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1.
Constraints on upward-going air showers using the Pierre Auger Observatory data
Emanuele De Vito, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, published scientific conference contribution

Abstract: The fluorescence detector (FD) of the Pierre Auger Observatory is sensitive to upward-going air showers with energies above 1017 eV. Given its operation time and wide field of view, the FD has the potential to support or constrain the “anomalous” observations by the ANITA detector, interpreted as upward-going air showers that would be indicative of Beyond Standard Model (BSM) physics. To this end, a search for upward-going air showers with the FD has been performed applying selection criteria that were optimized using 10% of FD data. Dedicated background simulations (downward-going events) have been performed to estimate our capability to distinguish candidates from false positives. Also dedicated signal simulations (upward-going events) have been used to estimate our sensitivity to such showers with a focus on the energy region close to the ANITA observations. Improved and updated results of the Pierre Auger Observatory exposure to upward-going showers will be presented after the unblinding of 14 years of FD data. Extensive simulations allow the FD exposure to be obtained at lower energies which are particularly relevant for the comparison with the ANITA results. A refinement of the method for signal discrimination and background rejection has also been applied. The implications are discussed under the assumption that the ANITA events were due to upward-going events.
Keywords: Pierre Auger Observatory, ultra-high energy cosmic rays, air showers, beyond standard model, fluorescence detectors, ANITA
Published in RUNG: 23.01.2024; Views: 288; Downloads: 6
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2.
The Cherenkov Telescope Array. Science Goals and Current Status
Rene A. Ong, Christopher Eckner, Gašper Kukec Mezek, Samo Stanič, Serguei Vorobiov, Lili Yang, Gabrijela Zaharijas, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2019, published scientific conference contribution (invited lecture)

Abstract: The Cherenkov Telescope Array (CTA) is the major ground-based gamma-ray observatory planned for the next decade and beyond. Consisting of two large atmospheric Cherenkov telescope arrays (one in the southern hemisphere and one in the northern hemisphere), CTA will have superior angular resolution, a much wider energy range, and approximately an order of magnitude improvement in sensitivity, as compared to existing instruments. The CTA science programme will be rich and diverse, covering cosmic particle acceleration, the astrophysics of extreme environments, and physics frontiers beyond the Standard Model. This paper outlines the science goals for CTA and covers the current status of the project.
Keywords: very-high-energy gamma-ray astronomy, Cherenkov Telescope Array (CTA), cosmic particle acceleration, astrophysics of extreme environments, physics beyond the Standard Model
Published in RUNG: 11.10.2023; Views: 531; Downloads: 7
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3.
Expected exclusion limits to TeV dark matter from the perseus cluster with the Cherenkov Telescope Array
Rémi Adam, Saptashwa Bhattacharyya, Judit Pérez Romero, Samo Stanič, Veronika Vodeb, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Miha Živec, 2023, published scientific conference contribution

Abstract: Clusters of galaxies are the largest gravitationally-bound structures in the Universe. They are composed of galaxies and gas (approximately 15% of the total mass) mostly dark matter (DM, accounts up to 85% of the total mass). If the DM is composed of Weakly Interacting Massive Particles (WIMPs), galaxy clusters represent one of the best targets to search for gamma-ray signals induced by the decay of WIMPs, with masses around the TeV scale. Due to its sensitivity and energy range of operation (from 20 GeV to 300 TeV), the Cherenkov Telescope Array (CTA) Observatory has a unique opportunity to test WIMPs with masses close to the unitarity limit. This will complement the searches for DM from other gamma-ray observatories as well as direct and collider experiments. The CTA Observatory is planning to search for gamma-ray emission, either its origin may be cosmic-ray (CR) or DM related, in the Perseus galaxy cluster during the first years of operation. In this poster, we will present the software created to perform the analysis using the ctools software and the corresponding results.
Keywords: Cherenkov Telescope Array, CTA, dark matter, standard model, dwarf spheroidal galaxies
Published in RUNG: 26.09.2023; Views: 557; Downloads: 4
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4.
Variability studies of active galactic nuclei from the long-term monitoring program with the Cherenkov Telescope Array
G. Grolleron, Saptashwa Bhattacharyya, Judit Pérez Romero, Samo Stanič, Veronika Vodeb, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Miha Živec, 2023, published scientific conference contribution

