Cosmic-ray studies of the CMS tracker January 28, 2009Posted by dorigo in news, personal, physics.
Tags: CMS, publications, silicon tracker
It is always nice to open the web browser in the morning, check the arxiv for new interesting preprints, and be surprised to find one’s own name in the author list. That is what happened to me today, while browsing lazily the list of new hep-ex papers, as my eyes set on “Performance studies of the CMS strip tracker before installation”.
The paper describes the full testing of a sector of the CMS tracker. The tracker (see picture on the right, showing a detail of its inner barrels) is a daring device made of many concentric barrels of silicon strip sensors. During the summer of 2007 a quarter of the device was fully instrumented, cooled, and read out while it was being exposed to cosmic rays, and a total of 4.5 million tracks were reconstructed, allowing to gain critical experience with its operation, and detailed studies of its tracking capabilities, the tuning of a simulation of the detector, and the development of advanced tools.
Of course I knew the paper was being prepared -the submitter is Patrizia Azzi, a member of my group in Padova (although she’s full-time at CERN)- but no, I did not contribute to it in any significant way and no, I had not even read the draft!
To be fair, the author list includes over 400 names, the members of the CMS Tracker Collaboration (people who were somehow involved in the construction of the tracker), so you should not run out screaming “Dorigo is a parasite!” -at least, I am not the only one! This is how things work in large collaborations: you focus on one or two studies at a time, on the time-scale of two-three years, but you do not just sign your papers: you sign all of them.
In retrospect, I should be even less severe with myself. Although the paper contains no results of mine, I did work on the analysis of the data. I did a study of multi-track events, trying to figure out how the presence of large amounts of hits close together could affect the tracking (a matter of relevance for LHC, where dozens of tracks will pack together within small volumes), and I studied the extraction of the angle of incidence of tracks from the width of clusters of charge in the silicon strips (tracks crossing a layer of silicon at normal incidence leave a ionization trail which gets collected in few strips, while tracks crossing with a large angle leave a signal in many adjoining strips).
Those studies did not end up providing a valuable addition to the paper -mostly because I did not conclude them- and they were left out of it, but I invested at least one month of work in them. Not much, but I do not feel a parasite after all: the paper is maybe the result of 20 or 30 man-years of studies, so each of the 400 authors contributed an average of less than one month of full-time work!