Of Particular Significance

Why the Higgs Matters, In A Few Sentences

POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON 03/20/2013

One of the big challenges facing journalists writing about science is to summarize a scientific subject accurately, clearly and succinctly. Sometimes one of the three requirements is sacrificed, and sadly, it is often the first one.

So here is my latest (but surely not last) attempt at an accurate, succinct, and maybe even clear summary of why the Higgs business matters so much.

`True’ Statements about the Higgs

True means “as true as anything compressed into four sentences can possibly be” — i.e., very close to true.  For those who want to know where I’m cutting important corners, a list of caveats will follow at the end of the article.

  • Our very existence depends upon the Higgs field, which pervades the universe and gives elementary particles, including electrons, their masses.  Without mass, electrons could not form atoms, the building blocks of our bodies and of all ordinary matter.
  • Last July’s discovery of the Higgs particle is exciting because it confirms that the Higgs field really exists.  Scientists hope to learn much more about this still-mysterious field through further study of the Higgs particle.

Is that so bad? These lines are almost 100% accurate… I’m sure an experienced journalist can cut and adjust and amend them to make them sound better and more exciting, but are they really too long and unclear to be useable?

Some False Statements about the Higgs

Meanwhile I would like to suggest we avoid the following statements, or anything like them.

  • The Higgs field and/or the Higgs particle were crucial to the Big Bang. [On the contrary, there’s no evidence that the Big Bang would have been stymied in the absence of the Higgs field and particle, or of anything directly related to them… despite what Professor Michio Kaku said earlier in the week on CBS news, to the embarrassment and annoyance of the physics community.]
  • All mass in the universe comes from the Higgs field and/or Higgs particle. [There are many things in the universe which don’t get their mass from the Higgs field, including atomic nuclei, the black holes at the centers of galaxies, and (probably) dark matter.  Meanwhile, the Higgs particle cannot give mass to anything.]
  • The Higgs field and/or Higgs particle gives ordinary matter its mass.  [Nope; although the Higgs field, by giving the electron its mass, makes ordinary matter possible, it doesn’t provide most of ordinary matter’s mass.  Most of an atom’s mass is in its nucleus, and thus in protons and in neutrons, particles which are not elementary and do not get most of their mass from the Higgs field.  Protons and neutrons get their masses from effects involving the strong nuclear force; they’d still have mass if there were no Higgs field.  And again, nothing gets its mass from the Higgs particle.]
  • The existence of the Higgs particle confirms Einstein’s theories. [Einstein had nothing to do with these ideas, which were developed after his death.]

Oh, and please let’s stop using “God Particle”.  Aside from the fact that it is the field, not the particle, that’s so important, the term makes it sound as though important religious questions can be answered by science, using experiments. Science is a powerful tool, but it has its limitations, and it cannot address questions of this sort.  No one benefits when scientists and/or the media confuse non-scientists into thinking that it can.

Addenda, Subtleties and Caveats

Now, in the interest of accuracy and precision, and so that any journalists and other non-scientists reading this understand exactly where I’m taking short cuts, here are some caveats and addenda to the two nearly-accurate statements that I gave above.

A first small caveat: I said the Higgs field “gives elementary particles” mass; I avoided saying “gives all elementary particles their mass” because it is likely that there are elementary particles that we haven’t yet discovered that don’t get their mass from the Higgs field.  This is probably true of the particles of dark matter, assuming that dark matter really is made from particles in the first place.  (In fact it is arguably true of the Higgs particle itself, but I don’t want to argue about this, because semantic issues immediately come up.)

The most important subtlety left out of the two statements above is that not only does the Higgs field exist, it is “on”, in a sense. If you could measure the Higgs field at any point in space (which we can’t actually do directly), you’d find it isn’t zero, because it is “on”; in fact it has just about the same value everywhere throughout the universe (at least in that part that we can observe.) By contrast, if the Higgs field were “off”, you’d measure it to be zero in most places. This is similar (though different in a couple of key ways) to another field you may know about, the electric field; it too can be “on” or “off” on average. If it were “on” in your vicinity then your hair would stand on end, just as when lightning is about to strike nearby, or when you’ve just taken off a wool hat in winter and static electricity is at work. On the other hand, the electric field exists (i.e., it is something real that can be measured) even when it is “off”, as it probably is where you’re sitting right now, with nicely behaved hair.

And so an important addendum to the second statement is that discovery of a Standard Model-like Higgs particle doesn’t just confirm the Higgs field exists; it confirms that the field is “on” — which is crucial, since if it were off, it wouldn’t be able to provide masses for elementary particles.

We must also now add an asterisk to the statement that electrons would be massless if there were no Higgs field. If the Higgs field did not exist at all, the statement is correct: electrons would be massless. However, if the Higgs field existed but were simply turned off somehow, and nothing else were changed, electrons would still have a very, very tiny mass, due to a funny quantum interplay of the strong nuclear force and small interactions between electrons and the (off) Higgs field. (Thanks to George Fleming for reminding me of this some time ago.) But this is really a small asterisk, because it remains true that atoms could not form at the current epoch of the universe; the warmth left over from the Big Bang would blow them apart. The correct statement in this case would be that electrons would have tiny, tiny masses compared to what they do in nature, and this would cause atoms to become extremely fragile and easily fall apart. So the basic idea is still right.

Another addendum: if the Higgs field were off, not just the electron’s mass but many other aspects of the world would be very, very different. It isn’t clear exactly what would happen, actually… it turns out that, for subtle reasons, it is rather hard to calculate the impact. (Professor Chris Quigg recently mentioned to me that he and his colleagues tried to compute the main effects, but found some important issues are too close to call.) It appears likely that there would be no atomic nuclei,  and/or the proton would be unstable, and/or stars couldn’t shine. What is certain is that the world would be unrecognizable, even if electrons managed through some alternative magic to keep their masses. So the electron’s mass is only a part of the story — the part that is easiest to understand, but not the only part — of why the Higgs field is crucial.

