Flavor Ratio Research Articles

Flavor ratios of astrophysical neutrinos interacting with stochastic gravitational waves having arbitrary spectra

We study the evolution and oscillations of fixed massive neutrinos interacting with stochastic gravitational waves (GWs). The energy spectrum of these GWs is Gaussian, with the correlator of the amplitudes being arbitrary. We derive the equation for the density matrix for flavor neutrinos in this case. In the two flavors approximation, this equation can be solved analytically. We find the numerical solution for the density matrix in the general case of three neutrino flavors. We consider merging binary black holes as sources of stochastic GWs with realistic spectra. Both normal and inverted mass orderings are analyzed. We discuss the relaxation of the neutrino fluxes in stochastic GWs emitted mainly by supermassive black holes. In this situation, we obtain the range of energies and the propagation lengths for which the relaxation process is the most efficient. We discuss the application of our results for the observation of fluxes of astrophysical neutrinos.

Prospects for high-elevation radio detection of >100 PeV tau neutrinos

Tau neutrinos are expected to comprise roughly one third of both the astrophysical and cosmogenic neutrino flux, but currently the flavor ratio is poorly constrained and the expected flux at energies above 1017 eV is low. We present a detector concept aimed at measuring the diffuse flux of tau neutrinos in this energy range via a high-elevation mountaintop detector using the radio technique. The detector searches for radio signals from upgoing air showers generated by Earth-skimming tau neutrinos. Signals from several antennas in a compact array are coherently summed at the trigger level, permitting not only directional masking of anthropogenic backgrounds, but also a low trigger threshold. This design takes advantage of both the large viewing area available at high-elevation sites and the nearly full duty cycle available to radio instruments. We present trade studies that consider the station elevation, frequency band, number of antennas in the array, and the trigger threshold to develop a highly efficient station design. Such a mountaintop detector can achieve a factor of ten improvement in acceptance over existing instruments with 100 independent stations. With 1000 stations and three years of observation, it can achieve a sensitivity to an integrated ℰ−2 flux of <10−9 GeV cm−2 sr−1 s−1, in the range of the expected flux of all-flavor cosmogenic neutrinos assuming a pure iron cosmic-ray composition.

Observable features in ultrahigh energy neutrinos due to active-sterile secret interactions

We consider the effects of active-sterile secret neutrino interactions, mediated by a new pseudoscalar particle, on high- and ultra high-energy neutrino fluxes. In particular, we focus on the case of 3 active and 1 sterile neutrino coupled by a flavor dependent interaction, extending the case of 1 active and 1 sterile neutrino we have recently examined. We find that, depending on the kind of interaction of sterile neutrino with the active sector, new regions of the parameter space for secret interactions are now allowed leading to interesting phenomenological implications on two benchmark fluxes we consider, namely an astrophysical power law flux, in the range below 100 PeV, and a cosmogenic flux, in the Ultrahigh energy range. First of all, the final active fluxes can present a measurable depletion observable in future experiments. Especially, in the case of only tau neutrino interacting, we find that the effects on the astrophysical power law flux can be so large to be already probed by the IceCube experiment. Moreover, we find intriguing features in the energy dependence of the flavor ratio.

Oscillation of high-energy neutrinos from choked jets in stellar and merger ejecta

We present a comprehensive study on oscillation of high-energy neutrinos from two different environments: blue supergiant progenitors that may harbor low-power gamma-ray burst (GRB) jets and neutron star merger ejecta that would be associated with short gamma-ray bursts. We incorporate the radiation constraint that gives a necessary condition for nonthermal neutrino production, and account for the time evolution of the jet, which allows us to treat neutrino oscillation in matter more accurately. For massive star progenitors, neutrino injection inside the star can lead to nonadiabatic oscillation patterns in the 1 TeV - 10 TeV and is also visible in the flavor ratio. For neutron star merger ejecta, we find a similar behavior in the 100 GeV - 10 TeV region and the oscillation may result in a $\nu_e$ excess around 1 TeV. These features, which enable us to probe the progenitors of long and short GRBs, could be seen by future neutrino detectors with precise flavor ratio measurements. We also discuss potential contributions to the diffuse neutrino flux measured by IceCube, and find parameter sets allowing choked low-power GRB jets to account for the neutrino flux in the 10 TeV - 100 TeV range without violating the existing constraints.

