169 research outputs found
Python-based framework for managing a base of complex data for music information retrieval
No full textLAUREA MAGISTRALENell’Era dell’Informazione, le modalità di fruizione e conservazione della musica sono cambiate rispetto a quelle della generazione precedente.
La diffusione del media digitale e l’alto grado di sofisticazione raggiunto dalle tecnologie informatiche permettono lo sviluppo di sistemi capaci di gestire vasti cataloghi musicali in base agli attributi del segnale stesso e alle informazioni assegnate da un utente al media.
L’informazione estratta dal segnale può però differire o addirittura non essere comparabile rispetto a ciò che l’essere umano percepisce dall’ascolto della traccia musicale.
Music Information Retrieval è un campo di ricerca in continua crescita che mira a produrre sistemi che assottiglino il divario tra la percezione sonora dell’ascoltatore e gli attributi empirici del segnale audio.
In questa tesi proponiamo un framework per la gestione di dati com- plessi estratti da segnali audio che faciliti la realizzazione di applicazioni nell’ambito del Music Information Retrieval.Diffusion of digital media and the high level of software sophistication allows development of systems that are capable to manage vast music catalogues. Catalogation is based on data extracted from signal and on data assigned by the user.
Extracted information can differ from what the listener perceives.
Music Information Retrieval, is a growing field of research that aims to produce systems that would narrow down the gap between listeners sound perception and the audio signal attributes.
In this thesis we propose a framework for managing complex data extracted from audio signals that would ease development of Music Information Retrieval Applications
Searches for Ultra-High-Energy Photons at the Pierre Auger Observatory
No full textThe Pierre Auger Observatory, being the largest air-shower experiment in the
world, offers an unprecedented exposure to neutral particles at the highest
energies. Since the start of data taking more than 18 years ago, various
searches for ultra-high-energy (UHE, ) photons have
been performed: either for a diffuse flux of UHE photons, for point sources of
UHE photons or for UHE photons associated with transient events like
gravitational wave events. In the present paper, we summarize these searches
and review the current results obtained using the wealth of data collected by
the Pierre Auger Observatory.Comment: Review article accepted for publication in Universe (special issue on
ultra-high energy photons
Search for the Anomalous Events Detected by ANITA Using the Pierre Auger Observatory
No full textA dedicated search for upward-going air showers at zenith angles exceeding 110° and energies E>0.1 EeV has been performed using the Fluorescence Detector of the Pierre Auger Observatory. The search is motivated by two "anomalous"radio pulses observed by the ANITA flights I and III that appear inconsistent with the standard model of particle physics. Using simulations of both regular cosmic-ray showers and upward-going events, a selection procedure has been defined to separate potential upward-going candidate events and the corresponding exposure has been calculated in the energy range [0.1-33] EeV. One event has been found in the search period between January 1, 2004, and December 31, 2018, consistent with an expected background of 0.27±0.12 events from misreconstructed cosmic-ray showers. This translates to an upper bound on the integral flux of (7.2±0.2)×10-21 cm-2 sr-1 y-1 and (3.6±0.2)×10-20 cm-2 sr-1 y-1 for an E-1 and E-2 spectrum, respectively. An upward-going flux of showers normalized to the ANITA observations is shown to predict over 34 events for an E-3 spectrum and over 8.1 events for a conservative E-5 spectrum, in strong disagreement with the interpretation of the anomalous events as upward-going showers
Search for photons above 1019eV with the surface detector of the Pierre Auger Observatory
No full textWe use the surface detector of the Pierre Auger Observatory to search for air showers initiated by photons with an energy above 1019 eV. Photons in the zenith angle range from 30 to 60 can be identified in the overwhelming background of showers initiated by charged cosmic rays through the broader time structure of the signals induced in the water- Cherenkov detectors of the array and the steeper lateral distribution of shower particles reaching ground. Applying the search method to data collected between January 2004 and June 2020, upper limits at 95% CL are set to an E−2 diffuse flux of ultra-high energy photons above 1019 eV, 2×1019 eV and 4×1019 eV amounting to 2.11×10−3, 3.12×10−4 and 1.72×10−4 km−2 sr−1 yr−1, respectively. While the sensitivity of the present search around 2×1019 eV approaches expectations of cosmogenic photon fluxes in the case of a pure-proton composition, it is one order of magnitude above those from more realistic mixed-composition models. The inferred limits have also implications for the search of super-heavy dark matter that are discussed and illustrated.The Pierre Auger Collaboration ... J.A Bellido ... R.W Clay ... B.R Dawson ... T.D Grubb ... V.M Harvey ... B.C Manning ... T Sudholz ... et al
