Atmospheric Neutrino Spectrum Research Articles

Atmospheric Neutrino Spectra: A Statistical Analysis of Calculations in Comparison with Experiment

Atmospheric Neutrino Spectra: A Statistical Analysis of Calculations in Comparison with Experiment

Examination of Calculations of the Atmospheric Muon and Neutrino Spectra Using New Measurements

The atmospheric muon and neutrino fluxes at energies from 10 GeV to 10 PeV are calculated with the Kimel–Mokhov (KM), SIBYLL 2.1, EPOS LHC, and QGSJET-II hadronic models for known parameterizations of the cosmic ray spectra by Zatsepin--Sokolskaya and Hillas–Gaisser. The calculations with the KM, EPOS LHC, and SIBYLL 2.1 models are agree well with the measurements of the atmospheric muon spectra in IceCube and IceTop experiments. The measurement of high-energy muon spectra indicates the presence of the prompt muon component at energies above 500 TeV, which is well reproduced in calculations with the quark-gluon string model. The calculations of the atmospheric muon neutrino spectrum performed for the KM, EPOS LHC, and SIBYLL 2.1 models give good fit with the measurement data of IceCube, ANTARES, and Super-Kamiokande experiments.

On the relevance of prompt neutrinos for the interpretation of the IceCube signals

The IceCube collaboration has discovered a new, cosmic component of high-energy neutrinos. Although neutrino oscillations suggest that the cosmic neutrino spectrum is almost the same for every neutrino flavor, the attempts to reconstruct it, based on different analyses, lead to different energy spectra below 100 TeV. In this work, we propose a phenomenological model that, assuming collisions between cosmic rays and hadrons as the production mechanism of high-energy neutrinos, yields quantitative expectations for each neutrino flavor. We discuss the detectability of the prompt component of the atmospheric neutrino spectrum, pointing out the most relevant dataset, which has to be muon-neutrino depleted and to cover the energy region 10–100 TeV. We argue that the prompt component can cause the spectral difference between the High-Energy-Starting-Event (HESE) and the through-going muon datasets. Finally, we point out the need for adopting a consistent model for the interpretation of the data, stressing that a separate treatment of the different datasets is, by converse, a suboptimal procedure.

Atmospheric neutrinos and the knee of the cosmic ray spectrum

The nature of the knee in the all-particle spectrum of cosmic rays remains subject of much investigation, especially in the aftermath of recent measurements claiming the detection of a knee-like feature in the spectrum of the light component of cosmic rays at energy ∼ 700 TeV, at odds with the standard picture in which the knee in the all-particle spectrum is dominated by light cosmic rays. Here we investigate the implications of this and other scenarios in terms of the measured flux of atmospheric neutrinos. In particular we discuss the possibility that the spectrum of atmospheric neutrinos in the region ≳ 50 TeV may provide information about the different models for the mass composition in the knee region. We investigate the dependence of the predicted atmospheric neutrino flux on the shape of the light cosmic ray spectra and on the interaction models describing the development of showers in the atmosphere. The implications of all these factors for the identification of the onset of an astrophysical neutrino component are discussed.

Measurement of the neutrino-oxygen neutral-current quasielastic cross section using atmospheric neutrinos at Super-Kamiokande

Neutral current (NC) interactions of atmospheric neutrinos on oxygen form one of the major backgrounds in the search for supernova relic neutrinos with water-based Cherenkov detectors. The NC channel is dominated by neutrino quasi-elastic (NCQE) scattering off nucleons inside $^{16}$O nuclei. In this paper we report the first measurement of NCQE cross section using atmospheric neutrinos at Super-Kamiokande (SK). The measurement used 2,778 live days of SK-IV data with a fiducial volume of 22.5 kiloton water. Within the visible energy window of 7.5-29.5 MeV, we observed $117$ events compared to the expected $71.9$ NCQE signal and $53.1$ background events. Weighted by the atmospheric neutrino spectrum from 160 MeV to 10 GeV, the flux averaged NCQE cross section is measured to be $(1.01\pm0.17(\text{stat.})^{+0.78}_{-0.30}(\text{sys.}))\times10^{-38}$ cm$^2$.

Results from the search for eV-sterile neutrinos with IceCube

The IceCube neutrino telescope at the South Pole has measured the atmospheric muon neutrino spectrum as a function of zenith angle and energy. Using IceCubes full detector configuration we have performed searches for eV-scale sterile neutrinos. Such a sterile neutrino, motivated by the anomalies observed in short-baseline experiments, is expected to have a significant effect on survival probability due to matter-induced resonant effects for energies of order 1 TeV. This effect makes this search unique and sensitive to small sterile mixing angle values. This work comprises results obtained using up-going muon neutrinos taken with one year of full detector configuration.

