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New Bounds On the Higgs Boson Mass 173

Posted by kdawson
from the pulling-in-the-walls dept.
As the LHC continues to run at half power for the next year+, the US-based Tevatron continues to crank out results. Reader hweimer writes "Three new papers in Physical Review Letters present the latest results for the Higgs boson mass coming from Fermilab's Tevatron. The new data mandates that the Higgs boson mass within the standard model lies between 115 and 150 GeV." A year back we discussed the Tevatron's previous shrinking of the search space for the Higgs "God particle."
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New Bounds On the Higgs Boson Mass

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  • by JoshuaZ (1134087) on Monday February 15, 2010 @08:10PM (#31150630) Homepage
    These are bounds for the mass of the Higgs boson assuming it exists. If it doesn't exist, this data is meaningless. What will presumably eventually happen is that we'll narrow the mass down to a very tiny bound (if it exists) which would be strong evidence for its existence. Or we might detect the Higgs boson using some other methods and higher energies, such as those at the LHC. Alternatively, if the Higgs boson doesn't exist then we may end up narrowing the upper and lower bounds until they cross each other. In that case the Standard Model will be wrong and we'll have an interesting day.
    • by JamesP (688957)

      And by the way, does it makes sense to talk about the mass of a particle that seems to be implicated in the origins of mass itself?!

      (Ok, maybe it does, still...)

    • by Dachannien (617929) on Monday February 15, 2010 @08:29PM (#31150778)

      These are bounds for the mass of the Higgs boson assuming it exists. If it doesn't exist, this data is meaningless.

      Film narrator: Remember, it's up to us. Bigfoot is a crucial part of the ecosystem, if he exists. So let's all help keep Bigfoot possibly alive for future generations to enjoy unless he doesn't exist. The end!

    • that we'll narrow the mass down to a very tiny bound (if it exists) which would be strong evidence for its existence.

      No it wouldn’t. Because that would be like saying: We searched the whole world for Bigfoot, except for this little hut here. So he must be in that hut.

      No he doesn’t. Because you still haven’t proven that he exists at all. :)

      • by elrous0 (869638) *
        IIRC, Steve Austin fought him several times in the 70's. That's proof enough for me.
      • by JoshuaZ (1134087)
        Not a good analogy. If we consistently got a specific mass range that was very narrow and we kept getting a consistent mass range that would be very hard to explain unless there was an actual object there.
        • by lewiscr (3314)

          The extend the analogy:

          We searched the whole world for Bigfoot, except for this little hut here. There's something we've never seen before inside the hut. So Bigfoot must be in that hut.

  • by hackerman (1649305) on Monday February 15, 2010 @08:51PM (#31150930)
    but the tevatron does more at ten
  • by YesIAmAScript (886271) on Monday February 15, 2010 @09:42PM (#31151228)

    Or is it massive enough that it must purchase two seats?

  • by mbone (558574) on Monday February 15, 2010 @11:20PM (#31151778)

    The new data mandates that the Higgs boson mass within the standard model lies between 115 and 150 GeV."

    No, it doesn't. Look at this graph [aps.org]. At a "3 sigma" level (and don't believe any new science that is not at the 3 sigma level or better), the mass of the Higgs (assuming it exists) is roughly between 115 and 225 GeV. To put it another way, a mass greater than the Tevatron exclusion zone at ~160 GeV is by no means ruled out.

    • Re: (Score:3, Insightful)

      by John Hasler (414242)

      > At a "3 sigma" level (and don't believe any new science that is not at the 3
      > sigma level or better),

      So I guess you reject pretty much all of biochemistry and medicine?

      • by JohnFluxx (413620) on Tuesday February 16, 2010 @04:46AM (#31153358)

        2 sigma means a 95% certainty, and 3sigma means a 99.7% certainty.

        So at just 2 sigma, 1 in 20 times you will get it wrong/fail. I would hope that in medicine and biochemistry, where it matters, that they do use 3 sigma certainty.

        In particle physics, a 5 or 6 sigma certainty is usually used for confirming a new particle, which means that you're wrong only once in a couple of million times (although guessing at the errors is probably itself the most significant error.

        • Re: (Score:3, Informative)

          by JamesP (688957)

          2 sigma means a 95% certainty, and 3sigma means a 99.7% certainty.

          So at just 2 sigma, 1 in 20 times you will get it wrong/fail.

          It doesn't work that way...

          I would hope that in medicine and biochemistry, where it matters, that they do use 3 sigma certainty.

