Changes between Version 2 and Version 3 of YETI08

Timestamp:

Apr 13, 2012, 9:13:24 AM (13 years ago)

Author:

Martin

Comment:

--

YETI08

@@ -13 +13 @@
 The biggest difficulty in generating events with multiple jets is to prevent double counting. For example, an event with three jets in the final state could have come from a three parton configuration of which all three showered into different jets, or a 2-parton event of which a third jet is generated by the parton shower (or even an 1 (or zero) parton event with two (or three) jets generated by the shower). The otherway around is also possible. A two jet final state could also have come from a three parton state, of which two parton are belonging to the same jet, and this could therefore lead to double counting with a two-parton sample of which both the partons are showered to a two jet final state.
 
-There are basically several schemes to avoid this double counting. MadGraph uses a method based on the MLM scheme (also a version of the CKKW method is implemented for more details see [wiki:Software.Matching this page]). It works as follows.
+There are basically several schemes to avoid this double counting. MadGraph uses a method based on the MLM scheme (also a version of the CKKW method is implemented for more details see [wiki:Matching this page]). It works as follows.
 
 Multi-parton events are produced by first generating all the diagrams belonging to the +0, 1, 2, 3, ... jet configurations. Any number of additional particles can be included, the more the 'better' the result will be. In practice, up to 3 jets is the maximum due to the large number of diagrams contributing to these high multiplicity states. For the $p\bar{p} \to Z/\gamma^* \to \mu^+\mu^- +0,1,2,3\textrm{ jets}$ sample, the proc_card can be found [attachment:proc_card.dat here]. Note that all the diagrams with multiplicities up to three jets will be generated (a couple of thousand diagrams) and this takes in general 1 or 2 hours or so.
@@ -21 +21 @@
 The third step is to shower the events. Now we have to make sure that we remove events that 'change the number of jets' to avoid the couple counting. A showered event is clustered to jets using a k_T jet algorithm with a jet measure cut-off (generally speaking 1.5-2 as large as the xqcut). This cut-off makes sure that no new jets are generated from a given parton level multiplicity: if an event generates an extra jet, it is removed from the event sample (except for the highest multiplicity samples, so that also events with 4, 5, 6 or even more jets are generated from the 3 jet sample). Because no new jets are generated for the low multiplicity samples, all double counting is removed. And because the minimum transverse momentum of a jet was equal to the xqcut, the full phase space is covered, and we are not removing too many events.
 
-For more technical details also have a look at this page about [wiki:Software.Matching Matching]. Also [wiki:Software.MatchChecker this page] has a lot of information about matching/merging and testing your event samples.
+For more technical details also have a look at this page about [wiki:Matching Matching]. Also [wiki:MatchChecker this page] has a lot of information about matching/merging and testing your event samples.