142 research outputs found
Anisotropy expectations for ultra-high-energy cosmic rays with future high statistics experiments
UHECRs have attracted a lot of attention due to their challengingly high
energies and their potential value to constrain physical processes and
astrophysical parameters in the most energetic sources of the universe. Current
detectors have failed to detect significant anisotropies which had been
expected to allow source identification. Some indications about the UHECR
composition, which may become heavier at the highest energies, has even put
into question the possibility that such a goal could be achieved soon.
We investigate the potential value of a new-generation detector, with 10
times larger exposure, to overcome the current situation and make significant
progress in the detection of anisotropies and thus in the study of UHECRs. We
take as an example the expected performances of the JEM-EUSO, assuming a
uniform full-sky coverage with a total exposure of 300,000 km2 sr yr.
We simulate realistic UHECR sky maps for a wide range of possible
astrophysical scenarios allowed by the current constraints, taking into account
the energy losses and photo-dissociation of the UHECRs, as well as their
deflections by magnetic fields. These sky maps, built for the expected
statistics of JEM-EUSO as well as for the current Auger statistics, as a
reference, are analyzed from the point of view of their intrinsic anisotropies,
using the two-point correlation function. A statistical study of the resulting
anisotropies is performed for each astrophysical scenario, varying the UHECR
source composition and spectrum as well as the source density.
We find that significant anisotropies are expected to be detected by a
next-generation UHECR detector, for essentially all the astrophysical scenarios
studied, and give precise, quantitative meaning to this statement. Our results
show that a gain of one order of magnitude in exposure would make a significant
difference compared to the existing detectors.Comment: 26 pages, 28 figure
Dark matter and Modified Newtonian Dynamics in a sample of high-redshift galaxy clusters observed with Chandra
We compare the measurement of the gravitational mass of 38 high-redshift
galaxy clusters observed by Chandra using Modified Newtonian Dynamics (MOND)
and standard Newtonian gravity. Our analysis confirms earlier findings that
MOND cannot explain the difference between the baryonic mass and the total mass
inferred from the assumption of hydrostatic equilibrium. We also find that the
baryon fraction at using MOND is consistent with the Wilkinson
Microwave Anisotropy Probe (WMAP) value of Comment: New Astronomy in pres
Absolute Fluorescence Spectrum and Yield Measurements for a wide range of experimental conditions
For the JEM-EUSO CollaborationThe fluorescence yield is a key ingredient in cosmic ray energy determination. It is sensitive to pressure, temperature and humidity. Up to now the fluorescence yield of the brightest line at 337 nm has been measured in an absolute way in one set of conditions, whereas fluorescence yields at the other wavelengths have been relatively measured for different conditions. Thus, absolute calibration for all the lines is unclear. We will do all measurements at once using the same apparatus: all the lines will be measured absolutely and not relatively for all conditions. For that we will use the 3-5 MeV electron beam of the PHIL accelerator (Photon Injector at LAL), shooting in a box filled with air at varying pressures, temperatures and humidity. Delta rays resulting from the beam collisions with Nitrogen are responsible for the light yield. The light detection probability should be independent of its emission point especially at the delta ray stopping point. The idea is to use an integrating sphere, encapsulated in a vessel where pressure, temperature and humidity can be varied. This sphere will have two ports for the beam (in and out), one more port dedicated to a NIST photodiode for calibration and another port feeding optical fibers going to: A) a grating spectrometer equipped with cooled CCD. B) a photomultiplier with BG3 filters to measure directly the integrated yield. Calibrations at the percent level, will give each line spectrum yields with a precision between 2 to 5%. A special issue will be to estimate the leakage due to "high energy" delta rays. Thus, we the air density will be increased, the beam energy will be lowered until the beam stops inside the sphere. Then, the energy loss will be precisely derived from the Bethe-Bloch formula. We will present the set-up
Machine Learning for Mini-EUSO Telescope Data Analysis
Neural networks as well as other methods of machine learning (ML) are known
to be highly efficient in different classification tasks, including
classification of images and videos. Mini- EUSO is a wide-field-of-view imaging
telescope that operates onboard the International Space Station since 2019
collecting data on miscellaneous processes that take place in the atmosphere of
