Beta
×

Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

First Definitive Higgs Result In 7 Years

kdawson posted about 6 years ago | from the you-want-mass-with-that dept.

Science 197

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."

cancel ×

197 comments

Sorry! There are no comments related to the filter you selected.

Overheard at the LHC (0)

Anonymous Coward | about 6 years ago | (#24487585)

It's alright guys, Fermilab found out some more about the Higgs Boson, you can start packing it up now.

Re:Overheard at the LHC (5, Informative)

Sockatume (732728) | about 6 years ago | (#24487679)

Don't joke about that, I'm sure I read about a paper last year which predicted a minimum Higgs mass just outside of the LHC's range. It must keep those involved awake at night.

Nothing to see here... (1)

PatrickThomson (712694) | about 6 years ago | (#24487639)

Like many others, I thought this meant the LHC had finally come online. It's just fermilab enjoying its last two days of relevancy ^_^

Re:Nothing to see here... (0)

Anonymous Coward | about 6 years ago | (#24488021)

fermilab enjoying its last two days of relevancy

Remember the adds on Slashdot for HP ProCurve gear touting the applications in LHC? Remember the magnet collapse problem at LHC that involved a retrofit of Fermilab designed magnets?

Basically "they" dug a big ring in Europe and filled it with US physics gear.

Re:Nothing to see here... (4, Informative)

Anonymous Coward | about 6 years ago | (#24491625)

FAIL.

Try again.

They filled it with a ton of European magnets (that worked), Japanese detectors (that worked), and US final focus magnets (that failed).

Sorry to burst your patriotic bubble.

Re:Nothing to see here... (5, Informative)

Gromius (677157) | about 6 years ago | (#24488481)

actually when I first heard about it, I thought it was a fermilab discovery. Theres been a lot of rumors flying around that CDF had something big. If this was it, I'm disappointed. Also for the record, fermilab is still very relevent. The most likely place for the Higgs given current experimental evidence is in the second easiest place for the Tevatron experiments to see it (115 GeV) but the hardest place for the LHC experiments to see it. So the Tevatron could well scoop the LHC, its not over.

Incidently, why is 115 GeV so hard for the LHC to see. Well at this point the Higgs is too light to decay to WW or ZZ (the W has mass of 80 GeV, Z 91GeV so needs Higgs mass of 160-180 GeV to open those channels). This means that a light Higgs of 115 GeV will decay into the heaviest particle availible to it (remember the more massive the particle, the strong the Higgs coupling) which is the bottom quark. At the Tevatron, the backgrounds to two bottom quarks isnt soo bad and the experimenters are all very experienced at tagging b quarks using their detectors. At the LHC you might as well give up so you have to go through the very rare vector boson fusion channel using a top quark loop to get two photons which itself has a bit of nasty background. Hence you will need 10 fb-1 of data which is *atleast* a years running at the LHC.

Re:Nothing to see here... (2, Funny)

JustOK (667959) | about 6 years ago | (#24489247)

GeV for mass seems odd. Why not use something more practical like percentage of mass of Library of Congress?

An update and a correction (5, Informative)

Roger W Moore (538166) | about 6 years ago | (#24489529)

At the Tevatron, the backgrounds to two bottom quarks isnt soo bad and the experimenters are all very experienced at tagging b quarks using their detectors.

Actually the background for b quarks at the Tevatron is ENORMOUS. b-quarks are produced by the strong interaction at rates far higher than they are produced from any possible Higgs decay. Identifying them is only half the problem: determining what produced them is the other half! The only way that we can see anything is via associated production of a Higgs and a W or Z boson (which are a lot easier to spot). This is a far rarer process than simple Higgs production.

At the LHC you might as well give up so you have to go through the very rare vector boson fusion channel using a top quark loop to get two photons which itself has a bit of nasty background.

You are actually a little out of date here. While the vector boson fusion channel is still used the decay is actually Higgs to two taus or VBF Higgs production with the two associated quarks being top quarks. At least in ATLAS we think that both of these channels will have a higher significance than the photon channel which was the original choice for a low mass Higgs.

Re:An update and a correction (0)

pallmall1 (882819) | about 6 years ago | (#24490901)

You are actually a little out of date here...

Yeah, and I was just about to correct him.

I really understood everything you guys said.

