Hi Chip,
I would not say that 100 TeV machine can completely cover the WIMP parameter space. More precisely, it can probe WIMP with mass around TeV in the most model independent way. This is probably the most interesting region of WIMP parameter space.
Fine-tuning is also a major reason to go to 100 TeV, as it can further probe the level of tuning by two more order of magnitudes. (whether it is 10^-4 or not depends on definition of fine-tuning)
For your reference, here is the paragraph in new physics group's summary report:
"The 33 TeV LHC or 100 TeV VLHC have unprecedented and robust reach for new physics that is evident even with
the preliminary level of studies performed so far. Higher energy gives significant enhancement of reach, corresponding to two orders of magnitude in fine tuning. Dark matter can be probed up to the natural WIMP scale of 1 TeV. Essentially any discovery at the LHC would be accessible at these machines and could be better studied there, making the case for these options even more compelling."
As Yuri said, I do see that there is quite a bit excitement about these physics motivations for going to 100 TeV. I would say such a machine is complementary to ILC in terms of physics scope.
Liantao
On Aug 18, 2013, at 11:56 AM, Raymond Brock wrote:
> Hi Tom
>
> That's a good point, and indeed the situation. What this refers to is the "holes" that are in some regions of parameter space in some LHC searches in which discovery would be hard or impossible. The ILC suffers few or no such spots and so is in some sense "unambiguous." A better word is required.
>
> Hi Chris
>
> You're right about the 2nd generation guys and the lack of comment to the other lepton colliders.
>
> Question: Did any of you hear any substantive suggestion that a VLHC should be the follow-on collider to LHC? I'm asking for a reason...the mention of ILC in this way is deemed as not representative of the whole community and as "there are also those who believe in that a 100 TeV proton machine should be next" (a quote from a prominent fellow).
>
> I personally don't think that 100% unanimity is required in order to emphasize one future program over others. But I'd really not heard this particular sentiment in any substantive way.
>
> best
> Chip
>
> On Aug 17, 2013, at 4:19 PM, Tom LeCompte <[log in to unmask]> wrote:
>
>> Hi Michael,
>>
>> I am not sure Line 119 says what we want it to say: " Experiments at lepton colliders allow unambiguous searches for new particles...". I don't think you mean the searches themselves are unambiguous (and by extension, that the searches at the LHC are ambiguous). Maybe you mean that the *interpretations* are unambiguous (or at least clearer) than at hadron colliders.
>>
>> See you Thursday,
>>
>> Tom
>>
>>
>> On 8/17/2013 5:35 PM, Peskin, Michael E. wrote:
>>> Dear Colleagues,
>>>
>>> Chip and I have been presenting at the DPF meeting and trying to catch up on our sleep.
>>> However, the work for Snowmass is not yet done. We have some important questions
>>> for you.
>>>
>>> I attach a draft of the highest-level Executive Summary of Snowmass. This is in a very
>>> preliminary state; please do not circulate it further. Chip and I ask in particular whether
>>> you are in agreement with the 3-paragraphs that relate specifically to Energy Frontier.
>>> I attach these at the end of this note. This document is under revision now, so please
>>> send your reactions as soon as possible.
>>>
>>> The executive summary will be the first part of a 30-page Snowmass summary document.
>>> That will include a 4-5 page summary of the results of the Energy Frontier study. Chip and I
>>> are working on our final revisions of a first draft. We will circulate that to this list tomorrow.
>>>
>>> The 30-page summary of Energy Frontier is not yet ready to be circulated. We are sorry for the
>>> delay. However, this document will follow closely the long version of Chip's talk given on Sunday
>>> at Snowmass. We just need to put this into prose.
>>>
>>> We would like to return to our scheduled phone meeting of the EF conveners this week and
>>> next week. I remind you that time is 11am PDT/ 2pm EDT Thursday, and that the coordinates are:
>>>
>>> August 22: 11:00 PDT / 2:00 EDT
>>> Contact information:
>>>
>>> You call: domestic... (877) 873-8018
>>> international... (636) 651-3182
>>>
>>> participant code: 290-043
>>>
>>> We will start the meeting promptly and end promptly after 1 hour.
>>>
>>> The agenda for this week is discussion of the two summary documents.
>>>
>>> I hope that your working group reports are headed toward completion by the end of the month.
>>> I promised written comments on the drafts, but -- please excuse me -- I did not send these yet.
>>> Please expect them early this week.
>>>
>>> Chip and I would like to thank you again for all of the work that you have put in thus far. Chip
>>> received much positive feedback on his talk at Snowmass, but, of course, the supporting work
>>> is yours. We are grateful.
>>>
>>> Best wishes,
>>>
>>> Michael
>>>
>>> --------------------------------------------------------------------------------------
>>>
>>>
>>> EF paragraphs in the Snowmass executive summary
>>> (In the full document, you will see that this is followed by paragraphs from the accelerator side)
>>>
>>>
>>> The mysteries of the newly discovered Higgs boson were a major theme at Snowmass. Much attention was given to the importance of studying the Higgs boson as closely as possible. At high energy accelerators, the “Energy Frontier,” there are three approaches: 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. This program is closely connected to the search for the dark matter particle and for flavor-changing rare decays; in both cases, the motivating theory is often associated with the Higgs and its symmetry-breaking.
>>>
>>> For at least the next fifteen years, the experiments at the Large Hadron Collider at CERN will drive this 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. They LHC will study rare decays using a sample of billions of top quarks, 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 proved their ability to work as global collaborations. Technology, insights, and leadership from the US have played important roles in these experiments.
>>>
>>> There is strong scientific motivation for continuing this program with lepton colliders. Experiments at lepton colliders allow unambiguous searches for new particles that complement those at the LHC. They can improve our precision knowledge of W, Z, and top by an order of magnitude, potentially bringing these measurements into confrontation with theory. They can reach sub-percent precision in the Higgs boson properties, 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 give these capabilities. The Japanese high energy physics community has named this facility as its first priority.
>>>
>>>
>>> -------------------------------------------------------------------------------------------
>>> 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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>
> ---------------------------------------------------------------
> Raymond Brock * University Distinguished Professor
> Department of Physics and Astronomy
> Michigan State University
> Biomedical Physical Sciences
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