At a CMS/Theory Workshop in Princeton

For Non-Experts Who've Read a Bit About Particle Physics

I spent yesterday, and am spending today, at Princeton University, participating in a workshop that brings together a group of experts from the CMS experiment, one of the two general purpose experiments at the Large Hadron Collider (where the Higgs particle was discovered.) They’ve invited me, along with a few other theoretical physicists, to speak to them about additional strategies they might use in searching for phenomena that are not expected to occur within the Standard Model (the equations we use to describe the known elementary particles and forces.) This sort of “consulting” is one of the roles of theorists like me. It involves combining a broad knowledge of the surprises nature might have in store for us with a comprehensive understanding of what CMS and its competitor ATLAS (as well as other experiments at and outside the LHC) have and have not searched for already.

A lot of what I’ll have to say is related to what I said in Stony Brook at the SEARCH workshop, but updated, and with certain details adjusted to match the all-CMS audience.

Yesterday afternoon’s back-and-forth between the theorists and the experimentalists was focused on signals that are very hard to detect directly, such as (still hypothetical) dark matter particles. These could perhaps be produced in the LHC’s proton-proton collisions, but could then go undetected, because (like neutrinos) they pass without hitting anything inside of CMS. But even though we can’t detect these particles directly, we can sometimes tell indirectly that they’re present, if the collision simultaneously makes something else that recoils sharply away from them. That sometime else could be a photon (i.e. a particle of light) or a jet (the spray of particles that tells you that a high-energy gluon or quark was produced) or perhaps something else. There was a lot of interesting discussion about the various possible approaches to searching for such signals more effectively, and about how the trigger strategy might need to be adjusted in 2015, when the LHC starts taking data again at higher energy per collision, so that CMS remains maximally sensitive to their presence. Clearly there is much more work to do on this problem.

56 responses to “At a CMS/Theory Workshop in Princeton

  1. kashyap vasavada

    Do the CMS people already have some events which they cannot explain by momentum conservation with the known particles?

    • They have a huge number of events; the question is whether they have more than expected with this property or that property. The answer right now is no, there’s no evidence of any excess; but how to search more effectively within this large set of events is part of what we’re discussing.

      • Antti Kangasvieri

        How large percentage of events can be reconstructed down to last particle in experiment like CMS or ATLAS? How much information is lost in CMS compared to ideal perfect detector?

  2. If you are at Princeton –

    And see Prof Eric Verlinde –

    Ask him if possible if he has any notions how a constantly emerging Space

    Could affect the dynamics of quantum particles ( their behavior generally and interaction )

    That would be an interesting question.

    I am sure he is already putting his mind to this – but probably centered around strings!

  3. Ben Gutierrez

    Hi Matt: I wanted to ask you, if supersymmetry is not present at TeV energies, a) How does this impact early universe cosmology b) What other solutions to the hierarchy problem may be there, perhaps electroweak baryons, or composite Higgs? thank you

  4. appear more easy full the universe with exotics particles than seeks mistakes in physics laws

  5. Jens Knudsen (Sili)

    Would there be any point in putting a version of one of the big DM detectors near on of the LHC interaction points, or is the expected flux far lower than the expected DM background signal?

    • The flux would be vastly lower, so indeed, there’s nothing to be gained.

      HOWEVER, if instead the LHC produced new particles which existed for a short time and then decayed to dark matter particles, then building a new detector next to an LHC detector might make sense. But we would only consider doing this if we first had some evidence for such particles, which currently we do not.

  6. Belief in science?
    Here’s a well written piece by Matthew Francis.

  7. Concerning the “trigger strategy”: As any choice of a strongly selective trigger may filter out interesting but unexpected events, would it be useful to run also a more weakly selective trigger for data that are stored for later (delayed) off-line processing? Is the idea of storing more data for off-line processing still followed for the 2015 runs?

  8. Matt,

    Why is it that there are not too many (actually non that I could find) good textbooks in particle physics experiments, just too many fragmented papers?

  9. How many higgs particles are there in the universe?
    And does not their mass add to the mass (or energy) of the universe? Does that not create problems in cosmological models ?

