Research profile dr. J.G. (Johan) Messchendorp

Research expertise and interest:

1.   Dynamics of color confinement (quarks, gluons), the formation of hadronic matter, and the origin of mass;

2.   Experimental searches for exotic forms of hadronic matter, in particular gluon-rich sub-atomic particles (glueballs, hybrids, etc.);

3.   Dynamics of few-nucleon systems and their relation to fundamental forces;

4.   “Needle-in-a-haystack” searches deploying data reduction techniques for complex (multi parameter) and large datasets;

5.   “In-situ” data processing algorithms for online event selection/data reduction.

Research mission

My research interests can be summarized in developing instruments and providing experimental data and methods that potentially make a break-through in our present understanding of the strong interaction. This interaction is responsible for the binding of quarks forming the building blocks of sub-atomic matter, such as protons, neutrons, and nuclei. As far as we presently understand, it is governed by the theory of Quantum Chromo Dynamics (QCD), a theory that is based on color-SU(3), one of the fundamental symmetries in nature. QCD is well understood at short-distance (high-energy) scales, much shorter than the size of a proton. In this regime, QCD can be accurately treated by using perturbative methods. Spectacular effects occur when the distance among quarks becomes comparable to the size of the proton. Under these conditions, in the regime of non-perturbative strong QCD, the force among the quarks becomes so strong that they cannot be further separated (color confinement). As a consequence of the strong coupling, we observe the relatively large mass of protons and neutrons, which is two orders of magnitude larger than the sum of the masses of the individual constituent quarks. This quantitatively yet-unexplained behavior is related to the self-interaction of gluons leading to the formation of gluonic flux tubes connecting the quarks. The nature of gluons also gives rise to the formation of exotic hadronic matter. In particular, the existence of so-called glueballs, hadrons that are purely made from strongly interacting massless gluons, has been predicted by QCD, and its discovery would be a major break-through in our understanding of color confinement and the origin of the mass of visible matter. My interest is to provide a better understanding of the strong interaction in the non-perturbative energy regime by planning, conducting and analyzing the results of precision experiments and, thereby, to search for exotic hadronic matter which is predicted, but so-far has not been observed unambiguously. These activities are embedded in the nuclear and hadron physics group at KVI-CART with as research theme “matter at extremes”.

Matter-antimatter annihilations with BESIII and PANDA

Exotic hadrons can be produced by the annihilation of matter with antimatter at various international particle accelerator facilities. My research activities are focused towards two complementary approaches, outlined below.

At BESIII in Beijing, China, intense beams of electrons and positrons are colliding at an energy regime of about 3-5 times the mass of the proton, thereby, forming a clean probe of the so-called vector meson states, primarily consisting of charm quarks. The decay products of these unstable mesons are registered using a large-scale detector composed of a massive number of sensors with a large variety in order to achieve enough sensitivity to identify the type of decay and to measure its production vertex, energy and momentum. The information of these sensors is analyzed offline to search for specific correlations that would allow to reconstruct the complete reaction topology of each electron-positron annihilation. Decay rates are measured and new forms of hadronic matter are identified via a multi-parameter statistical analysis. I have been active in the BESIII collaboration since 2009 and contributed to the discovery of a new class of four-quark states. The discovery is a major milestone in this field of research and has rigorously demonstrated the existence of unconventional hadrons as predicted by QCD.

PANDA will be the next generation experiment that will be sensitive to gluon-rich exotic matter. This experiment will take place in the near future at the FAIR facility near Frankfurt, Germany, and will be driven by the annihilation of a cooled beam of antiprotons with a proton target at an interaction rate that will be a new record in the field, and by developing a versatile detector with a significantly larger granularity than BESIII to cope with high rates. In contrast to the relatively clean, background free, BESIII environment, the challenge for PANDA lies in the online reduction of the huge yield of background events by three orders of magnitude to obtain data-transfer rates to storage devices that are manageable offline. For this, smart algorithms acting real-time and capable of reconstructing the full event topology on massively-parallel architectures are needed to separate background from signal candidate events.

The big data challenge in exotic matter searches

The complexity of sensors and data streams in my field of research has drastically increased in the last decade and has meanwhile reached its limits with the presently available technology for the future experiments in terms of scalability. A new paradigm is required which gives a window of opportunities in scientific computing. The key lies in searching for alternative methodologies for online pattern recognition. The development of intelligent algorithms with high throughput and reliability has become a new aspect in my research portfolio that would eventually enable me to search for exotic matter with the future PANDA experiment.

The technological developments for online computing which our group has taken up are concentrated around a few detector components of PANDA, namely the electromagnetic calorimeter, primarily used for the reconstruction of photons, and the straw-tube tracker, responsible for the momentum reconstruction of charged particles through a solenoid magnetic field. These detectors will play a decisive role in the online event selection and are, thereby, opportune as pilot cases. Our group has a leading role within the PANDA collaboration in the development of feature extraction algorithms for the calorimeter. Moreover, a collaboration with JBI has been established with the aim to exploit morphological geometry-based techniques for track reconstruction as a fast and scalable alternative to the available offline methods. These activities are an important seed within the “scalable computing” pioneer activities of DSSC and, thereby, form an ideal basis for further cross-fertilization with other communities within the consortium as well.

Websites:
Group website: http://www.rug.nl/kvi-cart/research/hnp/
Employee (corporate homepage): http://www.rug.nl/staff/j.g.messchendorp/