That’s important because there is yet one more asterisk about the electron and the Higgs. In the so-called Standard Model (the equations that we use to describe the known particles and forces) there is only one Higgs field and one Higgs particle, of the simplest possible type, and in that case my statements about the electron mass are true (still with the previous asterisk). But if the Standard Model isn’t quite right, there might be more than one Higgs field and more than one Higgs particle. If this turns out to be the case (and the experimentalists at the Large Hadron Collider are trying to find out), then we do not actually know yet that the Higgs field associated to the recently discovered Higgs particle — the field which definitely gives the W and Z particles much or all of their rather large masses — is truly the same as the Higgs field that gives the electron its relatively small mass. So the caveat here is that although at least one of the Higgs fields in nature must be responsible for the electron’s mass, we don’t yet know that the Higgs particle we’ve just discovered is associated to that particular field. (The field associated to the newly-discovered Higgs particle would still be crucial to our lives, however, because of its other important roles mentioned in the previous paragraph. Moreover, evidence is already rising that this field interacts with the heaviest cousin of the electron, a particle called the “tau”, which for technical reasons makes it more likely that it interacts with the electron too.  Still, strictly speaking the jury is out, and will be for a while.)

Despite these caveats and addenda (and maybe there are more I should add), I still think the above two statements are about as accurate as you can get without becoming technical and long-winded. And again, they are far more accurate than what often appears in print!


Colleagues: please feel free to suggest further improvements, and please point out further addenda, subtleties and caveats that I’ve overlooked; I’ll add them to this page.

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110 Responses

  1. It’s awesome to go to see this site and readeing the views of
    all colleagues about this post, while I am also zealous of getting familiarity.

  2. Hello, first of all, I really enjoyed reading both the initial post as well as the comments. I however have a question about how the Higgs-field works. I wonder wether it’s already known why certain particles interact to a greater measure with the Higgs-field (and therefore ‘providing’ it with more mass, for as far as I’ve understood the matter) than others?
    I seem to recall this being one of many problems listed upon finding proof of its existence (although I was led to believe it isn’t conclusive proof, since the observed energy peak merely allows for the Higgs boson to exist, and doesn’t necessarily prove the Higgs boson to be there (126GeV, if I’m not mistaken)).
    Could you correct me if my assumptions are wrong and, if possible, provide me with an answer for my question. Thanks in advance
    Wouter Baes

    1. 1) We have no idea why one field (and its particle) interact more strongly with the Higgs field than another — and thus we have no idea why the top quark is so much heavier than the electron. This is often called the “flavor problem” and it is one of the thorniest problems in particle physics.

      2) Evidence that the new particle is a Higgs particle is now very strong indeed, which is why the Nobel rize was awarded this year. For a slightly out-of-date summary, see http://profmattstrassler.com/2013/03/15/from-higgs-like-particle-to-standard-model-like-higgs/

  3. You write that there is evidence that the Higgs field interacts with the tau, and this gives some confidence that the same Higgs field must interact with the electron or else some modes of tau decay that we don’t see could occur. (If I understand you correctly.) Does this reasoning also apply to the muon? Do we currently expect that the same Higgs field interacts with all three, the electron, muon, and tau?

    Thanks for this site and all your efforts to explain these concepts!

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  5. I got confused when you first said that the Higgs gives (some) elementary particles their mass and then later said in fact the Higgs particle cannot give mass to anything. I had assumed that the particle and the field were just two ways of looking at this phenomenon, like the photon and light waves. Anyway, so what other elementary particles get their mass from the Higgs field? Quarks? P.S. I still like Michio, he’s got a certain style.

    1. The Higgs particle and the Higgs field are not just two ways of looking at the phenomenon. They are different things. The Higgs field gives mass, while the Higgs particle does not give mass.

  6. So, now that we have confirmation of the Higgs Boson and a better understanding of the energy levels around the Higgs Field, we are done, correct? But, then, I can (really I can) remember back to a time when the Electron was theorized to be made of even small particles. As it turned they were, and we were not done looking. So until the next discovery we are done, be we are not there yet. Just as we explore into the extremely small, others are looking into the very large, peering into space and back in time. What I find so interesting is that many images I have seen from particle accelerators, seem to look really familiar. Check out some of the NASA Hubble images and you may see what I mean.

    1. No, I’m afraid we’re certainly not done. We aren’t sure yet whether there is only one Higgs field; there could be more than one, and there’s a lot more work to do at the Large Hadron Collider to explore this possibility. Beyond that, though we now know that the known elementary particles get their masses from the Higgs field, we have no idea where the pattern of specific masses comes from: for instance, why the electron is millions of times heavier than neutrinos and hundreds of thousands of times lighter than W and Z particles, top quarks, and Higgs particles? We also have no idea why the forces that we observe in nature have the strengths that they do. I could go on (and in some post still to be written, I will.) And what the heck is the dark matter that makes up a substantial fraction of the universe’s energy budget? There are at least a couple of dozen loose ends, and we’ll be working for a long time to figure them out.

      The electron still appears to be an elementary particle; it is not known to be made from smaller things. Perhaps you are thinking of the proton.

      1. I meant to say proton, referring to the atom nucleus. But I must say I really like the term Quark. That was just a cool sounding particle!

  7. I have one question regarding what would happen if the Higgs field would become zero. Piscator mentioned there would be 6 light quarks: but wouldn’t there be 12? Each massive quark is a mixture of right- and left-chiral massless quark. Wouldn’t they become independent, thus doubling the amount of fermions? And also – would photons cease to exist, becoming again the original independent bosons of weak hypercharge and weak isospin?

