Fundamental Physics

DARK MATTER SEARCHES

Dark matter could be observed in VHE gamma-rays through its annihilation or decay products. Such signals are coming from cosmic places where dark matter is particularly concentrated, like in the galactic center, in dwarf spheroidal satellite galaxies, intermediate mass black holes and cluster of galaxies. Since the beginning of operations in 2004, MAGIC has searched for dark matter signals spending hundreds of hours of observations of different targets, and thus producing several high-impact results. Those include the most constraining limits to the WIMP annihilation cross-section for particle masses above few hundred GeV, from observations of dwarf spheroidal satellite galaxies. A combined analysis of MAGIC and Fermi-LAT observations of dwarf spheroidal satellite galaxies has been carried on, obtaining limits for dark matter particle masses between 10 GeV and 100 TeV - the widest mass range ever explored by a single gamma-ray analysis - and improving the previously published Fermi-LAT and MAGIC results by up to a factor of two at certain masses. Since clusters of galaxies are the largest known gravitationally bound structures in the Universe, with masses around 1015 M⊙, most of it in the form of dark matter, they have been also part of the dark matter searches with MAGIC. A deep survey of the Perseus cluster of galaxies has been conducted using almost 400 h of data recorded between 2009 and 2017. This was the deepest observational campaign so far on a cluster of galaxies in the very high energy range, and lead to the conclusion that dark matter particles have a decay lifetime longer than ∼1026s in all considered channels. This result represent the strongest limits on decaying dark matter particles from ground-based gamma-ray instruments.

Credits: Marie-Lou Gendron-Marsolais (Université de Montréal), Julie Hlavacek-Larrondo (Université de Montréal), Maxime Pivin Lapointe

LORENTZ INVARIANCE VIOLATION

Many quantum gravity theories predict a spontaneous breaking of Lorentz symmetry at energies on the order of the Planck energy or lower: this implies non-trivial dispersion relations for the photon in vacuum. As a consequence, gamma-rays of different energies, emitted simultaneously from astrophysical sources, could accumulate measurable differences in their time of flight until they reach the Earth. Such tests could be carried out in using fast variations of gamma-ray flux from pulsars, and also from active galactic nuclei (possibly at high redshifts) and gamma-ray bursts. MAGIC is studying this delicate topic on different sets of data: recently a study on constraining Lorentz Invariance Violation using the Crab pulsar emission in VHE has been published: a test on LIV has been performed involving an additional linear or quadratic dispersion relation term with energy for photons. No significant correlation between arrival time and energy of the pulsar photons has been observed, and upper limits on the linear and quadratic energy scale of LIV have been derived. This result brings back pulsars to the class of astrophysical objects that are useful (and competitive) to investigate time of flight differences of energetic photons.

Credits: NASA, ESA, G. Dubner (IAFE, CONICET-University of Buenos Aires) et al.; A. Loll et al.; T. Temim et al.; F. Seward et al.; VLA/NRAO/AUI/NSF; Chandra/CXC; Spitzer/JPL-Caltech; XMM-Newton/ESA; and Hubble/STScI.

TAU NEUTRINO HUNT: MAGIC AS A NEUTRINO DETECTOR

The recent discovery of an astrophysical flux of high-energy neutrinos by IceCube was a major step forward in the ongoing search for the origin of cosmic rays, since neutrino emission needs to be produced by hadronic interactions in astrophysical accelerators.The detection of tau neutrinos in particular is very important from both the astrophysical and particle physics point of view. It would give new information about the astrophysical tau neutrino flux, shed light on the emission mechanisms at the source, test the fundamental properties of neutrinos over extremely long baselines, and better constrain new physics models which predict significant deviations from equal fractions of all neutrino flavors. The MAGIC telescopes can point towards the horizon or a few degrees below across an azimuthal range of about 80 degrees. In this special configuration they can point directly to the sea, allowing the search for air showers induced by tau leptons arising from interactions of tau neutrinos in the Earth crust or the surrounding ocean. In a recent paper we show how such air showers can be discriminated from the background of very inclined hadronic showers by using Monte Carlo simulations. Taking into account the orography of the site, the point source acceptance and the event rates expected have been calculated for a sample of generic neutrino fluxes from photo-hadronic interactions in AGNs. With the recent discovery of broadband emission simultaneously with a neutrino event, the multimessenger era of astrophysics has begun and the MAGIC telescopes want to catch also one of the new messengers!

Credits: Lori Jones, for a lesson on Fundamental Particles at study.com