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First Definitive Higgs Result In 7 Years 197

Posted by kdawson
from the you-want-mass-with-that dept.
PhysicsDavid writes "In a suite of new results about the Higgs boson, Fermilab presents the first new definitive evidence on the (lack of) existence of the Higgs boson since the Large Electron Positron collider shut down in 2000. Fermilab hasn't found the Higgs, but can rule out a certain range of masses for the particle that is believed to create mass for all the other particles of nature. Other Higgs news suggests a new likeliest mass range of 115 to 135 GeV for the Higgs. These results were among those presented at the ICHEP 2008 conference currently wrapping up in Philadelphia."
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First Definitive Higgs Result In 7 Years

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  • Higgs (Score:5, Informative)

    by JohnFluxx (413620) on Tuesday August 05, 2008 @05:48PM (#24487673)

    Knowing the mass of the higgs is important because it tells us which of our theories is on the right track. For example, a very large higgs would rule out huge branches of string theory, almost killing it. Not finding it at all would rule super symmetry would destroy the standard model, with nothing left to stand it in place.

    The 'worst' case is that we find the higgs exactly where we expect it to be, confirming what we pretty much knew already, without adding any new real information.

    • Re:Higgs (Score:5, Insightful)

      by syousef (465911) on Tuesday August 05, 2008 @06:38PM (#24488233) Journal

      The 'worst' case is that we find the higgs exactly where we expect it to be, confirming what we pretty much knew already, without adding any new real information.

      Why is that the worst case? Science is the search for truth. Nature and reality don't change based on what we wish. That's the difference between science and magic/religion. We shouldn't care which theory wins out or what we gain from the knowledge. We should only care about which model most resembles what is real and measurable. Since we're talking about deductive reasoning, if we find that what we already know is correct, that still invalidates/eliminates entire other branches of enquiry. That means we don't have to waste time on those branches (unless there are other reasons to do so - and intellectual curiosity and the possibility of finding the unexpected might be reason enough - or we want further confirmation)

      What I'm trying to say is that any definite result is a good result and we shouldn't let our emotional biases get in the way of actually doing the science.

      • Re:Higgs (Score:5, Insightful)

        by Nutria (679911) on Tuesday August 05, 2008 @07:07PM (#24488557)

        We shouldn't care which theory wins out or what we gain from the knowledge. We should only care about which model most resembles what is real and measurable.

        Yes, that's what scientists should care about.

        But if you've built a life and well-known career based on something that appears to just have been invalidated, the typical human reaction isn't to accept it, and say, "oh well, time to cancel all my grants, give up my professorship, and start over, even though I'm 50 and have spent 1/2 my life 'studying' string theory".

        • Re:Higgs (Score:5, Insightful)

          by Minwee (522556) <dcr@neverwhen.org> on Tuesday August 05, 2008 @11:15PM (#24491353) Homepage

          A great philosopher described that best:

          "Alright!" bawled Vroomfondel banging on an nearby desk. "I am Vroomfondel, and that is not a demand, that is a solid fact! What we demand is solid facts!"

          "No we don't!" exclaimed Majikthise in irritation. "That is precisely what we don't demand!"

          Scarcely pausing for breath, Vroomfondel shouted, "We don't demand solid facts! What we demand is a total absence of solid facts. I demand that I may or may not be Vroomfondel!"

          "But who the devil are you?" exclaimed an outraged Fook.

          "We," said Majikthise, "are Philosophers."

          "Though we may not be," said Vroomfondel waving a warning finger at the programmers.

          "Yes we are," insisted Majikthise. "We are quite definitely here as representatives of the Amalgamated Union of Philosophers, Sages, Luminaries and Other Thinking Persons, and we want this machine off, and we want it off now!"

          "What's the problem?" said Lunkwill.

          "I'll tell you what the problem is mate," said Majikthise, "demarcation, that's the problem!"

          "We demand," yelled Vroomfondel, "that demarcation may or may not be the problem!"

          "You just let the machines get on with the adding up," warned Majikthise, "and we'll take care of the eternal verities thank you very much. You want to check your legal position you do mate. Under law the Quest for Ultimate Truth is quite clearly the inalienable prerogative of your working thinkers. Any bloody machine goes and actually finds it and we're straight out of a job aren't we? I mean what's the use of our sitting up half the night arguing that there may or may not be a God if this machine only goes and gives us his bleeding phone number the next morning?"