          No, they use usually btw 90/95% (if not lower).

          Also, WHAT, 3sigma is a huge space (especially in this kind of experiment).

        • Re: (Score:3, Interesting)

          by Rich0 (548339)

          So at just 2 sigma, 1 in 20 times you will get it wrong/fail. I would hope that in medicine and biochemistry, where it matters, that they do use 3 sigma certainty.

          I hate to burst your bubble, but in medicine you can't create cancer patients by blasting metals with cathode rays or however you make your particles in your accelerators. You also can store a sample of a quintillion patients in an ion trap. Sample sizes are just a tiny bit smaller in most clinical trials when compared to particle colliders.

          Clin

      • by mbone (558574)

        If it is new science, and it is not at least "3 sigma," it is simply not proven IMHO.

        Things are different if you are talking about using scientific results to guide action. Part of the art of leadership is making decisions in the face of incomplete information. So if my oncologist, say, says that there is a 75% chance that my cancer may respond to some new treatment, that may well be good enough. Heck, even 50% may be good enough, depending on how dire my case is. But for the new treatment to be considered

  • I'm lost. (Score:4, Interesting)

    by DJRumpy (1345787) on Monday February 15, 2010 @11:29PM (#31151832)

    I would imagine this is how my family and friends feel when I start speaking computer gibberish. I'd consider myself relatively competent to understand basic principles like gravity, mass, weight, etc, but can someone dumb this down?

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

    I know that's probably a hopeless request without some sort of basis in this field, but can someone give the "particle physics for dummies" equivalent here?

    I get the impression this is a hunt for some as yet unknown particle?

    • Re: (Score:2, Informative)

      by domulys (1431537)
      It so happens that there is a "simple English" version of that wikipedia entry:

      http://simple.wikipedia.org/wiki/Standard_Model [wikipedia.org]
      • by DJRumpy (1345787)

        Sometimes I'm still amazed at the oddest places that exist on the internet. I find this simple.wikipedia.org link much more 'readable' to the laymen.

        So if I'm reading the 'simple' version correctly, they are tying to narrow down the mass of the mysterious 4th Higgs Boson? These Bosons are the 'conduit' (I apologize if the terminology doesn't fit properly) that this energy flows through from fermion to fermion?

    • by mbone (558574)

      At one level, all you need to know is that the Standard Model "needs" this particle - no Higgs Boson, and the Standard Model may fall. Finding the Higgs (and thus its mass) should also help in making predictions in other areas, such as cosmology.

      As for why the Higgs Boson is needed, you might find this [ucl.ac.uk] interesting.

      • by DJRumpy (1345787)

        Is this Higgs particle increasing in mass because the fermion is passing through/near it, or does the fermion increase in mass as a result of passing through/near this Higgs particle? Or am I misunderstanding the mechanics of this and the additional mass is due to the 'clustering' of these fermions in close proximity to each other?

        Thanks for the link [ucl.ac.uk]. It does help visualize this a bit better.

        • by mbone (558574)

          You never see "naked" particles in QFT - they are always surrounded by a cloud of virtual particles attracted to them by various forces. The particle you can measure (say, an electron in a cathode ray tube) is always really a composite - the naked particle and its cloud of hangers on. So, the answer to your question is "yes" in both cases.

          The Higgs field was invented to give bosons mass (in the context of the standard model). The story (which I have heard several times, but don't know if it's true) is that

    • This would be a good start:
      http://btjunkie.org/torrent/TTC-VIDEO-Quantum-Mechanics/3952ebd7c605f10e9562955b4905c88b576299e71a57 [btjunkie.org]
      (Very simplified, but as I said: A good start. :)

    • Re:I'm lost. (Score:5, Informative)

      by zmooc (33175) <zmooc&zmooc,net> on Tuesday February 16, 2010 @06:27AM (#31153702) Homepage

      particle physics for dummies

      ALL (anti)matter, ALL forces, fields and waves and everything you can think of consists of particles. I'm not talking about neutrons and protons and the such, but even smaller particles known as subatomic particles or elementary particles. Most of us know the group of particles called quarks, but there are more groups of particle with cool names like leptons (an electron is a lepton) and bosons (a photon is a boson).

      We know that a LOT of nature shows some kind of symmetry; this is the same in elementary particle physics. From this, it has been deduced that several particles not yet detected must exist in order to fill in the gaps in the symmetry. It is those particles we are looking for and they are predicted by the Standard Model, which is an enourmous collection of theories that together attempt to describe our entire universe (with the exception of gravity) (and to unify the newtonian and einsteinian physics).