Earth in the UV range. Here we briefly present our results on the development
of ML-based approaches for recognition and classification of track-like signals
in the Mini-EUSO data, among them meteors, space debris and signals the light
curves and kinematics of which are similar to those expected from extensive air
showers generated by ultra-high-energy cosmic rays. We show that even simple
neural networks demonstrate impressive performance in solving these tasks.Comment: 10 pages, 3 figures, ICRC2023 conferenc
A proof of Price's Law on Schwarzschild black hole manifolds for all angular momenta
Price's Law states that linear perturbations of a Schwarzschild black hole
fall off as for provided the initial data decay
sufficiently fast at spatial infinity. Moreover, if the perturbations are
initially static (i.e., their time derivative is zero), then the decay is
predicted to be . We give a proof of decay for
general data in the form of weighted to bounds for solutions
of the Regge--Wheeler equation. For initially static perturbations we obtain
. The proof is based on an integral representation of the
solution which follows from self--adjoint spectral theory. We apply two
different perturbative arguments in order to construct the corresponding
spectral measure and the decay bounds are obtained by appropriate oscillatory
integral estimates.Comment: 43 pages, statement of Price's Law clarified and some minor
corrections, to appear in Adv. Mat
Heavy Neutrinos and Lepton Number Violation in lp Colliders
We discuss the prospects of studying lepton number violating processes in
order to identify Majorana neutrinos from low scale seesaw mechanisms at
lepton-proton colliders. In particular, we consider the scenarios of colliding
electrons with LHC energy protons and, motivated by the efforts towards the
construction of a muon collider, the prospects of muon-proton collisions. We
find that present constraints on the mixing of the Majorana neutrinos still
allow for a detectable signal at these kind of facilities given the smallness
of the Standard Model background. We discuss possible cuts in order to further
increase the signal over background ratio and the prospects of reconstructing
the neutrino mass from the kinematics of the final state particles.Comment: 18 pages, 5 figures, REVTeX
An evaluation of the exposure in nadir observation of the JEM-EUSO mission
We evaluate the exposure during nadir observations with JEM-EUSO, the Extreme Universe Space Observatory,on-board the Japanese Experiment Module of the International Space Station. Designed as a mission to explore the extreme energy Universe from space, JEM-EUSO will monitor the Earth's nighttime atmosphere to record the ultraviolet light from tracks generated by extensive air showers initiated by ultra-high energy cosmic rays. In the present work, we discuss the particularities of space-based observation and we compute the annual exposure in nadir observation. The results are based on studies of the expected trigger aperture and observational duty cycle, as well as, on the investigations of the effects of clouds and different types of background light. We show that the annual exposure is about one order of magnitude higher than those of the presently operating ground-based observatories.Fil: Adams, J. H.. University of Alabama in Huntsville; Estados UnidosFil: Ahmad, S.. Universite Paris Sud; FranciaFil: Albert, J. N..Fil: Allard, D.. Universite Paris Diderot - Paris 7; FranciaFil: Ambrosio, M.. Istituto Nazionale di Fisica Nucleare; ItaliaFil: Anchordoqui, L.. Medical College Of Wisconsin; Estados UnidosFil: Anzalone, A.. INAF; ItaliaFil: Arai, Y.. High Energy Accelerator Research Organization (KEK); JapónFil: Aramo, C..Fil: Asano, K.. Interactive Research Center of Science, Tokyo Institute of Technology; JapónFil: Ave, M.. Universidad de Santiago de Compostela; EspañaFil: Barrillon, P.. Universite de Paris; FranciaFil: Batsch, T.. National Centre for Nuclear Research; PoloniaFil: Bayer, J.. University of Tubingen; AlemaniaFil: Belenguer, T.. j Instituto Nacional de Técnica Aeroespacial (INTA); EspañaFil: Bellotti, R.. Universita’ degli Studi di Bari Aldo Moro and INFN; ItaliaFil: Berlind, A. A.. Vanderbilt University; Estados UnidosFil: Bertaina, M.. Universita di Torino; ItaliaFil: Biermann, P. L.. Karlsruhe Institute of Technology (KIT); AlemaniaFil: Biktemerova,. Joint Institute for Nuclear Research; RusiaFil: Blaksley, C.. Universite de la Sorbona Nouvelle; FranciaFil: Blecki, J.. Space Research Centre of the Polish Academy of Sciences (CBK); PoloniaFil: Blin-Bondil, S.. Universite de Paris; FranciaFil: Blumer, J.. Karlsruhe Institute of Technology (KIT),; AlemaniaFil: Bobik, P.. Institute of Experimental Physics; EslovaquiaFil: Bogomilov, M.. St. Kliment Ohridski University of Sofia; BulgariaFil: Bonamente, M.. University of Alabama in Huntsville; Estados UnidosFil: Briz, S.. Universidad Carlos III de Madrid,; EspañaFil: Supanitsky, Alberto Daniel. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin
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