So What Is It???

So What Is It? That’s the question one hears in all the bars and on all the street corners and on every Twitter feed and in the whispering of the wind. Everybody wants to know. That bump seen on the ATLAS and CMS two-photon plots! What… IS… it…?

ATLAS_CMS_diphoton_2015

The two-photon results from ATLAS (top) and CMS (bottom) aligned, so that the 600, 700 and 800 GeV locations (blue vertical lines) line up almost perfectly. The peaks in the two data sets are in about the same location. ATLAS’s is larger and also wider. Click here for more commentary.

Well, to be honest, probably it’s just that: a bump on a plot. But just in case it’s not — just in case it really is the sign of a new particle in Large Hadron Collider [LHC] data — let me (start to) address the question.

First: what it isn’t. It can’t just be a second Higgs particle (a heavier version of the one found in 2012) that is just appended to the known particles, with no other particles added in.  If you try to put that idea into the equations, you immediately find the new particle’s mass is so large that it (or anything similar) would decay very often to other known particles, and very rarely to photons.

[Like the Higgs particle, it would only interact with photons indirectly, via direct interactions with the other known particles (see figure 3 of this post); but unlike the Higgs particle, it is heavy enough that it can decay to any particle/anti-particle pair with which it has direct interactions (see figure 2 of the same post); and the direct effect beats any indirect effect.]

Therefore, if this idea were correct, either

  • no two-photon events would be observed yet, making the bump impossible, or
  • there would be tens of thousands of these new particles decaying to pairs of jets (from quark/anti-quark pairs), or to top quark/anti-quark pairs, or to charged lepton/anti-lepton pairs… any of which would have been easily seen in studies done by ATLAS and CMS using the 2011-2012 LHC data.

Now, this has a really interesting implication! If this bump is a real particle, there must be at least one other particle that makes such a two-photon bump possible.  That new particle (maybe heavy, or maybe lightweight) hasn’t yet been found by the ATLAS or CMS (or LHCb!) experiments, but is almost certainly accessible to them. In fact, signs of an additional particle or particles may already be obvious (or almost obvious) in their existing data. It might just be a question of looking in the right place and of asking the right question.

This is what a lot of theoretical work this week has been about: considering the options for what the two-photon bump’s source might be, and thinking about further consequences of its possible existence, as far as other particles and forces with which it might be associated.

(And yes, I admit it; I chased this ambulance too. Took the week off from work. Didn’t sleep much.)

So what is it? There are a lot of possibilities. It could be a simple elementary particle like the electron, interacting with known particles indirectly, as a result of direct interactions with some heavy, as yet unknown particles. It could be a composite object like a proton, made from objects bound together by a new force that we are about to discover. It might be that the photons to which it seems to decay aren’t photons after all, but are new particles that mimic photons in some way (an idea that goes back at least to 2000.) I certainly don’t know what it is, and neither does anyone else yet. But each of the many different ideas comes with predictions — predictions which in many cases lead to LHC signals that can be looked for NOW!

We’ll have to wait quite a while, six months to a year, before we have enough new data to see the bump either disappear or become a completely convincing signal of a new particle.  However, perhaps the bump is a clue … a clue that can lead us to a discovery that can happen much sooner.

BUT WHAT IS IT???? Sometime in the next few weeks I’ll write a non-expert’s guide to the various options. Probably this won’t happen before the holidays, but stay tuned in the New Year.

50 responses to “So What Is It???

  1. It can be a heavier Higgs particle for the simple reason that that sector of the Standard Model, taken by itself alone, has an exactly solvable qft.

  2. Whatever it is, I HOPE it will be at a mass of just below 700 Gev, to be precise 692 GeV (which I have been waiting for, for my little PET).
    It seems the more energy we put into these collisions the higher energy particles we find.
    To me it is like Russian dolls, the higher amounts of energy used in collisions opens the next level “doll”(with new higher energy particles inside). Perhaps there are a fractal infinity of smaller higher energy “Dolls” waiting to be opened,

    Now this is not the end. It is not even the beginning of the end. But it is, perhaps, the end of the beginning.
    Winston Churchill.