  8. I am basically excited about this, agree that the photon is a more appropriate poster-child for ‘godliness’ and … I get “hung up on words.” E.g., THIS IS TRUE: ■Our very existence depends upon the Higgs field, which pervades the universe and gives elementary particles, including electrons, their masses. Without mass, electrons could not form atoms, the building blocks of our bodies and of all ordinary matter.
    And then you write, THIS IS FALSE. And again, nothing gets its mass from the Higgs particle.]
    Obviously I’m missing something … from trying to read too much into this? Hung up on definitions? a comment, at your convenience, please.

  9. Being a “count the teeth” girl myself, and not a follower of “thus it is written,” I can appreciate this. Accuracy is so important to me, and I may not be the brightest bulb in life’s marquee, but if you need more words to explain it and do so ACCURATELY, take them.

  10. Reblogged this on Poke My Mon and commented:
    An interesting, informative read for those (like me) who had no idea what the whole ballyhoo about the Higgs discovery was about.

  11. I didn’t like this early comment, “Our very existence depends upon the Higgs field.” When you start on a certain line of thinking, it is easy to overlook other lines, just like in the game of chess.

  12. As someone trained in the news trade, I apologize on behalf of my profession for screwing it up so often. Many of my so-called “peers” these days are better suited for writing at a tabloid than reporting actual news. It is disturbing to think that people get the information that forms their opinions from such jokers.

  13. During 1980-1992, I lived near Fermilab. I taught high school physics nearby. From 1985-1992, I worked with the education office at Fermi coordinating the physics teacher portion of their summer science teacher institutes. We had a great time interacting with the physicists, hearing lectures, and getting special tours. Chris Quigg, mentioned above, was one of our best presenters. Leon Lederman was great. He was so supportive of our efforts. And, he tells great jokes.

    I watched some terrific advances made by the tevatron and the announcement of the top quark. I watched the SSC wither and die. And, I hoped they would be able to make some Higgs announcement. But, they didn’t quite have the data.

    Thanks for your comprehensive post. It also brings back some good memories.

    1. Glad you got a chance to see all that! Yes, Lederman is a great physicist, leader, and joker. The “joker” in him brought us the term “God Particle”; he went a little too far this time.

  14. I will follow your blog with interest. I agree with reviewcentrall and you about not calling it the God particle. However, my layman’s interest in physics does relate to how science and spirituality are coming together. I love that it seems that Quantum Mechanics seems to be proving what spiritual masters have been saying for millennia. Or am I wrong?

    1. Well, one has to be somewhat careful about concepts and viewpoints that look roughly the same when you read the words, but aren’t the same when you look at the details. After all, quantum mechanics isn’t just cool and amazing and weird — you actually can use the math of quantum mechanics to predict how nature behaves and to build things, like computers and cell phones and lasers and particle accelerators. So a few of the spiritual masters may have stumbled on the right words (while many others clearly didn’t) but that’s not the same as saying that they really understood what they were talking about…

      But trying to make sense of a very strange world requires thinking very broadly about it… if that brings ideas together for you, there’s no harm in it certainly, and maybe there’s some truth in it.

  15. A nice read. Although, I’m only a 16 year student and hence know nothing about the exact details of this so-called Higgs bosson, I’ve always found it interesting to read and follow. Thanks for the great article.

    1. 🙂 well, maybe it’s nice as a concept, but if it were up to me to name something the “God Particle”, I’d choose the “photon” (the particle of light), both because of its biblical reference and because we both see by and are warmed by the sun’s photons; plus the photon’s field, the electric field, holds our atoms together. You do know the name comes from someone who was trying to sell a book? In other words, the term “God Particle” doesn’t come from science, and it doesn’t come from religion — it’s all about $$$$. Not very nice actually.

  16. Reblogged this on INQUIES and commented:
    To keep ourselves updated about this Higgs particle and fields. Here’s a good blog about Higgs. Focus on the “false statements” and you will see how some of my knowledge about it were wrong. The thought that Higgs field interacts with all particles *with mass* was totally wrong — only elementary particles interact with the Higgs field. And not all!
    For technical details, the “Addenda …” section gives good background. Cheers and happy reading!

  17. Seems like a very informed and educated debate and commenting going on here and am sorry if what I’m going to say is a ‘party pooper’. It’s just that I came here to understand Higgs in ‘a few words’ but I’m no closer to understanding why Higgs matters. I admit i didn’t read the whole thing (too ‘heavy’ for me) because you lost me after the first few paras. Just saying. NOI 🙂

  18. I just saw this post on Freshly Pressed and realized I have missed the prequel! I enjoyed this so much I will have to go back and read previous posts. Thanks for sharing 🙂

  19. Most people care about practical applications.The Higgs holds together the universe, as we know it. Can we disrupt the field or hide from its effects, without danger? You explain the theory, but it doesn’t solve real world problems. Only the pretentious and high level physicists see this as exciting. It may or may not provide a stepping stone to something other than changing textbooks.

    1. Pretentious is in the eye of the beholder, but (a) we cannot disrupt the field, it would require too much energy; (b) if you don’t find it exciting, I feel sorry for you, for the universe is a magical place and it is sad that you cannot see or feel that; and (c) not everything we discover has practical use, but some things do; and sometimes it is a surprise. When the muon was discovered it seemed pretty useless, since it only survives about a millionth of a second, but it has indeed been put to practical use.

      1. I’m sorry to have offended you, but your title says, Why it matters.” You only reexplain what I read elsewhere. You write:

        Is that so bad? These lines are almost 100% accurate… I’m sure an experienced journalist can cut and adjust and amend them to make them sound better and more exciting, but are they really too long and unclear to be useable?

