Heavy elements and chemical enrichment in globular clusters

High resolution (R greater than or similar to 40 000) and high SIN spectra have been acquired with UVES on the VLT-Kueyen (Paranal Observatory, ESO Chile) for several MS turnoff stars (V similar to 17 mag) and subgiants at the base of the RGB (V similar to 16 mag) in three globular clusters (NGC 6397: NGC 6752 and 47 Tuc/NGC 104) at different metallicities (respectively [Fe/H] similar or equal to -2.0: -1.5; -0.7). A sample of 25 field halo subdwarves has also been taken with equal resolution and higher SIN. These data have been used in the framework of the ESO-LP "Globular Cluster Ages, Distances and Metallicities" to determine the abundances of several heavy elements in these three clusters: Sr, Y, Ba, and Eu. These are the first abundance determinations of neutron-capture elements for such an extended sample of scarcely evolved stars. These values together with the [Ba/Eu] and [Sr/Ba] abundance ratios have been used to test the self-enrichment scenario. A comparison is done with field halo stars and other well known globular clusters in which heavy elements have already been measured in the past at least in bright giants (V similar to 11-12 mag). Our results show clearly that globular clusters have been uniformly enriched by r- and s-process syntheses, and that even if globular clusters present usually "abundance anomalies" for some of the light metals, most of them exhibit neutron-capture element abundance patterns that are very similar to those of field halo stars at similar metallicities.