VerSi · Signatures of cosmic rays and new fundamental particles in the Very high energy sky

Signatures of cosmic rays and new fundamental particles in the Very high energy sky

The purpose of my research is to uncover the properties of cosmic rays and new fundamental particles by exploiting their Signatures in Very high energy radiations. The most fascinating open questions in our understanding of Nature, such as dark matter or the strong Charge-Parity (CP) problem suggest the presence of fundamental interactions Beyond the Standard Model of particle physics (BSM), and could be the next cosmic-ray-driven discovery. For example, the leading hypothesis is that dark matter is made of new particles, among which Weakly Interacting Massive Particles (WIMPs) are the most prominent candidates. New light particles, such as the axion and axion-like particles (ALPs) are often predicted in BSM theories solving e.g. the CP problem and, by interacting with photons, can leave an imprint on the spectra of cosmic accelerators. After acceleration, cosmic radiation propagates in the interstellar environment, bringing messages of its properties, including the presence or absence of BSM phenomena. Recently, tantalising anomalies have thrilled the community as potential hints for new physics phenomena. My project objective is to shed new light on them by exploiting current and forthcoming observations of the very high energy sky with innovative techniques. A long-standing excess of gamma-rays at GeV energies is measured towards the Galactic Center (GCE) with data from the Large Area Telescope (LAT) onboard the Fermi satellite, and could be the very first signature of particle dark matter in our Galaxy. Cosmic ray accelerators, such as millisecond pulsars (MSPs) could also explain the signal, but numerous modeling uncertainties prevent us from firmly assessing their contribution to the excess. MSPs are rapidly rotating neutron stars in which the period is decreased to milliseconds, and could accelerate particles up to TeV energies, producing high energy photons. In addition, an excess of positrons with respect to the flux produced by spallation of cosmic hadrons has been established with PAMELA and AMS-02 data. Although this could be explained by dark matter, recent multi-wavelength observations of halos of GeV-TeV photons around Galactic pulsars demonstrated that these objects could indeed be accelerators of cosmic positrons, producing halos of photon emissions when positrons interact with the interstellar medium. Finally, by inspecting the gamma-ray spectrum of various Galactic sources, hints for a modulation coming from photon-ALPs interactions have been found that are in tension with other, independent bounds. From one side, my project objective is to discover and characterise the multiwavelength emission around Galactic cosmic ray accelerators such as pulsars and MSPs using photons recorded at different wavelengths, and to build comprehensive, phenomenological modelling to tailor their searches in observational data. From the other side, we aim at investigating the properties of possible new fundamental particles by exploiting observations of very high-energy photons, and to robustly characterize the backgrounds for these searches.

Data: CORDIS, © European Union