        Accurate an clear, but I gave you why it does not excite. No need to get snotty in your reply.

        1. Awww, crocodile tears. If you accuse me and my colleagues of being “pretentious” in your comment, why would you expect a sweet-tempered reply?

          But in fact, if you read my reply carefully, you’ll see it isn’t snotty at all; I do, sincerely, without being snotty, feel sorry for you.

          An older version of you would have complained just as bitterly about general relativity — what good is it, you would have said, to know these little details about gravity that will never have any benefit to society? Well, Einstein would have told you he was sorry for you. And meanwhile, today general relativity is relevant for making global positioning systems (GPS) work… which neither Einstein nor an earlier version of you could have predicted. I have no idea if or when knowledge of the Higgs field will be useful for society — because I cannot predict the future or imagine technology that lies a century or two ahead of us. But what excites me (and many of your fellow humans) is that we all (not just physicists) have learned something profound and fascinating about nature, something whose benefits cannot possibly be known yet because it has just been discovered, but which will constitute knowledge available to all future human generations for purposes that we cannot imagine.

          1. Can you read your own writing? Look at your title and your post. You explain the findings , but try to justify your post after using such a title. Atom meant indivisible and we know that isn’t true. I know it might make a difference and making sound like I”m too stupid to realize such an obvious comment. You say in your post:

            amend them to make them sound better and more exciting

            If you see a problem with the excitement level then others may also see it. I put it in words why make it sound exciting is difficult. I didn’t mean to insult you but you obviously want to insult me. It would make more sense to see my point and apologize.

            1. I do apologize if you feel I have insulted you. I certainly feel you insulted me (and you haven’t apologized, you’ve piled on.) You could have made your points without using the phrasing you chose.

          2. I apologized in an earlier post. And I still say title doesn’t match your post. And I gave you why people don’t find it exciting. I’m not sorry for trying to make a point. Iran into intellectual bullies in the Navy’s Nuclear power program. I’m smart enough to know I’m dangerous. And I don’t like opening old wounds. I’m sure you are smarter. I don’t want to deal with you anymore. Bye and I apologize for my social miscue.

  20. I find it interesting how the Higgs news coincided not only on Einstein’s birthday but also with Pi Day on March 14! What is up with this?

    1. Out of 365 days in the year, quite a few of them are interesting. Could have happened on April Fool’s day or Higgs’s birthday or 2/2 or 3/3 or 4/4 or 5/5 or 6/6 or … (and should we make something of the fact that the announcement of the discovery in Europe occurred on US Independence Day?) In short: the probability of this news happening on an “interesting” day isn’t very low. Improbable coincidences happen every day.

  21. Didn’t we already knew that a Higgs field existed, since LEP2 at least, considering that the EW symmetry is broken and W and Z are massive gauge fields? What we didnt know, and in fact we dont know it quite yet even now, is if the Higgs field is a composite field. Think of a Higgless theory, nowadays finally falsified, they always have a Higgs field in them although no particle.

    1. We knew that EWSB existed but the form which it manifested itself was wide open,,,, Hence, the “No lose Theorem” for 1 TeV mass scale collider. Phenomenologically speaking, the jackpot appears to have been the smallest possible….

  22. This is addressed in the caveats section of this post. No, LHC data does not *directly* support the hypothesis that the electron gets its mass from the SAME Higgs field as gives mass to the W and Z. However, CMS data now supports the idea that the Higgs field corresponding to the observed Higgs particle gives mass to the tau lepton. If you try to introduce separate Higgs fields for taus and for electrons, you very easily can generate physics processes that we do not observe (rare tau decays forbidden in the Standard Model) — so there is *indirect* evidence, not directly convincing, that electrons probably get their mass (at least some of it) from the field corresponding to the discovered Higgs particle. This loophole won’t be closed for a while… and that is a clear weakness of the formulation that I’ve given here; it’s probably correct, but strictly speaking we won’t know for quite a while. Of course the W and Z masses are also very important in nature — if they were smaller, the weak nuclear interactions would be much more powerful, with all sorts of hard-to-calculate impacts. But the problem is that to explain the weak interactions, the W and Z particles, and why their masses are important is simply much, much too hard to explain in a sentence, or even a few paragraphs, to a non-expert audience. So I think this is the one place that a compromise really is necessary.

  23. I’m a little confused about why you keep saying in your post that the Higgs particle doesn’t give mass to anything. Presumably your point is that it’s the Higgs field — that is, its vev — that is responsible for giving masses to the elementary particles of the Standard Model. But a vev is just a coherent state of particles, after all.

    What am I missing here?

    1. What is a coherent state of particles?

      You are mistaking a mathematical fact for a physical one. A particle — a real particle, what anyone other than a physicist with too much math in his or her brain would call a particle — is a resonance; mathematically, it appears as a pole (possibly off the real axis) in a propagator. You cannot make coherent states out of particles; here, take twenty Higgs bosons, now go make a coherent state out of them. Not enough? here’s two hundred. Higgs particles have a lifetime of 10^-21 seconds; if a field were made from particles, really made from them (as opposed to expressible in terms of them in a mathematical sense) then why does a field have an infinite lifetime? Higgs particles have a mass of 125 GeV; where is the mass of the Higgs field, if it is *really* made from particles?

      A particle is a ripple in a field; a field is not made from its ripples in anything but the most abstruse, abstract sense. And the field is responsible for other particles getting mass; no particle, not even a giant collection of particles, can do that.

      The lesson here is not to confuse mathematical statements with physical ones.

  24. does the LHC data support that the electron and other light particles get their mass from the higgs field? cojld it not be that only the top quark and the W and Z bosons do so?