  3. I look forward to your non-expert’s guide. Happy Holidays! To All!
    sean s.

  4. Matt, I just wanted to let you know that even though you’re currently working in private industry this website is incredibly valuable as a place with no nonsense commentary and extremely accurate scientific information. I know you mentioned stepping away in a previous post and only updating every once in a while, but I hope that you reconsider and keep updating us well into the future. This site gets brought up constantly on other science related blogs and websites I visit, so there are clearly a hell of a lot of people that love to come here and gain a better understanding of fundamental/particle physics.

    I know it might be selfish, especially considering that you have real work to do, but if you can there are a hell of a lot of people that would be thrilled for you to continue the work. Happy Holidays to you and yours. Keep em coming

  5. Given the extreme indirectness that seems to be unavoidable in these matters, i.e., amazing short lifetimes and the maze of assumptions that go into reverse modeling from observed familiar particles, back through multiple interactions, farther and farther into unobservable realms, how confident can we be that the modeling is unique and corresponds to how nature really works, as opposed to a Ptolemaic model the reproduces the observations but does not correspond to how nature works?

    • As far as I know, the Standard Model is the simplest known model that reproduces observations made so far. If there were a simpler one that still matched observations, they’d use that instead.

    • The issue with the Ptolemaic model was that infinitely more levels of complexity were required to roughly match what was observed. With our current model we get excellent, sometimes astounding accuracy from a few basic assumptions, which is almost the reverse. Often we are limited simply by our ability to calculate the results of a simple theory with complicated results.

      There are areas where epicycles might be an issue, some approaches to trying to fit in dark matter or neutrino mass for example, but on the whole the theory is quite robust and, if not the final word, then largely correct.

  6. The width is what makes this nontrivial to deal with theoretically, and has allowed some people to claim that we are actually seeing a double resonance side by side.

  7. Have not checked this site in quite a while…I thought it might become active again (and I’m glad it did) with the news of the possibility of a new particle. I read with some distress about current US physics funding and the fact that you are now employed in the private sector…my condolences (I hope you are not a quant on wall street!). Anyway I don’t want to stray off topic…

    I will ask the same question that I have occasionally asked on your site in the past, for example in the comments section under your article: “Courses, Forces and(w) Einstein” back in June 2013 I asked:

    “ Since we are on the subject of additional particles, does anyone know if current LHC data precludes a 4th spin ½ charged lepton at around 360 to 370 GeV?”

    This lepton would be in a 4th ‘family’ all by itself (no associated quarks or neutrinos). It could be created with its antiparticle at around 720 to 740 GeV. I would expect a very quick decay to photons.

    So is it possible that this bump at around 750 GeV is this lepton I have been waiting for, or can it be ruled out?

    • You can’t ever rule anything out without knowing what other fields it couples to and how strongly.

      That’s how particle collider experiments work: you predict how often it should be produced and then once you collect enough statistics to show that it isn’t being produced at that rate or more, you’ve ruled it out.

  8. Matt : How do we know that it is even a boson ?

    • If it decays to two photons, it would have to be, by conservation of angular momentum. Photons have a spin of 1. Any particle with integer spin is a boson.

      • Yes, but they could have additional decay products that haven’t been seen yet, Do they actually know enough (say from energy-momentum conservation) to know that there is nothing else? After all, there is no place for such a particle in the standard model and we do know about the possibility for dark matter.
        How do they know, as a start that there isn’t a spin-1/2 neutrino that shot off in some direction.

        • Of course that would violate lepton conservation, but maybe some other particle (assuming we believe in lepton number conservation).

        • There can’t be any additional decay products, as they would carry away energy and there wouldn’t be a resonance at 750 GeV in that case.

  9. Could it also be bad software in the trigger algorithms?

    • PS: Maybe they should check the Higgs boson data for similar “ghosts”, sorry.

    • The exact same bug in both ATLAS and CMS? That’d be an amazing concidence.

      • I am not talking about a bug. I am talking about bad software. What exactly are they asking for in the “emulated algorithms” in the various trigger scenarios? Are they using “moulds” to cast signals where there are none? Are these signals a consequence of the scattering of energies from the collisions or energies caused by the triggers?

        • I don’t quite understand what you’re describing, but generally “bad software” and “bugs” are pretty much synonymous. If the software is doing what it should, then it’s good software. If it isn’t, then whatever it’s doing wrong is a bug.

