgs boson can be of an order a few hundred~\text{GeVs}. We analyze the detection of $h'$ at the Large Hadron Collider (LHC) for a center-of-mass energy $\sqrt{s}=14~\text{TeV}$ and integrated luminosity $L_{\text{int}}=300~{\text{fb}}^{-1}$ via di-Higgs channel: $h'\to hh\to b\bar{b}\gamma\gamma$ and also in the $ZZ$ channel: $h'\to ZZ\to 4\ell~(\ell=e,~\mu)$ at an integrated luminosity $L_{\text{int}}=3000~{\text{fb}}^{-1}$. We consider three benchmark points for this analysis with $m_{h'}=250~\text{GeV},~400~\text{GeV}$, and $600~\text{GeV}$. We show that promising signals with good statistical significances can be obtained in di-Higgs channel, with $2\gamma+2b$-jets final states.

Non-Unitarity in Neutrino mixing matrix and two and three flavored non resonant Leptogenesis from CP violation

Background/Objectives: We will study the effects of non-unitarity parameters from existing experimental constraints, on cLFV decays such as, μ →eγ, μ →τγ, τ →eγ, on generation of baryon asymmetry through leptogenesis and neutrino oscillation probabilities. Considering flavor effects in leptogenesis, we do a parameter scan of a minimal seesaw model in a type I Seesaw framework satisfying Planck data on baryon to photon ratio of the Universe, which lies in the interval, 5.8×10− 10 <YB < 6.6×10− 10(BBN). We predict values of lightest neutrino mass, and Dirac and Majorana CP violating phase δCP, α and β, for normal hierarchy and inverted hierarchy for one, two and three flavor leptogenesis regimes. It is worth mentioning that all these four quantities are unknown yet, and future experiments will be measuring them. Methods/Statistical analysis: In spite of several experimental verifications of neutrino oscillations and precise measurements of two mass squared differences and the three mixing angles, the unitarity of the leptonic mixing matrix is not yet established, leaving room for the presence of small non unitarily effects. We study their effects on generation of baryon asymmetry through leptogenesis. Considering flavor effects in leptogenesis, we do a parameter scan of a minimal seesaw model in a type I Seesaw framework satisfying Planck data on baryon to photon ratio of the Universe, which lies in the interval, 5.8 × 10−10 < YB < 6.6 × 10−10(BBN). Findings: We predict values of lightest neutrino mass, for normal hierarchy and inverted hierarchy for two and three flavor leptogenesis regimes. It is worth mentioning that all these four quantities, lightest neutrino mass, and Dirac and Majorana CP violating phase δCP, α and β, are unknown yet, and future experiments will be measuring them. Novelty/Applications: Unitarity in UPMNS matrix is not yet established, and hence it has left scope for testing non unitarity in the leptonic sector which will result in various implications of New Physics theories in predicting the values of leptonic CPV phase, δCP, Majorana phases, α, β and the absolute value of the neutrino masses. The interesting feature of our work is that we will evaluate the absolute value of lightest neutrino mass which is found to be consistent with the cosmological constraints on the sum of the neutrino mass bound, Σim( νi ) < 0.23 eV from CMB, Planck 2015 data (CMB15+ LRG+ lensing + H0). We note that absolute value of lightest neutrino mass is also not known so far, and hence our prediction made here may be tested in future when experiments (including neutrinoless double beta decay experiments) will determine its value in future. Keywords: Non unitarity; CP violation phase; Majorana phases; leptogenesis; Baryogenesis.

Status of the HOLMES Experiment

The absolute neutrino mass is still an unknown parameter in the modern landscape of particle physics. The HOLMES experiment aims at exploiting the calorimetric approach to directly measure the neutrino mass through the kinematic measurement of the decay products of the weak process decay of $$^{163}$$Ho. This low energy decaying isotope, in fact, undergoes electron capture emitting a neutrino and leaving the daughter atom, $$^{163}$$Dy$$^*$$, in an atomic excited state. This, in turn, relaxes by emitting electrons and, to a considerably lesser extent, photons. The high-energy portion of the calorimetric spectrum of this decay is affected by the non-vanishing neutrino mass value. Given the small fraction of events falling within the region of interest, to achieve a high experimental sensitivity on the neutrino mass, it is important to have a high activity combined with a very small undetected pileup contribution. To achieve these targets, the final configuration of HOLMES foresees the deployment of a large number of $$^{163}$$Ho ion-implanted TESs characterized by an ambitiously high activity of 300 Hz each. In this paper, we outline the status of the major tasks that will bring HOLMES to achieve a statistical sensitivity on the neutrino mass as low as 2 eV/c$$^2$$.