Impact of the magnetic horizon on the interpretation of the Pierre Auger Observatory spectrum and composition data
No full textThe flux of ultra-high energy cosmic rays reaching Earth above the ankle energy (5 EeV) can be described as a mixture of nuclei injected by extragalactic sources with very hard spectra and a low rigidity cutoff. Extragalactic magnetic fields existing between the Earth and the closest sources can affect the observed CR spectrum by reducing the flux of low-rigidity particles reaching Earth. We perform a combined fit of the spectrum and distributions of depth of shower maximum measured with the Pierre Auger Observatory including the effect of this magnetic horizon in the propagation of UHECRs in the intergalactic space. We find that, within a specific range of the various experimental and phenomenological systematics, the magnetic horizon effect can be relevant for turbulent magnetic field strengths in the local neighbourhood in which the closest sources lie of order Brms ≃ (50–100) nG (20 Mpc/ds)(100 kpc/Lcoh)1/2, with ds the typical intersource separation and Lcoh the magnetic field coherence length. When this is the case, the inferred slope of the source spectrum becomes softer and can be closer to the expectations of diffusive shock acceleration, i.e., ∝ E−2. An additional cosmic-ray population with higher source density and softer spectra, presumably also extragalactic and dominating the cosmic-ray flux at EeV energies, is also required to reproduce the overall spectrum and composition results for all energies down to 0.6 EeV
Impact of the magnetic horizon on the interpretation of the Pierre Auger Observatory spectrum and composition data
No full textThe flux of ultra-high energy cosmic rays reaching Earth above the ankle energy (5 EeV) can be described as a mixture of nuclei injected by extragalactic sources with very hard spectra and a low rigidity cutoff. Extragalactic magnetic fields existing between the Earth and the closest sources can affect the observed CR spectrum by reducing the flux of low-rigidity particles reaching Earth. We perform a combined fit of the spectrum and distributions of depth of shower maximum measured with the Pierre Auger Observatory including the effect of this magnetic horizon in the propagation of UHECRs in the intergalactic space. We find that, within a specific range of the various experimental and phenomenological systematics, the magnetic horizon effect can be relevant for turbulent magnetic field strengths in the local neighbourhood in which the closest sources lie of order B-rms similar or equal to (50-100) nG(20Mpc/ds)(100 kpc/L-coh)(1/2), with d(s) the typical intersource separation and L-coh the magnetic field coherence length. When this is the case, the inferred slope of the source spectrum becomes softer and can be closer to the expectations of diffusive shock acceleration, i.e., proportional to E-2. An additional cosmic-ray population with higher source density and softer spectra, presumably also extragalactic and dominating the cosmic-ray flux at EeV energies, is also required to reproduce the overall spectrum and composition results for all energies down to 0.6 EeV
A new cross-check and review of aerosol attenuation measurements at the Pierre Auger Observatory
No full textThe distribution of aerosols in the atmosphere above cosmic ray fluorescence detectors must be well characterised in order to precisely recover extensive air shower properties such as the calorimetric energy, E, and depth of shower maximum, Xmax. The Pierre Auger Observatory uses two centrally located laser facilities to measure the vertical aerosol optical depth profile (VAOD) every hour. It is assumed that the night with the clearest atmosphere each year is effectively aerosol free and that it is an appropriate reference to set the absolute scale of VAOD throughout that year. We review the successes of this method and its associated sources of systematic uncertainty, then present a new cross-check of measured VAOD using air shower events observed in stereo mode. Special attention is paid to quantifying the uncertainties on this result. As the technique is only sensitive to VAOD bias at a fixed altitude, we combine it with a study of aerosol profiles independently measured using a less-sensitive Raman lidar system. This allows us to derive a complete model of the upper limit on the possible bias in the average measured VAOD, which we attribute primarily to an uncertainty on whether the annual reference nights are completely aerosol free. We formulate a correction for this bias and apply it retroactively to all VAOD measurements, then repeat the analysis of the complete air shower dataset and discuss the small but significant effect of this new correction on E and Xmax. This correction is now fully integrated into the Auger analysis chain
