So... i've got the solution!
I'm trying to help you with my so poor english ^^
first you have to create a new 'usergroup' in joomla, call him for example : authorsarticles.
You must use 'public' group as a parent for him.
2) Go to 'Users' => 'acces level' => edit the 'special' level => add the new group 'authorsarticles' this level. (chek box)
3) go to 'website or site' (top left) => configuration => TAB 'rights' clic on the group 'authorsarticles'
check the box like the screen
4) Go to 'articles manager' => parameters => TAB 'rights'
check the box like the screen
5) Go to K2 'elements manager' and repeat the operation -> 4)
6) affect to a test member the 'authorsarticle' group
7) Connect you with this test member login... It's working!!!
I hope it's help you ;-)
This solution is give to me by SimonG moderator of the french joomla forum.