Hi Chip, Michael,

On this first question from the CF that we did not have time to discuss today:

Questions to us from the Cosmic Frontier, to be discussed today:

"HE1": • The message from the LHC seems to be that with data in hand, we consistently outperform

expectations for extraction of Higgs properties. How much is there really for an ILC to contribute?

What key assumptions are we making now that we could relax with ILC inputs?

This is a rather broad question covering the broad ranges of Snowmass studies (and beyond just Higgs 

boson study alone, as Chris points), so we will be answering this as the report takes it shape. At the same 

time we could have some examples. First of all, the wording of LHC outperforming expectations is 

questionable (perhaps people did not trust that LHC would do well, but it is a separate question) 

and the ILC/e+e- and LHC programs are really complementary. 

Chris has covered some of this, but I wanted to bring the examples such as spin or CP violation as 

the Higgs properties. LHC may indeed complete the measurements of spin well before any Higgs factory 

may have a chance to contribute (we know a lot now already). But then the next step is to measure / limit

CP-violation from Higgs kinematics, and this will be a long way for LHC. It will do well, but only as well 

as statistics allows. The Higgs factory would quickly outperform in statistics in the HZZ coupling, the 

golden coupling on LHC and even more so on the Higgs factory. So, this is one example to contradict 

the points hidden in the question asked. It is of course not enough to answer the question fully, but 

the goal of the Snowmass report is to lay out all these physics cases. 

Andrei

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