Sterile neutrinos in astrophysical neutrino flavor

In this paper, we study the effect of active-neutrino-sterile-neutrino mixing in the expected high-energy astrophysical neutrino flavor content. Non-unitarity in the measurement of the three-active neutrinos can be due to the existence of sterile neutrino states. We introduce the concept of the four-flavor tetrahedron in order to visualize the lack of unitarity in the astrophysical neutrino three-flavor triangle. We demonstrate that active-sterile neutrino mixings modify the allowed region of the astrophysical flavor ratio from the standard case. However, a projection of the four-flavor tetrahedron has restrictions of phase space similar to the three-flavor triangle. On the other hand, the initial presence of astrophysical sterile neutrinos drastically changes the scenario, and it allows an apparent unitarity violation in the three-flavor triangle space. Using current global fit constraints including the non-unitarity case, we also illustrate the allowed astrophysical neutrino flavor ratios. Thus, the measurement of the high-energy astrophyscal neutrino flavor content allows us to explore sterile neutrinos independently of the sterile neutrino mass scale. These are topics of investigation for current and future neutrino telescopes.

Influence of Cosmic-Ray Spectrum and Hadron—Nucleus Interaction Model on the Properties of High-Energy Atmospheric-Neutrino Fluxes

The neutrino/antineutrino flux ratios ( $${\nu _e}/{\overline \nu _e}$$ and $${\nu _\mu }/{\overline \nu _\mu }$$ ) and the flavor ratio $$\left( {{\nu _\mu } + {{\overline \nu }_\mu }} \right)/\left( {{\nu _e} + {{\overline \nu }_e}} \right)$$ clearly demonstrate the distinctions between the predictions of hadronic-interaction models for the production spectra of pions and kaons, which are the main sources of atmospheric neutrinos in the region of Eν ≲ 500 TeV. The values of the $${\nu /\overline \nu }$$ ratio are sensitive to variations in the π+/π−, π/K, and K+/K− meson ratios, which are determined by the cross sections for inclusive meson-production processes in hadron-nucleus (hA) collisions; the elemental composition of cosmic rays also exerts influence, through the p/n ratio, on the development of hadronic cascades and on the neutrino ratios. The difference in $${\nu /\overline \nu }$$ and in the flavor ratio for a number of hadronic-interaction models is shown on the basis of calculating neutrino fluxes at energies in the range between 102 and 108 GeV. A comparison of the calculated results with new experimental data shows the reliability of this calculation, which, on the whole, reflects correctly the mechanism of atmospheric-neutrino production. The spectra of atmospheric muon neutrinos from calculations based on the Kimel-Mokhov, SIBYLL 2. 1, and EPOS LHC models describe fairly well experimental results. At energies in the range of 1–500 TeV, the curves calculated within these models combined with the Hillas-Gaisser spectrum are close to the best fit to data from measurements in the IceCube experiment.

Matter effects and coherent effect of neutrinos produced from -ray bursts * * Supported in part by the Natural Science Foundation of China (11675131, 11775038, 11603005, 11847301), and by the Fundamental Research Funds for the Central Universities (2019CDJDWL0005)

Neutrinos produced from -ray bursts (GRBs) carry significant physical information. The electron density in the GRBs outflow is very large. In this study, we calculate the matter effect on neutrinos when they propagate through such a dense region. The average survival probability and the flavor ratio of neutrinos are determined. The ratio of resonant neutrino energy from different spherical shells provides the information of power index N for the power-law distribution of electrons in the hot fireball model. Electron density in the magnetic jet model is sufficiently lower than in the hot fireball model. The matter effect on neutrinos can be used to distinguish these two models. The coherent effect of strongly lensed PeV neutrinos is also discussed. The average survival probability of strongly-lensed electron neutrinos in the normal and inverted hierarchical cases are presented. The results show that this coherent effect can be used to determine the hierarchical mass of neutrinos.

The Effect of Ingredient Item Depiction on the Packaging Frontal View on Pre- and Post-Consumption Product Evaluations.