      Such particles have many hard-to-understand properties like spin, charge, mass etc. What we are looking for, however, is their specific energy. We do this by accelerating matter (protons typically) to incredible speed and then colliding it. In such a collision, enormous energies occur that cause elementary particles to cease to exist and create new elementary particles. All kinds of particles can sort of randomly be created during such a collision, but obviously the collision itself has to be powerful enough to reach at least the energy the particle we're looking for has. So we keep building more and more powerful particle accelerators in order to find these things. What we call the energy of such a particle is a bit complex; it sort of comparable to mass*speed, but that's not all there is to say about this; for example many particles have a fixed speed, namely the speed of light. Therefore, their mass is equivalent to their energy. That's the GeV number we're talking about here. Note that this is incredibly simplified; for example we don't really know the mass of the photon (except that it is 0 in rest, but photons don't exist in rest) but we DO know its' energy since we can measure that. Also, the charge is not factored into this equation. But, in general, elementary particle physicists think in "energy", not in "mass" or "speed".

      Anyway, around the point of collision, enormous detectors have been built that attempt to trap the particles created in the collision. These detectors generate a small electric current comparable to the energy of the particle that collided, which is measured. Think about them as antenna's. After millions and millions of such collisions, patterns start to emerge and we can deduce a specific particle has been created in our collisions. For example, you see a lot of collisions with this energy and a lot with that energy, but none with energy such and so. The result is sort of like a spectrogram (but again, it's way more complex than that).

      So in the case of the Higgs Boson, in this "spectrogram", we're looking for a peak somewhere between 115 and 150 GeV. This is obviously an incredibly simplified explanation, but I think this should make you understand just a bit more.

      • by Kupfernigk (1190345) on Tuesday February 16, 2010 @11:04AM (#31155210)
        Physicists have adopted the word "particles" to mean all kinds of different things, and I think this is a lot of the problem. It made sense when electrons, protons and neutrons first were discovered, because they had a relatively familiar kind of pointlike behavior even though this was not really correct. I have a nuclear physics textbook from the 1930s, and it is really interesting to see the state of confusion they were in at the time. (Memo to global warming denialists: there was also a lot of discussion about whether this stuff was or was not "real" and whether the experiments meant anything. This came to a sudden stop around mid-1945, for some obscure reason. However, I digress.)

        Most people use the word "particle" to mean a small solid object, and I think it is fair to say that quarks, gluons, and the Higgs can't meaningfully be categorised in this way. It is not surprising that early mathematical physicists often emphasised concentrating on the wave equations and not trying to assign physical meanings.

      • by chord.wav (599850)

        Thanks mate. Not only you helped parent, but many of us who are legos in this matter. Thanks for taking the time to write it.

    • I know that's probably a hopeless request without some sort of basis in this field, but can someone give the "particle physics for dummies" equivalent here?

      No, probably not, but if you're interested, I heartily recommended
      Warped Passages [amazon.com] by Lisa Randall. She spends first 80 or so pages reviewing physics in a manner accessible to those of us who took it in high school but need a refresher/update. But it does take those 80 or so pages under your belt so you can understand the rest of her book. Hence my appr

    • can someone give the "particle physics for dummies" equivalent here?

      I think you'll find that this page [timecube.com] makes it all pretty clear.

  • Determining the mass is fine, I guess, but what about size - is it bigger than a breadbox?

  • 115 GeV? Sounds like Fermilab is on half power too. When Europe gets there at full power, it will surely be 240 GeV. Ever heard of 'mains hum'?
  • I doubt any physicist would refer to the Higgs boson as "God particle" and that's obviously not the case in TFA. So why kdawson is feeding this idiotic meme ?

    Next time we speak about serious science are we going to refer the research subject's as "pixie dust" or "Satan ichor" ?

  • Just released yesterday I think. Some cool new stuff discovered at the rhic at brookhaven national labs. http://www.bnl.gov/bnlweb/pubaf/pr/PR_display.asp?prID=1074 [bnl.gov] "“This research offers significant insight into the fundamental structure of matter and the early universe, highlighting the merits of long-term investment in large-scale, basic research programs at our national laboratories,” said Dr. William F. Brinkman, Director of the DOE Office of Science. “I commend the careful approach
  • http://xkcd.com/702/ [xkcd.com]

    Well ...

    ... maybe not.

"Indecision is the basis of flexibility" -- button at a Science Fiction convention.

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