WHIZARD

New heavy particle decay width

Asked by Jian Zhang

Hi Whizard experts,

     I'm study a new heavy particle's signal at certain collider with one of its decay channel by using whizard3.03. UFO. I have two questions when I using whizard.
   1. How does Whizard automatically calculate the total decay width using known parameters (such as mass, couplings, etc.)？

   2. How to obtain the Physical integral Cross-Section?
       The whizard integrating the processes by using partial width not the total width. My setings like

   process pp_NP = p p => NP j
   process NP_ll = NP => ("e-" , "e+") + ("mu-" , "mu+")

   unstable NP ( NP_ll )

  integrate (pp_NP)

Question information

Language:
English Edit question
Status:
Solved
For:
WHIZARD Edit question
Assignee:
Juergen Reuter Edit question
Solved by:
Jian Zhang
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Juergen Reuter (j.r.reuter) said : 		#1

Dear Jian,
this question is similar to question https://answers.launchpad.net/whizard/+question/703313.
If you want Whizard to calculate all 1->2 decay channels you can do this with the command
unstable NP () { ?auto_decays = true }
Then Whizard takes the current values of masses and parameters from the UFO model and creates and calculates all
decay channels. This is described in Sec. 5.8.2 of the manual and is exemplified in the Whizard functional self test
(for SM decays) in share/tests/functional_tests/smtest_5.sin.

If you want to take into account explicit branching ratios in the event sample for an exclusive decay, you can e.g. set
weight = 0.25
before the integration of the production process to (re)weight the cross section by a BR of a quarter. You shouldn't do this
for more than one decay channel unless you add up the corresponding BRs for the different decay channels.
The weight factor is described in sec. 5.7.7.
Cheers,
   JRR (Juergen)

Revision history for this message
Jian Zhang (mnchn) said : 		#2

Dear Juergen,
Thanks, that solved my question.

regards,
Jian