Rewrite Rule with dynamic link

Question

I am trying rewrite rule:

From: http://example.com/login.php?new="dynamic string"

To: http://example.com/signup/?new_user="dynamic string"

My code:

RewriteRule ^login.php(.*)$ /signup/$1

But I cant get right result... I get:

http://example.com/?new_user="dynamic string"

Worked for me:

RewriteCond %{QUERY_STRING} new=(.*)
RewriteRule ^login.php(.*)$ /signup/?new_user=%1 [R=301,L]