Charla de Jordi Miralda

QCD axions as dark matter and their potential detection by gravitational microlensing

Jordi Miralda Escudé es ICREA Professor of Astrophysics Institut de Ciències del Cosmos

Abstract:The most distant single stars we have observed are in cases of extreme gravitational lensing magnification, when the source star crosses a lensing caustic of a cluster of galaxies that is affected by microlensing. This has enabled detections of stars at redshifts above unity with HST, and now with JWST to even fainter levels. If dark matter is smoothly distributed, microlensing should be caused only by intracluster stars, with rates and lightcurves of caustic crossings that have precise statistical predictions. Deviations from the shapes and other characteristics of these lightcurves are then a powerful probe to small-scale granularity in the dark matter, which is unavailable through other astronomical observations. In particular, if the QCD axion is present in the dark matter, minihalos predicted to have formed around the epoch of equalization can affect the lightcurves of stars that are supermagnified when crossing microlensing caustics.

Viernes 29 de septiembre, 12 horas, seminario de Física Nuclear . Online

Charla de Farida Fassi «Searches for New Physics at the LHC using challenging signatures with the ATLAS detector»

Lecturer:  Farida Fassi, Mohammed V University in Rabat, Faculty of Sciences. Morocco

Abstract: The Large Hadron Collider (LHC) at CERN, the largest and most complex machine ever built will extend the frontiers of particle physics with its unprecedented high energy and luminosity. The ATLAS experiment is the largest particle detector at LHC, targets to detect the tiny subatomic particles and study the fundamental constituents of matter to better understand the rules behind their interactions. The ATLAS experiment at the LHC has a broad search program covering a wide variety of models of physics beyond the Standard Model (BSM). Various BSM theories predict unique signatures that are difficult to reconstruct and for which estimating the background rate is also a challenge. With the large amount of data gathered by the Run-2 of the LHC, the production of four top quarks (𝒕𝒕 𝒕𝒕 ) has become a very interesting probe of the Standard Model (SM) and beyond. In the SM of particle physics, 𝒕𝒕 𝒕𝒕 production is an extremely rare process with a cross section of approximately 12 fb. In extensions of the SM with top-philic new states, the four-top production rate can be enhanced considerably. Highlights from recent new physics searches with the ATLAS detector at the CERN LHC will be presented. They include searches for the SM 𝒕𝒕 𝒕𝒕 and BSM 𝒕𝒕 𝒕𝒕 , among others. Results are based on analysis of proton-proton collision data recorded at a centre-of-mass energy of 13 TeV.

Viernes  28 abril, 10:30 horas, Seminario de Física Nuclear

Charla Pr. Farida Fassi ATLAS

Charla Antoine Kouchner «High Energy Neutrino Astronomy from the Deep Sea»

Antoine Kouchner ,  Laboratoire Astroparticule et Cosmologie (APC) Paris, is the ANTARES experiment spokesperson

Abstract: Messengers of the infinitely small, neutrinos provide us with valuable insights into the fundamental laws of physics. Messengers of the infinitely large, traveling on cosmological distances, they are privileged probes of cataclysmic astrophysical phenomena.

Neutrino Telescopes, buried deep in the sea/lake/ice are trying to meet this double challenge. These detectors consist of a 3D matrix of photomultipliers that detect the Cherenkov light inferred by the displacement of charged particles produced when neutrinos interact inside or around the detector.

After a brief historical introduction, I will review the latest results from the first generation deep-sea neutrino telescope ANTARES and the expectations and status of the next generation detector KM3NeT, both immersed in the Mediterranean Sea. In this context, synergies with Earth and Sea sciences will be mentioned.

Some emphasis will be placed on the potential of neutrino telescopes for the determination of the neutrino mass ordering through oscillation studies of atmospheric neutrinos in the GeV range (KM3NeT/ORCA) in the Mediterranean Sea.

Miércoles 26 abril, 12:10 horas, Seminario de Física Nuclear

 

Charla de Andrés del Pino Molina «Gaia’s revolution: An open window to our Galaxy and its surroundings»

© ESA

Lecturer: Andrés del Pino Molina. Centro de Estudios de Física del Cosmos de Aragón (CEFCA). Astrophysics researcher with a strong computational and statistic background. Interested in resolved stellar populations, galaxies dynamics, and star formation

Abstract: The Milky Way system (MW) harbors dozens of known dwarf galaxies. Some of these systems have been studied for decades, offering us a glimpse on how diverse dwarfs can be in terms of their star formation histories, chemical composition, masses, etc. This has raised questions about the origin of these systems and on the possible mechanisms involved in their evolution. From the dynamical standpoint, some of the most obvious mechanisms proposed invoke the interaction of dwarfs with their massive host galaxy. However, based mostly on N-Body predictions and just line-of-sight velocity measurements, the discussion about the strength and efficiency of these mechanisms have remained largely speculative. Thanks to its unprecedented astrometric precision, the Gaia mission has changed that, giving us access to accurate 3D systemic motions of many known dwarfs satellites of the MW. For the first time, we can study the orbital histories of the MW satellites, which can shed light on the nature versus nurture discussion for these systems. In this talk, I will present a general overview on how the internal properties of  dwarfs are linked to their orbital history and on how the interaction with the MW has shaped them into the system we observe today.

