Of Particular Significance

A New Era Dawns

POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON 07/05/2012

[July 6 UPDATE: very busy with work here, but I have finished a short article briefly describing the data, and why it is convincing that a new particle has been found.]

July 5: A wild day at the CERN laboratory yesterday, continuing into today and surely the rest of the week.  [If you’re a lay-person wondering what all the fuss is about, you might want to read my article “Why The Higgs Particle Matters“, or watch my year-old video clips that explain how one searches for the Higgs particle, or read the Higgs FAQ.]  [Very well-written and almost entirely accurate articles at both the New York Times and the BBC.]

The contrast from last December is profound.  After last December’s presentation on the search for the Higgs particle at the Large Hadron Collider [LHC], whose results I called “inconclusive” and other bloggers called “firm”, most ATLAS and CMS experimentalists I talked to were expressing, in public and in private, something between extreme caution and cautious optimism. I can’t count the number of times that senior experimentalists told me a story about a 3 sigma result that they’d seen disappear because of a subtle mistake. Though many theorists were convinced, many other theorists (despite what you hear from some other bloggers) shook their heads and expressed deep caution. Discussion at the CERN cafeteria and in the hallways focused on which parts of the data were most trustworthy and whether the discrepancies between what ATLAS and CMS had observed made the result unstable to small changes. All in all, despite what all the other bloggers said, I personally did not talk to a single experimentalist who felt the result was secure — which is not to say (this is an important distinction, please read carefully and please do not misquote) that anyone (including me) thought the hints were clearly a mirage. The problem, as I explained at the time, was that you could run an argument that made you confident in the hints, and you could also run an argument that made you lack confidence. Well, evidence isn’t firm until the argument in favor is a lot stronger than the argument against, and that wasn’t true in December.  The evidence did improve somewhat by March, though the improvements were kind of up and down.

By enormous contrast, after yesterday’s presentation I did not speak to a single person who expressed serious doubts that ATLAS and CMS had made a discovery. (The most negative comment was from an experimentalist who wished ATLAS and CMS hadn’t been forced, by the early-July scheduling of the ICHEP conference, to do their data analysis so soon; he would have preferred to have twice as much data and a result that left him with absolute confidence. Well, if that’s the worst thing anyone can say…) What’s changed from December is that every argument you can make comes out in favor of the result being real; I’ve been unable to think of any argument against it, nor have I spoken to anyone who has proposed one. All the conversation now is on what the discovery means and on what to do in coming months.

How did a result that was inconclusive in December become so convincing in July, with just a doubling of the amount of data? The answer, as far as I can tell, is that a number of things that could have gone wrong all went right. I’ll go through this in more detail later, but suffice it to say for now that the experts who operate the accelerator and the two detectors all proved, yet again, that they are extremely smart and capable, and on top of that, they had some good luck that brought them to results almost as strong as anyone could hope for. Only time will tell whether the two experiments both got a bit lucky with a statistical fluke or whether the Higgs is actually a bit easier to find than theorists expected — but on top of this, the LHC produced somewhat more collisions than estimated in advance, the experimenters dealt admirably with the extreme collision rates, many new techniques for improving the measurements were developed, and these numerous small bits of good news combined for a nearly best-case scenario. Yesterday’s results were close to the optimal that could have been possible, given the amount of data; to have both experiments see clear signs of a new particle with a mass of about 125 GeV/c2 in both of their “easy” searches (for Higgs particles decaying to two photons, and for Higgs particles decaying to two lepton/anti-lepton pairs) was a lot to ask for, but it’s what we got!

My goal for today and tomorrow, if I can squeeze it in — obviously my highest priority right now is conversations with my professional colleagues about interpreting the result and discussing what needs to be on the agenda for the rest of 2012 and 2013 — is to explain to you:

  • What does the current data actually show?
  • What in the data makes the evidence in favor of a new particle so convincing?
  • What elements of first-rate experimental technique and plain-old luck combined to make the result so strong?
  • Why I am personally so convinced (more than the experimentalists seem to be right now) that the new particle is a Higgs particle, as opposed to something else?
  • To what extent is this particle consistent with the simplest Higgs (a “Standard Model Higgs”) as opposed to a more complicated type?

