Joint IPPP Durham/Cockcroft Institute/ICFA Workshop on Advanced QED methods for Future Accelerators

• Published in: Journal of physics. Conference series 2009-11, Vol.198 (1), p.011001
• Main Authors: Bailey, I R, Barber, D P, Chattopadhyay, S, Hartin, A, Heinzl, T, Hesselbach, S, Moortgat-Pick, G A
• Format: Article
• Language: English
• Subjects: Beams (radiation); CERN; Charge density; Collisions; Critical field (superconductivity); Depolarization; Electromagnetic fields; Experiments; Feynman diagrams; Field strength; High energy electrons; Large Hadron Collider; Luminosity; Particle accelerators; Particle physics; Physics; Polarization; Quantum electrodynamics; Simulation; Spin dynamics; Transition probabilities; Uncertainty; Workshops
• ISSN: 1742-6596; 1742-6588; 1742-6596
• DOI: 10.1088/1742-6596/198/1/011001

The joint IPPP Durham/Cockcroft Institute/ICFA workshop on advanced QED methods for future accelerators took place at the Cockcroft Institute in early March 2009. The motivation for the workshop was the need for a detailed consideration of the physics processes associated with beam–beam effects at the interaction points of future high-energy electron-positron colliders. There is a broad consensus within the particle physics community that the next international facility for experimental high-energy physics research beyond the Large Hadron Collider at CERN should be a high-luminosity electron–positron collider working at the TeV energy scale. One important feature of such a collider will be its ability to deliver polarised beams to the interaction point and to provide accurate measurements of the polarisation state during physics collisions. The physics collisions take place in very dense charge bunches in the presence of extremely strong electromagnetic fields of field strength of order of the Schwinger critical field strength of 4.4×1013 Gauss. These intense fields lead to depolarisation processes which need to be thoroughly understood in order to reduce uncertainty in the polarisation state at collision. To that end, this workshop reviewed the formalisms for describing radiative processes and the methods of calculation in the future strong-field environments. These calculations are based on the Furry picture of organising the interaction term of the Lagrangian. The means of deriving the transition probability of the most important of the beam–beam processes – Beamsstrahlung – was reviewed. The workshop was honoured by the presentations of one of the founders, V N Baier, of the Operator method – one means for performing these calculations. Other theoretical methods of performing calculations in the Furry picture, namely those due to A I Nikishov, V I Ritus et al, were reviewed and intense field quantum processes in fields of different form – namely those present in intense lasers – were also presented. Within the Furry picture the lowest order physics processes are represented by one vertex Feynman diagrams. Additionally, higher order processes in the Furry picture are thought to be important and are still not fully studied. The Advanced QED methods workshop also benefited greatly from reports on ongoing and planned experimental work on quantum processes in intense external fields. Some of the experiments reviewed were the NA43 and NA63 experiments using