Abstracts of Interest
Selected by:
Cameron Snoswell
Abstract: 1909.12857
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Implications on the origin of cosmic rays in light of 10 TV spectral softenings
(Submitted on 27 Sep 2019)
Abstract: Precise measurements of the energy spectra of cosmic rays (CRs) show various kinds of features deviating from single power-laws, which give very interesting and important implications on their origin and propagation. Most recently, spectral softenings around 10 TV of various CR nuclei have been indicated by a few balloon and space experiments. In particular, the DArk Matter Particle Explorer (DAMPE) measurement about the proton spectrum clearly reveals such a softening with a high significance. Here we study the implications of these new measurements, as well as the groundbased indirect measurements, on the origin of CRs. We find that a single component of CRs fails to fit the spectral softening and the air shower experiment data simultaneously. In the framework of multiple components, we discuss two possible scenarios, the multiple source population scenario and the background plus nearby source scenario. Both scenarios give reasonable fits to the wide-band data from TeV to 100 PeV energies. Considering the anisotropy observations, the nearby source model is favored.
Abstract: 1909.12860
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Measurement of the cosmic-ray proton spectrum from 40 GeV to 100 TeV with the DAMPE satellite
(Submitted on 27 Sep 2019 (v1), last revised 1 Oct 2019 (this version, v2))
Abstract: The precise measurement of the spectrum of protons, the most abundant component of the cosmic radiation, is necessary to understand the source and acceleration of cosmic rays in the Milky Way. This work reports the measurement of the cosmic ray proton fluxes with kinetic energies from 40 GeV to 100 TeV, with two and a half years of data recorded by the DArk Matter Particle Explorer (DAMPE). This is the first time an experiment directly measures the cosmic ray protons up to ~100 TeV with a high statistics. The measured spectrum confirms the spectral hardening found by previous experiments and reveals a softening at ~13.6 TeV, with the spectral index changing from ~2.60 to ~2.85. Our result suggests the existence of a new spectral feature of cosmic rays at energies lower than the so-called knee, and sheds new light on the origin of Galactic cosmic rays.
Abstract: 1909.13106
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:5.5 years multi-wavelength variability of Mrk 421: evidences of leptonic emission from the radio to TeV
(Submitted on 28 Sep 2019)
Abstract: Mrk 421 is a high-synchrotron-peaked blazar featuring bright and persistent GeV and TeV emission. We use the longest and densest ongoing unbiased observing campaign obtained at TeV and GeV energies during 5.5 years with the FACT telescope and the Fermi-LAT detector. The contemporaneous multi-wavelength observations were used to characterize the variability of the source and to constrain the underlying physical mechanisms. We study and correlate light curves obtained by nine different instruments from radio to gamma rays and found two significant results. The TeV and X-ray light curves are very well correlated with lag, if any, shorter than a day. The GeV light curve varies independently and accurately leads the variations observed at long wavelengths, in particular in the radio band. We find that the observations match the predictions of leptonic models and suggest that the physical conditions vary along the jet, when the emitting region moves outwards.
Abstract: 1909.13131
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:A new possibility of the fast neutrino-flavor conversion in the pre-shock region of core-collapse supernova
(Submitted on 28 Sep 2019)
Abstract: We make a strong case that the fast neutrino-flavor conversion, one of the collective flavor oscillation modes, commonly occurs in core-collapse supernovae (CCSNe). It is confirmed in the numerical data obtained in realistic simulations of CCSNe but the argument is much more generic and applicable universally: the coherent neutrino-nucleus scattering makes the electron lepton number (ELN) change signs at some inward direction and trigger the flavor conversion in the outward direction in the pre-shock region. Although the ELN crossing is tiny and that is why it has eluded recognition so far, it is still large enough to induce the flavor conversion. Our findings will have an important observational consequences for CCSNe neutrinos.
