From Quarks to Hadrons: Low and Intermediate Energy Regime

The module starts with the early, still quite simple experimental setups in order to study the nuclear force, in order to motivate the ongoing, often very elaborate research activities that aim to clarify the least known aspects of the strong force. Some key publications are discussed in detail, focusing on processes at intermediate energies which are governed by fundamental symmetries and a rich resonance spectrum. Of special interest is the chiral symmetry, which can be used for a systematic perturbation calculus , featuring high predictive power for the ongoing experimental studies. This approach allows for testing the quark substructure of matter complementary to deep-inelastic scattering.

The lecture is thematically structured in two parts. First, the beginnings of investigations of strongly interacting particles from the 1940s until the 1960s are highlighted, showing the confirmation and the limitations of the Yukawa theory of meson exchange as nuclear force. In the second part, the further development of such low-energy aspects from the 1980s on is studied, leading to chiral perturbation theory and its experimental testing.

After successful participation in the module, the students are able to:

• understand experiments with strongly interacting particles, allowing to take on responsible work within the usually larger groups
• explain the elementary interactions of protons, neutrons, pions and more strongly-interacting particles in detail
• perform cross-section estimates for planned experiments and in data analysis

Successful participation in a particle and quantum physics module (e.g. PH0016) is recommended but not obligatory. 

This module consists of a lecture and an exercise class.

In the thematically structured lecture the learning content is presented. With cross references between different topics the universal concepts in physics are shown. In scientific discussions the students are involved to stimulate their analytic-physics intellectual power. By frequent encouragement of feedback, the students are motivated to explore the line of thought themselves, and scientific argumentation is exercised.

In dedicated exercises, the understanding of the mathematical relations are deepened by using the program package "root", which is either only presented or offered to be reproduced on the student's laptops, upon interest. Important scientific developments are highlighted by a detailed study of original literature.

Presentation is provided in PDF, smartboard

• A.W. Thomas & W. Weise: The Structure of the Nucleon, esp. chapter 6 and 7, Wiley-VCH, (2001)
• B. Povh, K. Rith, C. Scholz & F. Zetsche: Particles and Nuclei: An Introduction to the Physical Concepts, Springer, (2006)
• F. Halzen, A.D. Martin: Quarks and Leptons: An Introductory Course in Modern Particle Physics, Wiley, (1984)

There will be an oral exam of 25 minutes duration. Therein the achievement of the competencies given in section learning outcome is tested exemplarily at least to the given cognition level using comprehension questions and sample calculations.

For example an assignment in the exam might be:

• How the first vector meson resonance was discovered?
• Which properties govern the low-energy cross sections of nucleon-nucleon and meson-nucleon scattering, respectively?
• Which quasi-static properties of the hadrons point to their quark-gluon substructure?
• How is pion-pion low-energy scattering calculable and experimentally accessible, what are the relevant symmetry considerations here?

Participation in the exercise classes is strongly recommended since the exercises prepare for the problems of the exam and rehearse the specific competencies.