Abstract: Blazars are active galactic nuclei (AGN) with a relativistic jet oriented toward the observer. This jet is composed of accelerated particles which can display emission over the entire electromagnetic spectrum. Spectral variability has been observed on short- and long-time scales in AGN, with a power spectral density (PSD) that can show a break at frequencies below the well-known red-noise process. This break frequency in the PSD has been observed in X-rays to scale with the accretion regime and the mass of the central black hole. It is expected that a break could also be seen in the very-high-energy gamma rays, but constraining the shape of the PSD in these wavelengths has not been possible with the current instruments. The Cherenkov Telescope Array (CTA) will be more sensitive by a factor of five to ten depending on energy than the current generation of imaging atmospheric Cherenkov telescopes, therefore it will be possible with CTA to reconstruct the PSD with a high accuracy, bringing new information about AGN variability. In this work, we focus on the AGN long-term monitoring program planned with CTA. The program is proposed to begin with early-start observing campaigns with CTA precursors. This would allow us to probe longer time scales on the AGN PSD.
Keywords: Cherenkov Telescope Array, CTA, dark matter, standard model, dwarf spheroidal galaxies
Published in RUNG: 26.09.2023; Views: 600; Downloads: 7
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5.
Pybkgmodel - a background modelling toolbox for the CTA
Marcel C. Strzys, Saptashwa Bhattacharyya, Judit Pérez Romero, Samo Stanič, Veronika Vodeb, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Miha Živec, 2023, published scientific conference contribution

Abstract: Despite the advancement in background rejection techniques, observation of the very-high-energy gamma-ray sky by imaging atmospheric Cherenkov telescopes (IACTs) are subject to an irreducible background from gamma-like hadron- or electron-induced air showers. The determination of this residual background is crucial for accurate spectral and spatial measurements. The Cherenkov Telescope Array (CTA) will become the next generation of IACTs. To unveil its full potential, the improved reconstruction performance of CTA needs to be coupled with a reliable background estimate across the entire field of view. This may become especially important in the case of the planned surveys of large areas of the sky. In this contribution we will present pybkgmodel, an open-source python software package de-veloped for CTA. It aims at providing in a consistent way the various background modelling methods, based on the experience from current IACTs such as H.E.S.S, MAGIC, and VERITAS. It is designed as a toolbox allowing a user to easily choose the optimal reconstruction approach for various target regions or a combination of several algorithms. We will introduce the design of the package as well as demonstrate its functionality using data for the CTA Large-Sized Telescope prototype (LST-1).
Keywords: Cherenkov Telescope Array, CTA, dark matter, standard model, dwarf spheroidal galaxies
Published in RUNG: 26.09.2023; Views: 578; Downloads: 6
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6.
Dark matter searches in dwarf spheroidal galaxies with the Cherenkov Telescope Array
F. G. Saturni, Saptashwa Bhattacharyya, Judit Pérez Romero, Samo Stanič, Veronika Vodeb, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Miha Živec, 2023, published scientific conference contribution

Abstract: Dark matter (DM) is one of the major components in the Universe. However, at present its existence is still only inferred through indirect astronomical observations. DM particles can annihilate or decay, producing final-state Standard Model pairs that subsequently annihilate into high-energy �-rays. The dwarf spheroidal galaxies (dSphs) in the Milky Way DM halo have long been considered optimal targets to search for annihilating DM signatures in GeV-to-TeV �-ray spectra due to their high DM densities (hence high astrophysical factors), as well as the expected absence of intrinsic �-ray emission of astrophysical origin. For such targets, it is important to compute the amount of DM in their halos in a consistent way to optimize the �-ray data analysis. Such estimates directly affect the observability of DM signals in dSphs, as well as the DM constraints that can be derived in case of null detection. In this contribution, we present the results on the sensitivity of the Cherenkov Telescope Array (CTA) for DM annihilation and decay searches using planned observations of the Milky Way dSphs. We select the most promising targets among all presently known dwarf satellites, providing new determinations of their expected DM signal. This study shows an improvement of approximately an order of magnitude in sensitivity compared to current searches in similar targets. We also discuss the results in terms of cuspy and cored DM models, and investigate the sensitivity obtained by the combination of observations from different dSphs. Finally, we explore the optimal strategies for CTA observations of dSphs.
Keywords: Cherenkov Telescope Array, CTA, dark matter, standard model, dwarf spheroidal galaxies
Published in RUNG: 26.09.2023; Views: 614; Downloads: 4
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7.
Constraints on BSM particles from the absence of upward-going air showers in the Pierre Auger Observatory
Baobiao Yue, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, published scientific conference contribution

