Some comments embedded below:

On 8/23/13 5:56 PM, Peskin, Michael E. wrote:

>
> There is a strong scientific motivation for continuing this program
> with lepton colliders.

   In particular since our charge does not allow us to actually make a 
recommendation, I am with Graham in his suggestion to kick this up a 
notch by simply saying "very strong" or "compelling motivation".

Experiments at lepton colliders can reach
> sub-percent precision in the Higgs boson properties in a
> model-independent way, enabling discovery of percent-level deviations
> predicted in theoretical models.

   I strongly advocate putting the "unique" back in.  This option does 
bring unique capabilities and we should state that.

They can improve the precision of
> our knowledge of the $W$, $Z$, and top properties by an order of
> magnitude, allowing the discovery of predicted new physics effects.
> They search for new particles with unequivocal discovery or
> exclusion, complementing new particle searches at the LHC.  A global
> effort has now completed the technical design of the International
> Linear Collider (ILC) accelerator and detectors that will provide
> these capabilities.  The Japanese high energy physics community has
> named this facility as its first priority.
>
> The Snowmass study considered many other options for high-energy
> colliders that might be realized over a longer term.  These included
> higher energy linear colliders, circular e+e- colliders, muon
> colliders, and photon colliders. The study called out in particular
> the potential of a 100 TeV hadron collider for the exploration of
> electroweak symmetry breaking and dark matter and recommended more
> concerted work on its design and its physics capability.

   For the VLHC, this now drops mass reach and naturalness that are 
important components and should be put back.  The use of the word 
"recommended" seems to counter the reasoning that we are not supposed to 
be making a recommendation on the ILC, which is why the previous use of 
"opportune" seemed like a good fit.  I'm okay with the last piece of the 
phrase now replacing explicit description of a CDR & TDR.

   However, I still struggle with the fact that further mature studies 
and R&D on the muon collider, TLEP/circular machines, and the photon 
collider can _all_ benefit the field.  I'm trying to think of succinct 
wording that could include this.

   Regards,
               Rick

-- 
Rick Van Kooten  \ Telephone: (812) 855-2650  FNAL: (630) 840-3859
Dept. of Physics  \ HEP FAX:  (812) 855-0440
Indiana University \ e-mail:   [log in to unmask]
Swain Hall West 117 \ http://hep.physics.indiana.edu/~rickv/aboutme.html
Bloomington, IN 47405

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