101 research outputs found
The current status of orbital experiments for UHECR studies
Two types of orbital detectors of extreme energy cosmic rays are being
developed nowadays: (i) TUS and KLYPVE with reflecting optical systems
(mirrors) and (ii) JEM-EUSO with high-transmittance Fresnel lenses. They will
cover much larger areas than existing ground-based arrays and almost uniformly
monitor the celestial sphere. The TUS detector is the pioneering mission
developed in SINP MSU in cooperation with several Russian and foreign
institutions. It has relatively small field of view (+/-4.5 deg), which
corresponds to a ground area of 6.4x10^3 sq.km. The telescope consists of a
Fresnel-type mirror-concentrator (~2 sq.m) and a photo receiver (a matrix of
16x16 photomultiplier tubes). It is to be deployed on the Lomonosov satellite,
and is currently at the final stage of preflight tests. Recently, SINP MSU
began the KLYPVE project to be installed on board of the Russian segment of the
ISS. The optical system of this detector contains a larger primary mirror (10
sq.m), which allows decreasing the energy threshold. The total effective field
of view will be at least +/-14 degrees to exceed the annual exposure of the
existing ground-based experiments. Several configurations of the detector are
being currently considered. Finally, JEM-EUSO is a wide field of view (+/-30
deg) detector. The optics is composed of two curved double-sided Fresnel lenses
with 2.65 m external diameter, a precision diffractive middle lens and a pupil.
The ultraviolet photons are focused onto the focal surface, which consists of
nearly 5000 multi-anode photomultipliers. It is developed by a large
international collaboration. All three orbital detectors have multi-purpose
character due to continuous monitoring of various atmospheric phenomena. The
present status of development of the TUS and KLYPVE missions is reported, and a
brief comparison of the projects with JEM-EUSO is given.Comment: 18 pages; based on the rapporteur talk given by M.I. Panasyuk at
ECRS-2014; v2: a few minor language issues fixed thanks to the editor; to be
published in the proceeding
Inverse dualisation and non-local dualities between Einstein gravity and supergravities
We investigate non-local dualities between suitably compactified
higher-dimensional Einstein gravity and supergravities which can be revealed if
one reinterprets the dualised Kaluza-Klein two-forms in as antisymmetric
forms belonging to supergravities. We find several examples of such a
correspondence including one between the six-dimensional Einstein gravity and
the four-dimensional Einstein-Maxwell-dilaton-axion theory (truncated N=4
supergravity), and others between the compactified eleven and ten-dimensional
supergravities and the eight or ten-dimensional pure gravity. The Killing
spinor equation of the D=11 supergravity is shown to be equivalent to the
geometric Killing spinor equation in the dual gravity. We give several examples
of using new dualities for solution generation and demonstrate how -branes
can be interpreted as non-local duals of pure gravity solutions. New
supersymmetric solutions are presented including -brane with two
rotation parameters.Comment: 32 pages, Late
Global anisotropy of arrival directions of ultra-high-energy cosmic rays: capabilities of space-based detectors
Planned space-based ultra-high-energy cosmic-ray detectors (TUS, JEM-EUSO and
S-EUSO) are best suited for searches of global anisotropies in the distribution
of arrival directions of cosmic-ray particles because they will be able to
observe the full sky with a single instrument. We calculate quantitatively the
strength of anisotropies associated with two models of the origin of the
highest-energy particles: the extragalactic model (sources follow the
distribution of galaxies in the Universe) and the superheavy dark-matter model
(sources follow the distribution of dark matter in the Galactic halo). Based on
the expected exposure of the experiments, we estimate the optimal strategy for
efficient search of these effects.Comment: 19 pages, 7 figures, iopart style. v.2: discussion of the effect of
the cosmic magnetic fields added; other minor changes. Simulated UHECR
skymaps available at http://livni.inr.ac.ru/UHECRskymaps
An extensive-air-shower-like event registered with the TUS orbital detector
TUS (Tracking Ultraviolet Set-up) is the world's first orbital detector of