          I’m also not sure what you mean by the phrase “energies caused by the triggers”. The triggers simply decide which snapshots to keep and which ones to throw away as uninteresting.

          • Oaktree is asking whether the software might be biased in some way, altering the raw data. The first issue he brings up is whether the software is selectively discarding results, possibly favoring any data around a certain energy range, making it look like there’s an excess of events there when there isn’t.

            The second issue is whether the detecting equipment itself might be biased, being especially sensitive to collisions with a certain energy range or type, again making it appear like certain events occur in excess.

  10. Pingback: ¿Es un pájaro, es un avión? ¡No. es superbump! | Ciencia DiY

  11. Energy ≠ Mass. Without relativity energy = mass is nonsense.
    We cannot produce Natural Battery energy from mass, by off and on Higgs field.

    It is Majorana mass or higgs mass the Space is fundamental.
    Energy is the property of space, we understand it by the “flips (of various frequencies)” – as Spins and Goldstone mode (lefthand weak interaction) ?

    Without massless particles (momentum) there is no mass with higgs like field intereaction.
    High energy (frequency) in quantum reality is not mass – but more space – is a PARADOX – relatively Chose by nature as Mass – by quantum decoherence – what we observe and measure.

    More energy in LHC will create more energitic “particles”. If momentum is eleminated, it may turn into more space ?

    • We can only use some energies stored by goldstone mode during high energy events such as supernova, star explosions – like in rare earth materials – observed in our present symmetry group energies – in solid state physics ?

      • Particle means, momentum energy which always decay into photons – of present symmetry group energy – what we call spacetime.

        Mass means, interaction with external fields like Higgs – which always decay into higgs particle and neutrino – and then into “high energy” photons – but space.
        Because more energy is more “short Time” it live.

        The Majorana is intrinsic ?
        The difference between “Flip” of left and right handness – to get extra degree of freedom (mass) – and the Neutrino osscillation to Majorana (mass) – is only charge is replaced with flavour.
        But flavour is more “short lived (more high energy)” ??

    • EDWARD JOHNSON

      still not convinced attempts to understand how the universe works in purely classical physics we will arrive at the point we desperately want to be. The unknown phenomena ( mechanism ) is right under our noses but we choose not to believe it

      • According to Newton’s second law force is something that changes momentum of the test particle. If you see the momentum of the particle change, you deduce there is a force acting upon it.

        It is tunneling, radioactivity, got increased energy (non conservation), for short period – increasing the time period by adding momentum thru LHC energy ?

        It is non-conservation by dance of allmost non-repeating pattern – a failed rhythm.
        It is proton decay by failed rhythm – but as residual strong force ?

  12. It i lines the existence of supersymmetry for the Boson of Higgs? There is Antigos o ns?

  13. Pingback: Bookmarks for December 19th from 18:53 to 19:41 : Extenuating Circumstances

  14. A very small UFO?

  15. Gosh, I hate playing the Grinch but what if it’s nothing and goes away? Is this the end for the LHC then? I doubt if anyone will fund the next “LHC” so what happens to this area of science?

    • As far as I know CERN has already secured its funding for at least the rest of this decade. China is also in the process of building a new particle collider.

      If this year’s “bump” at 750 GeV proves to be nothing, that won’t doom the LHC. Negative results are useful in themselves – the LHC has put a lot of constraints on various theories and disproved others. There’s still every reason to keep on looking too.

  16. While the theories being batted around at this early stage disagree on the particulars, most agree that, so far, this data bump best fits the properties of an extended Standard Model gauge boson.
    “This is kind of like what we saw with the Higgs,”

    http://www.symmetrymagazine.org/article/july-2015/something-goes-bump-in-the-data

    • The lhe has that se eu Boson havia than the bb os on og higgs.would bê an others explain action tô asymmetry of particles antiparticles, as well as the breakdown of cp tô weaker.the interaçtions and breakdown pt that is there flexível deformations of spacetime, that of these deformations generate charges, and have then topological geometry for charges mass and the bom spacetime, that are notof the quantic vacuum

  17. Matt Strassler,

    Predictions and evidence have very little to nothing to do with science. The first is a parlor trick, the latter is subjective. We stumble,across huge ape – like footprints in the mud. You see Big,Foot, I see a prank. We BOTH evaluated the “evidence.”

