The group is leading an experiment at Jefferson Lab’s Hall D to measure the electromagnetic polarizability of the charged pion using the Primakoff reaction gamma Nucleus -> pi+ pi- Nucleus . The diagram below illustrates the general principle of the experiment. At very low momentum transfer to the recoil nucleus, the incident photon interacts with a photon from the nuclear Coulomb field. In this low momentum transfer limit, the production amplitude is related through known kinematic factors to the amplitude for gamma gamma -> pi+ pi- . In this process two photons collide to create two charged pions. The gamma gamma -> pi+ pi- amplitude is related to the pion Compton scattering amplitude by “crossing symmetry”, which is a formal technique from quantum mechanics. Sensitivity to the electromagnetic polarizability of the charged pion is obtained from the Compton scattering amplitude.
To learn more about what an electromagnetic polarizability is, especially for an elementary particle, go the web page for the Spin-polarizability Experiment at Mainz.
- Jefferson Lab proposal: can be found here here.
- Website for the JLab CPP experiment: Lots of useful information on the experiment and conference talks are posted here.
- Principles of Operation of Multiwire Proportional and Drift Chambers, Sauli. This is an old but very useful paper describing the physics principles of multi-wire proportional counters and drift chambers.
- Particle Detection with Drift Chambers , Blum and Rolandi. Also a very useful text, although more detailed and advanced than the Sauli paper, more at a graduate student and postdoc level.
- Reference guide on stringing the large MWPC’s.
- MWPC Gas Gain Studies by Mike Roberts
- Report on preparing the carbon tubes for stringing.
- Reference guide on CPPsim by Nick Miller.
Undergraduate Honors Thesis’s:
Developing Methods for Measuring the Pion Polarizability