Breaking cosmic degeneracies: Disentangling neutrinos and modified gravity with kinematic information

Searches for modified gravity in the large-scale structure try to detect the enhanced amplitude of density fluctuations caused by the fifth force present in many of these theories. Neutrinos, on the other hand, suppress structure growth below their free-streaming length. Both effects take place on comparable scales, and uncertainty in the neutrino mass leads to a degeneracy with modified gravity parameters for probes that are measuring the amplitude of the matter power spectrum. We explore the possibility to break the degeneracy between modified gravity and neutrino effects in the growth of structures by considering kinematic information related to either the growth rate on large scales or the virial velocities inside of collapsed structures. In order to study the degeneracy up to fully non-linear scales, we employ a suite of N-body simulations including bothf(R) modified gravity and massive neutrinos. Our results indicate that velocity information provides an excellent tool to distinguish massive neutrinos from modified gravity. Models with different values of neutrino masses and modified gravity parameters possessing a comparable matter power spectrum at a given time have different growth rates. This leaves imprints in the velocity divergence, which is therefore better suited than the amplitude of density fluctuations to tell the models apart. In such models with a power spectrum comparable to ΛCDM today, the growth rate is strictly enhanced. We also find the velocity dispersion of virialised clusters to be well suited to constrain deviations from general relativity without being affected by the uncertainty in the sum of neutrino masses.

Raman stimulated neutrino pair emission

A new scheme using macroscopic coherence is proposed to experimentally determine the neutrino mass matrix, in particular the absolute value of neutrino masses, and the mass type, Majorana or Dirac. The proposed process is a collective, coherent Raman scattering followed by neutrino-pair emission from |erangle of a long lifetime to |grangle ; gamma _0 + | erangle rightarrow gamma + sum _{ij} nu _i bar{nu _j} + | grangle with nu _i bar{nu _j} consisting of six massive neutrino-pairs. Calculated angular distribution has six (ij) thresholds which show up as steps at different angles. Angular locations of thresholds and event rates of the angular distribution make it possible to experimentally determine the smallest neutrino mass to the level of less than several meV, (accordingly all three masses using neutrino oscillation data), the mass ordering pattern, normal or inverted, and to distinguish whether neutrinos are of Majorana or Dirac type. Event rates of neutrino-pair emission, when the mechanism of macroscopic coherence amplification works, may become large enough for realistic experiments by carefully selecting certain types of target. The problem to be overcome is macro-coherently amplified quantum electrodynamic background of the process, gamma _0 + | erangle rightarrow gamma +gamma _2 + gamma _3+ | grangle , when two extra photons, gamma _2, gamma _3, escape detection. We illustrate our idea using neutral Xe and trivalent Ho ion doped in dielectric crystals.

The impact of baryonic physics and massive neutrinos on weak lensing peak statistics

ABSTRACT We study the impact of baryonic processes and massive neutrinos on weak lensing peak statistics that can be used to constrain cosmological parameters. We use the BAHAMAS suite of cosmological simulations, which self-consistently include baryonic processes and the effect of massive neutrino free-streaming on the evolution of structure formation. We construct synthetic weak lensing catalogues by ray tracing through light-cones, and use the aperture mass statistic for the analysis. The peaks detected on the maps reflect the cumulative signal from massive bound objects and general large-scale structure. We present the first study of weak lensing peaks in simulations that include both baryonic physics and massive neutrinos (summed neutrino mass Mν = 0.06, 0.12, 0.24, and 0.48 eV assuming normal hierarchy), so that the uncertainty due to physics beyond the gravity of dark matter can be factored into constraints on cosmological models. Assuming a fiducial model of baryonic physics, we also investigate the correlation between peaks and massive haloes, over a range of summed neutrino mass values. As higher neutrino mass tends to suppress the formation of massive structures in the Universe, the halo mass function and lensing peak counts are therefore modified as a function of Mν. Over most of the S/N range, the impact of fiducial baryonic physics is greater (less) than neutrinos for 0.06 and 0.12 (0.24 and 0.48) eV models. Both baryonic physics and massive neutrinos should be accounted for when deriving cosmological parameters from weak lensing observations.

