Instantons, which are nonperturbative solutions to Yang-Mills equations, provide a signal for the occurrence of quantum tunneling between distinct classes of vacua. They can give rise to decays of ...particles otherwise forbidden. Using data collected at the Pierre Auger Observatory, we search for signatures of such instanton-induced processes that would be suggestive of super-heavy particles decaying in the Galactic halo. These particles could have been produced during the post-inflationary epoch and match the relic abundance of dark matter inferred today. The nonobservation of the signatures searched for allows us to derive a bound on the reduced coupling constant of gauge interactions in the dark sector: α_{X}≲0.09, for 10^{9}≲M_{X}/GeV<10^{19}. Conversely, we obtain that, for instance, a reduced coupling constant α_{X}=0.09 excludes masses M_{X}≳3×10^{13} GeV. In the context of dark matter production from gravitational interactions alone, we illustrate how these bounds are complementary to those obtained on the Hubble rate at the end of inflation from the nonobservation of tensor modes in the cosmological microwave background.
Resumen: El Laboratorio Subterráneo ANDES está siendo planificado y diseñado para ser uno de los laboratorios más grandes y con mayor cobertura de roca en el Hemisferio Sur, el cual estará ubicado en ...la Cordillera de los Andes, en la zona del actual Paso Agua Negra que conecta las provincias de San Juan (Argentina) y Elqui (Chile). La diversidad de experimentos que se están planificando, entre ellos experimentos de búsqueda directa e indirecta de materia oscura y física de precisión de neutrinos, requieren de un conocimiento preciso del flujo esperado de muones atmosféricos de alta energía dentro del laboratorio. Estos son producidos durante la interacción con la atmósfera terrestre de astropartículas de alta y ultra alta energía, con energías entre 1012 y 1018 eV. En la componente de alta energía pueden encontrarse muones con energías de decenas de TeV, capaces de atravesar miles de metro de roca. Estimaciones previas realizadas a partir de suposiciones razonables sobre el tipo de roca esperada en la zona, mostraron que el flujo de muones esperado era compatible con el de otros laboratorios a una profundidad equivalente. En este trabajo, se realizaron simulaciones de flujo de lluvias atmosféricas extendidas en el sitio del laboratorio. A continuación, se seleccionaron aquellos muones con energía suficiente para alcanzar al laboratorio en base a su ángulo de incidencia y a la altura a la que ingresan en la montaña. Luego se modeló una función de transferencia utilizando los nuevos estudios geológicos disponibles actualmente que permiten disponer un modelo detallado de la distribución de roca en el interior de la montaña. Finalmente, se calculó numéricamente la interacción de estos muones con los diferentes tipos de roca a lo largo de su recorrido hacia el laboratorio utilizando el modelo de desaceleración continua, obteniéndose así que el flujo de muones esperado dentro del laboratorio es de 1,47±0,02 día−1 m−2 sr−1.
Simulated Annealing for volcano muography Vesga-Ramírez, A.; Sanabria-Gómez, J.D.; Sierra-Porta, D. ...
Journal of South American earth sciences,
August 2021, 2021-08-00, Letnik:
109
Journal Article
Recenzirano
Muography or muon radiography is a non-invasive emerging image technology relying on high energy atmospheric muons, which complements other standard geophysical tools to understand the Earth’s ...subsurface.
This work discusses a geophysical inversion methodology for volcanic muography, based on the Simulated Annealing algorithm, using a semi-empirical model of the muon flux to reach the volcano topography and a framework for the energy loss of muons in rock.
The Metropolis-Simulated-Annealing algorithm starts from an “observed” muon flux and obtains the best associated inner density distribution function inside a syntetic model of the Cerro Machín Volcano (Tolima-Colombia). The estimated initial density model was obtained with GEOMODELER, adapted to the volcano topography. We improved this model by including rock densities from samples taken from the crater, the dome and the areas associated with fumaroles.
