Changes between Initial Version and Version 1 of FAQ-General-3

Timestamp:

Mar 20, 2012, 4:17:38 PM (13 years ago)

Author:

trac

Comment:

--

FAQ-General-3

@@ +1 @@
+
+
+==== How do I change the mass of a particle that is assumed massless in MadGraph/MadEvent ? ====
+
+Several particles (light quarks, charm, he electron and the muon,..) are assumed to be massless in the SM implementation.  
+
+===== '''BEFORE CODE GENERATION'''  =====
+
+One can change this  by dowloading the full package and defining a new model.
+
+{{{
+> cd Models
+> cp sm sm_mc
+> cd sm_mc
+}}}
+
+and then edit the [http://cp3wks05.fynu.ucl.ac.be/cgi-bin/ViewVC/viewvc.cgi/MG_ME/Models/sm/particles.dat?view=markup particles.dat] by changing
+
+{{{
+c       c~        F        S      ZERO  ZERO    T    c    4. }}}
+
+into
+
+{{{
+c       c~        F        S      CMASS ZERO    T    c    4. }}}
+
+You then need to make sure this parameter is read in the lh_readin routine in [http://cp3wks05.fynu.ucl.ac.be/cgi-bin/ViewVC/viewvc.cgi/MG_ME/Models/sm/couplings.f?view=markup couplings.f]. You have to add it also in the [http://cp3wks05.fynu.ucl.ac.be/cgi-bin/ViewVC/viewvc.cgi/MG_ME/Models/sm/param_card.dat?view=markup param_card.dat] if it is not
+already there. Then you're ready to generate processes and events. 
+
+
+===== '''AFTER EVENT GENERATION''' =====
+
+One can change this  by acting directly on the event file with suitable script that change the mass and the four momenta of the interested particle
+in the final state '''by also reshuffling''' all other momenta to conserve overall momentum. Pythia will infact reject events where the energy momentum checkcount is not satisfied.
+
+
+-- Main.FabioMaltoni - 02 Mar 2009