SEARCH FOR NEUTRINOS AT EXTREME ENERGIES WITH THE PIERRE AUGER OBSERVATORYMarta Trini
, 2019, doctoral dissertation
Abstract: The detection of Ultra-High-Energy (UHE) neutrinos around and above 10 18 eV (1 EeV) can be the key to
answering the long-standing question of the origin of the UHE cosmic rays. The Pierre Auger Observatory
is the largest experiment that can detect the extensive air showers produced when the cosmic rays and
neutrinos interact in the earth’s atmosphere. In particular, with the Infilled array of the Surface Detector
of the Pierre Auger Observatory we can detect sub-EeV neutrino-induced particle showers. In this thesis
we demonstrate that it is possible to discriminate neutrino-induced showers from the background showers
produced by the more numerous nucleonic cosmic rays. The sensitivity to neutrinos is enhanced in the
inclined directions with respect to the vertical to the ground, where cosmic ray-induced showers starting in
the upper layers of the atmosphere are dominated by the muonic component of the shower, while deeply-
penetrating neutrino showers in contrast exhibit a large electromagnetic component. Based on this idea in
this thesis we have developed a search procedure for UHE neutrinos that consists on selecting inclined
events in the Infilled array of the Pierre Auger Observatory in which the signals in the water-Cherenkov
stations are spread in time, characteristic of the presence of electromagnetic component in the shower. We
have established a complete chain of criteria to first select the inclined events among the sample of all
events triggering the Infilled array, and then identifying those that have a large electromagnetic component
at ground, and hence can be considered as neutrino candidates. We have identified a single variable, the
so-called area-over-peak averaged over all of the stations in each event, as a suitable observable for neutrino
identification purposes. The neutrino selection was established using extensive Monte Carlo simulations of
the neutrino-induced showers in the Infilled array of Auger as well as a fraction of the data assumed to
be totally constituted of background nucleonic cosmic rays. Using these neutrino simulations we have also
computed the exposure of the Infilled array to UHE neutrinos in the period 1 January 04 - 31 December 2017.
Associated systematic uncertainties on the exposure are also described. Expecting no candidate neutrinos in
the period up to 31 December 2017, and adopting a differential neutrino diffuse flux dN ν /dE ν = k E ν −2 in
the energy range from 0.05 to 1 EeV, we have obtained a 90% C.L. upper limit on the all neutrino flavor,
k 90 < 7.97 × 10 −8 GeV cm −2 s −1 sr −1 .
Found in: ključnih besedah
Summary of found: ...question of the origin of the UHE cosmic rays. The Pierre Auger Observatory
is the largest... ... astroparticles, astrophysical neutrinos, cosmic rays showers, Pierre Auger...
Keywords: astroparticles, astrophysical neutrinos, cosmic rays showers, Pierre Auger Observatory, Infilled
Published: 03.10.2019; Views: 3810; Downloads: 136
Fulltext (6,02 MB)
Measurement of the proton-air cross section with Telescope Array's Black Rock Mesa and Long Ridge fluorescence detectors, and surface array in hybrid modeMitsuhiro Abe
, R. U. Abbasi
, T. Abu-Zayyad
, M. Allen
, R. Azuma
, E. Barcikowski
, J. W. Belz
, Jon Paul Lundquist
, S. A. Blake
, D. R. Bergman
, 2020, original scientific article
Abstract: Ultra high energy cosmic rays provide the highest known energy source in the universe to measure proton cross sections. Though conditions for collecting such data are less controlled than an
accelerator environment, current generation cosmic ray observatories have large enough exposures to collect significant statistics for a reliable measurement for energies above what can be attained in the lab. Cosmic ray measurements of cross section use atmospheric calorimetry to measure depth of air shower maximum (Xmax), which is related to the primary particle’s energy and mass. The tail of the Xmax distribution is assumed to be dominated by showers generated by protons, allowing measurement of the inelastic proton-air cross section. In this work the proton-air inelastic
cross section measurement, σ_inel_p−air, using data observed by Telescope Array’s Black Rock Mesa and Long Ridge fluorescence detectors and surface detector array in hybrid mode is presented. σ_inel_p−air is observed to be 520.1 ± 35.8 [Stat.] +25.0 −40 [Sys.] mb at √s = 73 TeV. The total proton-proton cross section is subsequently inferred from Glauber formalism and is found to be σ_tot_pp = 139.4 +23.4−21.3[Stat.] +15.0−24.0[Sys.] mb.
