Vim search pattern 'foo' but skip lines containing 'bar' without deleting any line

I want to use search and highlight in vim using pattern match. My first search criteria is to look for a string foo in a line. My second search criteria is to skip all foo if the same line contains bar in it. I don't want to delete all lines containing bar. My first search criteria meets with following:

/foo

My second criteria is not meeting with:

/foo.*\(bar\)\@<!

Example text:

1 foo
2 foo bar xx
3 fooobar
4 bar
5 xxx

(here I want to highlight line numbers 1 only)

What I am missing here?

Reference: http://vimdoc.sourceforge.net/htmldoc/pattern.html