Abstract: The Fluorescence Detector (FD) of the Pierre Auger Observatory has a large exposure to search for upward-going showers. Constraints have been recently obtained by using 14 years of FD data searching for upward-going showers in the zenith angle range [110◦, 180◦]. In this work, we translate these bounds to upper limits of a possible flux of ultra high energy tau-leptons escaping from the Earth into the atmosphere. Such a mechanism could explain the observation of "anomalous pulses" made by ANITA, that indicated the existence of upward-going air showers with energies above 10[sup]17 eV. As tau neutrinos would be absorbed within the Earth at the deduced angles and energies, a flux of upward-going taus could only be resulted from an unknown type of ultra high energy Beyond Standard Model particle penetrating the Earth with little attenuation, and then creating tau-leptons through interactions within a maximum depth of about 50 km before exiting. We test classes of such models in a generic way and determine upper flux limits of ultra high energy BSM particles as a function of their unknown cross section with matter.
Keywords: ultra-high energy cosmic rays, Pierre Auger Observatory, fluorescence detector, upward-going air showers, Beyond Standard Model particles
Published in RUNG: 26.09.2023; Views: 503; Downloads: 6
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8.
CTA sensitivity for probing cosmology and fundamental physics with gamma rays
Ievgen Vovk, Saptashwa Bhattacharyya, Barbara MARČUN, Judit Pérez Romero, Samo Stanič, Veronika Vodeb, Serguei Vorobiov, Gabrijela Zaharijas, Marko Zavrtanik, Danilo Zavrtanik, Miha Živec, 2021, published scientific conference contribution

Abstract: The Cherenkov Telescopic Array (CTA), the next-generation ground-based gamma-ray observatory, will have unprecedented sensitivity, providing answers to open questions in gamma-ray cosmology and fundamental physics. Using simulations of active galactic nuclei observations foreseen in the CTA Key Science Program, we find that CTA will measure gamma-ray absorption on the extragalactic background light with a statistical error below 15% up to the redshift of 2 and detect or establish limits on gamma halos induced by the intergalactic magnetic field of at least 0.3 pG. Extragalactic observations using CTA also demonstrate the potential for testing physics beyond the Standard Model. The best state-of-the-art constraints on the Lorentz invariance violation from astronomical gamma-ray observations will be improved at least two- to threefold. CTA will also probe the parameter space where axion-like particles can represent a significant proportion – if not all – of dark matter. Joint multiwavelength and multimessenger observations, carried out together with other future observatories, will further foster the growth of gamma-ray cosmology.
Keywords: Cherenkov Telescopic Array, ground-based gamma-ray observatory, beyond the Standard Model, extragalactic observations
Published in RUNG: 19.09.2023; Views: 535; Downloads: 6
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9.
Vhodna kontrola materialov v podjetju LedLuks po metodi AQL
Nino Stanič, 2022, undergraduate thesis

Abstract: Kontrola kakovosti postaja vedno pomembnejši dejavnik. Ker se standardi ves čas zaostrujejo, je potrebno nenehno prilagajati in izboljševati procese kontrole kakovosti. Dobro izpeljana vhodna kontrola prinaša številne prednosti za podjetje; skrajša lahko čakalne dobe za začetek izvedbe naročila, zmanjša izmet, dodatne dodelave ali zavrnitve v procesu in tudi znižuje ceno celotnega izdelka. Zato je izbira ustrezne metode za izvajanje vhodne kontrole zelo pomembna, saj za podjetje predstavlja najučinkovitejši način pregled dobavljenega materiala. V diplomskem delu s pomočjo testiranja ugotavljamo učinkovitost izboljšave vhodne kontrole po metodi sprejemljive kakovosti, angl. Acceptable Quality Level (AQL). V delu so predstavljeni vidiki metode AQL, način uporabe AQL, stanje vhodne kontrole v podjetju Ledluks, d. o. o., pred in po uvedbi nove metode ter ocena končnega stanja. Namen dela je preveriti in empirično pokazati izboljšanje stanja po implementaciji nove metode ter izpostaviti njene prednosti. Po definiciji metode in opisu obstoječega stanja so predstavljeni rezultati testiranja metode, kjer so jasno razvidne prednosti nove metode vhodne kontrole.
Keywords: Kakovost, kontrola, podjetje, AQL, stopnja, čas, standard
Published in RUNG: 30.09.2022; Views: 1552; Downloads: 91
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10.
Ultra-fast silicon detectors for CERN’S high-luminosity large hadron collider : written report
Adrián González Briones, 2022, research project (high school)

Keywords: standard silicon detectors, ionized particles, hadrontherapy, particle physics
Published in RUNG: 15.06.2022; Views: 1302; Downloads: 0
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