Maybe getting through this list will take me into next week. At some point I’ll write more about the implications of this being a simplest Higgs or not, but probably not before the middle of next week.   And hey, it’s also time to revise the Higgs FAQ!!!!

So stay tuned to this channel!  I’ll alert you when I finish writing the answer to each of these questions.

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78 Responses

  1. “… history shows that the wisdom of crowds is unreliable.” The folly of crowds might be more prominent than the wisdom of crowds — but consider the case of Wikipedia and crowd-pooled chess moves. These two examples seem to work surprisingly well. Let us grant that ATLAS/CMS has discovered a boson with spin either 0 or 2. Has any reputable physicist put forward a theory that can explain the new boson under the assumption that it is NOT the Higgs boson and the assumption that the Standard Model (without the Higgs boson) suffices to explain the new boson?

    1. You forget that when the Higgs boson was proposed most people (including Weinberg who introduced it into the electro-weak theory) didn’t believe it was right.

      You also forget that when Einstein proposed the photon most people thought it couldn’t be right for 15 years or so.

      Crowd-sourcing is a good way to go when you what you are trying to learn is a synthesis of existing ideas; it is a terrible way to go when you are trying to come to grips with new ideas.

  2. Hiya Matt! I echo Donna Miller’s comments above and Cathy’s words on FB a couple days ago. Thank you for the excellent work keeping us lay-people up to date on this phenomenal, ongoing achievement.
    PS: Hope you enjoyed your time at reunion! 🙂

  3. thanks matt,,i can imagine how busy you must be with the new data,i look forward to your posts,,,

  4. “Massive spin 2 particles are a challenge.” Why not take a wisdom-of-crowds approach and let particle physicists vote on the most likely candidates for a massive spin 2 composite boson?

  5. I thank you very much for this wonderful website and the answers that you provided in your articles and later to the questions. It’s amazing to see people asking the questions that I wanted to ask. Science does have a way to unite people. You might have answered the following question before. What empirical (or theoretical) evidence prompted scientist to look for the Higgs Boson mass in 100-200 GeV range? is it the top quark mass? Thanks.

    1. A combination of theory and experiment; the equations of the Standard Model (with full quantum corrections computed, so this isn’t easy!) tell you how the masses of the W, Z, top and Higgs are related (simplifying slightly), and having in experiment measured the W and Z with high precision and the top with moderate precision allows a low-precision estimate of the Higgs mass. Other measurements contribute indirectly also.

  6. First of all, thank you for your informative blog!

    The two-photon bump suggests that the particle found has either spin 0 or 2. Now if it has spin 2 (and therefore isn’t the Higgs particle), what would be the implications? Massless spin-2 particles are expected to be gravitons, but massive ones? Like gravitons, but just with shorter range / at higher energies (just like W/Z vs. photons)?

    Furthermore, there seems to be more interesting stuff going on at ICHEP. However, most stuff on the web is just about the Higgs, are there reports on the web about the other topics?

    1. Massive spin 2 particles are a challenge. Typical examples of massive spin 2 particles are composites (such as glueballs) or Kaluza-Klein modes of higher dimensional gravitons. But the theory of these things is not very well constrained, and typically other things show up when they do.

      The analogy “W’s are to photons as massive spin-2 particles are to gravitons” doesn’t work. Better: “rho mesons are to photons as massive spin-2 particles are to gravitons”. So now we have to look at what is different about rho mesons and W particles. Remind me, I don’t have time right now…

      Maybe the Resonaances blog is keeping up better than I am regarding ICHEP. As far as I am aware, there’s nothing coming out of ICHEP that can match what just happened, and there is plenty of time to catch up.

