Research subjects [2025]:
Most of my current research focuses on the description of gluons in high energy processes at particle collider, in particular on the simultaneous description of processes
in proton-proton collision at the Large Hadron Collider (LHC) at CERN and in electron-proton collisions at the Electron-Ion Collider (EIC) to be constructed at BNL (Long Island, NY).
Gluons are the force carriers of the strong interaction, which is one of the four fundamental forces of Nature. The microscopic theory of the strong interaction is the
quantum theory of quarks and gluons, called Quantum Chromodynamics (QCD). The distribution of gluons inside protons cannot be calculated, although there is lots of progress
using large computer simulations over the recent years. Following an idea by Richard Feynman one can describe the gluons inside protons by a function that can be extracted (fitted)
from experimental data from particle colliders. Feynman considered simple one-dimensional functions, but nowadays we study 3 or even 5 dimensional functions. With such distributions
one can address questions about the gluonic/mass radius of the proton or the pressure distribution of the proton. My own objective is to investigate whether a common gluonic
description of completely different classes of processes (exclusive, diffractive, and semi-inclusive) can be obtained. Until very recently these processes were studied by separate
communities and discussed at separate conferences, but now we start to uncover the aspects that they have in common and relate results that were always thought to be unconnected.
One of the best probes of gluon distributions are quarkonia. These are bound states of a heavy quark and antiquark, where the heavy quarks are charm or bottom quarks. The problem is
that the quarkonium production process itself is not fully understood yet. There is not a single study that can describe all available data well simultaneously. My objective is to
suggest ways to resolve this problem by combining specific studies at the LHC and the future EIC. This can best be done in combination with the study of gluon distributions, so hopefully
we can tackle these objectives simultaneously.
Besides these phenomenological research topics (theoretical studies directly related to experiments), I am also exploring physics beyond the Standard Model (SM) of elementary particles.
So far we have no experimental indications from the LHC for the existence of such new physics, but there are theoretical and astrophysical reasons to believe that our Standard Model is
not all there is, but is only an effective field theory that holds true at low energies. My objective is to use general guiding principles such as the amount of symmetry (the higher
the better) and naturalness (the less fine-tuning the better) to find a viable beyond the SM theory. It is easy to write down theories beyond the SM, but it turns out to be very
hard to find highly symmetric theories that naturally, i.e. without fine-tuning, lead to the Standard Model at low energies and satisfy the extremely stringent experimental
constraints on any new physics. Also, the objective is to keep the amount of (heavy) new particles that it will lead to to a minimum and it should offer explanations for several
features of the SM that seem accidental (the mixing patterns in the quark and the lepton sector, the mass values and hierarchies, the approximate global symmetries). All these
beg an explanation but it is very hard to find a simple and satisfactory one, while it is less hard to find far-fetched ones. The difficulty of finding a natural extension of the SM
could be viewed as "The fine-tuning problem of physics beyond the Standard Model".