          "That's right!" shouted Vroomfondel, "we demand rigidly defined areas of doubt and uncertainty!"

        • by geekoid (135745)

          Sorry, to bust your cynical bubble, but I've seen too many scientists close the book on a lifetime of research when the tests don't pan out.

          But you live in your little world were scientists rub their hands together and join in a global conspiracy to keep the truth hidden.

      • Re: (Score:3, Interesting)

        by Joe Snipe (224958)
        I can use deductive reasoning to find my way out of a forest, and it would indeed be the search for truth (the same as the search for scientific truth), but I will still be "emotionally biased" in that I will want the end of the forest to be right over the hill. I have no reason to stop if my hopes are incorrect. I am not sure why you posted this, syousef I think I am missing your point.
      • Re:Higgs (Score:5, Insightful)

        by Xtifr (1323) on Tuesday August 05, 2008 @08:23PM (#24489407) Homepage

        You're missing the point. This isn't about merely discovering random facts. Yes, it will be nice to know the facts, no matter what, but science is more than a random collection of unanalyzed facts. Some results will do more than merely give us another random truth to add to our collection; some results will allow us to falsify certain theories and not waste time on them any more, which is better than a result that leaves us just as confused as we are now.

        And in response to Nutria, who also commented: you have it exactly backwards. A result which eliminates more theories is a better result from a scientific POV. If this were about scientists clinging to their pet theories, then a result which left more theories open would be better (since it would allow more scientists to cling to their favorites), but that's pretty much the opposite of what JohnFluxx was suggesting.

      • Re: (Score:3, Funny)

        by Bloodoflethe (1058166)

        No no no, the technocracy would like you to think that nature and reality are immutable, but as any of the other orders will tell you, the technocracy is just better at convincing the majority that they are right.

      • by sjames (1099)

        It's worst case in the sense that it's not all that "interesting", it spurs no new thinking, suggests no departure from the theory stew we have now, etc.

        That says nothing about accepting or rejecting the data, etc, it's just not as "fun".

      • by geekoid (135745)

        It's a 'worse' case becasue it doesn't add anything new.
        Meaning, it won't be that interesting.

        If you find a safe in your backyard, the worse case scenario is that it's empty. It doesn't mean you don't want the truth, only that if it was filled with precious gems* it would be more exciting.

        *rolled from the AD&D DMG 1st ed.

    • Not finding it at all would rule super symmetry would destroy the standard model

      It would destroy the SM but would not necessarily rule out Supersymmetry. Existing SUSY models only require two Higgs doublets because we think the Higgs is the way the particles gain their masses and given that assumption SUSY will need at least two of them (though more are not excluded). If the Higgs mechanism is not the way the universe works then who says the new mechanism, whatever it is, will preclude the existence of SUSY? The main argument for SUSY (to explain a light Higgs) may be gone but there a

  • Would someone explain why mass is expressed in GeV? GeV sounds like a measure of electrical field strength.

    • Re:Newbie question (Score:5, Informative)

      by Free the Cowards (1280296) on Tuesday August 05, 2008 @05:54PM (#24487747)

      The electron volt [wikipedia.org] is a measure of energy. It is the energy gained by an electron accelerating through an electric field potential of one volt. And since energy and mass are equivalent [wikipedia.org], this miniscule measure of energy also makes for a useful miniscule measure of mass.

    • Re: (Score:3, Informative)

      by Dice (109560)

      It's a unit of energy that particle physicists use instead of mass. One eV is an electron-volt which is equal to the energy gained by an electron after being sent through a one volt potential. You can use E = m c^2 to convert between energies and masses.

    • Re: (Score:2, Insightful)

      by neurovish (315867)

      eV is a measure of "energy", the E in E=mc^2

      1 GeV = 1.783Ã--10^â'27 kg

      When you're dealing with things that are really tiny, it's easier to use GeVs than 10^-27 kgs.

    • by mcelrath (8027)

      GeV = giga electron volt = 10^9 eV. The electron volt (eV) is the amount of energy gained by an electron accelerated by a 1 volt potential.

