How is an experimental particle physicist evaluated? As an undergraduate student majoring in physics, I intend to apply for a Ph.D. in experimental particle physics. I have known that working as physicists in this field is kind of different, as they are always affiliated to a collaboration (like CMS in LHC) and may appear as authors in loads of related papers, resulting in high citations. Therefore it seems traditional evaluations of a researcher (focusing on the citations or h-index) do not work when assessing an excellent and famous experimental particle physicist.

Thus I am asking:


How are particle researchers assessed in reality, in the case when a Ph.D. applier is searching for and comparing professors in the similar field, or when a researcher is going to find a position as an assistant professor? Does the specific role of a scientist in the collaboration (say, the group leader) matter in this evaluation procedure?
How does university ranking play into this? What are the probable differences between professors in particle physics who work at a higher-ranked institution (ranked by physics major) and those who work at a lower-ranked one – given that they are both affiliated to some big collaboration. This question comes to me since it seems one cannot distinguish a famous particle physicist by the conventional method which is performed by university ranking.
I happened to be a member of my college's executive committee when an experimental particle physicist was being considered for promotion to tenure. She was, indeed, a member of a huge collaboration, so a typical paper of hers had perhaps 100 co-authors. The papers provided no information about what, specifically, she had contributed (and we know better than to pay much attention to citation counts and impact factors). The information we needed, about the quality and quantity of her work, was provided by numerous letters from external reviewers. ("External" means not in our university.) Ordinarily, the college requires that most external letters come from senior researchers who are not co-authors of the candidate's papers, but an exception is allowed in areas, like experimental particle physics, where only co-authors really know about the candidate's work.  My recollection (about 15 years old and therefore somewhat vague) is that the letters gave us very detailed information, not only about what the candidate had contributed but also about how efficiently she had done her part of the work.