Abstract: 1909.13198
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Analyzing the activity of neutrino emitter candidates: comparing TXS 0506+056 with other blazars
(Submitted on 29 Sep 2019)
Abstract: On 22nd of September 2017 the IceCube collaboration sent an alert for an EHE (Extreme High Energy) event, corresponding to the reconstruction of a muonic neutrino (IC-170922A) with energy $\sim290$ TeV. A multi-wavelength follow-up campaign associated this neutrino event with a gamma-ray flaring state of the BL Lac TXS 0506+056 located at z=0.3365. From the same position of the sky a muonic neutrino excess is observed in a time window of 110 days around 13th of December 2014. These observations together suggest TXS 0506+056 as a possible neutrino emitter. We report here a short and long term gamma-ray monitoring of this source and we compare it with other blazars selected following the criteria of being spatially correlated with an astrophysical muonic neutrino event observed by IceCube. A detailed study of source duty cycles, as well as the characterization of most significant flares is obtained through the Fermi-LAT data. We show the expected neutrino flux variability with different time binning assuming the gamma-rays observed by Fermi-LAT produced through pion cascades. These expectations are then compared with the IceCube discovery flux level searching for the optimal time bin in a multi-messenger context.
Abstract: 1910.00112
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:The Control Unit of the KM3NeT Data Acquisition System
(Submitted on 30 Sep 2019)
Abstract: The KM3NeT Collaboration runs a multi-site neutrino observatory in the Mediterranean Sea. Water Cherenkov particle detectors, deep in the sea and far off the coasts of France and Italy, are already taking data while incremental construction progresses. Data Acquisition Control software is operating off-shore detectors as well as testing and qualification stations for their components. The software, named Control Unit, is highly modular. It can undergo upgrades and reconfiguration with the acquisition running. Interplay with the central database of the Collaboration is obtained in a way that allows for data taking even if Internet links fail. In order to simplify the management of computing resources in the long term, and to cope with possible hardware failures of one or more computers, the KM3NeT Control Unit software features a custom dynamic resource provisioning and failover technology, which is especially important for ensuring continuity in case of rare transient events in multi-messenger astronomy. The software architecture relies on ubiquitous tools and broadly adopted technologies and has been successfully tested on several operating systems.
Abstract: 1910.00133
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Camera design and performance of the prototype Schwarzschild-Couder Telescope for the Cherenkov Telescope Array
(Submitted on 30 Sep 2019)
Abstract: The Schwarzschild-Couder Telescope (SCT) is a candidate technology for a medium-sized telescope within the Cherenkov Telescope Array, the next generation ground based observatory for very high energy gamma ray astronomy. The SCT uses a novel two-mirror design and is expected to yield improvements in field of view and image resolution compared to traditional Cherenkov telescopes based on single-mirror-dish optics. To match the improved optical resolution, challenging requirements of high channel count and density at low power consumption must be overcome by the camera. The prototype camera, currently commissioned and tested on the prototype SCT, has been developed based on millimeter scale SiPM pixels and a custom high density digitizer ASIC, TARGET, to provide 1600 pixels spanning a 2.7 degree field of view while being able to sample nanosecond photon pulses. It is mechanically designed to allow for an upgrade to 11,328 pixels covering a field of view of 8 degrees and demonstrating the full potential of the technology. The camera was installed on the telescope in 2018. We will present its design and performance including first light data.
Abstract: 1910.00451
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Measurement of the extragalactic background light spectral energy distribution with VERITAS
(Submitted on 1 Oct 2019)
Abstract: The extragalactic background light (EBL), a diffuse photon field in the optical and infrared range, is a record of radiative processes over the Universe's history. Spectral measurements of blazars at very high energies ($>$100 GeV) enable the reconstruction of the spectral energy distribution (SED) of the EBL, as the blazar spectra are modified by redshift- and energy-dependent interactions of the gamma-ray photons with the EBL. The spectra of 14 VERITAS-detected blazars are included in a new measurement of the EBL SED that is independent of EBL SED models. The resulting SED covers an EBL wavelength range of 0.56--56 $\mu$m, and is in good agreement with lower limits obtained by assuming that the EBL is entirely due to radiation from cataloged galaxies.
