Hi Michael.
Thanks for incorporating the comments. The text is improved (and I
also like the new naturalness bits.)
Some follow-up comments on version 10-12 are below - a mix of more
substantive comments and trivial English/phrasing, etc.
Regards,
Rick
Comments on Energy Frontier documents, v. 10-12
===============================================
Executive Summary
-----------------
o l. 36: I don't quite understand "does not explain the size of the
condensate" - what is meant by "size" in this context?
o l. 72: "The couplings of this boson to fermions roughly scale with
mass" (or else say that couplings to vector bosons scale as mass squared?)
o l. 87: "precisions of several percent"
o l. 89: "high significance" is still quite vague.
Suggest: "needed to uncover deviations from SM predictions with
significance high enough for indirect evidence or discovery of new physics"
o l. 204: "..., and to other invisible and exotic states."
Longer Energy Frontier Report
-----------------------------
o l. 28: "weakly interacting matter" - isn't it true that we only know
that it has to be gravitationally interacting? There may zero weak
interactions (...and not so good for direct detection...)
o l. 68: 400 fb-1 ? I thought it was 300 fb-1? Or 100 fb-1, LS2, + 300
fb-1?
" increase its data set by a further factor of ten." is then confusing
as it implies 4000 fb-1 instead of 3000 fb-1. Suggest "increase its
data set by a further factor up to 3000 fb-1".
o l. 78: "In Section 1.3" or "Section 1.3 describes"
o l. 108: "spin-0 doublet field"
o l. 277: "summed over four detectors"
o l. 314: "kappa_gamma, and kappa_gammaZ"
o l. 366: No definition of "6-parameter fit" ?
Also suggest adding sentence: "Although the model-independent results of
the lepton colliders do not require such a 6-parameter fit, such a fit
is used to facilitate comparisons to the hadron colliders."
o l. 392: "detectors, first evidence"
o l. 401: "spin-2 coupling"
o l. 408: Suggest inserting Andrei's sentence from the Higgs report and
tweaking, i.e.,
" The scalar Higgs couplings to massive vector bosons (ZZH
and WWH) are at tree level, while pseudoscalar couplings are expected to
be suppressed by a loop. CP-violating terms this vertex are therefore
masked by the large tree-level..."
o l. 462: \beta - \alpha (alpha not math command).
o Definitions of \alpha and \tan\beta are defined after first referred
to in the paragraphs above.
o l. 921: "Long-lived particles" (in subsection heading).
o l. 1046: space after ^{-1}.
o l. 1074: "Likely first evidence of the Higgs boson self-coupling"
o l. 1089: "It would study"
o l. 1092: "space between "ofall"; repeat the previous care in earlier
text in distinguishing decay modes undetectable at the LHC from
invisible and exotic decays.
o l. 1097, 1100: accuracy -> precision (more appropriate for a
measurement - lack of accuracy implies a systematic uncertainty giving a
bias. We need to assume that those are addressed in a typical careful
analysis).
o l. 1127: sentence scrambled up/with fragments.
o l. 1140: not sure if it is fair to say that these muon collider
results are "first results". Some of them have been reported long ago.
Probably just simply "promising results were reported at Snowmass".
o l. 1152: "at 250 GeV and below, and reasonable integrated luminosity
at 350 GeV" - needs to be fair here, i.e., the luminosity at 350 GeV is
higher than for the ILC, and about comparable for the ILC lumi-upgrade.
o l. 1158: "precise top quark mass to +/-100 MeV from tt(bar) threshold
at 350 GeV"
In the TLEP physics case paper: "The dominant systematic uncertainties
on the top quark mass are expected to be around \pm 100 MeV for the ILC,
and of the order of or smaller than the statistical uncertainties for
TLEP."
"An overall experimental uncertainty of 10 to 20 MeV is therefore
considered to be a reasonable target
for the top-quark mass measurement at TLEP."
The TLEP stat precision is 10 MeV, and they make the case of reducing
these systematics via TeraZ measurements, beam energy knowledge, etc.
