A small contribution of molecular Bremsstrahlung radiation to the air-fluorescence yield in the UV range is estimated based on an approach previously developed in the framework of the radio-detection ...of showers in the gigahertz frequency range. First, this approach is shown to provide an estimate of the main contribution of the fluorescence yield due to the de-excitation of the C 3Πu electronic level of nitrogen molecules to the B 3Πg one amounting to Y337=(6.05±1.50) MeV−1 at 800 hPa pressure and 293 K temperature conditions, which compares well to previous dedicated works and to experimental results. Then, under the same pressure and temperature conditions, the fluorescence yield induced by molecular Bremsstrahlung radiation is found to be Y330--400MBR=0.10 MeV−1 in the wavelength range of interest for the air-fluorescence detectors used to detect extensive air showers induced in the atmosphere by ultra-high energy cosmic rays. This means that out of ≃175 photons with wavelength between 330 and 400 nm detected by fluorescence detectors, one of them has been produced by molecular Bremsstrahlung radiation. Although small, this contribution is not negligible in regards to the total budget of systematic uncertainties when considering the absolute energy scale of fluorescence detectors.
Science with the Cherenkov Telescope Array The Cta Consortium, The Cta Consortium
The Astrophysical journal. Supplement series,
01/2019, Volume:
240, Issue:
2
eBook, Journal Article, Book
Peer reviewed
Open access
This book summarizes the science to be carried out by the upcoming Cherenkov Telescope Array, a major ground-based gamma-ray observatory that will be constructed over the next six to eight years. The ...major scientific themes, as well as core program of key science projects, have been developed by the CTA Consortium, a collaboration of scientists from many institutions worldwide. CTA will be the major facility in high-energy and very high-energy photon astronomy over the next decade and beyond. CTA will have capabilities well beyond past and present observatories. Thus, CTA's science program is expected to be rich and broad and will complement other major multiwavelength and multimessenger facilities. This book is intended to be the primary resource for the science case for CTA and it thus will be of great interest to the broader physics and astronomy communities. The electronic version (e-book) is available in open access.
The ANTARES telescope is well suited to detect neutrinos produced in astrophysical transient sources as it can observe a full hemisphere of the sky at all the times with a duty cycle close to unity ...and an angular resolution better than 0.5°. Potential sources include gamma-ray bursts (GRBs), core collapse supernovae (SNe), and flaring active galactic nuclei (AGNs). To enhance the sensitivity of ANTARES to such sources, a new detection method based on coincident observations of neutrinos and optical signals has been developed. A fast online muon track reconstruction is used to trigger a network of small automatic optical telescopes. Such alerts are generated one or two times per month for special events such as two or more neutrinos coincident in time and direction or single neutrinos of very high energy. Since February 2009, ANTARES has sent 37 alert triggers to the TAROT and ROTSE telescope networks, 27 of them have been followed. First results on the optical images analysis to search for GRBs are presented.
The ANTARES telescope has the opportunity to detect transient neutrino sources, such as gamma-ray bursts, core-collapse supernovae, flares of active galactic nuclei. In order to enhance the ...sensitivity to these sources, we have developed a new detection method based on the follow-up by optical telescopes of “golden” neutrino events, such as neutrino doublets coincident in time and space or single neutrinos of very high energy. The ANTARES collaboration has therefore implemented a very fast on-line reconstruction with a good angular resolution. These characteristics allow us to trigger an optical telescope network. Since February 2009, ANTARES is sending alert triggers once or twice per month to the two 25
cm robotic telescope of TAROT. This optical follow-up of such special events would not only give access to the nature of the sources, but also would improve the sensitivity to transient neutrino sources.
Atmospheric neutrinos are produced during cascades initiated by the interaction of primary cosmic rays with air nuclei. In this paper, a measurement of the atmospheric
νμ + ¯νμ energy spectrum in the ...energy range 0.1–200 TeV is presented, using data collected by the ANTARES underwater neutrino telescope from 2008 to 2011. Overall,
the measured flux is ∼25 % higher than predicted by the conventional neutrino flux, and compatible with the measurements
reported in ice. The flux is compatible with a single power-law dependence with spectral index γmeas = 3.58 ± 0.12. With the present statistics the contribution of prompt neutrinos cannot be established.
