•Cherenkov telescopes have the capability of detecting high energy tau neutrinos by searching for very inclined showers.•The detailed Monte Carlo simulations of trigger efficiencies and Hillas ...parameters for tau-induced showers are presented.•The calculated neutrino sensitivities in some cases are comparable or even better than corresponding neutrino sensitivities of the IceCube detector.
This paper investigates the potential to detect tau neutrinos in the energy range of 1–1000 PeV searching for very inclined showers with imaging Cherenkov telescopes. A neutrino induced tau lepton escaping from the Earth may decay and initiate an air shower which can be detected by a fluorescence or Cherenkov telescope. We present here a study of the detection potential of Earth-skimming neutrinos taking into account neutrino interactions in the Earth crust, local matter distributions at various detector sites, the development of tau-induced showers in air and the detection of Cherenkov photons with IACTs. We analyzed simulated shower images on the camera focal plane and implemented generic reconstruction chains based on Hillas parameters. We find that present IACTs can distinguish air showers induced by tau neutrinos from the background of hadronic showers in the PeV-EeV energy range. We present the neutrino trigger efficiency obtained for a few configurations being considered for the next-generation Cherenkov telescopes, i.e. the Cherenkov Telescope Array. Finally, for a few representative neutrino spectra expected from astrophysical sources, we compare the expected event rates at running IACTs to what is expected for the dedicated IceCube neutrino telescope.
•Cherenkov telescopes have the capability of detecting high energy tau neutrinos.•MC simulations of event rates for VERITAS and two proposed CTA sites are presented.•Neutrino sensitivities are ...comparable to the sensitivities of the IceCube detector.
Cherenkov telescopes have the capability of detecting high energy tau neutrinos in the energy range of 1–1000PeV by searching for very inclined showers. If a tau lepton, produced by a tau neutrino, escapes from the Earth or a mountain, it will decay and initiate a shower in the air which can be detected by an air shower fluorescence or Cherenkov telescope. In this paper, we present detailed Monte Carlo simulations of corresponding event rates for the VERITAS and two proposed Cherenkov Telescope Array sites: Meteor Crater and Yavapai Ranch, which use representative AGN neutrino flux models and take into account topographic conditions of the detector sites. The calculated neutrino sensitivities depend on the observation time and the shape of the energy spectrum, but in some cases are comparable or even better than corresponding neutrino sensitivities of the IceCube detector. For VERITAS and the considered Cherenkov Telescope Array sites the expected neutrino sensitivities are up to factor 3 higher than for the MAGIC site because of the presence of surrounding mountains.
A new method to derive an upper limit on photon primaries from small data sets of air showers is developed which accounts for shower properties varying with the primary energy and arrival direction. ...Applying this method to the highest-energy showers recorded by the AGASA experiment, an upper limit on the photon fraction of 51% (67%) at a confidence level of 90% (95%) for primary energies above 1.25 x 10(20) eV is set. This new limit on the photon fraction above the Greisen-Zatsepin-Kuzmin cutoff energy constrains the -burst model of the origin of highest-energy cosmic rays.
The discovery of an astrophysical flux of high-energy neutrinos by the IceCube Collaboration marks a major breakthrough in the ongoing search for the origin of cosmic rays. Presumably, the neutrinos, ...together with gamma rays, result from pion decay, following hadronic interactions of protons accelerated in astrophysical objects to ultra-relativistic energies. So far, the neutrino sky map shows no significant indication of astrophysical sources. Here, we report first results from follow-up observations, of sky regions where IceCube has detected muon tracks from energetic neutrinos, using the MAGIC telescopes which are sensitive to gamma rays at TeV energies. Furthermore, we show that MAGIC has the potential to distinguish air showers induced by tau neutrinos from the background of hadronic showers in the PeV-EeV energy range, employing a novel analysis method to the data obtained with high-zenith angle observations.
Abstract
Propagation of ultra-high energy photons in the solar magnetosphere gives rise to cascades comprising thousands of photons.
We study the cascade development using Monte Carlo simulations and ...find that the photons in the cascades are
spatially extended over millions of kilometers on the plane distant from the Sun by 1 AU.
We estimate the chance of detection considering upper limits from current cosmic rays observatories in order to provide an optimistic estimate rate of 0.002 events per year from a chosen ring-shaped region around the Sun.
We compare results from simulations which use two models of the solar magnetic field, and show that although signatures of such cascades are different for
the models used, for practical detection purpose in the ground-based detectors, they are similar.
The identification of primary photons or specifying stringent limits on the photon flux is of major importance for understanding the origin of ultra-high energy (UHE) cosmic rays. UHE photons can ...initiate particle cascades in the geomagnetic field, which leads to significant changes in the subsequent atmospheric shower development. We present a Monte Carlo program allowing detailed studies of conversion and cascading of UHE photons in the geomagnetic field. The program named PRESHOWER can be used both as an independent tool or together with a shower simulation code. With the stand-alone version of the code it is possible to investigate various properties of the particle cascade induced by UHE photons interacting in the Earth's magnetic field before entering the Earth's atmosphere. Combining this program with an extensive air shower simulation code such as CORSIKA offers the possibility of investigating signatures of photon-initiated showers. In particular, features can be studied that help to discern such showers from the ones induced by hadrons. As an illustration, calculations for the conditions of the southern part of the Pierre Auger Observatory are presented.