Found in: ključnih besedah
Summary of found: ...Ultra high energy cosmic rays provide the highest known energy source... ...cosmic rays, astroparticles, proton-air cross section...
Keywords: cosmic rays, astroparticles, proton-air cross section
Published: 04.02.2021; Views: 1566; Downloads: 0
Fulltext (1,99 MB)
Spatial extension of dark subhalos as seen by Fermi-LAT and the implications for WIMP constraintsAlejandra Aguirre-Santaella
, Judit Pérez-Romero
, Miguel Sánchez-Conde
, Javier Coronado-Blázquez
, 2022, original scientific article
Abstract: Spatial extension has been hailed as a “smoking gun” in the gamma-ray search of dark galactic subhalos, which would appear as unidentified sources for gamma-ray telescopes. In this work, we study the sensitivity of the Fermi-LAT to extended subhalos using simulated data based on a realistic sky model. We simulate spatial templates for a set of representative subhalos, whose parameters were derived from our previous work with N-body cosmological simulation data. We find that detecting an extended subhalo and finding an unequivocal signal of angular extension requires, respectively, a flux 2 to 10 times larger than in the case of a pointlike source. By studying a large grid of models, where parameters such as the WIMP mass, annihilation channel, or subhalo model are varied significantly, we obtain the response of the LAT as a function of the product of annihilation cross-section times the J-factor. Indeed, we show that spatial extension can be used as an additional “filter” to reject subhalos candidates among the pool of unidentified LAT sources, as well as a smoking gun for positive identification. For instance, typical angular extensions of a few tenths of a degree are expected for the considered scenarios. Finally, we also study the impact of the obtained LAT sensitivity to such extended subhalos on the achievable dark matter constraints, which are a few times less constraining than comparable point-source limits.
Found in: ključnih besedah
Summary of found: ...dark matter, cosmic rays and astroparticles, gamma-ray astronomy, particle astrophysics,...
Keywords: dark matter, cosmic rays and astroparticles, gamma-ray astronomy, particle astrophysics, particle dark matter
Published: 26.01.2023; Views: 213; Downloads: 0
Fulltext (4,53 MB)
Sensitivity of CTA to gamma-ray emission from the Perseus galaxy clusterJudit Pérez-Romero
, published scientific conference contribution
Abstract: In these proceedings we summarize the current status of the study of the sensitivity of the Cherenkov Telescope Array (CTA) to detect diffuse gamma-ray emission from the Perseus galaxy cluster. Gamma-ray emission is expected in galaxy clusters both from interactions of cosmic rays (CR) with the intra-cluster medium, or as a product of annihilation or decay of dark matter
(DM) particles in case they are weakly interactive massive particles (WIMPs). The observation of Perseus constitutes one of the Key Science Projects to be carried out by the CTA Consortium. In this contribution, we focus on the DM-induced component of the flux. OurDMmodelling includes the substructures we expect in the main halo which will boost the annihilation signal significantly. We adopt an ON/OFF observation strategy and simulate the expected gamma-ray signals. Finally we compute the expected CTA sensitivity using a likelihood maximization analysis including the most recent CTA instrument response functions. In absence of signal, we show that CTA will allow us to provide stringent and competitive constraints on TeV DM, especially for the case of
Found in: ključnih besedah
Summary of found: ...in galaxy clusters both from interactions of cosmic rays (CR) with the intra-cluster medium, or...
Keywords: dark matter, gamma-ray astronomy, galaxy clusters, cosmic rays and astroparticles
Published: 27.01.2023; Views: 204; Downloads: 7
Fulltext (0,00 KB)
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