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    The Higgs Mass In Atomic Mass Units
    By Tommaso Dorigo | March 20th 2012 09:09 AM | 29 comments | Print | E-mail | Track Comments
    About Tommaso

    I am an experimental particle physicist working with the CMS experiment at CERN. In my spare time I play chess, abuse the piano, and aim my dobson...

    View Tommaso's Profile
    Whenever I try to explain something about particle physics to a layman, I run into the problem of mass/energy units. A Giga-electronVolt is not something you may expect people to be familiar with, and on the other hand it is not appealing to explain directly how it is defined: "if you take an electron and accelerate it by passing it through a potential difference of one billion Volts, that's the energy it has at the end: one GeV": this distracts the listeners by forcing them to focus on electrostatics, with the potential outcome that the conversation may diverge due to additional questions, like "Does the electric field need be uniform ?" or even, "What is a potential difference ?".

    To avoid that kind of trouble you may make the choice of avoiding altogether to mention the funny unit, implicitly equating a GeV to a proton mass. This causes you to end up making statements like "The LHC produces collisions at an energy corresponding to 7000 proton masses", or something similar. The escamotage is effective, but imprecise -a proton only weighs 0.938 GeV, which is over six percent less than a full GeV. And six percent may or may not be relevant to the statements you make. If you do not want to live with that you need to make a correction on the fly, or change system.

    A nice, although somewhat problem-specific, solution to the above outreach issue has been concocted by Adrian Buzatu. A post-doc for Glasgow University, where he works at a competitor experiment, ATLAS, but collaborates with me by being a colleague in the CDF experiment, Adrian is also a science writer for a Romanian magazine, EVZ. Wanting to explain the progress made by the LHC experiments in constraining the allowed range of masses of the Standard Model Higgs boson from last summer's results to the most recent ones, Adrian compared the tentative Higgs mass values to the masses of heavy atoms. He thus came out with two sets of periodic tables of elements, with elements compatible with Higgs masses not yet excluded by direct searches highlighted in red.

    The Summer 2011 situation saw many elements of the table still compatible with experimental searches for the Higgs boson: these correspond to the mass range 114.4 GeV - 149 GeV, the one where the Higgs production hypothesis had not yet been disfavoured at 95% confidence level.




    However, the latest results show a dramatic narrowing down of the masses which are not disfavoured at 95% confidence level:



    I think this is a quite nice visualization of the progress made by ATLAS and CMS. For the original article by Adrian (in Romanian) see here.

    Comments

    lumidek
    "Whenever I try to explain something about particle physics to a layman, I run into the problem of mass/energy units. A Giga-electronVolt is not something you may expect people to be familiar with..."
    There is quite some universality here. A few weeks ago, I had this newspaper article on OPERA.

    http://motls.blogspot.com/2012/02/opera-and-italian-comrades.html 

    All the readers who responded called their mail "Italian comrades" because I used the sentence "Where did the Italian comrades made a mistake?" This was a parody of the Czech film "Cozy Dens" (the plot is placed to the mid 1960s) where an enthusiastic communist professional soldier, proud about the superiority of communist countries, distributes the plastic spoons from East Germany during a big Xmas dinner party. 

    All the spoons melt in the coffee and the father from the other family, a staunch anti-communist and traditional capitalist citizen (the teenage kids of these two guys date each other, of course, that's the main basis of the movie: the families finally got friendly) says "I would just be interested in where the comrades from GDR made the mistake". :-)

    Aside from this fun, all the confusion by the readers was about the units. Of course, the first, most self-confident one, was irritated by the sentence that the Higgs mass was 125 GeV (the last sentences of the article on neutrinos were on the value of the LHC and the Higgs). It is not a unit of mass, I was told. So I explained to him that GeV/c^2 is a unit of mass, according to any units, and physicists also love to set c=1 which means that we may say that even GeV is a unit of mass. Impossible to explain. I think he was an engineer so he may have been trained to be very picky about using the standardized engineering units for everything. But the idea that someone could use completely different units was unexplainable, despite our totally peaceful exchanges.


    Now, we spent so much time about this bullshit - about his psychological problem with the unit - so that he totally missed the point of the sentence which was announcing the most important discovery in particle physics in many many decades. This just sucks. Some brainwashing about being picky totally prevented this guy from seeing the truly important things.