  25. Hi Matt,

    I think the “true” statements are great, but the addenda may be confusing. The statement “If the Higgs field did not exist at all, electrons would be massless” can be misleading because, strictly speaking, it implies that we knew for sure before the LHC that the Higgs field had to exist, since we know that electrons have a mass. This would then cast doubts on your second “true” statement.

    1. I agree that is a weakness. I haven’t figured out how to deal with it; you need to introduce the field first to make it clear how important it is, and then explain why the particle is important to confirm the field exists. One way to do it would be to say specifically that the idea of the field was introduced in the 1960s… as a hypothesis. It’s the usual tradeoff of clarity and length. Up to the user, clearly.

  26. My point one was killed by unfortunate use of brackets that made the text disappear. The point, and it was really the key one, is that the discovery of the Higgs particle at the LHC is important because the Higgs particle’s existence is a necessary lynch pin of the Standard Model of Particle Physics formulated forty years ago that has explained all experimental results every since then including all of the results at the LHC, for which we previously had no direct evidence. It’s discovery provides proof to validate a critical hunch that particle physicists have been taking on faith for forty years. If the Higgs particle had not existed, this would have meant that there was a fundamental flaw with the most overarching and fundamental set of theories in all of physics. Its non-discovery would have meant that physicists were basically on the wrong track in trying to understand the laws of nature. It’s discovery establishes that they’ve been on the right track all along and can move forward on a firm foundation.

  27. My own two bits.

    1. <<>> not because it is mysterious but <<>>
    2. The field associated with the Higgs particle is important in the Standard Model of Particle Physics because in that theory it is the source of mass of all known fundamental particles such as electrons and quarks. Most of the mass of ordinary matter in the universe, however, is created by the interactions via what the Standard Model calls the “strong nuclear force” that bind particles called quarks together into protons, neutrons and other unstable particles that can be created in laboratories,
    3. Every experimental observation at the Large Hadron Collider is consistent with the Standard Model of Particle Physics formulated about forty years ago. The LHC has not definitively ruled out every possible theory other than the Standard Model, but has confirmed that if there are physics beyond the Standard Model as many physicists believe, that these “new physics” are only distinguishable from the Standard Model at energies higher than those reached by the LHC so far, or in other circumstances that all experiments to date have not been sufficiently sensitive to detect. Any “new physics” at the LHC energy scale must predict outcomes of the same order of magnitude of the Standard Model at the energies reached so far at the LHC in order to be consistent with experimental data.
    4. One of the main classes of beyond the Standard Model theories that would also be consistent with the LHC data to date is called “supersymmetry”. Supersymmetry is a class of physics theories which predicts the existence of slightly more than twice as many fundamental particles as scientistis have discovered to date and is attractive because it would provide reasons for many particle physics laws that are merely arbitrarily imposed in the Standard Model and provides different predictions than the Standard Model regarding dark matter and physics at energies found only immediately after the Big Bang in nature that could influence the nature of our universe today. The discovery of a Higgs particle with the properties that have been observed places more specific boundaries on the kinds of features and physical constant values that any supersymmetry theory consistent with experimental data must have, than any other discovery in physics in decades.

    “Our very existence depends upon the Higgs field, which pervades the universe and gives elementary particles, including electrons, their masses. Without mass, electrons could not form atoms, the building blocks of our bodies and of all ordinary matter.”

    Critque: There has never been any scientific doubt that we exist and that massive bodies in the universe exist. If there had been no Higgs particle creating a Higgs field, then we would have been mistaken about the reason that this was the case, not about our existence.

    Also, the Higgs field vev has had a value in the Standard Model that has been known and calculated with in a way that produces accurate results for forty years. The existence of the field was not in doubt before the LHC powered up. All of the BSM theories that were formulated to explain the possibility of a Higgs-less universe still created a Higgs field or the equivalent somehow or other.

    Critique: The focus on distinguishing between the Higgs field and the Higgs particle is an academic fine hair that confuses no one who understands the distinction between a particle and a field in quantum physics and doesn’t really lead astray anyone who doesn’t know the difference. While “particle” is a term whose technical meaning isn’t far removed from its vernacular English meaning, “field” has a far fuzzier meaning in vernacular English than it does in particle physics and certainly does not make distinctions between scalar fields like the Higgs field, vector fields like electromagnetism, and tensor fields like those of hypothetical quantum gravity theories.

    While the Higgs field is mathematically crucial to the SM, it also begs very important questions like why the inertial mass created by the Higgs field is equivalent to the gravitational mass of General Relativity. The Higgs mechanism of the SM provides answers but not understanding.

  28. Great read as usual!
    Since you’re talking about how Higgs does not confirm Einstein’s ideas. Let me ask you if I can take it one step further:
    – at the time general relativity was developed, there were just two forces: E&M and gravity. So the fact that the field theory approach to gravity was abandoned by Einstein seemed not so controversial.
    – since then, two more forces were discovered, and both of them seemed to be described by gauge field theories, just as E&M. The problem with the gauge field theory approach, for the last 30 years or so, was that it required this weird field that was always “on”, and this is why a lot of people were skeptical about the very existence of the Higgs.
    – so now that we actually have discovered such “always ‘on'” field, shouldn’t we be more adamant about developing field theory of gravity? I.e. Higgs discovery encourages us to go AWAY from Einstein?

    1. Yes, Planck will announce things tomorrow. I doubt what they’ve learned will teach us about dark matter per se, but we’ll see. Meanwhile, there’s no known link between the Higgs particle, Higgs field, and dark matter, but there are possible indirect links that have been suggested, and of course there’s still room for surprises.

  29. Hi, Matt–great summary! I take your phrase “Without mass, electrons could not form atoms…” to mean “Without mass, electrons could not combine with protons and neutrons to form atoms…”

    1. yes indeed. I debated whether that clarification was necessary — the usual balance of clarity and succinctness. A real journalist will have to decide whether to add your extra words, or play the game a different way.