We present the results of an analysis of the large angular scale distribution of the arrival directions of cosmic rays with energy above 4 EeV detected at the Pierre Auger Observatory including for ...the first time events with zenith angle between $60^\circ$ and $80^\circ$. We perform two Rayleigh analyses, one in the right ascension and one in the azimuth angle distributions, that are sensitive to modulations in right ascension and declination, respectively. The largest departure from isotropy appears in the $E > 8$ EeV energy bin, with an amplitude for the first harmonic in right ascension $r_1^\alpha =(4.4 \pm 1.0){\times}10^{-2}$, that has a chance probability $P(\ge r_1^\alpha)=6.4{\times}10^{-5}$, reinforcing the hint previously reported with vertical events alone.
Spherical harmonic moments are well-suited for capturing anisotropy at any scale in the flux of cosmic rays. An unambiguous measurement of the full set of spherical harmonic coefficients requires ...full-sky coverage. This can be achieved by combining data from observatories located in both the northern and southern hemispheres. To this end, a joint analysis using data recorded at the Telescope Array and the Pierre Auger Observatory above $10^{19}$ eV is presented in this work. The resulting multipolar expansion of the flux of cosmic rays allows us to perform a series of anisotropy searches, and in particular to report on the angular power spectrum of cosmic rays above $10^{19}$ eV. No significant deviation from isotropic expectations is found throughout the analyses performed. Upper limits on the amplitudes of the dipole and quadrupole moments are derived as a function of the direction in the sky, varying between 7% and 13% for the dipole and between 7% and 10% for a symmetric quadrupole.
Scintillating crystal-based hybrid photon detectors (X-HPDs) have been demonstrated as viable single photon detectors since 1996 in the Lake Baikal neutrino telescope. Prior to this, the Philips ...XP2600 was developed under the DUMAND program, while more recently developments at CERN have demonstrated the advantages of a true concentric geometry with a scintillator at the geometric centre of a spherical photocathode, giving almost 100% electrostatic collection efficiency over
3
π
solid angle coverage. We have started to develop a new series of quasi-spherical X-HPDs starting at 8
in. and progressing toward the maximum that can be fitted in a standard 17
in. optical pressure sphere for a future large deep sea neutrino telescope. The thrust of this R&D will be to investigate the industrialisation of the X-HPD to the point where it represents a significant cost reduction per cubic kilometre of instrumented volume compared to conventional PMTs, thereby allowing for extremely large telescope target volumes. Such gains will arise through an all-glass envelope, internal processing of a standard or enhanced bialkali photocathode, and either from cost reductions in the central scintillating crystal or from the use of a deposited phosphor viewed by a small PMT. Details of the development program and recent progress in the characterisation of prototypes will be presented.
The deep ocean is the largest and least known ecosystem on Earth. It hosts numerous pelagic organisms, most of which are able to emit light. Here we present a unique data set consisting of a 2.5-year ...long record of light emission by deep-sea pelagic organisms, measured from December 2007 to June 2010 at the ANTARES underwater neutrino telescope in the deep NW Mediterranean Sea, jointly with synchronous hydrological records. This is the longest continuous time-series of deep-sea bioluminescence ever recorded. Our record reveals several weeks long, seasonal bioluminescence blooms with light intensity up to two orders of magnitude higher than background values, which correlate to changes in the properties of deep waters. Such changes are triggered by the winter cooling and evaporation experienced by the upper ocean layer in the Gulf of Lion that leads to the formation and subsequent sinking of dense water through a process known as "open-sea convection". It episodically renews the deep water of the study area and conveys fresh organic matter that fuels the deep ecosystems. Luminous bacteria most likely are the main contributors to the observed deep-sea bioluminescence blooms. Our observations demonstrate a consistent and rapid connection between deep open-sea convection and bathypelagic biological activity, as expressed by bioluminescence. In a setting where dense water formation events are likely to decline under global warming scenarios enhancing ocean stratification, in situ observatories become essential as environmental sentinels for the monitoring and understanding of deep-sea ecosystem shifts.
PDF