    The proton mass is a way out, a standard one in popular books, too. But the Higgs mass is 133 proton masses. Numerically, it's just way too far from 125 which is why it sucks. I found some isotope that was very close to the Higgs mass, probably cesium of some kind. Of course that people get this point. But the equivalence of mass and energy is something that people don't really see. So they don't really understand that the energy - voltage and charges, the electricity equal to the households of Geneva that the LHC eats etc. - is what is converted to the mass of new particles. Those are great things - understood since 1905 pretty much - but people are almost never told these things. So I would say that even average enthusiastic readers of major newspaper's science/physics sections are still ignorant about E=mc^2 and its content, despite the T-shirt status of the equation. The idea that "c" is an exceptional speed among others is a taboo, too. And of course, one never gets any space in newspapers to explain those things so the ignorance about the fundamental issues is guaranteed to continue.


    vongehr
    the electricity equal to the households of Geneva that the LHC eats etc. - is what is converted to the mass of new particles ... even average enthusiastic readers of major newspaper's science/physics sections are still ignorant about E=mc^2 and its content,
    So are you apparently. Energy is inert, inertia is expressed in terms of mass. Energy is NOT converted into mass ever. Energy can take the form of matter, but the mass is just the inertia of the black box which does not change when the electron and positron inside annihilate. Are you perhaps a little too proud about what you actually understand and what you often only think you understand?
    lumidek
    I have no idea what your crackpottish babbling is supposed to mean. As far as I can say, you only confirm that you belong among the totally ignorant laymen. It's annoying when my important comment is polluted by similar junk and I can't even use a spray that would make you go away.
    Mass "m" may be measured by its inertia or the gravitational field around it but it still satisfies "E=mc^2".

    In the LHC rings, the protons are given what every sane person - i.e.. people not including you - call energy. It's obtained from the electric fields that accelerate the charged particles around the ring. The energy of a proton is now 4 TeV per proton. When these protons collide, they may create several or lots of top quarks or Higgs bosons which have the mass of 173 or 125 GeV/c^2. 

    That's their mass and they have a higher inertial mass (by two orders of magnitude) than the protons at rest. Again, all sane people call this property of the top quark or Higgs boson "mass". Again, you probably don't belong to this set. It's the whole point of my explanation that a box to measure the inertial mass will fail to include all the energy. In that way, you will only measure the rest mass of the system, at least if you follow the procedure you have described. But the LHC is increasing the energy of the protons although they are internally - in their rest frames - still the same protons. The constancy of the rest mass after acceleration is the reason why we never use the term "kinetic mass": the mass/energy one gains by a higher velocity is *always* called energy, not mass. And this increased total energy is nevertheless able to create particles of much higher inertial mass, up to 8 TeV/c^2.

    One may talk about "mass" and "energy" as two words for the very same quantity (or the same "kind" of a quantity) and that's how it's pretty much done in physics but those laymen can't swallow this identification - that was really my point.
    vongehr
    Sad to see how utterly impossible it is for you to grasp anything fundamental. c is a unit conversion constant, so what E = m c^2 is saying is basically E = m, i.e. they are one and the same (this far you seem to half grasp), but that strictly means that they are not converted into each other (and that is what you have written, dummy). Energy can take the form of matter, but it has always mass, it is not converted into mass! Go stop blogging and first understand some physics. Great physicists were primarily understanding physics; they were not just little math freaks. Sorry Lubos, but that is the hard reality of why you have as yet not and very likely will not contribute anything substantial in spite of your amazing mathematical prowess.
    lumidek
    When I start with the kinetic energy 2 x 4 TeV of two protons, collide them, and produce lots of jets and/or Higgs whose rest mass is in hundreds of GeV, well above the 0.938 GeV of one proton (the rest latent energy of the proton I started with), then I have converted the kinetic energy (a form of energy) to the mass (another form of energy, one which used to be thought of as being a "qualitatively different thing" before 1905) - or energy that manifests itself as the rest (plus kinetic) mass of the new particles. You may disagree about it but that's the last thing you can do against these and other facts.


    The reason why it's also right to say that energy is being converted to mass is that the "mass" is a form of energy that wasn't called "energy" at all prior to relativity, so it's nontrivial to convert *any* old-fashioned form of energy to the new form, the mass.

