Speaker
Alain Coc
(CSNSM,CNRS/IN2P3 and Universite Paris Sud)
Description
Primordial nucleosynthesis (BBN) has been used for the determination of
the baryonic density of the universe. It has now been superseded, for this
purpose, by the more precise determination provided by the analysis
of the CMB anisotropies by WMAP. Nevertheless, BBN is still very interesting
as when we look back into the history of the universe, this is the
last era for which, in principle, we know all the physics.
Deviation from BBN predictions can hence give hints on non-standard
Big Bang models.
It is thus important that nuclear reactions involved in BBN be known
with a good accuracy.
Two recent nuclear physics experiments have improved the reliability
of lithium calculated yields in standard big-bang nucleosynthesis.
The cross section for the 7Be(d,p)2alpha reaction has been directly
measured at BBN energies at Louvain-la-Neuve.
A coulomb break-up experiment has provided a better determination of
the D(alpha,gamma)6Li cross section over a wide energy range.
Nevertheless, the discrepancy between the primordial 7Li abundance
deduced from halo stars observations and BBN remains and the BBN
6Li production is still orders of magnitudes below the reported 6Li
observations in some halo stars.
Now that the baryonic density is accurately provided by the analysis
of the CMB anisotropies, BBN can be used to constrain non-standard
models: scalar-tensor theories of gravity for instance.
Author
Alain Coc
(CSNSM,CNRS/IN2P3 and Universite Paris Sud)
