Abstract
The Peccei and Quinn axions are low-mass pseudo-scalar neutral bosons whose existence was proposed to explain for the spontaneous breaking of the CP invariance in the early Universe. In the ...minimal (
SU
(2)
left
⊗
U
(1)) version of the leptonic sector of the electroweak lagrangian flavor neutrinos are massive. They are described as linear combinations of neutrino mass eigenstates and they oscillates between flavor states. However the mass mechanism which gives their masses is still unknown. In this talk we discuss a possible mechanism to explain for non-zero neutrino masses, which is based on the treatment of neutrino-axion interactions.
ABSTRACT
Blazars research is one of the hot topics of contemporary extragalactic astrophysics. That is because these sources are the most abundant type of extragalactic γ-ray sources and are ...suspected to play a central role in multimessenger astrophysics. We have used Swift$\_$xrtproc, a tool to carry out an accurate spectral and photometric analysis of the Swift-XRT data of all blazars observed by Swift at least 50 times between December 2004 and the end of 2020. We present a database of X-ray spectra, best-fit parameter values, count rates and flux estimations in several energy bands of over 31 000 X-ray observations and single snapshots of 65 blazars. The results of the X-ray analysis have been combined with other multifrequency archival data to assemble the broad-band Spectral Energy Distributions (SEDs) and the long-term light curves of all sources in the sample. Our study shows that large X-ray luminosity variability on different time-scales is present in all objects. Spectral changes are also frequently observed with a ‘harder-when-brighter’ or ‘softer-when-brighter’ behaviour depending on the SED type of the blazars. The peak energy of the synchrotron component (νpeak) in the SED of HBL blazars, estimated from the log-parabolic shape of their X-ray spectra, also exhibits very large changes in the same source, spanning a range of over two orders of magnitude in Mrk421 and Mrk501, the objects with the best data sets in our sample.
At present, a variety of dark matter (DM) density profiles are available in the literature, able to fit the observed rotation velocity curves in galaxies. These distributions may be classified ...according to nature and mass of the DM candidate, and their estimation of the concentration of DM on halo scales, as well as through their central regions. Examples of these distributions are the (empiric) Einasto or isotropic, the (N-body-simulation-based) Navarro–Frenk–White (NFW), or the (elementary-particle-based) Ruffini–Argüelles–Rueda (RAR), among others. In this work, we calculate the cross-sections for the interaction between neutrinos coming from astrophysical sources and DM particles subject to some of these distributions. Furthermore, we explore the changes in the neutrino oscillation patterns due to the different DM profiles used to represent the environment. From the results of the calculations it is concluded that both the cross-section and the neutrino oscillation pattern depend on the features of each of the adopted models for the DM distributions. For the case of the NFW and isotropic DM distributions the expected effects at Earth, for neutrinos coming from an extragalactic source, are noticeable while in the case of the RAR distribution the effects are restricted to a narrow region around the galactic center.
Neutrinos are produced in cosmic accelerators, like active galactic nuclei, blazars, supernova remnants and gamma-ray bursts (GRBs). On their way to the Earth they experience flavor oscillations. The ...interactions of the neutrinos coming from the source with other particles, e.g., intergalactic primordial neutrinos or heavy-mass right-handed neutrinos, on their way to the detector may transform the original wavepacket in pointer states. This phenomenon, known as decoherence, becomes important in the reconstruction of processes at the source. In this work, we study neutrino emission in short GRBs by adopting the Fireshell Model. We consider e−e+-pair annihilation as the main channel for neutrino production. We compare the properties of the neutrino flux with the characteristic photon signal produced once the transparency condition is reached. We study the effects of flavor oscillations and decoherence as neutrinos travel from the region near the black hole event horizon outward. We consider the source to be in thermal equilibrium and calculate energy distribution functions for electrons and neutrinos. To compute the effects of decoherence we use a Gaussian model. In this scenario, the emitted electron-neutrinos transform into pointer states consisting of 67.8% electron-neutrinos and 32.2% as a combination of mu and tau neutrinos. We found that decoherence plays an important role in the evolution of the neutrino wavepacket, leading to the detected pointer states on Earth.
In this work we use the recently measured neutron occupancies in the 76Ge and 76Se nuclei as a guideline to define the neutron quasiparticle states in the 1p0f0g shell. We define the proton ...quasiparticles by inspecting the odd-mass nuclei adjacent to 76Ge and 76Se. We insert the resulting quasiparticles in a proton–neutron quasiparticle random-phase approximation (pnQRPA) calculation of the nuclear matrix element of the neutrinoless double beta (0νββ) decay of 76Ge. A realistic model space and effective microscopic two-nucleon interactions are used. We include the nucleon–nucleon short-range correlations and other relevant corrections at the nucleon level. It is found that the resulting 0νββ matrix element is smaller than in the previous pnQRPA calculations, and closer to the recently reported shell-model results.
