Hi Everyone,
This has been a productive discussion. You saw from Michael last night the status. It's been complicated and the last revisions removed specific accelerator discussion into the "capabilities" section. Due to the blunt-force replanting of stuff from "above"
this section may still need editing.
Just an obvious statement from my perspective: we always will lust after higher energy. That's at some level not news. What seemed to grow out of Snowmass was enhanced in part by Markus' inspiring colloquium was the need to un-mothball the VLHC ideas that
I remember from being a co-convener of in the 2001 Snowmass meetings. Not much has happened since. To that extent, I know where Daniel is coming from. We need to get Foster back in the saddle!
Listening to what we've heard, I propose the following modifications from what Michael sent last night.
Red indicates where I've made suggestions based on Rick's recent comments and on Ashutosh's which people resonated with. The
coda is meant to underscore the important points that Eric, Chris, and Ron have made that I suspect we all agree with, but sometimes with nuance that's a step removed from the mission needs. Since for inexplicable reasons, P5 is
still not planning to include instrumentation in its deliberations, so the coda nudges against that as well…in a capacitively coupled manner. We can talk about this at our meeting this afternoon.
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. These questions call for a three-pronged
research program at high energy accelerators: first, to search for new particles with TeV masses predicted by models of electroweak symmetry breaking; second, to make precise measurements of the heavy particles $W$, $Z$, and the top quark, which can carry
the imprint of the Higgs; and, third, to measure the properties of the Higgs boson itself to very high precision. 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 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. Especially in its high-luminosity phase the LHC is expected to explore deeply for new particles produced through either
the strong or the electroweak interactions. The LHC will study rare decays using a sample of billions of top quarks and probe for new dynamics of $W$, $Z$, and Higgs at TeV energies. It will measure Higgs boson couplings at the few-percent level and provide
the first measurement of the Higgs self-coupling. The LHC experiments have already proven their ability to work as global collaborations. Technology, insights, and leadership from the US have played indispensible roles in these experiments.
There is strong scientific motivation for continuing this program with lepton colliders. Experiments at lepton colliders allow searches for new particles with unequivocal discovery or exclusion, complementing those at the LHC. They can improve the precision
of our knowledge of the $W$, $Z$, and top properties by an order of magnitude, potentially bringing these measurements into confrontation with theory. They can reach sub-percent precision in the Higgs boson properties in a unique, model-independent
way, allowing discoveries of percent-level deviations predicted in theoretical models. A global effort has now completed the technical design of the International Linear Collider (ILC), an accelerator 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 linear and circular e+e- colliders, muon colliders, and photon colliders. A complementary option with
great promise is a 100 TeV hadron collider, which has unprecedented potential reach for new physics associated with electroweak symmetry breaking, naturalness, and dark matter. Further investigations of the physics and technical issues would be opportune at
this time, leading to conceptual and technical design reports.
There is unanimous agreement that maintaining US leadership and continuing experience in experiment design and construction --- especially in accelerator R&D and construction --- is critical to achieving our universal particle
physics' scientific goals. To this end a balanced program of construction in the next decade and R&D towards new instrumentation and accelerator technologies targeting the decade after is every bit as important as our pure science goals.
best
Chip
On 8/22/13 8:57 PM, Peskin, Michael E. wrote:
Dear Colleagues,
I attach the most recent versions of the Snowmass Executive Summary and the
EF 5-page summary. We will discuss these in our meeting tomorrow.
The Executive summary got somewhat rearranged. The frontier conveners
wanted the capabilities sections pulled out and merged into a common section.
This means that the accelerator part of the LHC, ILC, and VLHC discussion
occurs much later in the document. But, please look it over. I did insert
language on the US leadership in high-field magnets.
Regarding the current top-level executive summary, I would like to see the _unique_ capabilities of e+e- machines stressed, and as one example:
"They can reach sub-percent precision in the Higgs boson properties, allowing discoveries of percent-level deviations predicted in theoretical models."
to
"They can reach sub-percent precision in the Higgs boson properties in a unique, model-independent way, allowing discoveries of percent-level deviations predicted in theoretical models."
This is just transferring some wording from the longer summary. I believe that we are all agreed that an "all hadron" option, i.e., HL-LHC -> HE-LHC/VLHC would definitely be missing out on important physics and capabilities and we want to make that clear.
Also a small suggestion: adding "at least", i.e.,:
"They can improve the precision of our knowledge of the $W$, $Z$, and top properties by at least an order of magnitude".
As to the rest of the VLHC discussion, let's talk about it tomorrow. The
new particles group would like a stronger endorsement of VLHC in the executive
summary. I am rather cool to this, because the VLHC is not on the table
now. It would be good to get more opinions from the members of
our group.
There is no denying that a ~100 TeV VLHC brings a lot to the table (including likely the best place for Higgs self-coupling) and we should say this, but with the caveats that Graham clearly points out. I do like Ashutosh's suggested wording encouraging a
conceptual design report which is what would be needed to come to more solid conclusion. We could preface his encouraging statement with "Although beyond the 20-year timeline of this report, further investigations of the physics and technical issues would
be opportune at this time..." (and indeed the same holds true for TLEP).
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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