Questions to be handled in the User Support Q&A sessions

The next session will take place on Tuesday, September 5th, at 9:30 am. in 40-RA-10. Please add your question here using the following format (you can edit this page by clicking on the Edit button top right) and send me a short mail with your subject just to notify. The answers will be given in the User Support session and they will appear in this page. If you are not at CERN, and cannot attend the sessions, you can still add your questions here (indicate that you will not attend the session). Please check the existing documentation, especially the CMSWorkbook before adding your question.


Your name and date, can/cannot attend the session

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Where can I find the data?

How do I know what data is available (real data from MTCC or simulation data) and how can I access it?


For the MTCC data (cosmic muons at CMS) see the instructions in the IGUANA web page, and in particular the data file location.

There are no large centrally produced simulated data sets, yet. For each release of the CMSSW packages, a set of of small event samples are produced which are mainly used to validate the release. Find the instructions how to access this data in the release validation samples page.

How to save cross section in the root file?

Sami Lehti, 21 Jul 2006

In an analysis containing several channels (signal+backgr), it is very helpful if some normalization constants, like cross section and preselection efficiency, can be stored in the root file. How is this done in practise (a working example would be nice)? How is the cross section read from the root file? Can the stored cross section be changed by hand afterwards? For example if i have 1M events in root file(s), and i get a new cross section from theorists, do i have to rerun the 1M events, or can i change the cross section value in the root file(s)? If yes, how?


1) How to add cross-section?

The mechanism to add a cross-section to the run or job (i.e. one number per run) is not yet ready, it is planned but not yet there (it is foreseen by the end of August, at the earliest)

Meanwhile, you can try the following solution which writes a number to each event.

2) How to change an entry in a root file?

-- KatiLassilaPerini - 13 Jul 2006

This topic: CMSPublic > CMSCommunicationsGroup > CMSCommunicationsProjects > WebHome > SWGuideUsersFAQ
Topic revision: r10 - 2006-08-28 - KatiLassilaPerini
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