Hi all,
I was quiet during yesterday's meeting, but I shared the feeling that the statement was too strong w.r.t new physics at 1 TeV.
My concern stems less from a deep understanding of the theoretical arguments which suggest the scale of NP needed to address the questions of the Higgs mass value and more from a skepticism that such theoretical arguments are totally bulletproof, given how much of the universe remains to be understood.
I like what Marcus has written, because the logic of it is fairly presented: our current understanding leads to questions for which new physics at the 1-10 TeV scale appears inescapable. I particularly like "have their crucial test at the TeV scale", because it leaves open the possibility that we'll find nothing at that scale and therefore be forced to revisit the assumptions which lead us there.
d
On Oct 10, 2013, at 10:57 PM, "Markus A. Luty" <[log in to unmask]> wrote:
> The first installment of my homework: here is my suggestion for what is now lines 31-41 of the 5-page summary. It is longer than what is there now, but I think these may be the most important lines in the document.
>
> The discovery of the Higgs particle establishes that the masses of elementary
> particles arise dominantly from interactions with the Higgs field that is turned
> on throughout the universe. We now have for the first time in the history of
> particle physics a theory all of whose ingredients have been experimentally
> verified, and that can be consistently extrapolated to energy scales many orders
> of magnitude above the energy scale of collider experiments. This historic
> achievement is not an end, but a beginning, because the standard model of
> particle physics leaves many fundamental questions unanswered. In the tradition
> of bold theoretical ideas such as the Higgs mechanism (recognized by this years'
> Nobel prize) particle physicists have proposed compelling ideas that address
> these important questions, and that have their crucial test at the TeV scale:
>
> * The fact that the observed Higgs particle is a scalar particle makes it very
> difficult to understand why its mass scale is smaller than much-larger
> fundamental mass scales such as the Planck scale. Addressing this problem
> requires significant additional structure: either supersymmetry (an extension of
> Einstein's spacetime symmetry), Higgs compositeness, or extra dimensions of
> space. All of these ideas predict a rich spectrum of particles at the TeV mass scale,
> typically including a larger Higgs sector.
>
> * The standard model does not account for the dark matter that makes up most of
> the matter of the universe. A stable particle at the Higgs mass scale with weak
> interactions with ordinary matter (a WIMP) is one of the simplest and compelling
> theories of dark matter. If dark matter is a WIMP it may be possible to study
> dark matter under controlled laboratory conditions in collider experiments.
>
> To summarize: \emph{Compelling ideas about fundamental physics predict new
> particles at the TeV energy scale that are potentially accessible to present and
> planned future accelerators. These experiments are the crucial tests of these ideas.
> Furthermore, if such particles are discovered, they can be studied in detail to
> determine their properties, leading to the establishment of new fundamental laws of
> nature.}
>
> The past successes of particle physics clearly call for us to continue and extend a three-pronged program of research in collider experiments:
>
> First, we must study the Higgs boson itself in as much detail as possible,
> searching for signs of a larger Higgs sector and the effects of new heavy
> particles.
>
> Second, we must search for small deviations in the standard model predictions
> for the couplings of the Higgs, W, Z, and top quark from new particles.
>
> Finally, we must directly search for new particles with TeV masses that can
> address important problems in fundamental physics.
>
> Markus Luty
>
> ============================================
> Physics Department
> University of California, Davis
> One Shields Avenue
> Davis, CA 95616
>
> Phone: +1 530 554 1280
> Skype: markus_luty
>
>
>
> On Thu, Oct 10, 2013 at 1:57 PM, Ashutosh Kotwal <[log in to unmask]> wrote:
> On Oct 10, 2013, at 4:03 PM, "Peskin, Michael E." <[log in to unmask]> wrote:
>
> > minutes of the EF phone meeting 10/8
> >
> > attending: Chip, Michael, Sally, Daniel, LianTao, Ashutosh, Cecilia, Reinhard, Markus, Andy White
> >
> > There are many items in these minutes that all of you need act on more or less immediately. Please read these minutes carefully. We summary the action items at the end.
> >
> > Our reports are overdue. We would like to send our reports to the Snowmass conveners on Tuesday, October 15.
> >
> > All line numbers refer to the 10-3 versions sent out last Friday.
> >
> > 1. From the group on the phone, and from the emails that we have received, you seem to be happy with the reports that we put together except for some specific points discussed below. Michael emphasized that, if you are not happy, you must speak up now. This is best done by sending email to snowmass-ef. Urgently, please.
> >
> > 2. Many of the people on the phone were uncomfortable with the language on likes 40-41 of the short report: "These puzzles imply that new particles with masses of the order of 1 TeV which resolve these questions will be found -- and will be accessible to existing and planned accelerators." They felt that "imply" was too strong and that the implication of 1 TeV rather than, say, 5 TeV was made in this sentence.
>
>
> what about replacing
>
> "…masses of the order of 1 TeV"
>
> by
>
> "...masses below about 10 TeV"
>
> just as an example, ATLAS studies have shown sensitivity to KK gluons -> ttbar in the 5 TeV range
>
> ------
>
> as far as the word "imply" goes, it seems to me that "imply" has a built-in caveat that it is an implication on the basis of a certain logic. In this case, the logic is that nature will avoid too much fine tuning. The 10 TeV number would make the fine tuning about 0.01%
> and the logic is that this is very uncomfortable amount of fine tuning
>
> So, I think we are protected in the legalistic sense if we do use the word "imply"
>
> Also, to me, the scale of how "strong" the language is, is no longer set by the "strength" of "there must be some new physics to explain massive gauge bosons…" which worked very well for SSC and LHC motivation. I don't think we have to normalize to that any more. I think we have to normalize to the "strongest" language we could use for ANY new physics, in the post-Higgs discovery, post-theta13, post-Planck…etc… world we live in now.
>
> regards,
> Ashutosh
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