In this paper we determined the minimum muon energy (a function of the arrival direction) needed to cross the volcanic building, the emerging integrated flux of muons, and the density profile inside a model of Cerro Machin. The present inversion correctly reconstructed the density differences inside the Machín, within a 1% error concerning our initial simulation model, giving a remarkable density contrast between the volcanic duct, the encasing rock and the fumaroles area.
•Geophysical inversion methodology for volcanic muography based on the Simulated Annealing algorithm.•The inversion algorithm correctly reconstructed the density differences inside the Machin, within a 1% error concerning our initial simulation model.•We estimate the emerging integrated flux of muons and the density profile inside a model of Cerro Machin Volcano (Tolima, Colombia).
Resumo Conscientes de la problemática relacionada con la motivación en el estudio de las carreras científicas, presentamos dos experiencias en las cuales se expone a estudiantes universitarios a ...ambientes, metodologías y técnicas del descubrimiento abordando problemas contemporáneos. Estas experiencias se desarrollaron en dos contextos complementarios: un curso de Introducción a la Física, en el cual se motiva a estudiantes de Física a la participación temprana en investigación, y un semillero de investigación multidisciplinario para estudiantes avanzados de pregrado en Ciencias e Ingeniería, el cual produjo incluso contribuciones a eventos internacionales. Si bien los resultados son preliminares y requieren más ediciones para ser estadísticamente significativos, consideramos que son alentadores. En ambos entornos se observó un aumento de la motivación de los estudiantes para continuar sus carreras haciendo énfasis en la investigación. En este trabajo, además de presentar el marco contextual en el cual se soportan las experiencias, describimos seis actividades concretas para vincular a los estudiantes con los ambientes de descubrimiento, las cuales creemos pueden ser replicadas en ambientes similares de otras instituciones educativas.
Abstract Being aware of the motivation problems observed in many scientific oriented careers, we present two experiences to expose college students to environments, methodologies and discovery techniques addressing contemporary problems. This experiences are developed in two complementary contexts: an Introductory Physics course, where we motivated physics students to participate in research activities, and a multidisciplinary incubator of research oriented to advanced undergraduate students of Science and Engineering (that even produced three poster presentations in international conferences). Although these are preliminary results and require additional editions to get statistical significance, we consider they are encouraging results. On both contexts we observe an increase in the students motivation to orient their careers with emphasis on research. In this work, besides the contextualization support for these experiences, we describe six specific activities to link our students to research areas, which we believe can be replicated in similar environments in other educational institutions.
Abstract
Results of a search for ultra-high-energy neutrinos with the Pierre Auger Observatory from the direction of the blazar TXS 0506+056 are presented. They were obtained as part of the follow-up ...that stemmed from the detection of high-energy neutrinos and gamma rays with IceCube, Fermi-LAT, MAGIC, and other detectors of electromagnetic radiation in several bands. The Pierre Auger Observatory is sensitive to neutrinos in the energy range from 100 PeV to 100 EeV and in the zenith-angle range from
θ
= 60° to
θ
= 95°, where the zenith angle is measured from the vertical direction. No neutrinos from the direction of TXS 0506+056 have been found. The results were analyzed in three periods: one of 6 months around the detection of IceCube-170922 A, coinciding with a flare period of TXS 0506+056, a second one of 110 days during which the IceCube collaboration found an excess of 13 neutrinos from a direction compatible with TXS 0506+056, and a third one from 2004 January 1 up to 2018 August 31, over which the Pierre Auger Observatory has been taking data. The sensitivity of the Observatory is addressed for different spectral indices by considering the fluxes that would induce a single expected event during the observation period. For indices compatible with those measured by the IceCube collaboration the expected number of neutrinos at the Observatory is well below one. Spectral indices as hard as 1.5 would have to apply in this energy range to expect a single event to have been detected.
