description of papers that have not been submitted to a venue?
Work in Progress might be good as it implies that there may still be some work to do in the writing - and even some uncertainty about the final title. In addition it also subtly says that you are still active and not resting on your old achievements. 

You could, in addition, mark each paper according to its readiness, or at least those that are ready for submission. 

I think that Research Papers carries a connotation that they are internal and may not be published.