      Finally, E=m c^2 so we generally interchange mass and energy as convenient. Strictly, we should write masses in units of GeV/c^2. However we generally set c=1 so there is no difference between mass and energy. Obviously, in engineering units mass and energy are not the same. However, one can always take a mass, and multiply by the speed of light (in whatever units

    • by Roger W Moore (538166) on Tuesday August 05, 2008 @08:13PM (#24489287) Journal
      Actually is it not. Mass is correctly expressed in units of GeV/c^2. Einstein showed that energy and mass are equivalent with his famous E=mc^2 relationship. Hence mass, m=E/c^2. Thus we can use units of energy/c^2 to measure mass. This is particularly useful in fields like particle physics because we often convert mass into energy, or vice versa, and so it is useful to know how much energy it takes to create a particle (or is released in a particle decay).

      Using units of 'GeV' for mass is actually very sloppy and technically wrong because energy and mass do not have the same dimensions and so cannot have the same physical units. The usual excuse is the use of natural units where c=1. However that '1' has dimensions associated with it and so to ensure that those dimensions are preserved you need to include it in the units. Hence mass is actually measured in 'GeV/c2' and not 'GeV'. Similarly momentum can me measured in units of 'GeV/c'.
    • An eV is a unit of energy. (1 Volt * the charge on 1 electron. A Volt has units of energy/charge, so the dimensions work out right: energy/charge * charge = energy.) At relativistic speeds, it's useful to express mass in units of energy. It's OK because mass is related to energy by E=mc^2, and it is often useful in relativistic calculations to write down the "total energy" of a particle (mass energy + kinetic energy).
  • In case anyone else is a confused about this as I was, apparently "by mass-energy equivalence, the electron volt is also a unit of mass. It is common in particle physics, where mass and energy are often interchanged, to use eV/c, or more commonly simply eV with c set to 1, as a unit of mass." And "1 GeV = 1.783×1027 kg." At least according to:

    http://en.wikipedia.org/wiki/Electron_volt [wikipedia.org]

  • by witte (681163) on Tuesday August 05, 2008 @05:55PM (#24487767)

    Not to diminish the importance of the work done at Fermilab, but the headline is very misleading.

    • by Nimey (114278)

      On Slashdot? Never!

    • Re: (Score:3, Funny)

      The headline is VERY misleading.

      There was no mention at all of what I learned this past Sunday. The minister stood right up and said at the beginning of his sermon that if the Higgs particle was 120GeV or less, that meant that Allah was god and the Muslims were right. If the mass was greater than 120GeV, then that meant that the resurrection and divinity of Jesus was right.

      He did say that the latest Fermi results ruled out ENTIRELY the Catholic view that the communion wafers actually turn into the body of C

  • by Dice (109560) on Tuesday August 05, 2008 @06:00PM (#24487825)

    Okay, I only have a 4 year degree in Physics so maybe someone can help me out on this. If this particle gives the property of mass then shouldn't it have a mass less than that of the lightest particles? According to a quick Google calculation [google.com] this thing out-masses an electron by 5 orders of magnitude.

    WTF?

    • Re: (Score:2, Informative)

      by digitrev (989335)
      Having a degree in physics means nothing if you didn't do anything in this branch of physics. First off, the electron is not the lightest particle. Strictly speaking, the electron neutrino weighs in at less than 2.2 eV, where the electron weighs in at 0.511 MeV. Then you have the tau neutrino, which weighs in at 15.5 MeV. Then you have the proton, which weighs 938 MeV. After that we have the tauon, which has a mass of 1.7 GeV. All of which, so far, are leptons. So while 135 GeV is fairly high, it's not unre
      • Re: (Score:3, Insightful)

        by Dice (109560)

        I took the entire undergrad QM sequence at my school, we covered Liboff cover to cover so I know a little. I am aware that the electron is not the least massive particle, however it is the least massive particle that I know of Google having built into its calculator function.

      • Re: (Score:2, Insightful)

        You missed the point. His point was that they are saying the elementary mass particle has more mass than a non-elementary mass particle. If a Higgs boson has more mass than an electron, what gives the electron its mass?