The current research focused on the (in)congruity between pictorial (ingredient item depiction) and textual (ingredient list) information on food packaging, namely, an apple–mango juice. Specifically, the influence of these information sources on expected and perceived flavor intensities, mismatched perceptions, perceived deception, and intention to purchase was studied by taking into account the possible moderating role of consumers’ thinking style. Three studies were performed, the first and third at a Dutch University by means of surveys and sensory tests, and the second via an online survey. The results showed that, overall, most consumers did not perceive the incongruity between pictorial and textual information as mismatching. However, a perceived mismatch from packaging, whether originated by the design manipulations or not, did increase perceived deception and lowered willingness to purchase. This effect was robust for both mismatches, among packaging elements (pre-consumption) and from expected and perceived flavor ratios (post-consumption), but was more substantial for the post-consumption mismatch. Although the moderating effect of cognitive processing style regarding expected and perceived flavor ratios from pictorial and textual (ingredient list) information was not confirmed, the results indicated that the effect of salient textual information is substantial, independent of a particular processing style or label usage.

Flavor of cosmic neutrinos preserved by ultralight dark matter

Within the standard propagation scenario, the flavor ratios of high-energy cosmic neutrinos at neutrino telescopes are expected to be around the democratic benchmark resulting from hadronic sources, $\left( 1 : 1 : 1 \right)_\oplus$. We show how the coupling of neutrinos to an ultralight dark matter complex scalar field would induce an effective neutrino mass that could lead to adiabatic neutrino propagation. This would result in the preservation at the detector of the production flavor composition of neutrinos at sources. This effect could lead to flavor ratios at detectors well outside the range predicted by the standard scenario of averaged oscillations. We also present an electroweak-invariant model that would lead to the required effective interaction between neutrinos and dark matter.

IceCube flavor ratios with identified astrophysical sources: towards improving new physics testability

Motivated by the discovery of the first high-energy astrophysical neutrino source, the blazar TXS 0506+056, we revisit the IceCube flavor ratio analysis. Assuming large statistics from identified blazars, collected in the forthcoming years by the IceCube detector and its successor IceCube-Gen2, we demonstrate that the constraints on several new physics scenarios in which the baseline dependent terms in neutrino oscillation probabilities are not averaged, can be improved. As a representative case, we consider pseudo-Dirac neutrinos while neutrino decay is also discussed.

High-energy neutrino interaction physics with IceCube

Although they are best known for studying astrophysical neutrinos, neutrino telescopes like IceCube can study neutrino interactions, at energies far above those that are accessible at accelerators. In this writeup, I present two IceCube analyses of neutrino interactions at energies far above 1 TeV. The first measures neutrino absorption in the Earth, and, from that determines the neutrino-nucleon cross-section at energies between 6.3 and 980 TeV. We find that the cross-sections are 1.30 +0.21 -0.19 (stat.) +0.39 -0.43 (syst.) times the Standard Model crosssection. We also present a measurement of neutrino inelasticity, using νμ charged-current interactions that occur within IceCube. We have measured the average inelasticity at energies from 1 TeV to above 100 TeV, and found that it is in agreement with the Standard Model expectations. We have also performed a series of fits to this track sample and a matching cascade sample, to probe aspects of the astrophysical neutrino flux, particularly the flavor ratio.

IceCube High Energy Starting Events at 7.5 Years - New Measurements of Flux and Flavor

The IceCube Neutrino Observatory at the South Pole, which detects Cherenkov light from charged particles produced in neutrino interactions, firmly established the existence of an astrophysical high-energy neutrino component. Here I present IceCube’s High-Energy Starting Event sample and the new results obtained with a livetime of about 7.5 years. I will focus on the new measurement of the flavor composition performed using this sample. IceCube is directly sensitive to each neutrino flavor via the single cascade, track and double cascade event topologies, the latter being the topology produced in tauneutrino interactions above an energy threshold of ~100 TeV. A measurement of the flavor ratio on Earth can provide important constraints on sources and production mechanisms within the standard model, and also constrain various beyond-standard-model processes.

