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Register a new userUncertainties in Atmospheric Muon-Neutrino Fluxes Arising from Cosmic-Ray Primaries
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Added by
Salvatore Davide Porzio
Publication date
2016
fields
Physics
and research's language is
English
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We present an updated calculation of the uncertainties on the atmospheric muon-neutrino flux arising from cosmic-ray primaries. For the first time, we include recent measurements of the cosmic-ray primaries collected since 2005. We apply a statistical technique that allows the determination of correlations between the parameters of the GSHL primary-flux parametrisation and the incorporation of these correlations into the uncertainty on the muon-neutrino flux. We obtain an uncertainty related to the primary cosmic rays of around $(5text{--}15)%$, depending on energy, which is about a factor of two smaller than the previously determined uncertainty. The hadron production uncertainty is added in quadrature to obtain the total uncertainty on the neutrino flux, which is reduced by $approx 5%$. To take into account an unexpected hardening of the spectrum of primaries above energies of $100$ $text{GeV}$ observed in recent measurements, we propose an alternative parametrisation and discuss its impact on the neutrino flux uncertainties.
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The fluxes of atmospheric muons and neutrinos are calculated by a three dimensional Monte Carlo simulation with the air shower code CORSIKA using the hadronic interaction models DPMJET, VENUS, GHEISHA, and UrQMD. For the simulation of low energy primary particles the original CORSIKA has been extended by a parametrization of the solar modulation and a microscopic calculation of the directional dependence of the geomagnetic cut-off functions. An accurate description for the geography of the Earth has been included by a digital elevation model, tables for the local magnetic field in the atmosphere, and various atmospheric models for different geographic latitudes and annual seasons. CORSIKA is used to calculate atmospheric muon fluxes for different locations and the neutrino fluxes for Kamioka. The results of CORSIKA for the muon fluxes are verified by an extensive comparison with recent measurements. The obtained neutrino fluxes are compared with other calculations and the influence of the hadronic interaction model, the geomagnetic cut-off and the local magnetic field on the neutrino fluxes is investigated.
Gamma-ray bursts (GRBs) have long been held as one of the most promising sources of ultra-high energy (UHE) neutrinos. The internal shock model of GRB emission posits the joint production of UHE cosmic ray (UHECRs, above 10^8 GeV), photons, and neutrinos, through photohadronic interactions between source photons and magnetically-confined energetic protons, that occur when relativistically-expanding matter shells loaded with baryons collide with one another. While neutrino observations by IceCube have now ruled out the simplest version of the internal shock model, we show that a revised calculation of the emission, together with the consideration of the full photohadronic cross section and other particle physics effects, results in a prediction of the prompt GRB neutrino flux that still lies one order of magnitude below the current upper bounds, as recently exemplified by the results from ANTARES. In addition, we show that by allowing protons to directly escape their magnetic confinement without interacting at the source, we are able to partially decouple the cosmic ray and prompt neutrino emission, which grants the freedom to fit the UHECR observations while respecting the neutrino upper bounds. Finally, we briefly present advances towards pinning down the precise relation between UHECRs and UHE neutrinos, including the baryonic loading required to fit UHECR observations, and we will assess the role that very large volume neutrino telescopes play in this.
Top-of-atmosphere (TOA) cosmic-ray (CR) fluxes from satellites and balloon-borne experiments are snapshots of the solar activity imprinted on the interstellar (IS) fluxes. Given a series of snapshots, the unknown IS flux shape and the level of modulation (for each snapshot) can be recovered. We wish (i) to provide the most accurate determination of the IS H and He fluxes from TOA data alone, (ii) to obtain the associated modulation levels (and uncertainties) while fully accounting for the correlations with the IS flux uncertainties, and (iii) to inspect whether the minimal force-field approximation is sufficient to explain all the data at hand. Using H and He TOA measurements, including the recent high-precision AMS, BESS-Polar, and PAMELA data, we performed a non-parametric fit of the IS fluxes $J^{rm IS}_{rm H,~He}$ and modulation level $phi_i$ for each data-taking period. We relied on a Markov chain Monte Carlo (MCMC) engine to extract the probability density function and correlations (hence the credible intervals) of the sought parameters. Although H and He are the most abundant and best measured CR species, several datasets had to be excluded from the analysis because of inconsistencies with other measurements. From the subset of data passing our consistency cut, we provide ready-to-use best-fit and credible intervals for the H and He IS fluxes from MeV/n to PeV/n energy (with a relative precision in the range [2-10%] at 1$sigma$). Given the strong correlation between $J^{rm IS}$ and $phi_i$ parameters, the uncertainties on $J^{rm IS}$ translate into $Deltaphiapprox pm 30$~MV (at 1$sigma$) for all experiments. We also find that the presence of $^3$He in He data biases $phi$ towards higher $phi$ values by $sim 30$~MV. The force-field approximation gives an excellent ($chi^2/$dof$=1.02$) description of the recent high-precision TOA H and He fluxes.
High-energy neutrinos from decays of mesons, produced in collisions of cosmic ray particles with air nuclei, form unavoidable background for detection of astrophysical neutrinos. More precise calculations of the high-energy neutrino spectrum are required since measurements in the IceCube experiment reach the intriguing energy region where a contribution of the prompt neutrinos and/or astrophysical ones should be discovered. Basing on the referent hadronic models QGSJET II-03, SIBYLL 2.1, we calculate high-energy spectra, both of the muon and electron atmospheric neutrinos, averaged over zenith-angles. The computation is made using three parameterizations of cosmic ray spectra which include the knee region. All calculations are compared with the atmospheric neutrino measurements by Frejus and IceCube. The prompt neutrino flux predictions obtained with thequark-gluon string model (QGSM) for the charm production by Kaidalov & Piskunova do not contradict to the IceCube measurements and upper limit on the astrophysical muon neutrino flux. Neutrino flavor ratio, $phi_{ u_ mu}/phi_{ u_e}$, extracted from IceCube data decreases in the energy range $0.1 - 5$ TeV energy contrary to that one might expect from the conventional neutrino flux. Presumable reasons of such behavior are: i) early arising contribution from decays of charmed particle, differing from predictions of present models, ii) revealed diffuse flux of astrophysical electron neutrinos. The likely diffuse flux of astrophysical neutrinos related to the PeV neutrino events, detected in the IceCube experiment, leads to a decrease of the flavor ratio at the energy below 10 TeV, that is in qualitative agreement with a rough approximation for theflavor ratio obtained from the IceCube data.
Gamma-ray bursts are short-lived, luminous explosions at cosmological distances, thought to originate from relativistic jets launched at the deaths of massive stars. They are among the prime candidates to produce the observed cosmic rays at the highest energies. Recent neutrino data have, however, started to constrain this possibility in the simplest models with only one emission zone. In the classical theory of gamma-ray bursts, it is expected that particles are accelerated at mildly relativistic shocks generated by the collisions of material ejected from a central engine. We consider neutrino and cosmic-ray emission from multiple emission regions since these internal collisions must occur at very different radii, from below the photosphere all the way out to the circumburst medium, as a consequence of the efficient dissipation of kinetic energy. We demonstrate that the different messengers originate from different collision radii, which means that multi-messenger observations open windows for revealing the evolving GRB outflows.
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