QCD: hadron structure and formation
Quarks and gluons are the fundamental constituents of nucleons (protons and neutrons). However, even now — after 50 years of Quantum Chromodynamics (QCD) — many questions about them remain. How are they distributed? How do they form hadrons? How much and in which way do they contribute to one of the most basic properties of nature, the nucleon spin?
Our group aims at answering these and other fundamental questions, in our quest for understanding the internal structure of nucleons, which, together with electrons, are the most important building blocks of ordinary matter.
The internal structure of hadrons is parameterized in terms of several multi-dimensional parton distributions, as transverse-momentum distributions (TMDs) or Wigner distributions. All of those encode different aspects of hadrons, correlations between the momenta and spins of the considered quark or gluon and its parent hadron.
At the same time, there are analogue functions that encode the hadronization process of quarks and gluons.
However, for now, we only have a fairly good picture in one dimension, since the multi-scale processes needed to access these multi-dimensional functions are very challenging from both the theoretical and phenomenological point of view, as well as from the experimental side.
Our group develops new tools to extract information from experiments at e.g. CERN, JLab, BNL or KEK, and future planned ones like the fixed-target experiments at CERN or the future Electron-Ion Collider in the United States.
Complementary frontiers in neutrino and dark matter physics
Neutrinos have weak interactions and, in the Standard Model of particle physics, zero mass. This makes them a clean probe of novel physics — them having a mass is the only uncontested laboratory evidence for the existence of new interactions. It also means they have a huge penetrating power and a very long lifetime, making them a clean probe of astrophysical and cosmological environments, where they are abundantly produced.
Despite the ubiquity of neutrinos, we are just beginning to fully understand their properties. In our group, we study laboratory data, together with astrophysical and cosmological observations, to pin down neutrino properties. The rapidly improving precision of astrophysics, cosmology, and laboratory experiments is thus an opportunity. It is also a liability, as interpreting observations depends more strongly on unknown physics that must be determined elsewhere. Hence, we also study the dependence of other inferences on unknown neutrino properties.
These same tools also allow us to use neutrinos as probes of other particle physics, astrophysics, and cosmology.
Similarly, the nature of dark matter is among the most pressing questions in fundamental physics. Its existence has been confirmed by several independent observations, yet we do not know its fundamental nature nor how it was produced after the Big Bang. In our group, we study how the properties of small-scale astrophysical structures (as small as 50 light-years) inform us on the properties of dark matter. At the same time, we study how these systems may be a window to understand open problems in astrophysics such as galaxy formation or reionization.
Our research links to current and future experiments such as Super-Kamiokande, JUNO, DUNE, IceCube, Planck, DES, DESI, or the Rubin Observatory. We extract new information from existing data, and we study the reach of future experiments.