Testing hadronic-model predictions of depth of maximum of air-shower profiles and ground-particle signals using hybrid data of the Pierre Auger Observatory
No full textWe test the predictions of hadronic interaction models regarding the depth of maximum of air-shower
profiles, Xmax , and ground-particle signals in water-Cherenkov detectors at 1000 m from the shower core,
Sð1000Þ, using the data from the fluorescence and surface detectors of the Pierre Auger Observatory. The
test consists of fitting the measured two-dimensional (Sð1000Þ, Xmax ) distributions using templates for
simulated air showers produced with hadronic interaction models E pos-LHC , QGSJ et-II -04, SIBYLL 2.3d and
leaving the scales of predicted Xmax and the signals from hadronic component at ground as free-fit
parameters. The method relies on the assumption that the mass composition remains the same at all zenith
angles, while the longitudinal shower development and attenuation of ground signal depend on the mass
composition in a correlated way. The analysis was applied to 2239 events detected by both the fluorescence
and surface detectors of the Pierre Auger Observatory with energies between 10 18.5 eV to 10 19.0 eV and
zenith angles below 60°. We found, that within the assumptions of the method, the best description of the
data is achieved if the predictions of the hadronic interaction models are shifted to deeper Xmax values and
larger hadronic signals at all zenith angles. Given the magnitude of the shifts and the data sample size, the
statistical significance of the improvement of data description using the modifications considered in the
paper is larger than 5σ even for any linear combination of experimental systematic uncertainties
Update on the searches for anisotropies in UHECR arrival directions with the Pierre Auger Observatory and the Telescope Array
No full textThe origin of ultra-high-energy cosmic rays (UHECRs), particles from outer space with energies E ≥ 1 EeV, is still unknown, though the near-isotropy of their arrival direction distribution excludes a dominant Galactic contribution, and interactions with background photons prevent them from travelling cosmologically large distances. This suggests that their sources must be searched for in nearby galaxy groups and clusters. Deflections by intergalactic and Galactic magnetic fields are expected to hinder such searches but not preclude them altogether. So far, the only anisotropy detected with statistical significance ≥ 5σ is a modulation in right ascension in the data from the Pierre Auger Observatory at E ≥ 8 EeV interpretable as a 7% dipole moment. Various hints for higher-energy, smaller-scale anisotropies have been reported. UHECR arrival direction data from both the Pierre Auger Observatory and the Telescope Array experiment have been searched for anisotropies by a working group with members from both collaborations; combining the two datasets requires a cross-calibration procedure due to the different systematic uncertainties on energy measurements but allows us to perform analyses that are less model-dependent than what can be done with partial sky coverage. We report a significant dipole pointing away from the Galactic Center and a ∼4.6σ anisotropy found when comparing the directions of UHECRs with a catalog of starburst galaxies
Mass Composition from 3 EeV to 100 EeV using the Depth of the Maximum of Air-Shower Profiles Estimated with Deep Learning using Surface Detector Data of the Pierre Auger Observatory
No full textWe present a new analysis for estimating the depth of the maximum of air-shower profiles, Xmax, to investigate the evolution of the ultra-high-energy cosmic ray mass composition from 3 to 100 EeV. We use a recently developed deep-learning-based technique for the reconstruction of Xmax from the data of the surface detector of the Pierre Auger Observatory. To avoid systematic uncertainties arising from hadronic interaction models in the simulation of surface detector data, we calibrate the new reconstruction technique with observations of the fluorescence detector. Using the novel analysis, we have a 10-fold increase of statistics at E > 5 EeV with respect to fluorescence detector data. We are able, for the first time, to study the evolution of the mean and standard deviation of the Xmax distributions up to 100 EeV. We find an excellent agreement with fluorescence observations and confirm the increase of the mean logarithmic mass hln(A)i and a decrease of the Xmax fluctuations with energy. The Xmax measurement at the highest — so far inaccessible — energies is consistent with a pure mass composition and a mean logarithmic mass of around ∼ 3 (estimated using the Sibyll 2.3d and the EPOS-LHC hadronic interaction models). Furthermore, with the increase in statistics, we find indications for a structure beyond a constant elongation rate in the evolution of Xma
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