  30. @Piscator
    “However Lambda_QCD is itself set by the Higgs field. The fact that the Higgs field is `on’ means the top, bottom and charm all decouple from the running of the strong coupling constant at their mass scales, and this happens only because the Higgs field give them mass.”
    If Lambda_QCD, a non-perturbative parameter of the theory, is set by the Higgs field then one ought to be able to somehow compute the Higgs mass from Lambda_QCD. Did anyone tried to derive such a link, at least in principle? What evidence there is that the top, bottom and charm decouple from the running of the QCD coupling constant? How can we be confident that this is indeed happening, without having a complete non-perturbative picture of how QCD works in the hadronization region?

    1. No, Ervin; I am afraid that’s not the way it works.

      a) The Higgs field’s average VALUE, not the Higgs particle’s MASS, has an impact on Lambda_QCD (the scale of quark confinement)

      b) Even then, the Higgs field’s value does not determine Lambda_QCD. It is merely one of several indirect and direct ingredients.

      c) If it were that easy to learn something about the Higgs particle’s mass, it would have been done long ago.

      d) A field affects the “running” (i.e. change) of the QCD coupling strength at a particular energy scale only if its corresponding particle has a mass-energy (i.e. E=mc^2 energy) below that energy scale; that is what @Piscator was referring to. Yes, there is extremely good evidence for this statement, from data… and that is because, for the top and bottom quarks, and to some degree for the charm quark, it happens in the perturbative (i.e. easily calculable) region of QCD, not in the non-perturbative region. Here is a link to a comparison of data and theory; not the most recent data, but it makes the point: http://backreaction.blogspot.com/2007/12/asymptotic-freedom-and-coupling.html

      1. ” Even then, the Higgs field’s value does not determine Lambda_QCD. It is merely one of several indirect and direct ingredients.”

        I apologize for sounding like devil’s advocate, but this seems to be contradicting what Piscator stated, namely that Lambda_QCD is “itself set by the Higgs field”. I agree that are more ingredients in the mix and this is precisely why I asked these questions in the first place.

        1. It does contradict what Piscator said, but not what he meant; he was speaking in shorthand. (That he and I understood each other is clear from the fact that we both agreed that 60% was the right number.) The strength of the strong nuclear force at the Planck distance, and the masses of all particles that carry the strong force, are the ingredients into Lambda_QCD. All of the quarks’ masses are proportional to the Higgs field’s value; other particles may exist that carry the strong force but have masses independent of the Higgs field. There can be a few other effects if the QCD force is actually embedded in a larger structure, such as occurs in Grand Unification of the non-gravitational forces.

          1. ” The strength of the strong nuclear force at the Planck distance, and the masses of all particles that carry the strong force, are the ingredients into Lambda_QCD.”…”other particles may exist that carry the strong force but have masses independent of the Higgs field. There can be a few other effects if the QCD force is actually embedded in a larger structure, such as occurs in Grand Unification of the non-gravitational forces.”

            With so many open questions and caveats surrounding the SM, I take your statements with a big grain of salt. There is little to no conclusive evidence today on physics above the low TeV scale, let alone what might happen at the Planck scale. I remain skeptical on many points of our discussions until we’ll sit on a much solid ground.

  31. hi matt,,a hypotheticall question to start with,,
    -can the higgs field exist in a hypothetically massless universe seperate from the bump or particle,,does the field remain unobserved,or wold it dissipate in the total absence of mass?in other words in area void of any force,field,or any mass/ system of mass,,,would the higgs be present yet unobserved in such a way that as soon as mass is introduced by an outside source is the higgs count within the area of void be accounted for by the number of higgs introduced with the mass,,or would we find the higgs count indicates the presence of shadow,or invisible higgs within that void,which even though they were for all intents and purposes absent from existance,would have still been there within the void, not absent,rather non of its properties had emerged to be measured yet,,

  32. If the Higgs field did not exist could compound objects like Protons and Neutrons, the objects that give us most of our mass form? In other words do the masses of quarks play a role in the ability of a proton neurtons and atomic nuciei’s ability to exist.?

    1. It’s remarkably complicated. Yes, protons and neutrons would form and have much of their mass, even if quarks were massless. (For subtle reasons — see the previous comment by j.conlon1 — they would be only about 40% or so as heavy, but that’s because the strong nuclear force would become a tiny bit weaker. And there are more subtleties because all six types of quarks would be light, not just two; for instance, instead of just protons and neutrons, there would be dozens of similar particles.) It is not at all clear what would happen to atomic nuclei, because the forces between protons and neutrons would be significantly changed. Indeed it is remarkably difficult to calculate what such a world would look like!

  33. Another technical subtlety (since you ask for them).

    The Higgs field is actually responsible for about 60% of the mass of the proton and the neutron.

    It is true that the proton and the neutron get their mass from non-perturbative QCD effects, and this mass is set by Lambda_QCD. *However* Lambda_QCD is itself set by the Higgs field. The fact that the Higgs field is `on’ means the top, bottom and charm all decouple from the running of the strong coupling constant at their mass scales, and this happens only because the Higgs field give them mass.

    If the Higgs field wasn’t `on’, there would be more fermions contributing to the gauge coupling running, and Lambda_QCD would be lower (based on 1-loop eqns I get around 100MeV rather than 250 MeV), and so the mass of the proton and neutron would be much smaller.

    Admittedly, if there were six light quarks, then ‘proton’ and ‘neutron’ might no longer be useful names for baryons. Nonetheless I think it is fair to say that a large chunk of the proton/neutron masses come from the Higgs field: as you changed the Higgs vev you would change the proton/neutron masses by significant amounts.