Abstract: 1910.00733
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Core-collapse Supernovae as Cosmic Ray Sources
(Submitted on 2 Oct 2019)
Abstract: Core-collapse supernovae produce fast shocks which expand into the dense circumstellar medium (CSM) of the stellar progenitor. Cosmic rays (CRs) accelerated at these shocks can induce the growth of electromagnetic fluctuations in the pre-shock medium. Using a self-similar description for the shock evolution, we calculate the growth time-scales of CR driven instabilities for SNe in general, and SN 1993J in particular. We find that extended SN shocks can trigger fast intra-day instabilities, strong magnetic field amplification, and CR acceleration. In particular, the non-resonant streaming instability can contribute to about 50 per cent of the magnetic field intensity deduced from radio data. This results in the acceleration of CR particles to energies of 1-10 PeV within a few days after the shock breakout.
Abstract: 1910.00992
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Sensitivity to Atypical Tau Initiated Air Showers For a High-Altitude Optical Cherenkov Detector
(Submitted on 2 Oct 2019)
Abstract: The ANITA collaboration has recently announced the supposed observation of two upward going cosmic ray showers at earth emergence angles $27^{\circ}$ and $35^{\circ}$ with reconstructed energy $\sim$0.6~EeV. Upward air showers (UAS) are expected from tau leptons resulting from the interaction of astrophysical neutrinos inside the Earth. However, at emergence angles larger than $20^{\circ}$, the probability of tau emergence from a neutrino is less than $10^{-7}$, which makes a standard model explanation for these signals difficult.
If confirmed by other experiments, these energetic events would strengthen the argument for physics beyond the standard model. Both the proposed EUSO-SPB2 and the POEMMA instruments will be equipped with optical Cherenkov detectors in order to measure the Cherenkov emission from UAS, which, if aimed low enough below the horizon, could, in principle, capture these events as well. An observation in the Cherenkov channel would help to rule out anthropogenic and other explanations for these events. We present here the sensitivity to the ANITA anamolous events for a balloon based and a satellite based Cherenkov detector, as could be realized in the upcoming EUSO-SPB2 mission and the proposed POEMMA mission, respectively.
Abstract: 1910.01172
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Test particle simulations of cosmic rays
(Submitted on 2 Oct 2019)
Abstract: Modelling of cosmic ray transport and interpretation of cosmic ray data ultimately rely on a solid understanding of the interactions of charged particles with turbulent magnetic fields. The paradigm over the last 50 years has been the so-called quasi-linear theory, despite some well-known issues. In the absence of a widely accepted extension of quasi-linear theory, wave-particle interactions must also be studied in numerical simulations where the equations of motion are directly solved in a realisation of the turbulent magnetic field. The applications of such test particle simulations of cosmic rays are manifold: testing transport theories, computing parameters like diffusion coefficients or making predictions for phenomena beyond standard quasi-linear theory, e.g. for cosmic ray small-scale anisotropies. In this review, we seek to give a low-level introduction to test particle simulations of cosmic rays, enabling readers to run their own test particle simulations. We start with a review of quasi-linear theory, highlighting some of its issues and suggested extensions. Next, we summarise the state-of-the-art in test particle simulations and give concrete recipes for generating synthetic turbulence. We present a couple of examples for applications of such simulations and comment on an important conceptual detail in the backtracking of particles.