Title of program:PRESHOWER 1.0
Catalogue identifier:ADWG
Program summary URL:
http://cpc.cs.qub.ac.uk/summaries/ADWG
Program obtainable: CPC Program Library, Quen's University of Belfast, N. Ireland
Computer on which the program has been thoroughly tested:Intel-Pentium based PC
Operating system:Linux, DEC-Unix
Programming language used:C, FORTRAN 77
Memory required to execute with typical data:<100 kB
No. of bits in a word:32
Has the code been vectorized?:no
Number of lines in distributed program, including test data, etc.:2567
Number of bytes in distributed program, including test data, etc.:25 690
Distribution format:tar.gz
Other procedures used in PRESHOWER
:IGRF N.A. Tsyganenko, National Space Science Data Center, NASA GSFC, Greenbelt, MD 20771, USA,
http://nssdc.gsfc.nasa.gov/space/model/magnetos/data-based/geopack.html, bessik, ran2 Numerical Recipes,
http://www.nr.com.
Nature of the physical problem:Simulation of a cascade of particles initiated by UHE photon passing through the geomagnetic field above the Earth's atmosphere.
Method of solution: The primary photon is tracked until its conversion into
e
+
e
−
pair or until it reaches the upper atmosphere. If conversion occurred each individual particle in the resultant preshower is checked for either bremsstrahlung radiation (electrons) or secondary gamma conversion (photons). The procedure ends at the top of atmosphere and the shower particle data are saved.
Restrictions on the complexity of the problem: Gamma conversion into particles other than electron pair has not been taken into account.
Typical running time: 100 preshower events with primary energy
10
20
eV
require a 800 MHz CPU time of about 50 min, with
10
21
eV
the simulation time for 100 events grows up to 500 min.
► A method for a time-dependent searches for neutrino multiple flares is presented. ► The method is sensitive to a few weak flares which are not individually detectable. ► For very short flares the ...method is more sensitive than a time-integrated analysis.
A method for a time-dependent search for flaring astrophysical sources which can be potentially detected by large neutrino experiments is presented. The method uses a time-clustering algorithm combined with an unbinned likelihood procedure. By including in the likelihood function a signal term which describes the contribution of many small clusters of signal-like events, this method provides an effective way for looking for weak neutrino flares over different time-scales. The method is sensitive to an overall excess of events distributed over several flares which are not individually detectable. For standard cases (one flare) the discovery potential of the method is worse than a standard time-dependent point source analysis with unknown duration of the flare by a factor depending on the signal-to-background level. However, for flares sufficiently shorter than the total observation period, the method is more sensitive than a time-integrated analysis.
The hydration behaviour of sixteen ashes, obtained from different commercial-scale fluidized bed combustors, has been investigated. Hydration is important for both ash disposal and reactivation of ...excess lime present in the ashes for further use in flue gas desulphurization. The techniques used were instrumental and conventional chemical analysis, thermogravimetry and X-ray diffraction. The ashes comprised both fly ash and bottom ash, with particle size less than 2
mm. The ashes were heat treated in air to oxidize free carbon and then hydrated with pressurized steam at about 170
°C, alone and with addition of pure CaO.
It has been shown that steam hydration is effective in quantitatively converting CaO to Ca(OH)
2, but in most cases the free lime content (i.e. CaO+Ca(OH)
2), expressed as CaO, decreases and added CaO enters into pozzolanic reactions with coal ash components, in part or even completely. Both the chemical evidence and X-ray phase analyses indicate that hydrated silicates and silicoaluminates are formed. The hydrated ashes are all able to take up additional SO
2 and it appears that the presence of amounts of Ca(OH)
2 detectable by phase analysis is not necessary for such capture.
Cosmic-ray photons above 10
19
eV can convert in the geomagnetic field and initiate a preshower, i.e. a particle cascade before entering the atmosphere. We compare the preshower characteristics at ...the southern and northern sites of the Pierre Auger Observatory. In addition to a shift of the preshower patterns on the sky due to the different pointing of the local magnetic field vectors, the fact that the northern Auger site is closer to the geomagnetic pole results in a different energy dependence of the preshower effect: photon conversion can start at smaller energies, but large conversion probabilities (>90%) are reached for the whole sky at higher energies compared to the southern Auger site. We show how the complementary preshower features at the two sites can be used to search for ultra-high energy photons among cosmic rays. In particular, the different preshower characteristics at the northern Auger site may provide an elegant and unambiguous confirmation if a photon signal is detected at the southern site.
The longitudinal profile of the most energetic cosmic-ray air shower measured so far, the event recorded by the Fly's Eye detector with a reconstructed primary energy of about 3.2
×
10
20 eV, is ...compared to simulated shower profiles. The calculations are performed with the CORSIKA code and include primary photons and different hadron primaries. For primary photons, preshower formation in the geomagnetic field is additionally treated in detail. For primary hadrons, the hadronic interaction models QGSJET 01 and SIBYLL 2.1 have been employed. The predicted longitudinal profiles are compared to the observation. A method for testing the hypothesis of a specific primary particle type against the measured profile is described which naturally takes shower fluctuations into account. The Fly's Eye event is compatible with any assumption of a hadron primary between proton and iron nuclei in both interaction models, although differences between QGSJET 01 and SIBYLL 2.1 in the predicted profiles of lighter nuclei exist. The primary photon profiles differ from the data on a level of ≃1.5
σ. Although not favoured by the observation, the primary photon hypothesis can not be rejected for this particular event.
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