Application of edible coatings in conservation of acerola

The acerola is a tropical fruit recognized for its high nutritional value, however, the high pereceability after harvest motivated by its climacteric behavior requires conservation techniques that allow the maintenance of its quality during the storage period. The edible coatings, in this context, are presented as alternatives since they form barriers on the fruits, restricting the gas exchanges, improving the visual aspect without compromising with the fruit flavor. Thus, this study aims to evaluate the application of edible coatings on the post-harvest quality of acerolas cv. Costa Rica during refrigerated storage (10 °C). Fruits of ripe acerolas were harvested in a commercial orchard, sanitized and immersed in three solutions (3%) of cassava starch, arrow starch and gelatine, in addition to the control represented by uncoated fruits for a period of 3 minutes. These were then dried and packed in styrofoam polystyrene trays coated with polypropylene plastic film (PVC) and stored under refrigeration (10 °C) for 12 days. The total fresh solids content (o Brix), titratable acidity (% malic acid), pH, TSS/AT ratio and sensorial analysis on the occurrence of wilting were evaluated every three days, visual appearance and the aroma of the fruits. The experimental design was completely randomized in a factorial scheme of 4x5, that is to say, (4 treatments: control, cassava starch, arrowroot starch and gelatin) and (5 storage times: 0, 3, 6, 9 and 12 days ), with five replicates and the experimental plot composed of 100 g trays. During the storage period, no significant difference was observed between the coatings used, however, their action on the fruits contributes to reduce the loss of fresh mass and to allow a better balance in the fruit flavor ratio (SST / AT) after 12 days . The films formed on the fruits did not compromise the chemical quality (soluble solids, titratable acidity and pH) maintaining similar behavior to the fruits of the control treatment. In addition, there was a reduction in the incidence of wilting and the loss of the characteristic aroma of the fruits, contributing to a better visual appearance. Thus, edible coatings based on cassava starch and arrowroot and gelatine are presented as effective alternatives in preserving the quality of acerolas during refrigerated storage.

Could a Hypercritical Accretion be Associated with the Atypical Magnetic-field Behavior in RX J0822-4300?

Recent X-ray observations in the central compact remnant of Puppis A and other young pulsars have provided convincing evidence about the anti-magnetar nature of the so-called central compact objects (CCOs). The measured period derivative, corrected by the proper movement, provides exceptionally low superficial magnetic fields for such sources. Using the dipole radiation canonical model, the superficial magnetic field of the CCO (RX J0822-4300) in Puppis A was estimated to be B ≃ 2.9 × 1010 G. In this paper, we present a numerical model to interpret the unusual magnetic-field behavior in RX J0822-4300. Using the magnetohydrodynamic simulations during the hypercritical accretion phase, we propose that a variety of MeV neutrinos is created given evidence about the submergence of the magnetic field in the pulsar. We investigate the production, propagation, oscillations, and detection of MeV neutrinos from this source. The detection of neutrino events with their flavor ratios would be a compelling signature of the decreasing evolution of the magnetic field not only in RX J0822-4300 but also in CCO candidates.

Hypercritical accretion scenario in central compact objects accompanied with an expected neutrino burst

The measurement of the period and period derivative, and the canonical model of dipole radiation have provided a method to estimate the low superficial magnetic fields in the so-called Central Compact Objects (CCOs). In the present work, a scenario is introduced in order to explain the magnetic behavior of such CCOs. Based on magnetohydrodynamic simulations of the post core-collapse supernova phase during the hypercritical accretion episode, we argue that the magnetic field of a newborn neutron star could have been early buried. During this phase, thermal neutrinos are created mainly by the pair annihilation, plasmon decay, photo-neutrino emission and other processes. We study the dynamics of these neutrinos in this environment and also estimate the number expected of the neutrino events with their flavor ratios on Earth. The neutrino burst is the only viable observable that could provide compelling evidence of the hypercritical phase and therefore, the hidden magnetic field mechanism as the most favorable scenario to explain the anomalous low magnetic fields estimated for CCOs.