    1. Correct; I fully agree (though as you suggest, it depends on exactly how you set the rules). This point is one I plan to write about, but only after I write the article about what “running of couplings” means — since otherwise it is rather incomprehensible to the public, even the well-read public. I’m not sure that a clear non-technical caveat can be written about this…

      I did try to be careful not to say that “the proton and neutron get none of their mass from the Higgs field” (which would arguably be partly false.) It’s sort of annoying that the fraction turns out, bizarrely, to be 60%. If it had been 3% we could ignore it; even at 30% we could still say that the majority of your mass has nothing to do with the Higgs field at all; and if it were 95% we could explain how really the Higgs field does, indirectly, provide almost all of your mass. But at 60% it’s in this grey zone, where it is not at all clear that explaining this point is really helpful or worth it. Anyway — yes, it does need to be addressed.

      1. Oh, and by the way, Chris Quigg told me it isn’t obvious whether the proton or neutron is heavier! The proton gets an electromagnetic boost, but the lightweight W and Z particles (which would now have masses around 40 MeV) provide a correction in the opposite direction. So Chris said it is too close to call… wow!

        1. Interesting! If low-energy supersymmetry ever gets discovered, one can also make a similar case that supersymmetry breaking is responsible for the vast majority of the baryonic mass (in this case I think \Lambda_QCD really shifts if you allow light squarks as well). Although I think by this point it is becoming a game of making statements that are technically correct but maximally confusing.

          1. Dear Professor –
            Love this blog. You are a great teacher. I know you like to keep things non-technical, but I love reading discussions like this one, even if I only understand a quarter of it.

    1. Prof. Strassler and Flakmeister,

      There may be, however, a subtle counterargument to the idea that the Higgs field pervades the entire observable universe. Nothing precludes formation of bound states of arbitrarily large numbers of Higgs bosons, whose binding energy is actually larger than than the sum of all Higgs masses. But, according to Veltman, such a bound state of negative total energy cannot go undetected: to quote him, having a large system of Higgs bosons “all over the universe is something that would be sensed by gravitation and calculations reveals that such a system would lead to a curved universe with the size of a football.”

        1. Are you saying that a Bose-Einstein condensate of an extended system of weakly interacting Higgs bosons with a 125 GeV mass is not possible? Why?

        2. The binding energy won’t be nearly enough. To get binding energy that large, you need strong forces not predicted by the Standard Model, and such strong forces would affect all the calculations of all of the processes by which the Higgs is produced and by which it decays. In short, an unexpected strong non-Standard-Model force would make the Higgs particle behave in a very non-Standard-Model-like way. Data rules this out.

          1. You are, however, making the tacit assumption that the Higgs self-interaction behaves the same way on cosmic scales as it does on the subatomic scale. We barely know the attributes of the Higgs near the EW scale and I don’t believe there are firm grounds to extrapolate on Bose-Einstein clusters of galactic scales. What if the binding force scales with the size of these clusters?

            I would be curious to see your analysis and Vetman’s side by side. In particular, what are the assumptions and how are the calculations carried out ?. Did Veltman overlooked something fundamental in computing the binding energy of arbitrarily many Higgs bosons?

  34. Your argument is compelling, but I remain a bit skeptical about exclusively relying on astrophysical observations to conclude that the Higgs field is constant across the universe. These observations are indirect pieces of evidence and we don’t know for sure whether there is interplay between the Higgs field and Dark Matter that might influence spectroscopic measurements.

    1. Earvin.
      it is alright to be skeptical, but, the onus is then on you to show any evidence (or motivation) of hypothetical effects. Empirically, efforts to look at the time dependence of alpha from quaser spectra imply that any effects at are at the level of 1 part in 100,000. That should give you an idea of what you are up against….

      So in the absence of any observable effects, you must accept the hypothesis that the Higgs is universal….

  35. Prof. Strassler,
    Overall, your posting is an accurate and concise description and it serves well the purpose of telling the true story to the general audience. Allow me to make a couple of suggestions:
    1) On the Higgs field you say that, “in fact it has just about the same value everywhere throughout the universe (at least in that part that we can observe.)”. This statement is exclusively inferred from theory but it has no experimental backing: there is no evidence that the Higgs field is a constant throughout the observable universe, although we have good reasons to believe that this must be the case.
    2) Few words about the unsettled challenges of the Higgs model would be beneficial. For instance, to my knowledge, the origin of the negative Higgs mass term in the potential is still poorly understood. The fine-tuning problem remains open and is amplified by the absence of low-scale SUSY. The lack of conformal symmetry induced by the Higgs mass is troubling, although one can make the argument that classical gravity suffers from the same anomaly. Vacuum stability about the EW scale is not settled yet. Finally, there are unsolved issues raised by Prof. Veltman on the rho-parameter and its connection to precision EW observables.

    1. Thanks.

      1) Hmm. We observe that atomic emission lines and absorption lines are the same across all galaxies that we can observe. If the Higgs field varied across the universe, masses of particles would vary, changing those emission and absorption lines in an easily observable way. Even a rather small variation would destabilize many atoms and nuclei, making galaxies very different or even impossible in those areas. So actually I think the evidence is quite strong. Do you have a specific counterargument?

      2) I’m not sure I would worry about Veltman’s concerns, but the other issues are all serious. But they are so darned technical. Maybe you are right they should go in the caveats as a general statement that there are many unsolved puzzles about how the Higgs field comes to do what it does. I do plan to write a long article about the problems with the Standard Model, and I can link the current post to it at that time.

