We study the implications of ultrahigh-energy cosmic-ray (UHECR) data from the Pierre Auger Observatory for potential accelerator candidates and cosmogenic neutrino fluxes for different combinations ...of nuclear disintegration and air-shower models. We exploit the most recent spectral and mass composition data (2017) with a new, computationally efficient simulation code, PriNCe. We extend a systematic framework, which has been previously applied in a combined fit by the Pierre Auger Collaboration, with the cosmological source evolution as an additional free parameter. In this framework, an ensemble of generalized UHECR accelerators is characterized by a universal spectral index (equal for all injection species), a maximal rigidity, and the normalizations for five nuclear element groups. We find that the 2017 data favor a small but constrained contribution of heavy elements (iron) at the source. We demonstrate that the results moderately depend on the nuclear disintegration (Puget–Stecker–Bredekamp, Peanut, or Talys) model and more strongly on the air-shower (EPOS-LHC, Sibyll 2.3, or QGSjetII-04) model. Variations of these models result in different source evolution and spectral indices, limiting the interpretation in terms of a particular class of cosmic accelerators. Better-constrained parameters include the maximal rigidity and the mass composition at the source. Hence, the cosmogenic neutrino flux can be robustly predicted. Depending on the source evolution at high redshifts, the flux is likely out of reach of future neutrino observatories in most cases, and a minimal cosmogenic neutrino flux cannot be claimed from data without assuming a cosmological distribution of the sources.
We discuss neutrino and cosmic-ray emission from Gamma-Ray Bursts (GRBs) with the injection of nuclei, where we take into account that a nuclear cascade from photo-disintegration can fully develop in ...the source. One of our main objectives is to test if recent results from the IceCube and the Pierre Auger Observatory can be accommodated with the paradigm that GRBs are the sources of Ultra-High Energy Cosmic Rays (UHECRs). While our key results are obtained using an internal shock model, we discuss how the secondary emission from a GRB shell can be interpreted in terms of other astrophysical models. It is demonstrated that the expected neutrino flux from GRBs weakly depends on the injection composition, which implies that prompt neutrinos from GRBs can efficiently test the GRB-UHECR paradigm even if the UHECRs are nuclei. We show that the UHECR spectrum and composition, as measured by the Pierre Auger Observatory, can be self-consistently reproduced in a combined source-propagation model. In an attempt to describe the energy range including the ankle, we find tension with the IceCube bounds from the GRB stacking analyses. In an alternative scenario, where only the UHECRs beyond the ankle originate from GRBs, the requirement for a joint description of cosmic-ray and neutrino observations favors lower luminosities, which does not correspond to the typical expectation from $\gamma$-ray observations.
The event generator Sibyll can be used for the simulation of hadronic multiparticle production up to the highest cosmic ray energies. It is optimized for providing an economic description of those ...aspects of the expected hadronic final states that are needed for the calculation of air showers and atmospheric lepton fluxes. New measurements from fixed target and collider experiments, in particular those at LHC, allow us to test the predictive power of the model version 2.1, which was released more than 10 years ago, and also to identify shortcomings. Based on a detailed comparison of the model predictions with the new data we revisit model assumptions and approximations to obtain an improved version of the interaction model. In addition a phenomenological model for the production of charm particles is implemented as needed for the calculation of prompt lepton fluxes in the energy range of the astrophysical neutrinos recently discovered by IceCube. After giving an overview of the new ideas implemented in Sibyll and discussing how they lead to an improved description of accelerator data, predictions for air showers and atmospheric lepton fluxes are presented.
The recent observations of muon charge ratio up to about 10 TeV and of atmospheric neutrinos up to energies of about 400 TeV has triggered a renewed interest into the high-energy interaction models ...and cosmic ray primary composition. A reviewed calculation of lepton spectra produced in cosmic-ray induced extensive air showers is carried out with a primary cosmic-ray spectrum that fits the latest direct measurements below the knee. In order to achieve this, we used a full Monte Carlo method to derive the inclusive differential spectra (yields) of muons, muon neutrinos and electron neutrinos at the surface for energies between 80 GeV and hundreds of PeV. The air shower simulator {\sc corsika} 6.990 was used for showering and propagation of the secondary particles through the atmosphere, employing the established high-energy hadronic interaction models {\sc sibyll} 2.1, {\sc qgsjet-01} and {\sc qgsjet-ii 03}. We show that the performance of the interaction models allows makes it possible to predict the spectra within experimental uncertainties, while {\sc sibyll} generally yields a higher flux at the surface than the qgsjet models. The calculation of the flavor and charge ratios has lead to inconsistent results, mainly influenced by the different representations of the K/\(\pi\) ratio within the models. Furthermore, we could quantify systematic uncertainties of atmospheric muon- and neutrino fluxes, associated to the models of the primary cosmic-ray spectrum and the interaction models. For most recent parametrizations of the cosmic-ray primary spectrum, atmospheric muons can be determined with an uncertainty smaller than \(^{+15}_{-13}\)% of the average flux. Uncertainties of the muon- and electron neutrino fluxes can be calculated within an average error of \(^{+32}_{-22}\)% and \(^{+25}_{-19}\)%, respectively.