    I know about the Dark energy/higgs conjecture, but that is NOT my question.

    • Different theories predict different number of Higgs bosons and of course they will add on to the current cosmological constant problem. Here is paper I worked on which predicts 4 spin 0 bosons which could be higgs and does simulteanously resolve the cosmological constant problem A follow up is currently in its second month of review by a mainstream journal on particle physics. P.S. there is a missing 2pi in this paper for the expression k=2pi/r

      • I was hoping for matt to answer, but thanks for jumping in. Your paper looks interesting , although I doubt it will make the mainstream. But can you elaborate on how mainstream looks at this problem. Thanks again.

        • Prof Matt has discussed about the second Higgs on his blog

        • Yes I understand that it will take many conferences and papers to shift the paradigm of the mainstream researchers. It took a great open mind like that of Max Planck to recognise Einstein and bring him into the mainstream. Einstein inturn recognised Bose whose paper was rejected by the mainstream journals and only through the influence of Einstein could Bose’s paper be published and accepted under the new title Bose-Einstein statistics. Andre Linde faced similar problems.

      • Ah, the crystal lattice. Perhaps with a little improvement here and there it will offer something of value. I think the most important thing with this sort of thing is to avoid confusion between space and spacetime, between spatial curvature and spacetime curvature, and between photons and gravitons, which are virtual particles. And like Matt says, a virtual particle is not a particle.

        • Thanks a lot John for you thoughts.I have had fiur reviews fron mainstrem researchers Three are in favour of giving it a more rigorous mathematical platform and are of the same opinion that it has promise. The fourth is not infavour of the idea that spacetime is a lattice gauge field and prefers particles as points whose location in spacetime is parametrized by points (x,t).

      • Ervin Goldfain

        I am afraid I am skeptical of your work. Here is why:
        1) Spacetime quantization is known to violate Lorentz invariance and be at odds with Special Relativity.
        2) As you probably know, there are many unsolved challenges of the Higgs scalar in the Standard Model. It is likely that four spinless bosons would complicate these problems further.
        3) The presence of additional scalars would have impacted some of the already measured cross-sections and branching ratios.

        • In my paper LIV does not occur because a given photon will travel in an eigen state of spacetime appropiate to its four momentum and still move at the speed of light. 2 the four spinless bosons could be yet unknown scalar fields that solve problems you mention and otgers such as CP in QCD. 3. I am still to work out if what you suggest in 3 is correct. However look at the solutions that my paper provides.These solutions are what make other researchers see a promising solution to problems in fundamental physics.If you look at it from that angle you will find that there are minor problems to be rectified inorder to make it a far reaching idea

          • Ervin Goldfain


            1) The speed of light can only be unambiguously defined on a continuum manifold. In this context, your attempt to reconstruct Special Relativity and Lorentz symmetry from a discrete space-time model remains questionable from the outset.
            2) To be compelling, the hypothesis of additional four scalar bosons must be shown to consistently integrate with the current particle content and dynamics of the Standard Model. Your paper lacks in this regard.
            3) The solutions you suggest are among a large spectrum of scenarios currently available in hep-th. In my opinion, relying on Planck scale physics/UV completion and the yet-unproven graviton is heading in the wrong direction.

            Please understand that this blog is not appropriate for this discussion. There are other venues and forums where these ideas can be shared and debated. This is my last reply on your paper.

            Kind regards,

            Ervin Goldfain

          • Marcel van Velzen

            Hello Stuart,
            We actually already know there exist 4 scalar fields. Usually people speak about the Higgs scalar field as the only scalar field but in reality 4 scalar fields have to be introduced in the Standard Model. 3 of these fields provide mass to the W (+ and -) and the Z, the remaining one is the Higgs.
            See Weinberg’s article:

            And his remarks:
            “Salam and I assumed that the culprit is what are called scalar fields, which pervade all space.”
            “… one of the four scalar fields we introduced …”

          • Dear Marcel

            So the 4 scalar fields intrinsic in my theory are completely natural? Thats great.This is progress.It is people who see the true potential in an idea that carry scientific progress into the future.
            On another happy note, one of the Titans of European theoretical physics has come forth to give my paper a rigourous mathematical platform so that skeptics can see its true potential.
            Thanks Marcel for your much appreciated support.

