Search for Neutrino Oscillations in Appearance Mode with the OPERA Experiment

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 $\nu_{\mu} \rightarrow \nu_{\tau}$ oscillation in appearance mode, also allowing to perform a $\nu_{e}$ appearance search. We review the data simulation and the analysis chains implemented to search for $\nu_{\tau}$ 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 $\nu_{\mu} \rightarrow \nu_{\tau}$ oscillation search are examined. The topologies of the two first $\nu_{\tau}$ candidate events are presented. Finally, we review the status of the $\nu_{e}$ appearance search and present the constraints set by the OPERA experiment on the mixing angle $\theta_{13}$ and on the LSND/MiniBooNE anomaly.Comment: Mini-review of the OPERA experiment analysis status (October 2013), 9 pages, 5 figures, to appear in Proc. HEPFT-201

Electromagnetic cascade masquerade: a way to mimic γ\gamma--axion-like particle mixing effects in blazar spectra

Context. Most of the studies on extragalactic {\gamma}-ray propagation performed up to now only accounted for primary gamma-ray absorption and adiabatic losses ("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 {\gamma}-axion-like particle (ALP) oscillation. On the other hand, there are many hints that a secondary component from electromagnetic cascades initiated by primary {\gamma}-rays or nuclei may be observed in the spectra of some blazars. Aims. We study the impact of electromagnetic cascades from primary {\gamma}-rays or protons on the physical interpretation of blazar spectra obtained with imaging Cherenkov telescopes. Methods. We use the publicly-available code ELMAG to compute observable spectra of electromagnetic cascades from primary {\gamma}-rays. For the case of primary proton, we develop a simple, fast and reasonably accurate hybrid method to calculate the observable spectrum. We perform 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 {\gamma}-rays), and several versions of the hadronic cascade model (for the case of primary proton). We distinguish the following species of hadronic cascade models: 1) "basic hadronic model", where it is assumed that the proton beam travels undisturbed by extragalactic magnetic field and that all observable {\gamma}-rays are produced by primary protons through photohadronic processes with subsequent development of electromagnetic cascades /abridgedComment: Accepted by A&A. 25 pages, 31 figures. Corrected fig. 5, fig. 7; new explanations for fig. 6--7; several typos fixed wrt v.

Results and prospects on registration of reflected Cherenkov light of EAS from cosmic particles above 10^{15} eV

We give an overview of the SPHERE experiment based on detection of reflected Vavilov-Cherenkov radiation (Cherenkov light) from extensive air showers in the energy region E>10^{15} eV. A brief history of the reflected Cherenkov light technique is given; the observations carried out with the SPHERE-2 detector are summarized; the methods of the experimental datasample analysis are described. The first results on the primary cosmic ray all-nuclei energy spectrum and mass composition are presented. Finally, the prospects of the SPHERE experiment and the reflected Cherenkov light technique are given.Comment: 4 pages, 3 figures, Proc. PANIC-201