JNDI Name of UserTransaction?

[Joerg Friede]

Hi,

in my EJB, i'm trying to lookup a UserTransaction object through JNDI using
ctx.lookup("java:comp/UserTransaction");

which does not work. I also tried several other names which did not work 
either.

Can somenone tell me, how to obtain the Usertransaction (JNDI-Name, 
other setup required?) through JNDI in Geronimo 1.1?

Thanks in advance, Joerg Friede