Speaker
Dr
Vassilis Spanos
(University of Patras)
Description
We will be discussing the scenario that the gravitino
is the lightest supersymmetric particle and the
long-lived next-to-lightest sparticle (NSP) is either the neutralino
or the stau. We calculate the dominant two- and three-body decays of both
neutralino and stau NSPs, and model the electromagnetic and hadronic decay
products using the PYTHIA event generator and a cascade equation.
If stau is the NSP, it can form bound states with
several nuclei. These bound states may affect the cosmological abundances of Li6 and
Li7 by enhancing nuclear rates that would otherwise be strongly
suppressed. We consider the effects of these enhanced rates on the final
abundances produced in Big-Bang nucleosynthesis (BBN), including
injections of both electromagnetic and hadronic energy during and after BBN.
Generically, the introduction of these bound states drives
light element abundances further from their observed values;
however, for small regions of parameter space bound state effects
can bring lithium abundances in particular in better accord
with observations.
We show that in regions where the stau is the NSP with a lifetime longer
than 10^3-10^4 sec, the abundances of Li6 and Li7 are far in excess of
those allowed by observations. For shorter lifetimes of order 1000 sec, we
comment on the possibility in minimal supersymmetric and supergravity
models that stau decays could reduce the \li7 abundance from standard BBN
values while at the same time enhancing the \li6 abundance.
Author
Dr
Vassilis Spanos
(University of Patras)