      1. Re (1): We can directly observe quantities that depend on electron mass, up quark mass, down quark mass, and W boson mass beyond Earth and can indirectly observe quantities related to the sum of the neutrino masses. We can’t observe quantities that depend on second or third generation quark masses or on muon or tau masses beyond Earth and up quark mass and down quark mass are only observable as mediated through proton and neutron masses that are quite insensitive to fairly meaningful adjustments in up and down quark mass (particularly if the relative values were the same).

        Many version of SUSY with its multiple Higgs bosons (some of which would be many TeV in mass) and a Higgs field that is a composite of the separate fields that these multiple Higgs bosons create, would be particularly prone to local variation in high energy environments, I would think.

        Many of the observable are sensitive to relative fundamental particle mass and not absolute Higgs field strength. If the Higgs field were 3% weaker in some distant pulsar’s system adjusting masses proportionately across the board than it was on Earth (similar to the effect of a unit conversion from feet to meters that would change the numbers but no their relative values), might just make us think that the red shift is different than it actually is by 3% or the square or square root of 3% of something like that. A change in say, the relative strength of the electron coupling to the down quark coupling, would wreck absolute havoc.

        Honestly, we only know the absolute value of the up quark and down quark mass and a fortorari their Higgs field couplings to +/- 50% and +/- 30% respectively and only know the ratio of their masses to +/- 100% (measuring relative to the smaller value), even though we know the proton mass, neutron mass and strong force coupling constant to about four significant digits or more. We can’t even compute the proton mass from first principles to more than an accuracy of about 1% despite having what we believe to be the exact laws of nature expressed mathematically at that energy scale, a four significant digit accuracy coupling constant, the exact quantum numbers of all of the particles involved, and far more precise electroweak constant and speed of light and Planck’s constant and Higgs vev values, 0.6% accuracy top quark mass measurements, and very exact masses of protons, neutrons, charged leptons, and some of the more common baryons. The weak force coupling constant (which is another lynch pin of the electroweak unification theory that predicted the Higgs boson in the first place) doesn’t even have a strong anthropic principle constraint – no one can say with confidence that the universe would be much different if it were +/- say 30% different.

        One could also imagine the Higgs field having localized variations, e.g. being stronger at greater distances from the nearest large black hole, which would give rise to dark matter-like behavior that has been ascribed to some other cause, or Higgs field variations explaining large scale structure in the universe, or having values that depend on the strength of the local electromagnetic field (since the homogeneity of electromagnetic charge balance in the universe is very fine grained).

        The SM and SUSY (excluding SUGRA) have nothing to say one way or the other about how strong gravitational fields could influence the Higgs field anyway (e.g. in the vicinity of neutron stars and black holes), nor does it have anything to say about the Higgs field strength in the vicinty of boundary conditions (the Big Bang and the “outer boundary” of the Universe post-Big Bang. In general, very little theoretical work has been done on variations in the Higgs field strength because there has been no theory where adjusting it helps advance whatever motivates that theory. Similarly, if the Higg field strength systemically varied with peaks and troughs of gravity waves, it isn’t obvious that we’d notice any difference since they would average out and look like experimental noise or systemic errror, even though that would be a very important fact of quantum gravity theories.

        This isn’t to say that any of that is probable or well motivated. But, a theory consistent with experimental data in which one or more Higgs fields have strengths that vary in different parts of the universe is far less experimentally constrained than for example, the MSSM which must be just so to fit the experimental data at the LHC.

        1. Look, this is too long for a comment. Please just write a blog post somewhere, and let us know where it is. I can’t really permit one person to take such a huge chunk of comment space, because it tends to stop further comments from coming in.

  36. Your points are correct, but the Higgs field is in no way sufficient to give the neutrino a mass. In both cases (a) and (b) there must be additional particles getting a mass from a different mechanism. In some sense part of the neutrino masses is for sure not coming from the Higgs field.

    But I agree that this is a bit beyond the discussion about the Higgs, hence neutrinos are not a very good example.

    1. Hmm. Your statement doesn’t seem correct if the neutrino masses are pure Dirac; we do need to add right-handed neutrinos, but why must they “get mass from a different mechanism”?

      About Majorana masses, I agree, though my statement in my summary above is merely that the Higgs field is necessary; “if the Higgs field were zero, the known elementary particles (including neutrinos!) would be massless.” I agree the Higgs field is not sufficient; you need to generate the interaction between the neutrinos and the Higgs field somehow. (Of course we don’t even know how the interaction between the electron and the Higgs field is generated; that too probably requires unknown particles and fields.) However, even then, wouldn’t we simply say that it is the right-handed neutrinos that are the particles that don’t get their masses from the Higgs field — not the left-handed neutrinos that we have already discovered?

  37. “I said the Higgs field “gives elementary particles” mass; I avoided saying “gives all elementary particles their mass” because it is likely that there are elementary particles that we haven’t yet discovered that don’t get their mass from the Higgs field. ”

    Indeed, we know of elementary particles whose mass is not given by the Higgs field: neutrinos!

    1. Ah! a common misconception! Neutrinos MUST also get their mass from the Higgs field. It’s an important though technical point. Either

      a) neutrinos get their masses just the same way electrons do, via what is known as a Dirac mass term, in which they interact with the Higgs field just like other particles, or

      b) neutrinos get their masses via what is known as a Majorana mass term (perhaps involving a see-saw mechanism where they mix with heavy neutrinos that get their mass some other way) but that still means they interact with the Higgs field; unlike the electron, quarks, etc, they interact with the Higgs field *squared*.

      You cannot give neutrinos a mass without having them interact with the Higgs field. The symmetries of the Standard Model do not allow it! Technically speaking: a mass term for a neutrino without a Higgs field violates SU(2) x U(1) gauge invariance.

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A decay of a Higgs boson, as reconstructed by the CMS experiment at the LHC


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POSTED BY Matt Strassler

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POSTED BY Matt Strassler

POSTED BY Matt Strassler

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