Signatures of hidden particles in strong external fields

• Applicant: Professor Dr. Carsten Müller
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2014 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 258838303

With the availability of high-intensity laser pulses and other sources of strong electromagnetic fields, novel bridges currently emerge from optics and atomic physics to other branches of contemporary physics. As a striking example, we shall explore in this project how high-precision polarimetric and spectroscopic techniques, in combination with the aforementioned strong field sources, can be utilized to probe the existence of theoretically predicted, but hitherto unobserved, very weakly interacting particles with low masses. Among them are so-called axions, paraphotons and minicharges which have been put forward as central keys for solving fundamental open questions in nuclear and particles physics.Considerable experimental efforts to search for these hidden particles are being carried out worldwide. While none of them has been detected so far, constraints on the allowed range of particle parameters (such as mass and charge) have been imposed. It is the task of theory to support these searches by developing advanced schemes where signatures of these hypothetical particles might be easier to observe. The present theoretical project aims to contribute to this endeavour by exploring various plausible effects which the existence of such hidden light particles would induce. In particular, nonlinear quantum corrections to Maxwell's theory shall be studied, leading to modifications of the optical properties of the physical vacuum in the presence of a strong (laser) field. Also tiny shifts of the electronic energy levels in atoms subject to an external magnetic field will be evaluated. A diversity of theoretical techniques is planned to be used, including effective actions, standard perturbation theory, the vacuum polarization tensor and the optical theorem.The general goal of our study is to significantly improve the attainable upper limits on the hidden particle parameters as compared with the most stringent constraints established by current laboratory-based searches. This way, the potential for discovery (or exclusion) of novel fundamental particles by corresponding experiments will be enhanced substantially, rendering nonlinear optics and atomic physics in strong external fields a complementary low-energy route to unravel the basic building blocks of matter in our universe.

• DFG Programme: Research Grants