    Evidence is a subjective concept. Science is about rational explanations and theories which play back frame by frame like a movie. After that, after presented to the jury , the scientists’ job is done.

    The LHC is a joke. HOW can CONCEPTS break in bits?

    • Corky the Ungroomed

      Have you ever considered that your everyday human intuition isn’t necessarily the ultimate arbiter of truth?

      How is a prediction a parlor trick? One says “I predict that X will happen because of Y” and then one searchs for X happening by doing lots of Y.

      Evidence is not subjective. What you are talking about is interpretation of that evidence. Interpretation of evidence isn’t uniformly subjective, it has degrees of subjectivity. It’s certainly possible for one interpreter to be a lot more objective (i.e unbiased) than another (i.e one with an obvious axe to grind against anything that doesn’t fit his preconceived world view).

      Finally, there are thousands of potential theories to explain the universe, all of which are interally consistent, but without reference to obsevations – i.e interpreting evidence – there’s no way to say which is right. And what is it that we refer to observation? – yep, you guessed it, the predictions.

      The only argument you have against any of this is “I don’t understand it, therefore it’s false”.

      • Mike Huttner umderstands science. It is NOT about predictions and parlor tricks. Proests, back in the day, made,predictions by paying attention and appeared powerful and god like to the peasants.

        You can watch an apple fall to the ground TEN THOUSAND times and you still will not understand HOW , Z the mechanism. You can observe the seasons every day of your life ,,YET NOT umderstand HOW they work, the physical mechanism.

        General Relativity USES GRAVITY TO,EXPLAIN GRAVITY. WHY would objects follow this curvature.,WHY would the Earth fall into the sun?What force makes planets follow,this curvature and warping. It is usingmgravity itself to explain gravity. What is space time? It is a CONCEPT. NOTHING MORE. NOTHING CANNOT CURVE OR WARP.

        There are alternatemexplanations for Eddington’s experiment. Evidence is subjective.

        Deep explanation is the goal of science , NOT prediction. Predictions have nothing to do with science and amoumt to parlor tricks. Predictioms are what mathemagix/mythematician style fizzicists do at their monasteries……

        • Corky the Ungroomed

          Scientific predictions are not “parlour tricks”. Scientific predictions are not like priests making wild conjectures. Predictions are a natural result of a theory. A scientist makes a theory to explain evidence, and the implications of that theory (i.e the mechanisms it proposes) mean the scientist should be able to observe other phenonema (that in fact may have already been observed). It’s a means of checking whether a theory is true or false. This is what a prediction is. You have yet to make any sensible argument against this.

          Evidence is not subjective. All your arguments, not counting the cod nihilism, are simply supporting my point that the interpretation might be subjective but not the evidence itself. And yes, there is more to judging evidence than simply ‘opinion’. In fact if you think everything is simply opinion then I don’t see why you’d ever be arguing with anyone about anything, since you’d have no basis for anything other than “like, it’s just my opinion, man”.

          If you want to understand how space-time can be curved and how time dilation works, why not learn the math? If you’re not willing to learn the math, how can you criticize? You seem to think that the only limits on reality are your own current ability to understand it, and anything that isn’t immediately graspable by everyday intuition is necessarily false. This is the kind of thinking that Flat-Earthers use. Do you really want to be like them?

          You obviously have an interest in this subject in general, so that’s a good thing. I suggest you stop watching dubious youtube pseudoscience and get stuck in to proper science instead.

      • Everyone has a,world view and biases. EVERY single person. Scientists are people first and NO LESS BIASED than any other profession. Evidence will be filtered through that no matter how hard you try. Evidence is OBSEVER DEPENDENT BY definition. And evidence is a SUBJECTIVE CONCEPT by its definition , its very nature and in principle.

        Look up the underdertermination of theory……… Carnaedes has excellent YouTube videos explaining this. This is a problem and there is no way to choose between the rival theories other than OPINION.