  7. This is really exciting! Thank you, Matt, for explaining what’s going on with the Higgs particle. In an earlier post, you expressed some disappointment that the blog had not reached a larger audience and many physicists explaining things in slightly different ways creates some confusion.

    I think that the blog makes a valuable contribution to laypeople understanding particle physics. Even it is to a smaller audience than you planned, you are still educating people. Some confusion is inevitable, but I find the benefits to outweigh the costs. For example, until I started reading your articles, I thought that a proton had three quarks (each with 1/3 the proton’s mass) that shot gluons back and forth. I had no idea about the sea of virtual quarks inside a proton, or that most of the proton’s mass was actually NOT in the quarks themselves. I was particularly surprised to find out about the virtual strange quarks and antiquarks in the proton.

    Please keep the blog, Matt. You’re doing great work.

  8. Prof. Strassler: You asked the question, “Has it occurred to you that the bump would be observed also when the accelerator is off?” My idea is that the proton beam itself acts as an antenna that receives ultra-high-energy cosmic rays in the form of paradigm-breaking (PB) photons. These hypothetical PB photons are not secondary cosmic rays with GeV or TeV energies but primary cosmic rays with vastly higher energies. I see no reason why PB photons could not in principle penetrate through the atmosphere and rock layers. My guess is that the proton beam acts as an antenna for the PB photons and creates a diffraction pattern at a characteristic antenna frequency, and then this antenna frequency is somehow falsely interpreted as a boson with spin 0 or spin 2. If you grant my premise that PB photons actually exist, then can you please explain in somewhat more detail why my idea is foolishly wrong?

  9. Hello, congratulations for the website- There is one thing that troubles me: if the Higgs bosons are everywhere, giving the mass to the other particles, why do we need to create them in a collision? If they aren’t everywhere…how do the particles actually interact with them to get the mass? Is this due to the difference between field and particle that you mention throughout (and I don’t fully understand)?

  10. Matt, the analogy used notwithstanding, we could say poetically the particles drank honey from the sea of Higgs field, but is there therefore a precise formulation of how that mass is acquired. Do not see any equations to show the exact process how its done.. One would be tempted to believe there is not any and each way it could happen.

  11. Sorry, but I should correct myself. The Z-gamma direct production is possible at tree level through quark – anti-quark annihilation. Kinematic cuts should be able to reduce this, though.

    1. The real problem with Higgs –> Z + photon is that you have to hope for the Z to decay to an electron-positron or muon-antimuon pair; that costs you a factor of about 15. So Higgs –> four leptons is larger than Higgs –> two leptons + photon, and it has more background, as you noted. Eventually this will be measured but it’s not as quick as two photons and four leptons.

  12. I’ve been wondering why the Z-gamma channel hasn’t been a part of the “easy” searches. Glancing at a branching ratio plot (e.g. http://physics.stackexchange.com/questions/3773/shape-of-the-higgs-branching-ratio-to-zz ), it looks like the BR to Z-gamma is about half that of gamma-gamma at 125 GeV. It seems to me that this would be a fine compliment to the gamma-gamma and ZZ* analyses, with significant overlap in the actual analysis. Tag a Z, then look for a high pT photon (with some isolation criteria). And if there really is some enhancement in the diphoton channel, then maybe you would see it here, too, since the relevant loop diagrams at least affect the SM loops in the same way.

    I can’t personally come up with any major backgrounds that you wouldn’t have to deal with in other searches. The non-Higgs SM direct production of Z-gamma is fairly small being absent at tree level. A quick search for TeVatron/LHC results didn’t change my mind about this, the only LHC result I found being a CMS diboson paper with 36/pb of luminosity.

  13. Every other fundamental particle discovered to date the quarks, leptons and gauge bosons of the standard model has spin, an intrinsically quantum mechanical property that determines its fate. The Higgs, however, does not and if we are correct its spin = 0.

    The spin of the quarks and leptons is ultimately responsible for the structure of matter, including the properties of nuclei and the electronic structures that govern all of chemistry. The spin of the gauge bosons gives rise to the forces of nature, ranging from electricity and magnetism to nuclear reactions and gravity.