ultra-high-energy cosmic rays (UHECRs). It was launched into orbit on 28th
April 2016 as a part of the scientific payload of the Lomonosov satellite. The
main aim of the mission was to test the technique of measuring the ultraviolet
fluorescence and Cherenkov radiation of extensive air showers generated by
primary cosmic rays with energies above ~100 EeV in the Earth atmosphere from
space. During its operation for 1.5 years, TUS registered almost 80,000 events
with a few of them satisfying conditions anticipated for extensive air showers
(EASs) initiated by UHECRs. Here we discuss an event registered on 3rd October
2016. The event was measured in perfect observation conditions as an
ultraviolet track in the nocturnal atmosphere of the Earth, with the kinematics
and the light curve similar to those expected from an EAS. A reconstruction of
parameters of a primary particle gave the zenith angle around 44 but an
extreme energy not compatible with the cosmic ray energy spectrum obtained with
ground-based experiments. We discuss in details all conditions of registering
the event, explain the reconstruction procedure and its limitations and comment
on possible sources of the signal, both of anthropogenic and astrophysical
origin. We believe this detection represents a significant milestone in the
space-based observation of UHECRs because it proves the capability of an
orbital telescope to detect light signals with the apparent motion and light
shape similar to what are expected from EASs. This is important for the
on-going development of the future missions KLYPVE-EUSO and POEMMA, aimed for
studying UHECRs from space.Comment: 24 pages; v2: important changes to address comments by the anonymous
referee; main conclusions unchange
EUSO-SPB1 mission and science
The Extreme Universe Space Observatory on a Super Pressure Balloon 1 (EUSO-SPB1) was launched in 2017 April from Wanaka, New Zealand. The plan of this mission of opportunity on a NASA super pressure balloon test flight was to circle the southern hemisphere. The primary scientific goal was to make the first observations of ultra-high-energy cosmic-ray extensive air showers (EASs) by looking down on the atmosphere with an ultraviolet (UV) fluorescence telescope from suborbital altitude (33 km). After 12 days and 4 h aloft, the flight was terminated prematurely in the Pacific Ocean. Before the flight, the instrument was tested extensively in the West Desert of Utah, USA, with UV point sources and lasers. The test results indicated that the instrument had sensitivity to EASs of ⪆ 3 EeV. Simulations of the telescope system, telescope on time, and realized flight trajectory predicted an observation of about 1 event assuming clear sky conditions. The effects of high clouds were estimated to reduce this value by approximately a factor of 2. A manual search and a machine-learning-based search did not find any EAS signals in these data. Here we review the EUSO-SPB1 instrument and flight and the EAS search
Neutrino Target-of-Opportunity Observations with Space-based and Suborbital Optical Cherenkov Detectors
Cosmic-ray accelerators capable of reaching ultra-high energies are expected to also produce very-high energy neutrinos via hadronic interactions within the source or its surrounding environment. Many of the candidate astrophysical source classes are either transient in nature or exhibit flaring activity. Using the Earth as a neutrino converter, suborbital and space-based optical Cherenkov detectors, such as POEMMA and EUSO-SPB2, will be able to detect upward-moving extensive air showers induced by decaying tau-leptons generated from cosmic tau neutrinos with energies ∼10 PeV and above. Both EUSO-SPB2 and POEMMA will be able to quickly repoint, enabling rapid response to astrophysical transient events. We calculate the transient sensitivity and sky coverage for both EUSO-SPB2 and POEMMA, accounting for constraints imposed by the Sun and the Moon on the observation time. We also calculate both detectors\u27 neutrino horizons for a variety of modeled astrophysical neutrino fluences. We find that both EUSO-SPB2 and POEMMA will achieve transient sensitivities at the level of modeled neutrino fluences for nearby sources. We conclude with a discussion of the prospects of each mission detecting at least one transient event for various modeled astrophysical neutrino sources
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