applying cuts on CKKW matched samples

[Generic User (don't modify these fields)]

SHERPA has a set of routines to apply cuts on matrix-element level. But what if you want to apply some stringent cuts on CKKW matched samples. As I understand you cannot apply cuts more stringent than the matching condition on ME. But is there a way to apply cuts on hadron level (after hadronization)? For example order SHERPA to store in hepmc event file only events with 4 jets with pT > 100 GeV. I know there is something called njetfinder but it is unclear to me on what level are these cuts applied.

best regards Wojciech Kotlarski

[Frank Siegert]

From a technical point of view it is possible to apply ME level cuts in matched samples. The NJetFinder you have mentioned is one example that can be used there. Obviously, and independent from whether the samples are matched or not, you'll always have the question of the inclusivity of the sample at hadron level then.

One can also select events at the hadron level with the help of the (little documented) internal analysis module. More information and an example can be found in ticket #80 (​https://projects.hepforge.org/sherpa/trac/ticket/80).

[Generic User (don't modify these fields)]

Thank you very much for a quick reply. The method you mentioned that allows to select events at the hadron level is exactly what I was looking for. I was able to apply a cut that selects events with at least one electron with p_T > 10 GeV by putting the following lines in the Trigger sections

Finder 11 10. -20. 20. Counts -11 1 -1

The question is how to make a combined cuts. Namelly, how to accept only events with either an electron or muon with p_T > 10 GeV. It is easy to implement a series of cuts but I cannot find a proper syntax for an alternative choices.

[Frank Siegert]

I'm not familiar enough with the internal analysis module, so I hope another Sherpa can help out here.

[Jan Winter]

There are at least 2 ways of incorporating what you'd like to do. Before pointing these out, I'd like to mention that you can get a general idea about what handles are available within Sherpa's analysis package by running Sherpa adding SHOW_ANALYSIS_SYNTAX=1 to the command line. This will not run Sherpa but rather print out the list of analysis handles.

If your cuts are not too complicated you probably can do everything using "Trigger"(s), the selection trigger should define your electrons/muons by including

Finder 11 10.0 -20. 20.; Finder -11 10.0 -20. 20.; Finder 12 10.0 -20. 20.; Finder -12 10.0 -20. 20.;

Then you can define your exclusive lists in a second step eg via

Trigger { InList Selected; OutList excle+;

Counts 11 1 1; Counts -11 0 0; Counts 12 0 0; Counts -12 0 0;}

and so forth.

Another way would be to use "MomSel", use SHOW_ANALYSIS_SYNTAX=1 to learn more about how to apply it. Above example should translate to this:

MomSel { InList Selected; OutList excle+; Tags 11 -1 N 1 1;

Tags -11 -1 N 0 0; Tags 12 -1 N 0 0; Tags -12 -1 N 0 0;}

If you use OUTPUT=8 (it's either 7 or 8, I always mix it up) you'll get an overview of the sherpa internal analysis lists (as you named them) where you may control your selections. These listings you'll get right before the event record will be shown.

Hope this helps.

[Generic User (don't modify these fields)]

Than you have few lists which you should merge. I presume that you have to use MergeLists. But what if you have the same event that passed through two criteria. For example, lets assume that you had an event with an electron and a muon, both with p_T > 20 GeV. Than you will have two lists with the same event. The question is: does MergeLists remove doubling entries?