    The Higgs, though, is different; it has no spin. Its spinless state allows it to condense and fill the vacuum. Higgs condensate is therefore thought of as being responsible for mass: particles travelling through the condensate experience a drag that slows their motion and gives them mass. The more the drag, the greater the mass.

    1. Hmm… I think you’re kind of over-emphasizing this. Quarks and antiquarks combine to form a spin-zero composite object that condenses because of the strong nuclear force. And we don’t know yet that the Higgs itself isn’t composite.

      Moreover, the Higgs providing mass really is not anything like drag (despite various people’s analogies). If it were, then a static particle wouldn’t have a mass; and also, you could measure your motion relative to the Higgs field. But you cannot measure motion relative to the Higgs field — you are always static with respect to it — and particles have a mass no matter whether they move or not.

      1. How about this …

        1. We live in a 3D universe because three are the minimum dimensions required to create massive particles.

        Why …

        2. I believe there is no such condition as a rest state (zero motion), every joules of energy is in motion (in transition). So when any point of energy expands (high density to low density or visa verse) whether it is the Big Bang or electron-positron annihilation, the process is not spontaneous, as Dirac theorized, put occurs in a finite time intervals, Planck’s time, tp, (or lower?). The energy-time uncertainty principle, Delta-E x Delta-t ~ h, also points to this time interval mechanism, i.e. the time in the energy-time uncertainty is the time interval the quantum state remains the same, unchanged. …

        So …

        If the time interval is not zero then there will be an expansion of “space”, Delta-X ~ Delta-t, i.e. motion and hence velocity. I speculate that c is the velocity that “came out of the wash” at the Big Bang, i.e. proportional to the initial conditions at t = 0. Hence if space (variable energy densities) is expanding at a finite velocity, c, then the distances between the isothermal “rays” will increase and hence create normal rays, the radiation is no longer collimated. It is this mechanism that creates vortices, “rotation” and hence oscillatory waves that lead to standing waves and “massive” particles.

        So …

        If I can further my speculation a bit more, I would say as we have seen so far through the SM, quanta, repetitive ans stable states of energy, will exist for the first fundamental “particle” created by the expansion, Higg’s boson.

        Hence, my question to you, Sir. Could the Higg’s boson = Dirac’s particulate aether?


        How close am I in my interpretation of a “particle”?

        In the standing spherical wave concept, the energy in that sphere (packet) is E = h * c / lambda. where h is Planck’s constant, c is the speed the peak moves in the sphere and lambda is 2r (r is the spacial radius of the sphere).

        It takes the “peak” energy (density?) 720 degrees to make one cycle around the sphere (oscillating 90 degrees at a time from the center to the “surface” (amplitude?) of the sphere and back to the center).

        The spin is the intrinsic rotation of the peak around an axis to complete one cycle (through x, y and z, i.e. 720 degrees). This intrinsic rotation is what gives the “particle’s angular momentum.

        The electric charge is a measure of the effect by the “electric” field created by the peak oscillating between the center of the sphere to the “surface”. The electric field is the gradient of energy created in a grid of all the particles in the universe.

        The mass is the measure of the momentum transferable from one particle to another and is created by oscillatory motion of the peak confined in a spherical space (quantum confinement, quanta space).

        Speculations from my interpretation:

        1) The radius of the sphere for any type of particle is derived by the principle of least action, the resultant effects of all the fields acting on the particle.

        2) The attraction force, quantum gravity, is created by the oscillatory nature of the “wave” within the spherical space. When the peak moves to the surface it creates a negative pressure (tending towards “empty” space in the center) and by the principle of least action must return to the center. Like all other fields, gravity likewise is the summation of these (quanta) negative pressures by all the particles in the universe. hence, the gravity “wells” are greatest where there is a dense coalescing of particles, galaxies, stars, planets, etc.