    A careful terminological scrutiny makes it clear that it is nonsensical to say that "matter" is a form of energy. Matter isn't a physical quantity (something with a value and units) at all (it is a qualitative, philosophical concept) so it cannot be a form of a physical quantity; matter is an object, and a vaguely defined one, for that matter, which may denote either just some particles or all particles in the Universe (with the latter, inclusive definition, it makes no sense to talk about things becoming matter because everything that exists in science is matter). The form that the kinetic energy took after the collision isn't matter, it's mass (of the new matter particles), much like a part of a kinetic energy of a car acquires the form  of (i.e. gets converted to) the potential energy when the car gets to the hill. The conversion of one type of mass/energy to another is about moving the values from one term to another term in a particular decomposition of the total mass/energy into pieces.

    It's a completely standard science language to talk about mass being converted to energy or various forms of energy and vice versa, see e.g. these 2 million pages with preprints:

    https://www.google.cz/search?sourceid=chrome&ie=UTF-8&q=site%3Aarxiv.org+conversion+mass+energy 
    Arrogant people ignorant of basic physics like you shouldn't have been accepted to the basic school where they were taught how to write. If this mistake hadn't occurred, you and your fellow trolls wouldn't be flooding the Internet with offensive junk today.

    vongehr
    Why don't you just admit having made a mistake mister mysogAGWdeny? This isn't the broken refframe. Less ranty ranty, more thinky thinky, how is that for a change? You cannot convert energy into mass, period! The mass stays exactly the same before and after (so does the total energy, since it is the same). I'm out bro.
    lumidek
    Because I haven't made any mistake, jerk. Why don't you just admit to yourself that you don't have any credentials or knowledge to try to "correct" high-energy physicists when they talk about high-energy processes? You are just a deluded armchair physicist, the same type of a crank whom I talked about before, except that the Czech ones weren't as aggressive as you are.
    The collisions at the LHC convert a part of the kinetic energy of the colliding protons to the mass of new particles.  Period, asshole.
    vongehr
    You do not even know that the energy/mass equivalence and conversion does not need high energy physics? Wow do you know little about science. Dear Lubos - that you know nothing but HEP does not mean HEP is the world. BTW: One of us is actually still an active scientist and not just a right wing blogger ranting on the intertubes.
    lumidek
    Well, personal attacks are nice. Your institution, whatever it is,  is clearly a parasitic institution that should be abolished or bombed or otherwise liquidated because it is responsible for harboring aggressive unproductive imbeciles such as you.
    High-energy physics, pretty much by definition, *is* the discipline of science that knows about *everything* about these possible conversions of energy or mass from one form to another. 
    And by the way, in contrast with your deluded statements, one needs a sufficient energy for energy-mass conversion, at least equal to the rest mass of the matter particle that is being created or destroyed in the process. To create a Higgs boson "matter" out of energy, one needs at least 125 GeV which is a lot of energy - something that is only studied by high-energy physics.
    The lightest massive particles are neutrino but their production cross sections are so small that no one has a chance to observe mass-energy conversion involving just neutrinos and e.g. photons. The next-to-lightest particles are electrons whose latent energy or rest mass is 0.511 MeV. That's energy close to the energies produced in nuclear physics - not a coincidence - so science that studies the pair-creation or annihilation of electron-positron pairs surely can't be classified as low-energy physics, to say the least.

    You're a fucked-up stupid parasitic commie. The propagation of very low-quality aggressive people such as you across the university world (who get there and are being kept there by other commies *exactly* and *only* because they're commies) is what made me leave the Academia. Even after the years when I don't interact with this stinky environment on a daily basis, I am still sick of it.

    vongehr
    one needs a sufficient energy for energy-mass conversion
    Already just warming a substance will increase its mass - you are still confusing inertia and matter. Lubos: Filthy language does not work with real scientists. We all know that political correctness around women issues broke your neck in academia. That you for such a silly little non-issue like mass/matter would try to stick it to a fellow critical scientist against PC-establishment-academia who once defended you, well, what can I say Lubos. We all know you have those issues, so I guess I just take out my benevolent smile.
    lumidek
    I am not confusing any inertia and matter. Before your words, I hadn't used the word "matter" (which is a qualitative philosophical word, not a quantity) at all. I may only implicitly or explicitly identify mass and gravitational mass and inertial mass and conserved mass etc. and I am doing so because all these concepts are, due to various fundamental principles, totally equivalent in physics! If you don't know things like the equivalence principle, why don't you  first learn those things before you spam the blogosphere with your ignorance?
    I am only carefully distinguishing the total relativistic mass and the rest mass - because they're different. In the case of LHC protons, they differ by the multiplicative ratio of 4,000 or so, the so-called Lorentz factor. It's damn important to distinguish them. That's why I stress that it's important to say that the Higgs bosons and other particles at the LHC are not being created from the (rest) mass of the original protons - which would be way too insufficient - but from the kinetic energy or, equivalently, the relativistically enhanced "total mass".