        • by dAzED1 (33635)
          interaction with the higgs? Electrons having as part of their fundamental nature a bond of some static nature with an explicit number of higgs? Hell, I dunno - not a physics person :)
      • by sconeu (64226)

        Isn't the proton a hadron?

        • by Muad'Dave (255648)

          Isn't the proton a hadron?

          Yes, but if it doesn't 'decay' within 4 hours, it must seek medical attention immediately.

      • by inertialFrame (259221) <tevaughan@@@gmail...com> on Tuesday August 05, 2008 @06:46PM (#24488299) Homepage Journal

        Having a degree in physics means nothing if you didn't do
        anything in this branch of physics.

        That seems a bit strong. A physics degree does mean that you can
        reasonably expect an explanation to be understood without too much
        effort on your part.

        First off, the electron is not the lightest particle. Strictly
        speaking, the electron neutrino weighs in at less than 2.2 eV, where the
        electron weighs in at 0.511 MeV. Then you have the tau neutrino, which
        weighs in at 15.5 MeV. Then you have the proton, which weighs 938 MeV.
        After that we have the tauon, which has a mass of 1.7 GeV. All of which,
        so far, are leptons.

        I can see where you're going, but you made a careless error. The proton
        is not a lepton.

        In the standard model, leptons and quarks are fundamental particles.
        Leptons and quarks are reflections of each other through a certain
        symmetry. But a quark never appears by itself. A quark-antiquark pair
        is called a meson (which is a boson because it has whole-integer quantum
        spin), and a triplet of quarks, like a proton or neutron, is called a
        baryon (which is a fermion because it has half-integer quantum spin). A
        hadron is any particle that interacts through the strong force; this
        includes mesons and baryons but not leptons.

      • by mcelrath (8027)

        Sorry, your post contains several errors.

        There are three neutrinos corresponding to electron, muon, and tau, and all three of them weigh less than 1 eV. Furthermore, they all mix with each other, so there are three states, but each is a mixture of electron, muon, and tau-type neutrinos.

        The W and Z bosons weigh 80 GeV and 90 GeV respectively. The top quark weighs 172 GeV. The theory would be consistent with a higgs of any mass below about 200 GeV. We have searched in many experiments at lower energie

        • by pbhj (607776)

          You clearly knows more about this than I do; but calling the different neutrinos a mixture of the three flavours of neutrino seems a little lacking.

          e, muon and tau neutrinos undergo flavour oscillation, ie change type, but they appear still to be different particles - the particles comprise a mixture of flavour eigenstates that interfere through a mismatch in the mass eigenstates. No I don't understand it fully but a simple mental-model analog might be beat frequencies produced by sound waves in constructiv

          • by mcelrath (8027)

            The three physical (mass eigenstate) neutrinos [nu_1, nu_2, nu_3] are mixtures of the three interaction states [nu_e, nu_mu, n_tau] and are related by a rotation matrix R called the MNS matrix. It's just a matrix rotation.

            Today we do believe we understand the "solar neutrino problem" in terms of mixing of the three states. For the solar neutrinos, in fact mixing due to matter is dominant (rather than mixing due to the masses). There are numerous neutrino experiments going on today, but so far they have

            • by pbhj (607776)

              Thanks - I didn't know about Double CHOOZ or Daya Bay, seems I'm a bit out of touch!

              One more question - do you view the 3 neutrinos mass eigenstates as 3 distinct neutrino type's or as 3 representations of one neutrino with an internal mix of flavours, or something else.

              This is where my internal model of particle-wave duality comes a bit unstuck. Like visualising hyperspatial forms (hypercubes or whatever), never could quite lock it down.

    • by Jazzer_Techie (800432) on Tuesday August 05, 2008 @06:25PM (#24488113)
      It sounds like you're thinking about the Higgs giving mass to particles by being a constituent of them. (That is a perfectly reasonable linguistic interpretation of ``give mass to'', but it doesn't reflect the physics.)