        3) These oscillations that some have coalesced to “particles” (standing waves) where created by the expansion of the energy, space, and time system. The expansion of the universe (energy and space) could not be done isotropically because of the time factor, i.e. instantaneity is not possible and hence energy expanded in a non-uniform densities. These variations in energy densities patterns grow more and more complex leading to the “coalescing” of space, (formation of “particles”).

        4) The fields and particles have a duality in the sense that all the particles create the fields and each particle effects another through these fields.


        Fields Particles

        Are fields the interaction of particles of the same characteristics (quantum numbers)?

        In reality the universe is a collection of different particles at different densities and arrays. The fundamental being either the Higgs (or similar) or the graviton (or similar). In other words, as the universe cooled down the first array of particles (and hence filed) were (was) created (coalesced), (Higgs, graviton, something else). As the temperature further dropped more type particles were create (coalesced at different quantum numbers), some interacted with the fundamental field and some did not (reasons could be coincidence of Nature and nothing to do about meeting human’s math).

        So, I ask the question, if everything is made of energy at different densities, then what is energy?

        PS; What is energy?

        I would like to quote Narendra Katkar in one of his papers, “The Speed of Light, A Fundamental Retrospection to Prospection”

        “The Universe is a process of Absolute transformation,
        from Cosmic Primal Energy, CPE to Quantum to
        Radiation and back to CPE Vacuum State.
        CPE → QE → RE→ CPE
        Energy is never created neither lost.
        “Everything essentially is Energy”
        What is Energy? …!!! ”


  14. If the Higgs boson has a mass of 125 GeV/c^2, then what is the predicted mass for its Higgsino superpartner?

  15. Q. Since the Higgs boson can decay in more than one way, does this indicate another particle (field, maybe gravity (graviton)) is in play and/or that the fundamental particle have a structure (spherical shell)?

    1. No. Almost every particle that can decay can do so in more than one way. It just means that a most particles interact with more than one other particle.

      1. Q1. Now that they have a strong confidence of a “light” Higgs (at 125 Gev), could / would they go back and rehash the renormalisation-group equations (RGEs) of the SM to possibly create new physics to associate the Higgs field to quantum gravity (graviton)?

        I ask this question in the context that since the Higgs is so light it puts it very close to a unstable (or metastable) vacuum region. (Ellis et al 2009, http://arxiv.org/pdf/0906.0954v2.pdf) … So, could there be a possibility that the same mechanism that created the gravity field (gravition) also created the Higgs, i.e. Mass ~ f (graviton) ~ f (Higgs) and/or Mass ~ f (graviton, Higgs) ~ f ( spacial vortices due to the expansion of space when the singularity, Big Bang, blow up) ?

        Q2. If the above conjecture could be possible, would it be indicating that the (“a”) universe could be cyclic? i.e. the vacuum repeatedly fluctuates from stable (now) to unstable (singularity, “the quartic Higgs self-coupling runs at high energy towards lower values. At some point it would turn negative indicating that the vacuum is unstable. In other words the universe could in theory spontaneously explode at some point releasing huge amounts of energy as it fell into a more stable lower energy vacuum state.), then blows up, “spontaneous” supersymmetry breaking again (Big Bang).

  16. Hi Prof Strassler,

    Why would ATLAS and CMS possibly produce different results?
    What exactly characterizes a Higgs particle, as opposed to a different particle with the same mass, say the roughly 125GeV or 126 GeV? How do we know which mass ranges for the Higgs particle (s) would make sense or not?

    I was reading your very exciting and lucid posts, but the second question kept coming back as I might have missed it while reading the posts. I see that you are going to follow up with blog posts answering the larger questions – thanks for your effort to make the discovery clear to the laypeople!

    1. At present, the differences between ATLAS and CMS are consistent with the sort of differences that would arise from statistical fluctuations in the data and to small technical uncertainties — these are *preliminary* results and the numbers *will* change a little bit. If what we’re seeing is real, those differences will disappear in time. So at this point there are no large discrepancies between what the two experiments are seeing and I have no concerns about it. As for what mass range makes sense for the Higgs — anything below about 800 GeV would have in principle been fine. At around 800 GeV the Higgs lives such a short time that it basically doesn’t exist as a particle anymore.