    You're not any anti-PC guy. You're a textbook example of what is wrong about the aggressive spreading of PC. I just read your rant supporting the Chinese communist part.

    http://www.science20.com/alpha_meme/tibet_and_buddhism_stay_liberated-86473 


    It's really distasteful. Bundeswehr shouldn't waste resources by traveling to 10,000-mile-distant obscure destinations; they should go after enemies of the civilization such as you.
    vongehr
    So the equivalence principle is only valid for high energies? Hmmm. And supporting Hu Jintao is now PC in academia? I must have missed some intriguing refframe articles there spreading those news. Lubos: It is never too late, you know. If you try and let people help you, it will be all fine. SSRI's may be indicated. Try them please, you can't lose much, but you can win a lot.
    lumidek
    I haven't written that the equivalence principle requires high energies. I wrote that it is a universally valid principle in physics, a principle that makes it correct to identify two concepts, inertial and gravitational mass, something you have (insanely) criticized me for. 
    And then I wrote that the mass-energy conversion requires high enough energy - at least equal to the rest mass of the particles that are produced/annihilated. Note that the previous sentence doesn't contain any "equivalence principle". You really seem illiterate. 

    Supporting the top Chinese communist monkey is surely PC (to say the least) in the Chinese Academia. It is the standard among the left-wing loons such as you that have a disproportionate concentration in the Western Academia, too. Licking asses of the top Chinese communists is what assholes such as James Hansen and Al Gore - not just you - are doing all the time and they have *never* been criticized by anyone in the shitty left-wing environment of the Academia. 
    http://motls.blogspot.com/2011/01/hansen-chinese-communists-have-to-lead.html 

    So yes, it is PC in the Academia these days to support the Chinese communist criminals.

    vongehr
    I thought I leave Lubos the last word, as he apparently lost it completely, but since he tells people I just suck up to Chinese, I will answer one very last time here, just to make one thing publicly clear: Political opinion in Chinese hard science is not supported, neither are foreigners that have any opinion. Of course Lubos never knows such intricacies.

    (BTW Lubos:
    to identify two concepts, inertial and gravitational mass, something you have (insanely) criticized me for.
    You just came from a parallel universe or so? I criticized you for the mistake of writing
    the electricity equal to the households of Geneva that the LHC eats etc. - is what is converted to the mass of new particles
    Now shut up and take some Zoloft!)
     then I wrote that the mass-energy conversion requires high enough energy - at least equal to the rest mass of the particles that are produced/annihilated
    This would explain why my torch battery is always flat. It must be radiating away all its energy as neutrinos.
     
    Thank you for the including the plots in an article, Tommaso.

    I also agree with Lubos's comment. In this particular case, we compare mass with mass, so it should be more easily understood than the general case when comparing energy (of an accelerated proton) with mass.

    Thank you for including the plots and mentioning me in your article, Tommaso.

    I also agree with Lubos that for the general public it is confusing to compare energy and mass. In the case of these images, we are only compare a mass with other masses, so the comparison is easy to understand.

    I was pleasantly surprised from my audiences when presenting these kind of images that they actually ask themselves: if the Higgs boson is so massive, how does it exist inside the light atoms? And then I explain that the Higgs boson is actually a virtual particle all of the time. But that it has to become real in order to observe it, and for it to become real we need a lot of energy in our accelerators to produce the very heavy Higgs boson. But the audience never asked me how can the Higgs boson give mass to light particles until they saw this type of diagram which shows it a lot heavier than light atoms.

    vongehr
    how does it exist inside the light atoms? ... how can the Higgs boson give mass to light particles
    The Higgs mechanism allows/gives the mass, not the Higgs Boson.
    I agree that it is more accurate the way you phrased it. For the general public, though, both are precise enough, since the particle acquires mass by interacting with virtual Higgs bosons.