In this work we report on the effects of short-range correlations upon the matrix elements of neutrinoless double beta decay (0νββ). We focus on the calculation of the matrix elements of the ...neutrino-mass mode of 0νββ decays of 48Ca and 76Ge. The nuclear-structure components of the calculation, that is the participant nuclear wave functions, have been calculated in the shell-model scheme for 48Ca and in the proton–neutron quasiparticle random-phase approximation (pnQRPA) scheme for 76Ge. We compare the traditional approach of using the Jastrow correlation function with the more complete scheme of the unitary correlation operator method (UCOM). Our results indicate that the Jastrow method vastly exaggerates the effects of short-range correlations on the 0νββ nuclear matrix elements.
Aims. We study the time variation of the fine structure constant, α, and the Higgs vacuum expectation value v, during the Big Bang nucleosynthesis (BBN). Methods. We computed primordial abundances of ...light nuclei produced during the BBN stage by including resonances in the leading reaction rates which reduce the primordial abundance of beryllium. We performed this calculation considering that α and v may vary during the BBN. Using observable data on deuterium, 4He, and 7Li, we set constraints on the variation of the fundamental constants. Results. Results indicate a null variation of α and v, while the best-fit value for the baryon-to-photon ratio agrees well with the WMAP value. Conclusions. We found that the variation of α is null within 3σ, the variation of v is null within 6σ, and the preferred value of the baryon-to-photon ratio is in good agreement, within 3σ, with the value extracted using the WMAP data. We improve the fits respect to previous works.
In this Letter we make an estimate of the time delay between signals, recorded at detectors on Earth, of neutrinos and photons originated in a short gamma-ray burst. We describe the geometry and ...dynamics of the system according to the Fireshell model. The delay in the photon's arrival time is produced because the system is originally opaque to radiation; thus, the photons remain trapped and thermalize until the transparency condition is reached. We calculate the time interval between neutrino emission and photon emission in the black hole frame and transform it to the observer frame using Lorentz transformations. We obtain a difference in the arrival time at Earth of .
Aims. Open Universe for Blazars is a set of high-transparency multi-frequency data products for blazar science, and the tools designed to generate them. Blazars are drawing growing interest following ...the consolidation of their position as the most abundant type of source in the extragalactic very high-energy γ-ray sky, and because of their status as prime candidate sources in the nascent field of multi-messenger astrophysics. As such, blazar astrophysics is becoming increasingly data driven, depending on the integration and combined analysis of large quantities of data from the entire span of observational astrophysics techniques. The project was therefore chosen as one of the pilot activities within the United Nations Open Universe Initiative, whose objective is to stimulate a large increase in the accessibility and ease of utilisation of space science data for the worldwide benefit of scientific research, education, capacity building, and citizen science. Methods. Our aim is to deliver innovative data science tools for multi-messenger astrophysics. In this work we report on a data analysis pipeline called Swift-DeepSky based on the Swift XRTDAS software and the XIMAGE package, encapsulated into a Docker container. Swift-DeepSky downloads and reads low-level data, generates higher level products, detects X-ray sources, and estimates several intensity and spectral parameters for each detection, thus facilitating the generation of complete and up-to-date science-ready catalogues from an entire space-mission data set. Results. As a first application of our innovative approach, we present the results of a detailed X-ray image analysis based on Swift-DeepSky that was run on all Swift-XRT observations including a known blazar, carried out during the first 14 years of operations of the Neil Gehrels Swift Observatory. Short exposures executed within one week of each other have been added to increase sensitivity, which ranges between ∼1 × 10−12 and ∼1 × 10−14 erg cm−2 s−1 (0.3–10.0 keV). After cleaning for problematic fields, the resulting database includes over 27 000 images integrated in different X-ray bands, and a catalogue, called 1OUSXB, that provides intensity and spectral information for 33 396 X-ray sources, 8896 of which are single or multiple detections of 2308 distinct blazars. All the results can be accessed online in a variety of ways, from the Open Universe portal through Virtual Observatory services, via the VOU-Blazar tool and the SSDC SED builder. One of the most innovative aspects of this work is that the results can be easily reproduced and extended by anyone using the Docker version of the Swift-DeepSky pipeline, which runs on Linux, Mac, and Windows machines, and does not require any specific experience in X-ray data analysis.
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