  17. Thanks for your insight — again! Two questions: Does the Higgs give mass to itself, too? Any reason for why its mass is so big?

    1. The Higgs field contributes some of the mass of the Higgs particle, but not all of it; there is an additional intrinsic contribution whose source is not known or easily discovered… so don’t expect an answer anytime soon. As for why its mass is so big — or small — we do not know.

  18. Wonderful discovery! I have a question, Prof Strassler. So as I understand, each particle is associated with its own field. Does this mean that there are as many fields across the universe as there are elementary particles? While this may explain a lot things we see, to me this looks a bit inelegant – multiple fields intersecting, overlaying, each creating particles. Could it be that there are only two fields – a Higgs Field and another field that gives rise to all other particles at various excitation levels? Thanks.

    1. It may look inelegant, but remember, we aren’t mathematicians, and we’re not in the business of elegance; we’re in the business of prediction. The inelegance of the Standard Model is legendary, but so is its extraordinary effectiveness. And you can bet that lots of people have tried to make it look more elegant, or embed it into something more elegant. No one has ever succeeded — and I have to admit your proposal does not sound promising. You will have great difficulty explaining why the Higgs field has such a diverse range of couplings to the matter particles, and you will have a terrible time explaining the photons, W’s, Z’s and gluons… Sorry! We need either more data or a truly brilliant new insight to deal with this long-standing problem.

  19. Not that it matters but I for one am not convinced. Sure it’s not a fluke at this point but it may very well be some error in the background estimation or data processing, or something completely novel. After all it’s not so surprising there is some discrepancy between predictions and data, we are probing the unknown. I reserve judgement until we have all the detailed measurements of the parameters of this Higgs candidate and know how they compare with SM predictions.

    BTW if the parameters of this hypothetical particle agree with SM then it is SM Higgs, if they don’t then it is non-SM Higgs, so under what conditions would you declare it not a Higgs boson at all?

    1. Let me explain why it is very unlikely to be an error in the background estimation or data processing. Remember: there are four measurements here, ATLAS photons, ATLAS leptons, CMS photons, CMS leptons. A mistake or data processing problem is unlikely but possible in any one. But all four show a notable and signficant bump, and all four bumps are within about a GeV of one another. That’s extremely uncharacteristic for mistakes or data processing issues. This is why I, personally, am very confident. Not all 5 sigma effects are created equal — but this is one of the most robust that you could ask for.

      It is not a Higgs boson if it does not come from a field that gives mass to the W and Z particles. We can test this by looking at whether it is produced along with W and Z particles, and decays to W and Z particles, with the required rates.

    1. If it survives a doubling of the data, or if ATLAS shows the same thing, yes, that will be very odd indeed. The statistics is still too low to get excited; when the Z boson first appeared at SLAC, the first dozen events suggested the resonance had two peaks instead of one. With more statistics the effect went away. Small statistics leads to all sorts of weird effects.

  20. I feel like I watched the moon landing again! (Including the weight of more work to be done.) Thank you!

  21. Do you remember this time last year with 1/fb of data, CMS and ATLAS both saw a small excess at around 135 GeV? Which disappeared over the coming months as more data was added?

    I think that must have been a major factor for some scientists remaining cautious, and rightly so.

    1. It was at 143 or so. And I wrote all about it at the time, http://profmattstrassler.com/articles-and-posts/the-higgs-particle/why-the-hints-of-higgs-currently-rest-on-uncertain-ground/

      It wasn’t a major factor, only in the sense that good scientists know this kind of thing happens all the time and weren’t surprised (as you can see from my article about it, which was written before the hints went away). So it was just a reminder of something all the experts know… that you can’t trust hints, you need strong evidence from at least two experiments.

