Github search api doesn't show branch name while getting pull requests

I am trying to get pull requests using github search rest api for a time range like below.

https:///api/v3/search/issues?q=repo:foo/foo+type:pr+state:open+created:2021-11-01…2021-11-09&per_page=100

But the output doesn’t show associated branch. I could get it from pulls api which gives under head->ref the branch name but want to get using search api.

Any help is appreciated.