To keep this at +/-100 MeV doesn't seem quite fair. Their estimate
would give ~14 MeV (in quadrature), but possibly just put 20 MeV?
o l. 1166: spelling "wioth"
On 10/12/13 8:49 PM, Peskin, Michael E. wrote:
>
>
> Folks,
>
> Please find another version of the short and long Energy Frontier reports attached. This version incorporates input from
> Soeren, Markus, Sally, and Chip. More changes are still required, so please send it your requests. We have to finalize
> this report in the next few days.
>
> I believe that i am now up to date on making changes, so if changes you recommended have not been made, you need to write to
> me again.
>
> Please refer to changes by line number and version number. There are now 3 versions in play 10-3, 10-11, and 10-12.
> If you have not started reading yet, read the 10-12 version.
>
> Best wishes,
>
> Michael
>
> p.s. I have accepted all changes, modified in response to the complaint, or written back with a query except in one case.
> Markus recommended a large rewriting of section 1.2.2 (Naturalness). I like the current version better. Markus' version
> is below. The two versions are very different in tone. Please give your recommendations.
>
> -------------------------------------------------------------------------------------------
> 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/
> ---------------------------------------------------------------------------------------------
>
>
> Lines 152-196. I do not think that naturalness is a "bothersome hint" or a "slippery principle." I think it can be explained in very basic physical terms. I suggest the following:
>
> "Naturalness" is at bottom the use of dimensional analysis to estimate unknown parameters. If a quantity such as the Higgs mass is sensitive to a physics associated with a mass $M$, then dimensional analysis suggests that the Higgs mass should be of order $M$. Of course, this does not take into account the possibility that this dependence is absent, in which case we expect to have a good reason why this sensitivity is absent, such as a symmetry or some kind of decoupling.
>
> Decades of theoretical work in quantum field theory has shown that elementary scalar masses are generically sensitive to physics at higher scales, and only three mechanisms have been established that can avoid this sensitivity. These are supersymmetry, (SUSY), Higgs compositeness, and extra dimensions. Each of these predict a rich spectrum of new states at the scale where the new structure becomes apparent. In SUSY, these consist of the superpartners of all known particles, while in both composite and extra-dimensional models we expect towers of massive resonances. (The fact that the phenomenology is qualitatively similar is the first sign that extra-dimensional models are in fact a realization of Higgs compositeness, a fascinating and deep equivalence that was discovered in string theory and has propagated to particle phenomenology and back again to fundamental theory.)
>
> These mechanisms allow the Higgs mass to be calculated from other more fundamental parameters, and they confirm the expectations of naturalness in the sense that the Higgs mass is indeed sensitive to the new particles associated with SUSY or compositeness. The Higgs mass therefore cannot be much smaller than the scale $M$ of new particles predicted in these models. The Higgs mass can be much smaller than $M$ only if there is an unexplained accidental cancellation, or "fine tuning."
>
> We can see the naturalness problem even without knowing what the new fundamental physics is. If we simply assume that there is *some* new physics at a scale $M$ we can estimate the sensitivity of the Higgs mass to new physics at the scale $M$ by computing quantum loops in the standard model with a cutoff of order $M$. The parameter in the Higgs potential then receives corrections of order
>
> Eq. (1.4) with $M$ instead of $\Lambda$
>
> where $g_{Htt}$ is the same Yukawa coupling as in (1.2), $\alpha_w$ and $\lambda$ are the couplings of these particles, and $\theta_w$ is the weak mixing angle. Note that all terms are proportional to $M^2$, simply as a result of the fact that it is the Higgs mass squared that appears in the Lagrangian. Experience with many specific models teaches us that if there is new physics at the scale $M$, (1.4) gives a reasonable estimate of the contribution of new physics at the scale $M$ to the Higgs mass. The suppression factors in (1.4) mean that the natural expectation for the scale $M$ is that it cannot exceed the Higgs mass by about a factor of 10.
>
> Although there is no general agreement on how to quantitatively measure the (un)naturalness of a given model, it is clear that the degree of tuning required to obtain $m_h \ll M$ grows quadratically with $M$. This means that if we increase the sensitivity to heavy particle masses by a factor of 10, we increase our probing of naturalness by a factor of 100. This provides a very strong motivation to for searches at the largest possible energies.
>
>
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--
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]
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Bloomington, IN 47405
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