  22. Your excitement is contagious, Professor.

    Mostly likely a stupid question, but here we go anyway.

    Is the Higgs field anything like a magnetic field and may we someday be able to manipulate the Higgs field like we do magnetic fields?

    1. It’s not entirely like a magnetic field — they do both exist at every point in space, but magnetic fields are spin-one (they point in some direction) while the Higgs field is more like the density of air or the temperature of the air (it doesn’t point in any direction).

      It is very hard to manipulate the Higgs field — we’ve just made our first waves in it! Magnetic fields are much easier because it takes very little energy to get them moving around. But of course it wasn’t easy to manipulate magnetic fields a few hundred years ago, so predicting what will be possible by the year 2500 doesn’t seem wise.

  23. Hi Matt

    I tried to ask this question on today’s live blog on “Nature” site (btw, that was very interesting indeed, good job from you and 2 other guys), but I wasn’t lucky to get through. What do you think, how much is possible to be done in looking for Higgs exact specs before long LHC break next year. Is there any chance we will get at least some answers still this year or at least based on 8TEV data? Or should we already start being very patient and wait for results from 14TEV beams in few years from now?

    1. Oh, we’ll get a lot of information this year, and next year, based on this year’s 8 TeV data. And then we’ll get a lot more at 13-14 TeV. But no specs that you measure in data are ever “exact”; they just gradually get better. If the Higgs is really the simplest type, all that will happen over the next few years is that the data will get more and more and more consistent with the predictions of the simplest case. Of course we all hope that something happens that is more complex and instructive, but that’s up to nature.

  24. @Patrick: You claim, “Photons from cosmic rays cannot reach the detector …” I conjecture that your claim is false. I conjecture that paradigm-breaking photons caused by inverse Compton scattering from relativist jets explain the GZK paradox.
    Admittedly, I can’t suggest how such paradigm-breaking photons could explain the bump.

    1. Admittedly. Has it occurred to you that this bump would be observed also when the accelerator is off? And it would be much easier, because there would be no background events to get in the way?

    2. You only mention possible sources of high energy photons. I did never claim that cosmic high energy photons do not exist. In fact, HESS and other gamma telescope have measured plenty of GeV and TeV photons. This does not change the fact, that they won’t reach any of the LHC detectors, because those photons create showers in the atmosphere and do never reach the ground.

      Inverse compton scattering is a totally different physical mechanims than the mentioned GZK effect. Inverse compton scattering in relativistic jets is a possible source of photons in the energy range of GeV to TeV. GZK photons would have a much higher energy and haven’t been observed yet. Photons at both energy scales would be stopped in the atmosphere and would create an air shower, which can be observed by ground based telescopes and surface detectors (e.g. by the Auger Observatroy).

  25. @David Brown: The only particles from cosmic rays which will reach the detectors and produce a signal are Muons. These Muons can be easily filtered out in the data analysis, because they enter the detector from above and leave them below. Muons which are created in collisions and subsequently decays start from the beam pipe and travel only through half of the detector. So the effects from cosmic rays are indeed ruled out in all analyses.

    The most important channel for the Higss discovery is the decay of the Higgs into two high energy photons (H -> γγ). Photons from cosmic rays cannot reach the detector and if they could, they couldn’t explain the bump which we see at 125 GeV. The only reasonable explanation for the bump at 125 GeV in the photon spectrum is a Boson with a mass of 125 GeV with spin 0 or 2.

  26. “What’s changed from December is that every argument you can can make comes out in favor of the result being real …” I am not convinced that adequate attention has been paid to spurious data caused by cosmic rays. According to Wikipedia, “About 89% of cosmic rays are simple protons or hydrogen nuclei, 10% are helium nuclei or alpha particles, and 1% are the nuclei of heavier elements. These nuclei constitute 99% of the cosmic rays. Solitary electrons (much like beta particles, although their ultimate source is unknown) constitute much of the remaining 1%.” Have the experts thoroughly ruled out confounding effects from cosmic rays?

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