Calculation of atmospheric high-energy neutrino spectra and the measurement data of IceCube and ANTARES experiments

Presented are results of calculation of the atmospheric neutrino spectra in the energy range from 100 GeV to 10 PeV using the QGSJET-II and SIBYLL 2.1 models of hadron–nuclear interactions and two experimentally based Zatsepin–Sokol’skaya and Hillas–Gaisser models of the cosmic ray spectrum. It is shown that rare decays of short-lived neutral kaons produce about one third of the flux of electron neutrinos and up to 10% of muon neutrinos at energies above 100 TeV. The calculated spectra agree satisfactorily with the IceCube and ANTARES measurement data. The measurement errors leave open the possibility of a contribution from decays of charmed particles to fluxes of muon neutrinos with energies above 500 TeV and electron neutrinos with energies above 30 TeV.

The comparison of the calculated atmospheric neutrino spectra with the measurements of IceCube and ANTARES experiments

We calculate the atmospheric neutrino spectra in the energy range of 102 − 107 GeV using the hadronic models QGSJET-II, SIBYLL 2.1 and the parameterizations of cosmic ray spectra by Zatsepin-Sokolskaya, and Hillas-Gaisser supported by experiments. It is shown that rare decay mode of short-lived neutral kaons produce about 30% of the electron neutrino flux and up to 10% of muon neutrinos at energies above 200 TeV. Comparative analysis of our calculations based on the Ƶ(E, h)-function approach and those obtained with use of the new MCEq-method (A. Fedynitch et al.) demonstrates the close agreement of both calculations. The comparison of calculated neutrino spectrum to the experimental data shows that IceCube and ANTARES measurements leave opened window for the prompt neutrino flux contribution obtained with the quark-gluon string model (QGSM).

Searches for Sterile Neutrinos with the IceCube Detector.

The IceCube neutrino telescope at the South Pole has measured the atmospheric muon neutrino spectrum as a function of zenith angle and energy in the approximate 320GeV to 20TeV range, to search for the oscillation signatures of light sterile neutrinos. No evidence for anomalous ν_{μ} or ν[over ¯]_{μ} disappearance is observed in either of two independently developed analyses, each using one year of atmospheric neutrino data. New exclusion limits are placed on the parameter space of the 3+1 model, in which muon antineutrinos experience a strong Mikheyev-Smirnov-Wolfenstein-resonant oscillation. The exclusion limits extend to sin^{2}2θ_{24}≤0.02 at Δm^{2}∼0.3 eV^{2} at the 90%confidence level. The allowed region from global analysis of appearance experiments, including LSND and MiniBooNE, is excluded at approximately the 99%confidence level for the global best-fit value of |U_{e4}|^{2}.

Характеристики потока нейтрино высоких энергий в атмосфере Земли

The processing of the IceCube experiment data, obtained during 988 days (2010-2013), revealed 37 high-energy neutrino-induced events with deposited energies 30 TeV - 2 PeV. The hypothesis of an astrophysical origin of these neutrinos is confirmed at the statistical confidence level of 5.7 standard deviations. To identify reliably the neutrino events, a thorough calculation of the atmospheric neutrino background is required. In this work we calculate the atmospheric neutrino spectra in the energy range 100 GeV - 10 PeV with usage of several hadronic models and a few parametrizations of the cosmic ray spectra, supported by experimental data, which take into account the knee. It is shown that rare decays of short-lived neutral каоns K0_s contribute more than a third of the total electron neutrino flux at the energies above 100 ТeV. The account for kaons production in pion-nucleus collisions increases the electron neutrino flux by 5-7 % in the energy range 10^2 -10^4 GeV. Calculated neutrino spectra agree on the whole with the measurement data. The neutrino flavor ratio, extracted from the IceCube data, possibly indicates that the conventional atmospheric electron neutrino flux obtained in the IceCube experiment contains an admixture of the astrophysical neutrinos in the range 20 − 50 TeV.

Development of a general analysis and unfolding scheme and its application to measure the energy spectrum of atmospheric neutrinos with IceCube: IceCube Collaboration.

