62 research outputs found
Constraints on the extragalactic magnetic field strength from blazar spectra based on 145 months of Fermi-LAT observations --- Supplementary material
No full textThis project contains the software and data underlying the paper 'Constraints on the extragalactic magnetic field strength from blazar spectra based on 145 months of Fermi-LAT observations' by E. I. Podlesnyi, T. A. Dzhatdoev, and V. I. Galkin (arXiv:2204.11110).
Please read the README.md file before running any project programs.This research was partly funded by the Interdisciplinary Scientific and Educational School of Lomonosov Moscow State University "Fundamental and Applied Space Research". The work of E.P. and T.D. on the VHE -ray propagation in the intergalactic medium was supported by the Russian Science Foundation, grant No. 22-12-00253. E.P. thanks the Theoretical Physics and Mathematics Advancement Foundation "BASIS" (Contract No. 20-2-10-7-1) for the student scholarship
Search for Neutrino Oscillations in Appearance Mode with the OPERA Experiment
No full textThe present paper highlights the data analysis status of the OPERA experiment. The experiment was designed to perform the neutrino interactions analysis on event-by-event basis, and optimized to search for νμ → ντ oscillation in appearance mode, also allowing to perform a νe appearance search.The present paper highlights the data analysis status of the OPERA experiment. The experiment was designed to perform the neutrino interactions analysis on event-by-event basis, and optimized to search for oscillation in appearance mode, also allowing to perform a appearance search. We review the data simulation and the analysis chains implemented to search for interactions. The main kinematical parameters sensitive to the neutrino flavor are discussed, the uncertainties of the event parameter estimation are reviewed, and the main sources of background for the oscillation search are examined. The topologies of the two first candidate events are presented. Finally, we review the status of the appearance search and present the constraints set by the OPERA experiment on the mixing angle and on the LSND/MiniBooNE anomaly
On the sensitivity of the spatial-angular distribution of the Cherenkov light in extensive air showers to the mass composition of primary cosmic rays with energies of 1015–1016 eV
No full textConstraints on the extragalactic magnetic field strength from blazar spectra based on 145 months of Fermi-LAT observations
No full textProperties of the extragalactic magnetic field (EGMF) outside of clusters and
filaments of the large-scale structure are essentially unknown. The EGMF could
be probed with -ray observations of distant (redshift )
blazars. TeV rays from these sources are strongly absorbed on
extragalactic background light photons; secondary electrons and positrons
produce cascade rays with the observable flux dependent on EGMF
parameters. We put constraints on the EGMF strength using 145 months of
Fermi-LAT observations of the blazars 1ES 1218+304, 1ES 1101-232, and 1ES
0347-121, and imaging atmospheric Cherenkov telescope observations of the same
sources. We perform a series of full direct Monte Carlo simulations of
intergalactic electromagnetic cascades with the ELMAG 3.01 code and construct a
model of the observable spectra inside the point spread functions of the
observing instruments for a range of EGMF strengths. We compare the observed
spectra with the models for various values of the EGMF strength and
calculate the exclusion statistical significance for every value of . We
find that the values of the EGMF strength G are excluded at a
high level of the statistical significance for all the four
options of the intrinsic spectral shape considered (power-law, power-law with
exponential cutoff, log-parabola, log-parabola with exponential cutoff). The
value of G is not excluded; it is still a viable option of the
EGMF strength. These results were obtained for the case of steady sources.Comment: 10 pages, 6 figures, 2 tables. Published in MNRAS. This is the
authors' version, not the final typeset. Minor main text changes w.r.t. v2,
two appendices added. Supplementary material is available at
https://doi.org/10.5281/zenodo.648335
Cascades from primary gamma rays and nuclei as a source of background in searches for oscillations between photons and axion-like particles
No full textTesting models of extragalactic γ-ray propagation using observations of extreme blazars in GeV and TeV energy ranges
No full textSignatures of blazar spectra in the electromagnetic and hadronic intergalactic cascade models
No full textElectromagnetic cascade masquerade: a way to mimic<i>γ</i>-axion-like particle mixing effects in blazar spectra
No full textContext. Most of the studies on extragalactic γ-ray propagation performed up to now only accounted for primary γ-ray absorption and adiabatic losses, known as the “absorption-only model”. However, there is growing evidence that this model is oversimplified and must be modified in some way. In particular, it was found that the intensity extrapolated from the optically-thin energy range of some blazar spectra is insufficient to explain the optically-thick part of these spectra. This effect was interpreted as an indication for γ-axion-like particle (ALP) oscillation. On the other hand, there are many hints that a secondary component from electromagnetic cascades initiated by primary γ-rays or nuclei may be observed in the spectra of some blazars.