      In these theories, mass arises of interactions with the Higgs boson. Thus, the Higgs being massive doesn't exclude less massive particles.
    • Re: (Score:3, Informative)

      by dougr650 (1115217)
      The "rest mass" of particles has to do with how strongly they couple to the Higgs field (as well as the intrinsic value of the H field in a vacuum), and doesn't really have anything to do with the mass of the Higgs. Particles do not have mass because they are composed of (presumably lighter) Higgs particles, they have mass because they interact with the Higgs field, if the theory is correct. The problem is that we don't understand very well how the Higgs quanta couple to the H field, so it's difficult to
    • by dwye (1127395)

      Okay, I only have a 4 year degree in Physics

      More than I do. I transferred out in my third year, as I realized that I wanted a job instead of, not after, a PhD.

      If this particle gives the property of mass then shouldn't it have a mass less than that of the lightest particles?

      The reported mass of the Higgs is the rest mass of a real Higgs particle. Mass, according to the theory, comes from interaction with a field of virtual Higgs particles, not a real Higgs merging with a real particle. Thus, if anything

  • In other news... (Score:3, Insightful)

    by Pictish Prince (988570) <wenzbauer@gmail.com> on Tuesday August 05, 2008 @06:22PM (#24488085) Journal
    Cryptozoologists have narrowed down the possible habitat range of the Abominable Snowman. Spokesman for the research team, Dr. Justin Wanker, said "We've got him pinned down now!"
  • Can someone explain to me why we need something to give mass to something? Can't it just be that matter warps space-time? Since Mass and Energy are equivalent, why can't it just be that energy/mass warps space-time, and that mass is simply the effect we observe in the hree dimensional universe of this warping?

    Occam's Razor says the whole concept of the Higgs Boson and the Higgs Field are wrong, much like String Theory.

    • Re: (Score:2, Informative)

      by RedOctober (10155)

      Occam's Razor would indeed say that, if it wasn't the case that the Standard Model is a very well tested model for particle physics.

      The Higgs mechanism is part of the Standard Model. One of the predictions of this Model is that the quantum of the Higgs field, the Higgs boson, exists. Unfortunately, if it doesn't, it means something has gone seriously wrong with the model, because it's been successful in explaining a great many things.

      • Am I the only one who sees a problem with the circular logic of saying, "We need some particle to give particles mass -- wait, what gives mass to the particle that gives particles mass?"

        Either mass is an intrinsic value of matter, perhaps based off of the total potential energy bound up in the matter, or according to the standard model, mass is imbued to particles by a special particle which imbues them with mass. Whence then comes the original mass?

        • by Urkki (668283)

          Are you suggesting that mass is some kind of magical property of matter that affects magically? That doesn't really fly with science. No, there needs to be some kind of mechanism for the effect of particle's mass to interact with other particle's masses. Without the mechanism, "mass" has no meaning since it doesn't do anything. But clearly mass does something, so there must be some mechansim for masses to interact, either with "space-time continuum" or directly with other masses. Also there needs to be expl

        • by hweimer (709734)

          Am I the only one who sees a problem with the circular logic of saying, "We need some particle to give particles mass -- wait, what gives mass to the particle that gives particles mass?"

          It doesn't mean that the Higgs gives mass to all particles, only to some of them. The standard model requires some particles (gauge bosons) to be massless, otherwise the whole theory leads to inconsistent results. For photons and gluons, this is fine, as current experimental results are consistent with these particles being massless. However, W and Z bosons, are all but massless -- they are even 100 times heavier than protons!

          To fix this inconsistency, some very smart physicists came up with the idea to int

        • Re: (Score:3, Informative)

          > Am I the only one who sees a problem with the circular logic

          Apparently, yes.

          For one thing, it's "extra mass", not "mass". The mass of the electron is fully accounted for by it's self-energy. If you integrate the EM field energy over the electron's field, then apply E=mc^2 to that result, you get the right answer.

          Higgs is only needed for particles that do not follow this rule, like quarks. Quarks are heavier than their otherwise obvious self-energy can explain. So we postulate another form of "charge" (

    • by ceoyoyo (59147)

      Why does mass/energy warp space-time? What is space-time anyway? Furthermore, why does mass/energy resist being accelerated? Why is the resistance to acceleration always in the exact same proportion to the gravitational effects?

      For that matter, why is the universe expansion accelerating? Why does it appear to have undergone the process we call inflation?

      The Higgs field can explain all of those things in a way we've never been able to do before. Occam's Razor says the concept of "space-time" as somethin

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