Jueves 30 marzo, 12 horas

On line ( Zoom)

 

Charla de G. Raffelt: «Stars as Particle-Physics Laboratories: Old Ideas and New Developments»

Georg G. Raffelt, Max-Planck-Institut für Physik. His research is in the areas of theoretical astroparticle physics and cosmology. In particular, it revolves around weakly interacting particles (neutrinos, the hypothetical axion, or weakly interacting dark matter candidates), their role in astrophysics and cosmology.

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Charla de Miguel A. Pérez Torres: «SKA: the mother of all radio telescopes»

SKA

Miguel Á. Pérez Torres, research scientist at the Instituto de Astrofísica de Andalucía (IAA-CSIC, Granada, Spain) and collaborator of the DFTUZ

Abstract The Square Kilometre Array (SKA) project is an international effort to build the world’s largest radio telescope. The SKA is expected to conduct transformational science to improve our understanding of the Universe and the laws of fundamental physics, monitoring the sky in unprecedented detail and mapping it many times faster than any current facility.
The SKA  will not be a single telescope, but a collection of telescopes spread over long distances in the Southern Hemisphere. In this talk, I will give an overview of the SKA project and its science goals, which range from the cradle of life in exoplanets up to shedding light on the Epoch of Reionization and the Dark Ages of the Universe.

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Charla de Tomislav Terzić : «Measuring Lorentz invariance violation with Cherenkov telescopes – from observations to setting constraints»

Cherenkov telescopes are instruments optimized for detection of very high energy (VHE, E > 100 GeV) gamma rays from astrophysics sources. They play a crucial role in testing possible consequences of Quantum Gravity (QG), such as violation or deformation of Lorentz symmetry. In both cases, the photon dispersion relation is modified, making the photon group velocity energy dependent, and possibly modifying kinematics and dynamics of electromagnetic interactions. These tiny effects are vastly below the sensitivity of present-day laboratories. However, if real, they could be measured using VHE gamma rays of astrophysical origin. Cosmological distances that they cross serve as a natural amplifier for the QG effects. While no deviations from the special relativistic predictions have been detected, strong constraints have been set on modified photon dispersion relations.
In this session we will explain the process of testing implications of modified photon dispersion relations on VHE gamma rays using Cherenkov telescopes. We will cover different stages from observations, Cherenkov telescopes’ data analysis, statistical methods employed, and finally setting constraints on the QG energy scale.

Jueves 12 mayo, 12 horas, seminario de Física Nuclear, on-line  (Google Meet)

Cartel

Charla de Diego Blas: «Soundscape of gravitational waves: a new tool to access the fundamental blocks of the Universe»

Diego Blas is a researcher at UAB (Universidad Autónoma de Barcelona) and IFAE (Instituto de Física de Altas Energías). His research interests are in theoretical physics, gravitation and cosmology.

Abstract: In this talk, current and future efforts to detect gravitational waves from Earth and space observatories will be reviewed. Diego will also emphasise the physical consequences of these searchers, in particular regarding fundamental physics (primordial cosmology, dark matter, modified gravity…)

Viernes 6 mayo, 12 horas, seminario de Física Nuclear. On-line (Google-meet)

Charla de Diego Blas (cartel)

 

Charla de Carlos López Sanjuan: La evolución espectral de enanas blancas con J-PLUS

J-PLUS

Dr. Carlos López Sanjuan is a researcher at CEFCA (Centro de Estudios de Física del Cosmos de Aragón).

Abstract: White dwarfs are the degenerate compact remnants of stars with masses below 8 Msun. They do not have an internal source of energy and just cool down with time. In addition, they show a diversity of atmospheric compositions in their spectra, with sources presenting hydrogen (H) lines (DA type), helium (He) lines (DO and DB type), metal lines (DZ type), and featureless spectra (DC type) among others. In this seminar we present our recent work about the spectral evolution of white dwarfs with effective temperature (i.e., their age) using the Javalambre Photometric Local Universe Survey (J-PLUS). We analysed 5926 white dwarfs with r <= 19.5 mag in common between the white dwarf catalogue presented in Gentile Fusillo et al. 2021, defined from Gaia EDR3, and J-PLUS DR2. We estimated their effective temperature (Teff), surface gravity, parallax, and spectral type; and the probability of having a H-dominated atmosphere (p_H) for each source. Our analysis yields a 21 +- 3% increase in the fraction of He-dominated white dwarfs from Teff = 20000 K to  Teff = 5000 K.

Horario: 12:00, del jueves 10 de marzo, en el seminario de Física Nuclear. On-line

 

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