An efficient method for calculating inclusive conventional and prompt atmospheric leptons fluxes is presented. The coupled cascade equations are solved numerically by formulating them as matrix ...equation. The presented approach is very flexible and allows the use of different hadronic interaction models, realistic parametrizations of the primary cosmic-ray flux and the Earth's atmosphere, and a detailed treatment of particle interactions and decays. The power of the developed method is illustrated by calculating lepton flux predictions for a number of different scenarios.
Charm production in SIBYLL Engel, Ralph; Fedynitch, Anatoli; Gaisser, Thomas K ...
arXiv.org,
02/2015
Paper, Journal Article
Odprti dostop
SIBYLL 2.1 is an event generator for hadron interactions at the highest energies. It is commonly used to analyze and interpret extensive air shower measurements. In light of the first detection of ...PeV neutrinos by the IceCube collaboration the inclusive fluxes of muons and neutrinos in the atmosphere have become very important. Predicting these fluxes requires understanding of the hadronic production of charmed particles since these contribute significantly to the fluxes at high energy through their prompt decay. We will present an updated version of SIBYLL that has been tuned to describe LHC data and extended to include the production of charmed hadrons.
This paper presents the studies of the background contribution to the \(H \rightarrow 4l\) searches originating from the processes of off-shell (virtual) photon emissions and their conversions into ...lepton pairs accompanying the production of \(Z/ \gamma ^*\)-bosons at the LHC. They extend the analyses of the irreducible background presented in the ATLAS and CMS Higgs papers by taking into account the emissions of off-shell photons by parton showers. Including these effects does not change significantly the Higgs-searches background level, provided that the transverse momentum of each of the final-state leptons is restricted to the range of \(p_{T, l} > 7\) GeV. In the kinematical region extended towards lower lepton transverse momenta the parton-shower contribution becomes important. A measurement method for pinning down the parton-shower effects is proposed.
Muons and neutrinos from cosmic ray interactions in the atmosphere originate from decays of mesons in air-showers. sibyll-2.3c aims to give a precise description of hadronic interactions in the ...relevant phase space for conventional and prompt leptons in light of new accelerator data, including that from the LHC. sibyll is designed primarily as an event generator for use in simulation of extensive air showers. Because it has been tuned for forward physics as well as the central region, it can also be used to calculate inclusive fluxes. The purpose of this paper is to describe the use of sibyll-2.3c for calculation of fluxes of atmospheric leptons.
We investigate whether the emission of neutrinos observed in 2014–2015 from the direction of the blazar TXS 0506+056 can be accommodated with leptohadronic multiwavelength models of the source ...commonly adopted for the 2017 flare. While multiwavelength data during the neutrino flare are sparse, the large number of neutrino events (13 ± 5) challenges the missing activity in gamma-rays. We illustrate that two to five neutrino events during the flare can be explained with leptohadronic models of different categories: a one-zone model, a compact-core model, and an external radiation field model. If, however, significantly more events were to be accommodated, the predicted multiwavelength emission levels would be in conflict with observational X-ray constraints, or with the high-energy gamma-ray fluxes observed by the Fermi Large Area Telescope, depending on the model. For example, while the external radiation field model can predict up to five neutrino events without violating X-ray constraints, the absorption of high-energy gamma-rays is in minor tension with the data. We therefore do not find any model that can simultaneously explain the high event number quoted by IceCube and the (sparse) electromagnetic data during the neutrino flare.
We discuss the production of ultra-high-energy cosmic ray (UHECR) nuclei and neutrinos from blazars. We compute the nuclear cascade in the jet for both BL Lac objects and flat-spectrum radio quasars ...(FSRQs), and in the ambient radiation zones for FSRQs as well. By modeling representative spectral energy distributions along the blazar sequence, two distinct regimes are identified, which we call "nuclear survival" -- typically found in low-luminosity BL Lacs, and "nuclear cascade" -- typically found in high-luminosity FSRQs. We quantify how the neutrino and cosmic-ray (CR) emission efficiencies evolve over the blazar sequence, and demonstrate that neutrinos and CRs come from very different object classes. For example, high-frequency peaked BL Lacs (HBLs) tend to produce CRs, and HL-FSRQs are the more efficient neutrino emitters. This conclusion does not depend on the CR escape mechanism, for which we discuss two alternatives (diffusive and advective escape). Finally, the neutrino spectrum from blazars is shown to significantly depend on the injection composition into the jet, especially in the nuclear cascade case: Injection compositions heavier than protons lead to reduced neutrino production at the peak, which moves at the same time to lower energies. Thus, these sources will exhibit better compatibility with the observed IceCube and UHECR data.