We report a measurement of the energy spectrum of cosmic rays above 2.5×1018 eV based on 215 030 events. New results are presented: at about 1.3×1019 eV, the spectral index changes from ...2.51±0.03(stat)±0.05(syst) to 3.05±0.05(stat)±0.10(syst), evolving to 5.1±0.3(stat)±0.1(syst) beyond 5×1019 eV, while no significant dependence of spectral features on the declination is seen in the accessible range. These features of the spectrum can be reproduced in models with energy-dependent mass composition. The energy density in cosmic rays above 5×1018 eV is 5.66±0.03(stat)±1.40(syst)×1053 erg Mpc-3.
Abstract
A search for time-directional coincidences of ultra-high-energy (UHE) photons above 10 EeV with gravitational wave (GW) events from the LIGO/Virgo runs O1 to O3 is conducted with the Pierre ...Auger Observatory. Due to the distinctive properties of photon interactions and to the background expected from hadronic showers, a subset of the most interesting GW events is selected based on their localization quality and distance. Time periods of 1000 s around and 1 day after the GW events are analyzed. No coincidences are observed. Upper limits on the UHE photon fluence from a GW event are derived that are typically at ∼7 MeV cm
−2
(time period 1000 s) and ∼35 MeV cm
−2
(time period 1 day). Due to the proximity of the binary neutron star merger GW170817, the energy of the source transferred into UHE photons above 40 EeV is constrained to be less than 20% of its total GW energy. These are the first limits on UHE photons from GW sources.
Abstract
Lorentz invariance violation (LIV) is often described by dispersion relations of the form
E
i
2
=
m
i
2
+
p
i
2
+δ
i,n
E
2+n
with delta different based on particle type
i
, with energy
E
, ...momentum
p
and rest mass
m
. Kinematics and energy thresholds of interactions are modified once the LIV terms become comparable to the squared masses of the particles involved. Thus, the strongest constraints on the LIV coefficients δ
i,n
tend to come from the highest energies. At sufficiently high energies, photons produced by cosmic ray interactions as they propagate through the Universe could be subluminal and unattenuated over cosmological distances. Cosmic ray interactions can also be modified and lead to detectable fingerprints in the energy spectrum and mass composition observed on Earth. The data collected at the Pierre Auger Observatory are therefore possibly sensitive to both the electromagnetic and hadronic sectors of LIV. In this article, we explore these two sectors by comparing the energy spectrum and the composition of cosmic rays and the upper limits on the photon flux from the Pierre Auger Observatory with simulations including LIV. Constraints on LIV parameters depend strongly on the mass composition of cosmic rays at the highest energies. For the electromagnetic sector, while no constraints can be obtained in the absence of protons beyond 10
19
eV, we obtain δ
γ,0
> -10
-21
, δ
γ,1
> -10
-40
eV
-1
and δ
γ,2
> -10
-58
eV
-2
in the case of a subdominant proton component up to 10
20
eV. For the hadronic sector, we study the best description of the data as a function of LIV coefficients and we derive constraints in the hadronic sector such as δ
had,0
< 10
-19
, δ
had,1
< 10
-38
eV
-1
and δ
had,2
< 10
-57
eV
-2
at 5σ CL.
Abstract
A catalog containing details of the highest-energy cosmic rays recorded through the detection of extensive air showers at the Pierre Auger Observatory is presented with the aim of opening ...the data to detailed examination. Descriptions of the 100 showers created by the highest-energy particles recorded between 2004 January 1 and 2020 December 31 are given for cosmic rays that have energies in the range 78–166 EeV. Details are also given on a further nine very energetic events that have been used in the calibration procedure adopted to determine the energy of each primary. A sky plot of the arrival directions of the most energetic particles is shown. No interpretations of the data are offered.
Ultra-high-energy photons with energies exceeding 1017 eV offer a wealth of connections to different aspects of cosmic-ray astrophysics as well as to gamma-ray and neutrino astronomy. The recent ...observations of photons with energies in the 1015 eV range further motivate searches for even higher-energy photons. In this paper, we present a search for photons with energies exceeding 2 × 1017 eV using about 5.5 yr of hybrid data from the low-energy extensions of the Pierre Auger Observatory. The upper limits on the integral photon flux derived here are the most stringent ones to date in the energy region between 1017 and 1018 eV.
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