  18. The Mythematicians and Mathemagicians who comprise modern Fizzix need to get their stuff together. They are all spouting different definitions for the word hypothesis. Fields are a concept. Physics studies objects, things with shape and location. Draw energy. Draw a,field. Draw space -time. Howmcan the Earth go around the Sun many more times for a person who rocketed into space compared to his twin left on Earth? Obviously it cannot.

  19. Wrong . Evidence Is SUBJECTIVE in principle as it is observer dependent. Youmare arguing agaimst the PRINCIPLE AND NATURE of evidence. It is subjective. Interpretation IS SUBJECTIVE

    Two theories every now and then BOTH make the same predictions and get the same result . There is no way to choose between them other than opinion.

    YOU are trying to persuade and thatmis NOT the job of a scientist. Present a rational consistemt theory and your job is done. There is NO WAY to show a theory to be right. YOU are attempting to PERSUADE the jury with “evidence” which is SUBJECTIVE by ITS VERY NATURE. It is something we will never know. Develop a deep explanation with abioity to be plahed frame by frame like a movie to the jury.JOB DONE.

  20. There is a PARADOX, Involution of phase change of being to nothing – the local broken symmetry (ssb) is no longer – caused tunneling.

    Due to radioavtivity neutrinos were discovered. Weak reaction, with its short distance can cause tunneling.
    Tunneling need high energy. If high energy, short lived and unobservable.
    LHC energy increased the momentum – the bump is an observable high cosmological constant – otherwise at low energies, is an unObservable due to the very short life time.

  21. The Weinberg angle, in the equation is also varying as a function of the momentum transfer, Q – coupling value locks as constant.

    The quantum vacuum is the state in which no photons are present in any of the modes of the radiation field. However the vacuum only remains empty of particles for inertial observers. If instead we posit an observer in a uniformely accelerated frame of reference, then what was a vacuum state becomes a thermal bath of photons for the accelerated observer. And what is true for accelerated observers is similarly true for regions of space-time. Momentum transfer can increase the thermal bath (vacuum energy). ?
    So Alpha increases by momentum – means not a black hole but increase in cosmological constant ?

    “The physical reality of Time dilation and Rest mass cannot coexist.”

  22. Reblogged this on Current Affairs and commented:
    So what is it? Matt Strassler on “the bump seen on the ATLAS and CMS two-photon plot” at the LHC

  23. Mathematical Fizzix is not part of actual Nature. It is a human invention-math. Our axioms. Predictions are what the Mathemagicians do. Prediction did not open any flood gates for learning. Slick priests of the day simply paid attention and ACCURATELY predicted. The POINT is they did not understand and had no EXPLANATION as to HOW….And NEITHER do the mathematifal Fizzicists. You can predict all day long . It is MEANINGLESS. THE GOAL is to UMDERSTAND. And have very deep explanataions for phenomena. EXPLANATION is what allowed progress. There are many others who recognize this but will not speak up. Everything from medicine to physics is corrupted. Chicanery in journals everywhere, politics, career loss, ostracized etc. etc.

    Evidence IS OBSERVER DEPENDENT by nature and totally subjective by its very nature. Evidence is a subjective thing by nature, the very concept. Eddington experimemt was very biased. Other explanations exist. The Twin Paradox? WHy would theEarth go 50 TIMES. around the Sun for the Earth bound twin , yet only ONCE for one twin flying in space, simply because he was flying out in space at great speed? General Relativity and time dilation are IRRATIONAL AMD WRONG.

    Carneades( his video probes science as curently done is NOT RATIONAL), Mike Huttner, Bill Gaedes, all of them provide fabulous powerful argumemts against Mathemagical Fizzix. Huttner favors EXPLANATION AND RATIONALITY.

    • Time dilation is a physical reality at relativity level, so it assumes the particle and black hole.
      But at quantum level due to uncertanity principle, time get shorter but energy increases – means increase in cosmoligical constant and space – no particle no black hole.

      It is a Musical chair at speed of light. If the higgs like field is Tachyonic, the color charges dancing around the chair sit and again dancing around the chair.
      The symmetry broken while sitting is the mass we observe. There is a failed rhythm in the pattern – for a period. If the period is more short, more is the energy. ?

  24. I’m eagerly looking forward to the “non-experts guide to the various options” for this particle in the New Year.