Rare Events searches with Cherenkov Telescopes

Ground-based Imaging Cherenkov Telescope Arrays observe the Cherenkov radiation emitted in extended atmospheric showers generated by cosmic gamma rays in the TeV regime. The rate of these events is normally overwhelmed by 2-3 orders of magnitude more abundant cosmic rays induced showers. A large fraction of these 'background' events is vetoed at the online trigger level, but a substantial fraction still goes through data acquisition system and is saved for the offline reconstruction. What kind of information those events carry, normally rejected in the analysis? Is there the possibility that an exotic signature is hidden in those data? In the contribution, some science cases, and the problems related to the event reconstruction for the current and future generation of these telescopes will be discussed.Comment: Proceedings of the "The Roma International Conference on Astroparticle Physics (RICAP) 2016". Submitted to EPJ Web of Conference

Gamma-ray, Particle and Exotic Physics at TeV energies with the MAGIC telescopes

MAGIC is an instrument composed of a pair of telescopes for gamma- ray and cosmic-ray astrophysics in the TeV range. It is operating for more than a decade now, and is one of the current best performing instruments in this field, specifically at low energies, where it achieves the largest sensitivity. MAGIC pursues a strong program in galactic and extragalactic gamma-ray science. Its catalog of blazars, radiogalaxies and galaxy clusters observations as well as supernovae, novae, pulsar wind nebulae, pulsars and binary systems has now increased to several tens of detected targets. In addition, MAGIC is suited for cosmic ray searches, being sensitive to the signatures of earth-skimming tau-neutrinos, cosmic antiprotons, and others. Furthermore, MAGIC has a strong fundamental physics program, with searches for particle dark matter, Lorentz Invariance violations, axion-like particles and primordial black hole evaporation, providing important recent constraints in some relevant cases. Finally, MAGIC has a follow-up program of Gravitational Waves events. Few highlights topics will be discussed in this contribution.Comment: Proceedings of the 11th SciNeGHE workshops, 18-21 October 2016, Pisa, Italy. To appear in Il Nuovo Cimento

A review of the past and present MAGIC dark matter search program and a glimpse at the future

The MAGIC TeV gamma-ray telescopes have devoted several hundreds hour of observation time in about a decade, to hunt for particle dark matter indirect signatures in gamma rays, from various candidate targets of interest in the sky: the galactic center, satellite galaxies, galaxy clusters and unidentified objects in other bands. Despite the effort, no hints are present in MAGIC data. These observation are nevertheless not unusable. MAGIC indeed derived the most robust upper limits in the TeV range than any other instrument. These results, for the time being, only mildly constrain some classic dark matter models, but are of use in the construction of dark matter models for the next searches, that consider also the negative results from accelerator and direct-detection experiments. In the contribution, we discuss and review MAGIC results, putting them into context, and in perspective with the next generation of ground-based Cherenkov telescopes. We will briefly inform about future MAGIC projects regarding dark matter searches.Comment: XXV ECRS 2016 Proceedings - eConf C16-09-04.

A decade of dark matter searches with ground-based Cherenkov telescopes

In the general scenario of Weakly Interacting Massive Particles (WIMP), dark matter (DM) can be observed via astrophysical gamma rays because photons are produced in various DM annihilation or decay processes, either as broad-band or line emission, or because of the secondary processes of charged particles in the final stages of the annihilations or the decays. The energy range of the former processes is accessible by current ground-based Imaging Atmospheric Cherenkov telescopes (IACTs, like H.E.S.S., MAGIC and VERITAS). The strengths of this technique are: a) the expected DM gamma-ray spectra show peculiar features like bumps, spikes and cutoff that make them clearly distinguishable from the smoother astrophysical spectra, b) the expected DM spectrum is universal and therefore by observing two or more DM targets with the same spectrum, a clear identification (besides detection) of DM would be enabled. The role of IACTs may gain more importance in the future as the results from the LHC may hint to a DM particle with mass at the TeV or above, where the IACTs sensitivity is unsurpassed by other experiments. In this contribution, a review of the search for DM with the current generation of IACT will be presented.Comment: Proceedings of the 4th RICAP Conference (Rome, 2013). This version has some typo corrections with respect to the published version, as well as an updated Fig.