We present the development and application of a generic analysis scheme for the measurement of neutrino spectra with the IceCube detector. This scheme is based on regularized unfolding, preceded by an event selection which uses a Minimum Redundancy Maximum Relevance algorithm to select the relevant variables and a random forest for the classification of events. The analysis has been developed using IceCube data from the 59-string configuration of the detector. 27,771 neutrino candidates were detected in 346 days of livetime. A rejection of 99.9999 % of the atmospheric muon background is achieved. The energy spectrum of the atmospheric neutrino flux is obtained using the TRUEE unfolding program. The unfolded spectrum of atmospheric muon neutrinos covers an energy range from 100 GeV to 1 PeV. Compared to the previous measurement using the detector in the 40-string configuration, the analysis presented here, extends the upper end of the atmospheric neutrino spectrum by more than a factor of two, reaching an energy region that has not been previously accessed by spectral measurements.

IceCube: From Oscillations to PeV Neutrino Events

With IceCube and its low-energy extension DeepCore, an instrument with a combined energy range from tens of GeV to EeV has been commissioned. It measures the atmospheric neutrino spectrum from the lower energies where neutrinos oscillate to energies as large as 100 TeV with a statistic of more than 100,000 events per year. The initial results suggest that IceCube can measure the oscillation parameters in an energy range that exceeds existing observations by one order of magnitude, thus opening a new window on neutrino physics. We also discuss the observation of PeV-energy events that cannot be accommodated by the flux anticipated by extrapolation of present atmospheric neutrino measurements.

IceCube Neutrinos: from Oscillations to PeV-Energy Events

With IceCube and its low-energy extension DeepCore, a neutrino detector with an energy reach from tens of gigaelectronvolt to exaelectronvolt has been commissioned. It measures the atmospheric neutrino spectrum from the lower energies where neutrinos oscillate to energies as large as 100 TeV with a statistic of more than 100,000 events per year. The initial results suggest that IceCube can measure the oscillation parameters in an energy range that exceeds existing observations by 1 order of magnitude, thus opening a new window on neutrino physics. We emphasize the search for sterile neutrinos particularly relevant to cosmology. We also discuss the first observation of (PEV) petaelectronvolt-Energy events that cannot be accommodated by the flux anticipated by extrapolation of the present atmospheric neutrino measurements.

Muon energy reconstruction in the ANTARES detector

The energy reconstruction of both neutrino-induced muons from neutrino interactions in the vicinity of the detector and of muons from cosmic ray air showers contributes indispensable information for a broad range of physics analyses, e.g. by increasing the sensitivity in neutrino point source searches or in offering access to observables such as the atmospheric neutrino spectrum. Currently, four energy reconstruction methods are implemented in the ANTARES data analysis framework, ranging from estimates based on photon counting and the total charge deposited in the detector to methods based on probability density functions and Artificial Neural Networks. These four methods, their performance and systematic studies of the energy resolution capabilities of the ANTARES detector are presented.

BEAMING NEUTRINOS AND ANTI-NEUTRINOS ACROSS THE EARTH TO DISENTANGLE NEUTRINO MIXING PARAMETERS

A MINOS result seemed to hint a different anti-neutrino mass splitting and mixing angle with respect to the neutrino ones, offering a hint for a CPT violation in lepton sector. However more recent MINOS data reduced the neutrino-antineutrino differences leading to a narrow discrepancy almost compatible with no CPT violation, hard to be disentangled. Moreover last a few years of OPERA activity on tau appearance is still un-probed (one unique event). Both flavor muon-tau mixing, tau appearance and eventual CPT violation disentanglement need more tools to be enhanced. Atmospheric muon neutrino spectra and anisotropy in Deep Core at ten-tens GeV (yet unpublished) may test the muon-tau conversion but they can hardly reveal such last tiny MINOS CPT asymmetry. We show how the longest baseline neutrino oscillation available, crossing most of the Earth diameter, within an OPERA-like experiment from CERN (or FERMILAB) to ICECUBE-Deep Core neutrino detector at 21 GeV energy, may at best disentangle even last tiny CPT violation (within 6 sigma a year) while testing at highest rate tau-antitau appearance. We propose the muon neutrino disappearance or (for any CPT violation) the partial anti-muon appearance at the longest distances. Such a tuned detection experiment may lead to a clear and strong signature of tau or anti-tau generation (even within its neutral current noise background events): nearly one antitau or two tau a day. The tau appearance signal is above (or within) 10 sigma a year, even for 1% OPERA-like experiment. Peculiar configurations for theta_13 angle test and hierarchy neutrino mass test may also be addressed by a Deep Core-PINGU array detector observing electron neutrino shower at 6 GeV neutrino energy windows.

