Project lead: Arūnas Kučinskas

Team members: P. Bonifacio, E. Caffau, W. Chantereau, C. Charbonnel, V. Dobrovolskas, C. J. Hansen, J. Klevas, E. Kolomiecas, A. J. Korn, C. Lardo, A. Mucciarelli, N. Prantzos

Rationale: Current scenarios for the origin of multiple stellar populations (MPs) in globular clusters (GCs) require that stars with anomalous light element abundances (second population, 2P) were formed from material processed by first population (1P) polluter stars, diluted with the gas of proto- cluster composition. Unfortunately, the details of this dilution process, a key element in the understanding of MP formation, are still largely unknown. To fill in this gap, we will determine the dilution factor in globular cluster NGC 6752, by measuring the difference between Be abundance in the 1P and 2P red giant branch stars. Although difficult for spectroscopic studies in GC stars, Be is ideal "dilution-meter" because it is produced through cosmic ray spallation and it can be only destroyed in stars. Hence, combined with the newly determined abundances of other key light and heavy elements, the new data will help to put tighter constraints on the formation and early evolution of the GCs.