El telescopi MAGIC aporta llum al coneixement de la matèria fosca

La matèria fosca és el component majoritari de l'Univers: hi ha quatre vegades més matèria fosca que matèria normal. Tot i així, és una gran desconeguda: no emet ni absorbeix la llum directament i només es veu afectada per la força de la gravetat. Ara bé, quan dues partícules de matèria fosca col·lisionen, es poden aniquilar i generar raigs gamma, que són fotons amb milions de vegades més energia que la llum visible, i que poden ser detectats per instruments com el telescopi MAGIC, un experiment europeu situat a l'illa canària de La Palma. En aquest article, en què han participat investigadors de la UAB, es presenta la cerca de matèria fosca de MAGIC en l'objecte que es creu que és el més dominat per la matèria fosca del firmament i que es troba en els veïnatges de la nostra pròpia galàxia: una galàxia satèl·lit de la Via Làctia anomenada Segue 1.La materia oscura es el componente mayoritario del Universo: hay quatro veces mas materia oscura que materia normal. Sin embargo, es una gran desconocida: no emite ni absorbe luz directamente y sólo se ve afectada por la fuerza de la gravedad. Ahora bien, cuando dos partículas de materia oscura colisionan, se pueden aniquilar y generar rayos gamma, que son fotones con millones de veces más energía que la luz visible, y que pueden ser detectados por instrumentos como el telescopio MAGIC, un experimento europeo situado en la isla canaria de La Palma. En este artículo, en el que han participado investigadores de la UAB, se presenta la búsqueda de materia oscura de MAGIC en el objeto que se cree que es el más dominado por la materia oscura del firmamento y que se encuentra en las vecindades de nuestra propia galaxia: una galaxia satélite de la Vía Láctea llamada Segue 1.Dark matter is the major component of Universe: there is four times more dark matter than normal matter. But it is quite unknown: it does not emit or absorb light directly, but has a very important gravitational effect. However, when two dark matter particles collide, they may annihilate and produce different particles, including gamma-rays, which are photons million times more energetic than visible light and which can be detected by instruments like the MAGIC telescope, a European experiment located on the Canary Island of La Palma (Spain). This article, in wich UAB researchers participated, presents searches for dark matter using MAGIC by observing the object believed to be the most dark matter dominated in the vecinities of our own galaxy: a satellite galaxy of the Milky Way called Segue 1

Indirect search for dark matter with Cherenkov telescopes

Ground-based Cherenkov telescopes, also referred to as Imaging Atmospheric Cherenkov Telescopes, (IACTs) are array of large detectors, placed at moderate altitude, that catch the secondary induced Cherenkov emission produced in extensive atmospheric showers of particles generated by cosmic gamma rays. They are sensitive in the GeV-TeV region, and complete at high energy the MeV-GeV sensitivity of gamma-ray satellite experiments such as Fermi-LAT. In many of the possible realization of dark matter, this particle is stable because it is the lightest in some extension of the Standard Model. For this reason, indirect signatures from dark matter can come from annihilation events that take place in astrophysical environment. In this report, we briefly summarize the importance of gamma rays as probe for dark matter particle annihilations. We summarize current achievements and discuss future prospects

CTA - A Project for a New Generation of Cherenkov Telescopes

Gamma-rays provide a powerful insight into the non-thermal universe and perhaps a unique probe for new physics beyond the standard model. Current experiments are already giving results in the physics of acceleration of cosmic rays in supernova remnants, pulsar and active galactic nuclei with almost a hundred sources detected at very-high-energies so far. Despite its relatively recent appearance, very high-energy gamma-ray astronomy has proven to have reached a mature technology with fast assembling, relatively cheap and reliable telescopes. The goal of future installation is to increase the sensitivity by a factor ten compared to current installations, and enlarge the energy domain from few tens of GeV to a hundred TeV. Gamma-ray spectra of astrophysical origin are rather soft thus hardly one single size telescope can cover more than 1.5 decades in energy, therefore an array of telescopes of 2,3 different sizes is required. Hereafter, we present design considerations for a Cherenkov Telescope Array (CTA), a project for a new generation of highly automated telescopes for gamma-ray astronomy. The status of the project, technical solutions and an insight in the involved physics will be presented.Comment: (6 pages, Procs. of the 2nd RICAP Conf., Rome, Italy, 2009

First results of the two square meters multilayer glass composite mirror design proposed for the Cherenkov Telescope Array developed at INFN

The Cherenkov Telescope Array (CTA) is a future ground-based gamma-ray astronomy detector that will consist of more than 100 Imaging Atmospheric Cherenkov Telescopes of different sizes. The total reflective surface of roughly 10 000 m$^2$ requires unprecedented technological efforts towards a cost-efficient production of light-weight and reliable mirror substrates at high production rate. We report on a new mirror concept proposed for CTA developed by INFN, which is based on the replication from a spherical convex mold under low pressure. The mirror substrate is an open structure design made by thin glass layers at the mirror's front and rear interspaced by steel cylinders. A first series of nominal size mirrors has been produced, for which we discuss the optical properties in terms of radius of curvature and focusing power