Speaker: Pizzone R.G.

Dipartimento di Metodologie Chimiche e Fisiche per l'Ingegneria, Catania 
Laboratori Nazionali del Sud, Catania 


"Li, Be and B destruction in astrophysical environments:
 indirect cross section measurements" 


Big efforts have been devoted in the last years to the study
of light elements abundance. Definitively their importance
is strongly related to cosmology as well as to stellar evolution.
In fact from Li, Be, B abundance hints on the primordial nucleosynthesis
can be achieved, and they play a crucial role for testing and 
understanding the stellar structure models. These isotopes are mainly
destructed by proton capture; thus proton induced reaction cross-section
on Li, Be and B are a major input for studying several astrophysical 
scenarios. One of the main difficulties in the experimental nuclear 
astrophysics field is that cross sections must be measured at thermal 
energies, much smaller than Coulomb barrier. Therefore such small cross
sections (generally of the order of nanobarn or picobarn) cannot be easily
measured and many advanced experimental efforts have been proposed. 
Moreover the presence of the electron screening effect in laboratory measures
requires extrapolations. In order to by-pass these difficulties, many 
indirect methods have been developed; among them the Trojan Horse Method
has shown to be particularly suitable to the study of charged particle
induced reactions. This experimental method has been widely applied by the 
ASFIN collaboration at LNS Catania. Recent measurements of 6 Li(p;a0) 3He,
7 Li(p; a) 4 He, 9 Be(p;a) 6 Li, 11 B(p; ao ) 8 Be will be discussed 
in details and compared with data available from direct measurements 
compilations. Future developments and experiments will also be examined
in details.