Aims. We study the impact of electromagnetic cascades from primary γ-rays or protons on the physical interpretation of blazar spectra obtained with imaging Cherenkov telescopes.
Methods. We used the publicly-available code ELMAG to compute observable spectra of electromagnetic cascades from primary γ-rays. For the case of primary proton, we developed a simple, fast and reasonably accurate hybrid method to calculate the observable spectrum. We performed the fitting of the observed spectral energy distributions (SEDs) with various physical models: the absorption-only model, the “electromagnetic cascade model” for the case of primary γ-rays, and several versions of the hadronic cascade model for the case of primary protons. We distinguish the following species of hadronic cascade models: 1) the “basic hadronic model”, in which it is assumed that the proton beam travels undisturbed by the extragalactic magnetic field and that all observable γ-rays are produced by primary protons through photohadronic processes with subsequent development of electromagnetic cascades; 2) the “intermediate hadronic model”, which is the same as the basic hadronic model, but the primary beam is terminated at some redshift zc; and 3) the “modified hadronic model” that includes the contribution from primary, redshifted and partially-absorbed, γ-rays.
Results. Electromagnetic cascades show at least two very distinct regimes labelled by the energy of the primary γ-ray (E0): the one-generation regime for the case of E0 100 TeV and redshift to the source zs > 0.02. Spectral signatures of the observable spectrum for the case of the basic hadronic model, zs = 0.186 and low energy (E 200 GeV the spectrum is much harder for the case of the basic hadronic model. In the framework of the intermediate hadronic model, the observable spectrum depends only slightly on the primary proton energy, but it strongly depends on zc at E > 500 GeV. As a rule, both electromagnetic and hadronic cascade models provide acceptable fits to the observed SEDs. We show that the best-fit model intensity in the multi-TeV region of the spectrum in the framework of the electromagnetic cascade model is typically greater than the one for the case of the absorption-only model. Finally, for the case of blazar 1ES 0229+20
Momentum measurement by the multiple Coulomb scattering method in the OPERA lead-emulsion target
No full textA new method of momentum measurement of charged particles through multiple Coulomb scattering (MCS) in the OPERA lead-emulsion target is presented. It is based on precise measurements of track angular deviations carried out thanks to the very high resolution of nuclear emulsions. The algorithm has been tested with Monte Carlo pions. The results are found t
Evidence for nu(mu) -> nu(tau) appearance in the CNGS neutrino beam with the OPERA experiment
No full textThe OPERA experiment is designed to search for nu(mu) -> nu(tau) oscillations in appearance mode, i.e., through the direct observation of the tau lepton in nu(tau)- charged current interactions. The experiment has taken data for five years, since 2008, with the CERN Neutrino to Gran Sasso beam. Previously, two nu(tau) candidates with a t decaying into hadrons were observed in a subsample of data of the 2008-2011 runs. Here we report the observation of a third nu(tau) candidate in the tau(-) -> mu(-) decay channel coming from the analysis of a subsample of the 2012 run. Taking into account the estimated background, the absence of nu(mu) -> nu(tau) oscillations is excluded at the 3.4 sigma level
- …
