JOHAN BIJNENS Research Interests

My main interest is in theoretical hadronic and high-energy physics. This is the study of Quantum Chromo Dynamics at low energies and effects of the strong interaction in the study of rare decays, CP violation, mixings, determination of quark masses, etc. Hadronic physics thus straddles the boundary between nuclear and high-energy physics. In addition I am interested in other applications of nonperturbative methods.

• My publication list can be obtained from SPIRES.
• I am involved in various European collaborations: FLAVIAnet: Entering the high-precision era of flavour physics through the alliance of lattice simulations, effective field theories and experiment; I3HP: Study of Strongly Interacting Matter and HEP-EST:an EU funded graduate school in Lund.
• Chiral Perturbation Theory: A lot of my work is in doing higher order calculations in the low-energy effective field theory of quantum chromodynamics. This theory is known as Chiral Perturbation Theory.
• In precision experiments at low energies many processes involve hadrons directly or indirectly. In order to get the best constraints on the underlying standard model physics (or beyond), it is necessary that all strong interaction effects are calculated to a sufficient precision. My work involves several examples of this in various settings, often using Chiral Perturbation Theory.
• Various precision observables need to have hadronic effects calculated. These often go under the name of nonleptonic matrix-elements. This is important in weak decays, but also for the muon anomalous magnetic moment.

Some examples of my work, links lead to the SPIRES data base, from where one can go on to find the papers.

• The introduction of the electro-magnetic Penguin
• Work on Kaon decays and CP violation. In weak non-leptonic decays the interplay of weak and strong interactions can lead to enormous enhancement factors. If we do not understand these we should be very aware that our predictions for the rest are very uncertain. Our approach which combines Chiral perturbation theory, Models and QCD in a consistent fashion has had reasonable success in explaining Kaon decays to two-pions and neutral Kaon mixing. Some of the relevant papers here are
  • Neutral Kaon mixing and the solution to matching models-QCD running
  • Epsilon'/epsilon or direct CP violation
  • Neutral Kaon mixing with a better hadronic approximation
  • Some pitfalls in hadronic approximations
• Some work using QCD sum rules
  • Determining quark masses
  • Quark mass effects in Lightcone sum rules for formfactors
• One of the simplest strong interaction processes is pi-pi scattering. It has now been calculated at next-to-next-to-leading order in both two and three-flavour Chiral Perturbation Theory.
• We are working on improving the calculation of kaon semileptonic decays. This has two goals, improving the accuracy with which we now the down-strange mixing angle, which is a fundamental parameter in the standard model, and improving the precision on the parameters needed for pi-pi scattering. Examples of published results are
  • Kl4
  • Kl3 without and with isospin breaking
• A lot of work was done in extending Chiral Perturbation Theory to two-loop order and applying it to varoious processes of physical interest. This is described in the review.
• Experimental verification of anomalies at high precision. There will be future experiments both on pi,eta decays and photon-pi-pi-pi vertices. The quantitative corrections to the prediction from the anomaly need to be studied in more detail. I have been very involved in formulating Chiral Perturbation Theory needed for this, see the review and the NLO Lagrangian
• The hadronic light-by-light contribution to the muon anomalous magnetic moment. The first full analysisand more recent updates in 2001 and 2007.
• Work in Chiral Perturbation Theory relevant for connection with numerical lattice QCD in partially quenched QCD as well as finite volume. See my talk at LATTICE 2007 for more relevant results.

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This document was last modified Monday, 12-Jun-2023 08:32:14 CEST