Investigation of Compression Modes in Nuclei Far from Stability
The density of matter in a nucleus is extremely high: about 10000 billions more dense than gold, which in turn is 20 times more dense than water. In nature, only collapsed stars and black holes have a higher density. Nevertheless, it is possible to further compress nuclear matter: nuclei can be squeezed and elongated like a spring, of course in three dimensions. Oscillations that are created in this way are called compression modes of the nucleus. Their characteristics are closely related to the very nature of nuclear matter (expressed by its "equation of state") but also to the macroscopic phenomenon of the late stages of the evolution of a star, where density may reach those extraordinary values.
Information about the rate at which nuclear matter can be compressed is difficult to obtain. Experimentally, it can be determined by studying a particular class of collisions between nuclei, for which only a small momentum is transferred to a target nucleus. The response of the nucleus is then similar to that of an elastic medium, in which compression and expansion waves are established in so-called giant resonances.
We intend to study such compression modes in a large range of nuclei, in order to better constrain the present known value of the compressibility. Because some of those nuclei only exist for a very short time, we will optimise a cunning detection technique, which employs a modern version of the well-known particle-tracking detectors.