    Actually, I really don't like that. Virtual particles are a lot more confusing than the relationship between mass and energy, and they're not really relevant here anyway (we don't need to compute diagrams with Higgs loops in order to determine the leading-order masses of the gauge bosons and fermions).

    lumidek
    Right, Adrian. Comparing masses with masses only is a way to avoid the laymen's dissatisfaction. But there's still a question whether it's a good idea to avoid this "confrontation" with Einstein's insights of 1905 or whether one should eventually face the difficult task of explaining it to the folks....


    The Higgs field gives the masses to fermions and W/Z-bosons via the interactions with them and the nonzero vev. In some very precise sense, one may view the nonzero Higgs vev (condensate) to be a condensation of the Higgs bosons. If one starts with a hypothetical h=(0,0) vacuum for the Higgs doublet, it is also possible to produce the vacuum with h=(v,0) as a coherent state, i.e. a heavily multiparticle state with lots of Higgs bosons - real Higgs bosons excitations.


    The true vacuum in Nature wants to be at h=(v,0) because of the Higgs potential. This Higgs potential may be interpreted as interactions between multiple Higgs bosons (including a quartic i.e. 4-body interaction) and these interactions are what makes it energetically favorable to fill the space with the Higgs condensate rather than keeping it empty at h=(0,0).

    Of course, excitations around the actual, symmetry-breaking vacuum  carry the mass 125 GeV of the physical Higgs bosons, they're very heavy. But the mass of excitations depends on the environment around which we expand. The symmetry-preserving h=(0,0) state is unstable and the Higgs excitations' mass over there is different than it is in the physical stable vacuum - in fact, the Higgs excitations are tachyonic around that point (a reason to see that they want to get condensed a bit).

    Those are words that one really understands with the full machinery of QFT only. However, things like the energy-mass equivalence are simpler and should be understandable even without the QFT formalism. It's bad that the society hasn't managed to make this insight a widely appreciated one.
    rholley

      
    For a chemist like me, a very useful comparison, as is this from Wikipedia:

    1.6 to 3.4 eV: the photon energy of visible light.



    And thanks for linking the original paper in Romanian.  Trajan was here!

    (Which is why they’re still speaking Latin.)
     
     
     
    Robert H. Olley / Quondam Physics Department / University of Reading / England
    Whenever I try to explain something about particle physics to a layman, I run into the problem of mass/energy units.
    Now I'm confused. What exactly is "a layman"? Would it be fair to describe anyone who gets their knickers in a twist over the equivalence principle as "a layman"?

    Nice show, lads. For a couple of laymen.
     
    Sorry Sascha Vongehr, the physics of thread has been arbitrated by Sweetser and the verdict is in: You're FOS. But the needless provocation gives you +1 anyway.

    From Outer Space?

    I'm pleased to see a measure of the Higgs variance that is appropriate to the isospin concept in terms of which the Higgs was defined by Higgs himself. Isospin ignores differences between protons and neutrons, as does atomic number. What emerges is just the limit beyond which nuclei are intrinsically unstable, a measure related to the bullk modulus as now stated in terms of covalent radii here: http://arxiv.org/abs/1102.0869.

    As for the metaphysics, you can stuff it, with the bully-boy bluster.

    I did this game time ago and I run against a funny thing, that the U shape (of M shape, more precisely) of the distribution of fission products -equivalent, the distribution of known excited states, as most of this knowledge comes from such product- starts to peake at the scale of the W boson: http://dftuz.unizar.es/~rivero/research/bhist.jpg. For some time I though if somehow nuclei have a mass higher that W were able to have more excited states and then more phase space avalaible for the fission to decay into them.

    Ah, the histogram is actually more spectacular in the NZ plane http://dftuz.unizar.es/~rivero/research/NZ.jpg where the highest peak of the distribution [of known beta decays beta decays listed in the NUDAT database] is really seem to be next to 80.38 GeV, or 74.87 amu.

    Let me add, that it was more spectacular in 3D, over the NZ plane... regretly I have only a contour plot, http://dftuz.unizar.es/~rivero/research/NZ.jpg but you can still see how the peak [of the number of known beta decays listed in the NUDAT database] s very near of the 75 amu, the weight of the W boson.