Abstract: 1910.01186
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Cosmic-Ray Interactions in the Solar Atmosphere
(Submitted on 2 Oct 2019)
Abstract: High-energy particles enter the solar atmosphere from Galactic or solar coronal sources, producing an "albedo'' source from the quiet Sun, now observable across a wide range of photon energies. The interaction of high-energy particles in a stellar atmosphere depends essentially upon the joint variation of the magnetic field and the gas, which heretofore has been characterized parametrically as P ~ B^alpha with P the gas pressure and B the magnitude of the magnetic field. We re-examine that parametrization by using a self-consistent 3D MHD model (Bifrost) and show that this relationship tends to P ~ B^{2.9+-0.1} based on the visible portions of the sample of open-field flux tubes in such a model, but with large variations from point to point. This scatter corresponds to the strong meandering of the open-field flux tubes in the lower atmosphere, which will have a strong effect on the prediction of the emission anisotropy (limb brightening). The simulations show that much of the open flux in coronal holes originates in weak-field regions within the granular pattern of the convective motions seen in the simulations.
Abstract: 1910.01415
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Neutrino oscillations in gravitational waves
(Submitted on 3 Oct 2019)
Abstract: We study spin and flavor oscillations of neutrinos under the influence of gravitational waves (GWs). We rederive the quasiclassical equation for the evolution of the neutrino spin in various external fields in curved spacetime starting from the Dirac equation for a massive neutrino. Then, we consider neutrino spin oscillations in nonmoving and unpolarized matter, a transverse magnetic field, and a plane GW. We show that a parametric resonance can take place in this system. We also study neutrino flavor oscillations in GWs. The equation for the density matrix of flavor neutrinos is solved when we discuss the neutrino interaction with stochastic GWs emitted by coalescing supermassive black holes. We find the fluxes of cosmic neutrinos, undergoing flavor oscillations in such a gravitational background, which can be potentially measured by a terrestrial detector. Some astrophysical applications of our results are considered.
Abstract: 1910.01471
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Modelling ice birefringence and oblique radio wave propagation for neutrino detection at the South Pole
(Submitted on 3 Oct 2019)
Abstract: The Askaryan Radio Array (ARA) experiment at the South Pole is designed to detect high-energy neutrinos which, via in-ice interactions, produce coherent radiation at frequencies up to 1000 MHz. In Dec. 2018, a custom high-amplitude radio-frequency transmitter was lowered into the 1700 m SPICE ice core to provide test sources for ARA receiver stations sensitive to vertical and horizontal polarizations. For these tests, signal geometries correspond to obliquely propagating radio waves from below. The ARA collaboration has recently measured the polarization-dependent time delay variation, and report more significant time delays for trajectories perpendicular to ice flow. Here we use fabric data from the SPICE ice core to construct a bounding model for the ice birefringence and the polarization time delays across ARA. The data-model comparison is consistent with the vertical girdle fabric at the South Pole having the prevailing horizontal crystallographic axis oriented near-perpendicular to ice flow. This study presents the possibility that ice birefringence can be used to constrain the range to a neutrino interaction, and hence aid in neutrino energy reconstruction, for in-ice experiments such as ARA.
Abstract: 1910.02005
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Towards a reconstruction of Supernova Neutrino Spectra in JUNO
(Submitted on 4 Oct 2019)
Abstract: Observation of supernovae (SN) through their neutrino emission is a fundamental point to understand both SN dynamics and neutrino physical properties. JUNO is a 20kton liquid scintillator detector, under construction in Jiangmen, China. The main aim of the experiment is to determine neutrino mass hierarchy by precisely measuring the energy spectrum of reactor electron antineutrinos. However due to its properties, JUNO has the capability of detecting a high statistics of SN events too. Existing data from SN neutrino consists only of 24 events coming from the SN 1987A,the detection of a SN burst in JUNO at $\sim 10 kpc$ will yield $\sim 5 x 10^{3}$ inverse beta decay (IBD) events from electron antineutrinos, about 1500 from proton elastic scattering (pES) above the threshold of 0.2 MeV, about 400 from electron elastic scattering (eES), plus several hundreds on other CC and NC interaction channels from all neutrino species.
This page created: Tue Oct 8 10:11:57 CST 2019 by csnoswel
For a printable title listing click here
For details on generating this page see the instructions. If there are problems with this page (and I expect there will be from time to time) contact Jose.
For previous lists of abstracts of interest click Previous abstracts of interest