Explanation of IceCube spectrum with \u03bd \u2192 3\u03bd neutrino splitting in a \u03bd2HDM model

A single power law flux spectrum of high energy neutrinos does not adequately explain the entire 60 TeV to 10 PeV event spectrum observed at IceCube, specially the excess of PeV events and the lack of Glashow resonance events expected at 6.3 PeV cannot be simultaneously explained by a single power law source neutrino flux. Here we consider a model of neutrino splitting ν → 3ν over cosmological distances. Starting from a single power-law spectrum expected from the astrophysical sources, we show that by adjusting the decay length and spectral index one can give a better fit to the observed IceCube events over the entire 1 TeV-6 PeV, compared to that from a single power spectrum. For ν → 3ν neutrino splitting, the flavor ratios of the daughter neutrinos are different from the standard oscillation or invisible decay cases and can be used as a test of this scenario. We propose a ν2HDM where a light Higgs (∼0.1 eV) mediates neutrino splitting via a one-loop box diagram. The split in the masses of the scalars in the doublet gives a large contribution to the oblique T parameter which is severely constrained. This constraint from the S,T,U oblique parameters can be evaded by the introduction of an extra vector lepton doublet and with mass ∼ 200 GeV.

Resolution of RD/[formula omitted] puzzle

One of the exciting results in flavor physics in recent times is the RD/RD⁎ puzzle. The measurements of these flavor ratios performed by the B-factory experiments, BaBar and Belle, and the LHCb experiment are about 4σ away from the Standard Model expectation. These measurements indicate that the mechanism of b→cτν¯ decay is not identical to that of b→c(μ/e)ν¯. This charge lepton universality violation is particularly intriguing because these decays occur at tree level in the Standard Model. In particular, we expect a moderately large new physics contribution to b→cτν¯. The different types of new physics amplitudes, which can explain the RD/RD⁎ puzzle, have been identified previously. In this letter, we show that the polarization fractions of τ and D⁎ and the angular asymmetries AFB and ALT in B→D⁎τν¯ decay have the capability to uniquely identify the Lorentz structure of the new physics. A measurement of these four observables will lead to such an identification.

Exploring the Universe with Neutrinos: Recent Results from IceCube

In 2013, the IceCube Neutrino Observatory located at the geographic South Pole detected evidence for a diffuse astrophysical neutrino flux above ∼60 TeV. To this day, IceCube has operated with full detector configuration for more than 6 years. The observed astrophysical neutrino flux has been confirmed with >6σ significance with both events starting within the detector (all flavor) and events traversing through the Earth (νμ charged-current). Somewhat equal flavor ratio of astrophysical neutrinos is expected at Earth assuming standard thorough oscillation. A search for tau neutrinos has been carried out but yielded null result. No neutrino sources have been found to contribute significantly to the diffuse flux at this point. In this paper, we will review the current status of the astrophysical neutrino flux, discuss the quest for neutrino point sources and overview the proposed design and physics potentials of the future IceCube-Gen2.

Neutrino lines from majoron dark matter

Models with spontaneously broken global lepton number can lead to a pseudo-Goldstone boson as a long-lived dark matter candidate. Here we revisit the case of singlet majoron dark matter and discuss multiple constraints. For masses above MeV, this model could lead to a detectable flux of monochromatic mass-eigenstate neutrinos, which have flavor ratios that depend strongly on the neutrino mass hierarchy. We provide a convenient parametrization for the loop-induced majoron couplings to charged fermions that allows us to discuss three-generation effects such as lepton flavor violation. These couplings are independent of the low-energy neutrino parameters but can be constrained by the majoron decays into charged fermions.

Sterile neutrinos and flavor ratios in IceCube

The flavor composition of astrophysical neutrinos observed in neutrino telescopes is a powerful discriminator between different astrophysical neutrino production mechanisms and can also teach us about the particle physics properties of neutrinos. In this paper, we investigate how the possible existence of light sterile neutrinos can affect these flavor ratios. We consider two scenarios: (i) neutrino production in conventional astrophysical sources, followed by partial oscillation into sterile states; (ii) neutrinos from dark matter decay with a primary flavor composition enhanced in tau neutrinos or sterile neutrinos. Throughout the paper, we constrain the sterile neutrino mixing parameters from a full global fit to short and long baseline data. We present our results in the form of flavor triangles and, for scenario (ii), as exclusion limits on the dark matter mass and lifetime, derived from a fit to IceCube high energy starting events and through-going muons. We argue that identifying a possible flux of neutrinos from dark matter decay may require analyzing the flavor composition as a function of neutrino energy.