Changes between Initial Version and Version 1 of FAQ-General-13

Timestamp:

May 15, 2012, 12:13:00 PM (13 years ago)

Author:

Johan Alwall

Comment:

--

FAQ-General-13

@@ +1 @@
+
+
+=== What are the default dynamic factorization and renormalization scales in !MadEvent? ===
+
+Since v.4.2.17, there is a new default dynamical scale choice in run_card.dat file: 
+
+{{{
+#*********************************************************************
+# Renormalization and factorization scales                           *
+#*********************************************************************
+ F        = fixed_ren_scale  ! if .true. use fixed ren scale
+ F        = fixed_fac_scale  ! if .true. use fixed fac scale
+ 91.1880  = scale            ! fixed ren scale
+ 91.1880  = dsqrt_q2fact1    ! fixed fact scale for pdf1
+ 91.1880  = dsqrt_q2fact2    ! fixed fact scale for pdf2
+ 1        = scalefact        ! scale factor for event-by-event scales
+}}}
+
+
+i.e., variable factorization and renormalization scales,set to the central mT^2 scale after kT-clustering of the event.
+For a single heavy particle, this corresponds to the M^2+pT^2, 
+for pair of heavy particles it is the geometric mean of M^2+pT^2 for each particle, 
+for massless particles it is the pT^2 of the last pair after clustering. 
+If the last clustering is a t-channel colorless exchange (as, e.g., in WBF),  the two fact. scales are set to the last mT^2 values on either side. 
+These scales are overridden by scales defined in [http://bazaar.launchpad.net/~madteam/madgraph5/trunk/view/head:/Template/SubProcesses/setscales.f setscales.f], if they are returned as non-0.
+
+See [wiki:FAQ-General-2 How do I implement my own renormalization/factorization scales in MadEvent ?] for information about how to implement your own scales in MadEvent.