          • kashyap vasavada

            @stuart. Standard model Higgs is a 4 component complex field. This does not make it four different particles. This would be similar to a single Dirac electron having 4 component wave function or field. But if you believe strongly in your model, surely go ahead. I have heard that eventually crazies model wins!!!

          • @kayshyap
            The Higgs is a 4 component field that we know. Weinberg and Salam proposed 4 scalar fields which is what Marcel was talking about.

          • kashyap vasavada

            @Stuart. There was no reply button in your last answer. So I used the previous post’s reply button. The way I understand Weinberg-Salam’s electroweak theory is that there is a complex two component field (i.e. 4 degrees of freedom). Out of that three are eaten up by W(+ -) and Z to get their masses. The left over presumably appears as a single particle at a mass of ~ 125 Gev. I realize this is a crude picture replacing intricate theory of spontaneously broken symmetry with gauge invariant Lagrangian. But it may capture the essential physics. May be Marcel or Matt can clarify this. Of course, there could be more than one Higgs particle. In fact super symmetry requires it but not the standard model.

          • A skeptic in the crowd

            Multiple Higgs (as in supersymmetry) is certainly a possibility, although not a shred of evidence exists today to back it up. It is unclear how the existence of multiple (presumably heavy) Higgs bosons would impact the long list of open problems associated with the Standard Model.

          • @kashyap
            Also take note of what Weinberg is suggesting in the article Marcel cites. Weinberg is suggesting that the newly discovered Higgs-like particle could be one of the 4 scalar fields he and Salam predicted given the low mass of the particle. A true Higgs boson would be way massive than the one discovered.

          • Marcel van Velzen

            Dear Stuart,
            Your paper is certainly interesting enough to be read and could potentially contain some important ideas but it is also possible that an expert immediately spots weak points. It certainly needs more field theoretic basis especially to connect the different spin states to the known bosonic force fields. However, in the standard model 4 real scalar fields (actually 4 Hermitian operators) are introduced that produce only ONE Higgs boson and 3 longitudinal polarisations that the 3 massless vector bosons need to be promoted to massive vector bosons. Therefore, the suggested 4 scalar fields in your article do not have to pose a problem. I wish you good luck!

          • @Marcel
            Thanks for your encouragement. I will continue to consult with the experts with the intention of building a stronger theoretical basis.

          • kashyap vasavada

            @Stuart. Again no reply button on your last answer! May be webmaster is telling us to cut it out!! Any way, you may want to read Weinberg’s papers, rather than just N.Y times article. It seems to me that this may be largely a matter of semantics in a popular article for general public. My understanding is that when he talks about four fields, he does not mean four independent fields. These are part of a complex doublet (phi1…4) combining phi1+i phi2 and phi3+i phi4. Of course, I would not mind being corrected or over ruled!

          • @kashyap
            Can you please cite and provide a link to Weinberg’s paper.Recall that it was Weinberg who wrote the N.Y.times paper and those are his thoughts.

          • Marcel van Velzen

            Of course you’re correct, the scalar fields together form a doublet under SU(2). Instead of his papers I would recommend Stuart to read Weinberg’s books on field theory but these are very advanced. The Higgs mechanism is very well explained in:
            Gauge Theory of Elementary Particle Physics
            Ta-Pei Cheng and Ling-Fong Li

          • Thanks a lot. The important thing like you said in your penultimate post is to”.. link the four spin states to the known bosonic forces..” Your contributions including Kashyaps’ are valuable will continue my research and consultations.Mucha gracias

          • @kashyap
            Can you kindly look at the spin states that give rise to 0 spin bosons in my paper.Notice that each member of the following spin state pairs a) & c) and b) & d) is related to the other by some mirror symmetry. Can this suggest hints of a complex doublet? What is your take on that?

  10. Is math the correct (sufficient) tool to use to make progress in completing the physics? Could holographs (with motion) be a better tool?

