I found the solution.
#lvcreate -L size -n VM_NAME-disk xen-data
#lvcreate -L size -n VM_NAME-swap xen-data
Then a byte by byte copy
#dd if=/dev/mapper/vg-xen-original.foo.com--disk of=/dev/mapper-vg-xen-copy.foo.com--disk
#dd if=/dev/mapper/vg-xen-original.foo.com--swap of=/dev/mapper-vg-xen-copy.foo.com--swap
Et Voià !!!