CONSTRAINTS ON THE OPERA SUPERLUMINAL NEUTRINOS

The OPERA collaboration has recently reported the superluminal neutrinos with velocity of (vν - c)/c ~ 2.5 × 10-5. This result can be explained in the Lorentz invariance violation (LIV) models. The modified dispersion relation of neutrino lead to modified kinematics of the processes the neutrinos involved. For processes that neutrinos in the final states the processes are suppressed. We find to allow the neutrino production process π → μ + νμ, the neutrino energy should be less than about 5 GeV if taking a large LIV parameter ~ O(10-5) implied by OPERA data. For the processes that neutrinos in the initial states new processes that are forbidden in the LI scenario may open, such as the ν → ν + γ or ν → ν + e+ + e-, which lead neutrinos to lose energy quickly. As the atmospheric neutrino spectrum agrees well with expectation without LIV we find it can constrain the neutrino LIV parameter to ~ O(10-12), which is 7 orders smaller than the value measured at OPERA. We further propose to study the astrophysical neutrino spectra, which can constrain the neutrino LIV parameter down to O(10-15).

Foreseeing Neutrino spectra in Deep Core

In the present paper we evaluate the effect of neutrino flavor mixing and possible CPT violation (MINOS like) for up-going atmospheric muon neutrinos measured with the Deep Core detector of the IceCube Neutrino Observatory at South Pole. Our evaluation of rate and spectrum is based on the known Cosmic Ray flux and its consequent atmospheric neutrino spectrum derived at Super-Kamiokande, and it takes into account propagation and flavor mixing inside the Earth, interaction into the Deep Core (variable) volume, and projection along the physical Deep Core detector. Our results differ from other ones; however when the Deep Core results will be available our predictions can be compared directly with them. Interestingly, the Minos CPT violation hint might be confirmed or not.The observed spectrum should also exhibit an anomalous minimum, due to neutrino oscillation, offering a "silent" narrow detection window for neutrinos with energies around 20 GeV, which could be very useful for a new Neutrino Astronomy.

Constraints and Tests of the OPERA Superluminal Neutrinos

The superluminal neutrinos detected by OPERA indicate Lorentz invariance violation (LIV) of the neutrino sector at the order of 10(-5). We study the implications of the result in this work. We find that such a large LIV implied by OPERA data will make the neutrino production process π → μ + ν(μ) kinematically forbidden for a neutrino energy greater than about 5 GeV. The OPERA detection of neutrinos at 40 GeV can constrain the LIV parameter to be smaller than 3×10(-7). Furthermore, the neutrino decay in the LIV framework will modify the neutrino spectrum greatly. The atmospheric neutrino spectrum measured by the IceCube Collaboration can constrain the LIV parameter to the level of 10(-12). The future detection of astrophysical neutrinos of galactic sources is expected to be able to give an even stronger constraint on the LIV parameter of neutrinos.

Search for astrophysical neutrinos in the Baikal neutrino project

The currently running NT200 and NT200+ Baikal neutrino telescopes and the prospects for development of the Baikal Neutrino Project are briefly descr⇊ed. Preliminary results of the search for neutrino events correlated with cosmological gamma-ray bursts at the NT200 are presented. The feasibility of developing a method for acoustic detection of ultrahigh-energy neutrinos in the Baikal Neutrino Project is discussed. The calculation results for the energy spectrum and zenith-angle distributions of atmospheric neutrinos in the energy range from 10 to 107 GeV obtained within various high-energy hadron-nucleus interaction models are presented.

Search for a diffuse flux of astrophysical muon neutrinos with the IceCube 40-string detector

The IceCube Neutrino Observatory is a 1 km$^{3}$ detector currently taking data at the South Pole. One of the main strategies used to look for astrophysical neutrinos with IceCube is the search for a diffuse flux of high-energy neutrinos from unresolved sources. A hard energy spectrum of neutrinos from isotropically distributed astrophysical sources could manifest itself as a detectable signal that may be differentiated from the atmospheric neutrino background by spectral measurement. This analysis uses data from the IceCube detector collected in its half completed configuration which operated between April 2008 and May 2009 to search for a diffuse flux of astrophysical muon neutrinos. A total of 12,877 upward going candidate neutrino events have been selected for this analysis. No evidence for a diffuse flux of astrophysical muon neutrinos was found in the data set leading to a 90 percent C.L. upper limit on the normalization of an $E^{-2}$ astrophysical $\nu_{\mu}$ flux of $8.9 \times 10^{-9} \ \mathrm{GeV \ cm^{-2} \ s^{-1} \ sr^{-1}}$. The analysis is sensitive in the energy range between $35 \ \mathrm{TeV} - 7 \ \mathrm{PeV}$. The 12,877 candidate neutrino events are consistent with atmospheric muon neutrinos measured from 332 GeV to 84 TeV and no evidence for a prompt component to the atmospheric neutrino spectrum is found.