  11. A skeptic in the crowd

    A four-dimensional space-time lattice DOES NOT have four vertices, so you need many more scalar bosons than four to fill these vertices. There is simply no connection between the four scalar fields in the electroweak symmetry breaking mechanism that generates the W, Z masses and your graviton model!
    Stop fooling yourself….these are serious questions, no Titan can save a model based on ad-hoc assumptions.

    • My model does not use vertices. The lattice cell itself is the graviton.It can also be viewed as the effective field.I do not make ad- hoc assumptions. Please read my paper carefully. Like Ervain is suggests if you have comments please forward them to my email address on the paper to avoid using someone’s blog to debate issues the owner did not endorse.Others are doing so.

      • A skeptic in the crowd

        “The lattice cell itself is the graviton”

        This in itself is clearly an ad-hoc assumption, with no firm physical foundation. How do you unambiguously define a quantum particle of spin 2 on a discrete space-time that defies Special Relativity to begin with and lives well above the Standard Model scale?. Are you aware of the great challenges that both perturbative quantum gravity and lattice field theory face? You don’t seem to take any of the above criticisms seriously and prefer to rather brush them away…

        • Please read the paper before you comment and answer me via my email address if you are giving me the much needed constructive criticism.
          P.S.I do appreciate every comment you say and I carefully consider it not brush aside.So more please but via my email.

          • a skeptic in the crowd

            I apologize but emailing you and starting a full-blown discussion on my objections is a time commitment that I currently cannot sign up to. Unfortunately, it is my opinion there are too many unsupported extrapolations that lie at the foundations of your paper. Perhaps other people would be willing to continue this discussion.

          • @A skeptic in the crowd
            Thanks for a healthy dose of skepticism. Much appreciated. thank you.

          • Sounds like an interesting paper, where can I read it? I have some ideas that could explain spinors, rotations of space as it expands from t=0. I believe that rotation must have happened instantaneously at t=0 in order for a field(s) to be created or else the vacuum collapses again to steady state. I also believe the singularity is not a single point but rather one isotropic state.

            In your models, could the temperature start not from a high and cool down but from one low value and increase once space started to expand and then started decrease (cooling) when the particles started forming.

            I perceived particles to be charged space created by the initial spinors that must of been moving at extremely high velocities, c is the transition between free and trapped energy. i.e. mass can only exist below c.

          • Hie Oaktree
            Here is the link
            All I do in my paper is take a finite length of the spacetime continuum, break it down into Fourier components and analyze them. I do not dwell into initial conditions.

          • Hello Stuart, thanks for the link and a very interesting paper. I am always skeptical about the use of quantization techniques. Did these processes lead to determine the natural eigen states or did they create the eigen states?

            I believe our math is not sufficient to deduce the reality of space-time because it is only a best curve approximation regardless of the scale.

            If the gravitons or at such a low energy was prevent the vacuum from collapsing to zero? In other words since we lives in a universe of disturbances, oscillations, should there not be an external force that maintains the unstable space-time continuum?

            Can holographs be used the create the models of the various theories?

          • Hie Oaktree
            Thanks for reading my paper. I clearly do not understand the question ‘Did these processes lead to determine the natural eigen states or did they create the eigen states?’
            Like I have mentioned before all I do is take a finite length of the space-time continuum, break it down into Fourier components and analyse them. In my paper the quantum vacuum and space-time are inextricably linked via the uncertainty principle. You could consider it as the equivalence of four momentum space and space-time i.e different sides of the same coin so one cannot exist without the other. The cosmological constant represents the lowest Eigen state (zero point energy) of space-time therefore the vacuum does not collapse to zero.

          • Point being if you have infinite eigen states of these “quantized pockets (volumes) of energy, but our math can only draw a set of finite points because we cannot “see” or deduce all, then we don’t know the whole story. Much like a big puzzle and we have only a few pieces in hand and infinite missing.

            My main point is quantization is necessary of our tools but is placing a limit to our understanding and even worst may lead us in the wrong directions and will be wasting a lot of time and careers.

            Can we come up with better tools and/or better experiments and sensors?

            I hope they can finish JWST in my life time. :-)