Speaker
Description
The experimental setup and results of the first search for invisible decays of ortho-positronium (o-Ps) confined in a vacuum cavity are reported. No evidence of invisible decays at a level $\text{Br}\left(\text{o-Ps}\to\text{invisible}\right) < 5.9\cdot10^{-4}$ (90 % C. L.) was found. This decay channel is predicted in Hidden Sector models such as the Mirror Matter (MM), which could be a candidate for Dark Matter. Analyzed within the MM context, this result provides an upper limit on the kinetic mixing strength between ordinary and mirror photons of $\varepsilon < 3.1\cdot10^{-7}$ (90 % C. L.). This limit was obtained for the first time in vacuum free of systematic effects due to collisions with matter. An upgraded confinement cavity and an improvement to the triggering system are also presented, which will improve the sensitivity to $\varepsilon\simeq10^{-9}$.This is more than one order of magnitude below the current Big Bang Nucleosynthesis limit and in a region of parameter space of great theoretical and
phenomenological interest.
The experimental setup will also allow us to measure the o-Ps decay rate. Currently, the experimental uncertainty of the o-Ps decay rate is at 140 ppm precision; this exceeds the theoretical accuracy (1 ppm level) by two orders of magnitude. We propose a method that relies on the o-Ps confinement cavity and the granularity of the surrounding calorimeter to subtract the time dependent pick-off annihilation rate of the fast backscattered positronium from the o-Ps decay rate prior to fitting the distribution. Therefore, this measurement will be free from the systematic errors present in the previous experiments and thus could reach the ultimate accuracy of a few ppm level to confirm or confront directly the higher order QED corrections.
| Affiliation | IPA, ETHZ |
|---|---|
| Academic position | Post doc |
| Email address | carlosv@phys.ethz.ch |
