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Register a new userA polarisation modulation scheme for measuring vacuum magnetic birefringence with static fields
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A novel polarisation modulation scheme for polarimeters based on Fabry-Perot cavities is presented. The application to the proposed HERA-X experiment aiming to measuring the magnetic birefringence of vacuum with the HERA superconducting magnets is discussed.
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We present the current status of the BMV experiment. Our apparatus is based on an up-to-date resonant optical cavity coupled to a transverse magnetic field. We detail our data acquisition and analysis procedure which takes into account the symmetry properties of the raw data with respect to the orientation of the magnetic field and the sign of the cavity birefringence. The measurement result of the vacuum magnetic linear birefringence k_mathrm{CM}$ presented in this paper was obtained with about 200 magnetic pulses and a maximum field of 6.5,T, giving a noise floor of about $8 times 10^{-21}$,T$^{-2}$ at $3sigma$ confidence level.
When exposed to intense electromagnetic fields, the quantum vacuum is expected to exhibit properties of a polarisable medium akin to a weakly nonlinear dielectric material. Various schemes have been proposed to measure such vacuum polarisation effects using a combination of high power lasers. Motivated by several planned experiments, we provide an overview of experimental signatures that have been suggested to confirm this prediction of quantum electrodynamics of real photon-photon scattering.
This paper describes the 25 year effort to measure vacuum magnetic birefringence and dichroism with the PVLAS experiment. The experiment went through two main phases: the first using a rotating superconducting magnet and the second using two rotating permanent magnets. The experiment was not able to reach the predicted value from QED. Nonetheless the experiment set the current best limits on vacuum magnetic birefringence and dichroism for a field of $B_{rm ext} = 2.5$ T, namely, $Delta n^{rm (PVLAS)} = (12pm17)times10^{-23}$ and $|Deltakappa|^{rm (PVLAS)} = (10pm28)times10^{-23}$. The uncertainty on $Delta n^{rm (PVLAS)}$ is about a factor 7 above the predicted value of $Delta n^{rm (QED)} = 2.5times10^{-23}$ @ 2.5 T.
We propose a novel technique that promises hope of being the first to directly detect a polarization in the quantum electrodynamic (QED) vacuum. The technique is based upon the use of ultra-short pulses of light circulating in low dispersion optical resonators. We show that the technique circumvents the need for large scale liquid helium cooled magnets, and more importantly avoids the experimental pitfalls that plague existing experiments that make use of these magnets. Likely improvements in the performance of optics and lasers would result in the ability to observe vacuum polarization in an experiment of only a few hours duration.
QED vacuum can be polarized and magnetized by an external electromagnetic field, therefore acting as a birefringent medium. This effect has not yet been measured. In this paper, after having recalled the main facts concerning Vacuum Magnetic Birefringence polarimetry detection method and the related noise sources, we detail our Monte Carlo simulation of a pulsed magnetic field data run. Our Monte Carlo results are optimized to match BMV experiment 2014 data. We show that our Monte Carlo approach can reproduce experimental results giving an important insight to the systematic effects limiting experiment sensitivity.
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