Direct Search for keV-Sterile Neutrino in Nuclear Decay. Troitsk Nu-Mass (Scientific Summary)

We present a brief review of experimental status in searching for hypothetical sterile neutrino in nuclear decay in laboratory testing. The main idea is based on search for an additional small component in the β-spectrum or a shift in the internal electron conversion energy. For example, in a three-body β-decay it looks like a kink in the continuous spectrum shifted by the value of sterile neutrino mass from the spectrum endpoint. After a short general motivation for such a search we discuss the way how to find sterile neutrino in the nuclear β-decay and present the current status of upper limits on sterile neutrino mixing with electron antineutrino. The advantages and problems arising in the precise measurements of β-spectrum are demonstrated on the basis of the “Troitsk nu-mass” experiment by presenting the all measurement and analysis procedures in details. At the end we discuss the nearest future of such experiments.

Accurate fitting functions for peculiar velocity spectra in standard and massive-neutrino cosmologies

We estimate the velocity field in a large set of N-body simulations including massive neutrino particles, and measure the auto-power spectrum of the velocity divergence field as well as the cross-power spectrum between the cold dark matter density and the velocity divergence. We perform these measurements at four different redshifts and within four different cosmological scenarios, covering a wide range in neutrino masses. We find that the nonlinear correction to the velocity power spectra largely depends on the degree of nonlinear evolution with no specific dependence on the value of neutrino mass. We provide a fitting formula based on the value of the rms of the matter fluctuations in spheres of 8 h−1 Mpc, describing the nonlinear corrections with 3% accuracy on scales below k = 0.7 h Mpc−1.

Neutrino mixing from finite modular groups

We study the lepton flavor models, whose flavor symmetries are finite subgroups of the modular group such as $S_3$ and $A_4$. In our models, couplings are also nontrivial representations of these groups and modular functions of the modulus. We study the possibilities that these models realize realistic values of neutrino masses and lepton mixing angles.

Neutrino mass and neutrinoless double beta decay in SO(10) GUT with Pati–Salam symmetry

We demonstrate how a class of non-supersymmetric SO(10) GUT with asymmetric left–right theory SU(2)L × U(1)R × U(1)B−L × SU(3)C and Pati–Salam theory SU(2)L × SU(2)R × SU(4)C as intermediate symmetry breaking steps leads to successful gauge coupling unification satisfying proton decay constraints. The motivation behind this work is two fold: firstly to study the renormalization group evolution equations for gauge couplings by keeping right-handed neutral gauge boson ZR around LHC energy range leading interesting dilepton searches at collider while fixing charge partner of the gauge boson WR at very high scale; secondly to explain neutrino masses and associated lepton number violating process like neutrinoless double beta decay in three possible cases depending on how SU(2)L × U(1)R × U(1)B−L × SU(3)C breaks down to SM. The presence of Pati–Salam symmetry and Pati–Salam symmetry with D-parity (discrete left–right symmetry leading to gL = gR) at highest scale is to allow two gauge couplings and thereby ensuring precision unification for gauge couplings. We focus on neutrino mass and neutrinoless double beta decay for one particular case where TeV scale asymmetric left–right theory is spontaneously broken down to SM with non-zero VEV of both Higgs doublets with B − L = −1 and Higgs triplets with B − L = 2. We include one extra fermion singlet per generation in order to implement gauged extended seesaw where light neutrino mass is governed by dominant type-II seesaw mechanism whereas type-I seesaw contribution is cancelled out. Since light neutrino mass formula is independent of Dirac neutrino mass matrix, the value of Dirac neutrino mass is taken to be up-type quark mass matrix which is a characteristics of Pati–Salam symmetry relating quarks with leptons. This can lead to non-unitarity effects in leptonic sector and induce lepton flavor violation. We present analytic relation for effective Majorana mass parameter and corresponding half-life arising from new physics contributions due to purely left-handed currents through exchange of heavy right-handed neutrinos and sterile neutrinos. We numerically estimate effective Majorana mass parameter and half-life versus lightest neutrino mass and derive lower bound on lightest neutrino mass by saturating with experimental bounds like GERDA Phase-II, KamLANDZen and EXO.