I have somewhat mixed feelings about 100 TeV (VSSC?) machine. It appeals to
many of us almost at a primal level. It is also heartening to see some aggressive
thinking in spite of the nattering nabobs of negativism in Washington. 

I do not suggest changing wording, but the discussion leads me to say something about the
muon collider, which is also an aggressive project, but one which does have some
support from the DOE. That effort could be endangered if there is not enough community
knowledge. 

There was very little muon collider physics presence at Snowmass.The community
working on it is very small and, although there is accelerator R&D support,
from DOE there is no support for physics and detector studies. The physics case for
a high energy muon collider is similar to that for CLIC, but with the possibility of extending
the energy reach to 10 TeV. To my mind the central issue from the physics and detector
side was the ability to deal with the intense backgrounds from beam decays in the
collider.  At Snowmass we were able to show, for the first time in full simulation, that
these backgrounds could be controlled by proper timing cuts and detector
segmentation (A. Mazzacane in the Instrumentation/Energy frontier joint session).
There are clearly detector compromises inherent in dealing with the muon collider
background and we now are in a better position to quantify them.

We do not know if the accelerator can be built, but I, at least, am fairly confident that
detectors can make measurements with modest compromises in resolution.  This
capability may be very important if we eventually find new physics in the 1-10 TeV range.

Sorry for the rant, but I have been consumed by the Instrumentation Frontier and felt I
had to say my belated piece.

Ron

On Aug 23, 2013, at 17:59, "Markus A. Luty" <[log in to unmask]> wrote:

The new sentence on the VLHC is substantially weaker than the one in the version that we discussed in today's meeting, and that seemed to me to get essentially unanimous support.

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.

I recommend we change back to the old wording, something like

The study in particular called out a 100 TeV hadron collider,
which has unprecedented potential reach for new physics associated with
electroweak symmetry breaking, naturalness, and dark matter.
Further work on its design and its physics capability...


Markus Luty

============================================
Physics Department
University of California, Davis
One Shields Avenue
Davis, CA 95616

Phone: +1 530 554 1280
Skype: markus_luty



On Fri, Aug 23, 2013 at 2:56 PM, Peskin, Michael E. <[log in to unmask]> wrote:
Folks,

We met today to discuss the Snowmass summaries.  In fact, the whole hour was taken up with a
discussion of the paragraphs in the top-level executive summary.

I attach a new version, then the minutes.  Here is the new version:

--------------------

Energy Frontier. The mysteries of the newly discovered Higgs boson were a major theme at Snowmass.  The properties of the Higgs boson raise crucial questions that guide large parts of the future particle physics program. Indeed, this discovery changes everything. It calls for a three-pronged research program at high energy accelerators:  first, to determine the properties of the Higgs boson as accurately as possible, second, to make precise measurements of the heavy particles $W$, $Z$, and the top quark, which can carry the imprint of the Higgs field; and, third, to search for new particles with TeV masses predicted by models of electroweak symmetry breaking. Questions about the Higgs boson also inspire the search for the dark matter particles and for flavor-changing rare decays, since in both cases the motivating theory often comes from models of the Higgs boson and its role in symmetry-breaking.

For at least the next fifteen years, the experiments at the Large Hadron Collider at CERN will drive the Energy Frontier program forward. The Higgs boson discovery at the LHC now becomes a precision study of the properties of this particle.  The high-luminosity LHC will measure Higgs boson couplings at the few-percent level and provide the first measurement of the Higgs self-coupling.  The steps of the LHC to 300 fb$^{-1}$ and then to 3000 fb$^{-1} will explore deeply for new particles produced through either the strong or the electroweak interactions.  They will probe for new dynamics of $W$, $Z$, and Higgs at TeV energies and study rare decays using a sample of billions of top quarks.  The LHC experiments have already proven their ability to work as global collaborations. Detector and accelerator components, technology and physics insight, and leadership from the US have played indispensible roles.

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

In all of the projects listed above, US leadership in developing experimental and accelerator technology is playing a critical role. These US initiatives are essential to meet the world-wide scientific goals in particle physics.


-------------------------------

It is still not perfect.  Please send proposed changes to this list by the end of the day tomorrow (Saturday).



Now to the minutes of the meeting

Present were:

Chip, Michael, Sally, Markus, Tom L., Daniel, Andrei, Cecilia, Rick, Kaustubh, Reinhardt, Yuri, Graham, Andy W., Soeren, Liantao, Robin

The main criticisms of the previous version were:

   Not enough emphasis on Higgs.  Higgs should be first in all lists.
  Among longer-term accelerator projects, there was special interest in VLHC, and this out to be called out.
  Some emphasis needed on US contributions and US "leadership"

Chip and I hope that these concerns are addressed in the new version above.

Thanks,

Michael


-------------------------------------------------------------------------------------------
  Michael E. Peskin                           [log in to unmask]
  HEP Theory Group, MS 81                       -------
  SLAC National Accelerator Lab.        phone: 1-(650)-926-3250
  2575 Sand Hill Road                       fax:     1-(650)-926-2525
  Menlo Park, CA 94025 USA              www.slac.stanford.edu/~mpeskin/
---------------------------------------------------------------------------------------------
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