Mike's mail 20170621 - Githubissues

Hi Yu-Ting,

On 06/21/2017 08:11 AM, Yu-Ting Shen wrote: Hi Mike and Jesse, In the simplified model, I didn't see the Z and W decays, but I did see N2 --> N1 + Z (BR=0.9) N2 --> C1+ + W- (BR=0.05) N2 --> C1- + W+ (BR=0.05) C1+ --> N1 + W+ (BR=1.0)

MadGraph and MadSpin ignore these BR's, unfortunately. Pythia would follow them if we allowed the EWKinos to decay in Pythia, but we don't do that.

There are two lines about the Z and W

#         PDG            Width
DECAY        23     2.49520000E+00   # Z width (SM calculation)
DECAY        24     2.08500000E+00   # W width (SM calculation)
#

Does it mean that the Z and W decays are specified in other file?

Z and W decays are done in MadSpin:

https://svnweb.cern.ch/trac/atlasoff/browser/Generators/MC15JobOptions/trunk/common/MadGraph/MadGraphControl_SimplifiedModel_higgsino.py7

See lines 115 and 174, for example.

The model gets the BR's completely wrong, so we rescale the sigmaBR for these samples during the analysis according to the NLO cross section, the simplified model BR of N2-> Z N1 (100% in this case), and then the Z*->ll BR. This is all described in the internal note, so you can look there for some of the details and exact numbers. There's also a lot of discussion on this in various (closed) Jira threads, you can do some archaeology there if you want more context.

Unfortunately I'll be away for the next week and a half, so if you have other urgent questions on this, I hope Jesse and others will be able to help. Using Jira for these questions may enable more people to jump in with answers, so don't be afraid to update HIGGSINO-28 with any questions you might have.

Cheers,

-Mike

ytatus94 / Higgsino

Mike's mail 20170621 #28