And I've got a copy of Duke Nukem Forever, too! :D)

!7years (1)

Veggie13 (1055730) | about 6 years ago | (#24487649)

Isn't it 2008 right now?

Re:!7years (1)

azzuth (1177007) | about 6 years ago | (#24487945)

Isn't it 2008 right now?

Yeah, but there are those pesky things called months.

Re:!7years (1)

VoltCurve (1248644) | about 6 years ago | (#24488045)

I hate those. I hate those so much! Death to Smarch!

Higgs (4, Informative)

JohnFluxx (413620) | about 6 years ago | (#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 (1, Interesting)

Anonymous Coward | about 6 years ago | (#24487821)

Isn't string theory dying? 25 years or so of intense research by the best brains in the field of physics, yet nothing remotely scientific has come out of it. It appears to be more of a religion than science. Nothing testable, no predictions, setting the background to coax out the result. Plus the "them and us" attitude the believers have these days all string theorist exhibit.

Re:Higgs (1)

AJWM (19027) | about 6 years ago | (#24487933)

Isn't string theory dying?

Yep, Netcraft confirms it.

Re:Higgs (4, Funny)

Spy der Mann (805235) | about 6 years ago | (#24487971)

Isn't string theory dying?

Nope. It's just tangled up.

*Rimshot*

Re:Higgs (1)

JustOK (667959) | about 6 years ago | (#24489277)

They might be near the end of their rope, but they might find its a mobius string, or find something else notty.

Re:Higgs (4, Funny)

pallmall1 (882819) | about 6 years ago | (#24490929)

Isn't string theory dying?

Knot yet.

Re:Higgs (3, Insightful)

Sockatume (732728) | about 6 years ago | (#24487935)

You didn't read the parent post at all, did you? I mean, it says right there that higgs mass is one of the testable predictions of string theory.

Re:Higgs (2, Interesting)

mcelrath (8027) | about 6 years ago | (#24488723)

Wrong, the higgs mass is absolutely not a prediction of string theory. Any higgs mass can be accommodated in principle. Every measurement rules out branches of string theory. But a heavy higgs would rule out a wide class of favorite string models.

Re:Higgs (2, Interesting)

Sockatume (732728) | about 6 years ago | (#24488867)

If there exists a higgs mass which would falsify a "wide class" of string theories, then that is a testable prediction of those theories. ("Higgs mass must be less than X"). Therefore, it is no longer valid to state that string theories as a class are untestable.

Re:Higgs (1)

Sockatume (732728) | about 6 years ago | (#24488989)

(This isn't to say that string theories which don't have testable predictions, or whose only predictions are practically untestable, get off because their neighbours are well-behaved. I'm just saying it's absurd to talk of the untestability of the entire class of string theories when a practical test for favoured theories has just been outlined in the post you're replying to.)

Re:Higgs (1, Interesting)

Anonymous Coward | about 6 years ago | (#24489659)

You're wrong. String theory as a class is "untestable" because, regardless of experimental outcome, subsets of string theory are constructable/exist; in other words, no matter what experiments show, the class "string theory" will not be wrong.

Poor string theorists will always construct voidable models which can be disproven--the good theorists however will always have an infinitude of models which can not.

Re:Higgs (1)

dwye (1127395) | about 6 years ago | (#24488789)

> I mean, it says right there that higgs mass is
> one of the testable predictions of string theory.

It is only testable if we find it; if they (do/can) redefine the theory to explain why it isn't found, if it isn't found, then it is effectively no more testable than Free Will, or that YHWH designed the Universe to appear that it was old to test our faith in a Young Creation, or any other religious statement about the Universe that you might despise.

This is what the AC post is complaining about. Not really unreasonable, since there was a recent paper suggesting that the Higgs mass was just beyond where the LHC could possibly find it.

Re:Higgs (1)

Sockatume (732728) | about 6 years ago | (#24488917)

You argue that string theory would have to be reformulated to remain valid if it faced contradictory evidence, like all scientific theories. And then you compare it to young earth creationism, where the "god is tricking us" gambit means that YEC is equally valid regardless of the evidence presented. I'm not sure how this works.

If string theory could remain valid even when contradictory evidence was presented, then it would be equivalent to young earth creationism, but as you point out, that is not the case.

Re:Higgs (0)

Anonymous Coward | about 6 years ago | (#24489933)

String theory can always remain valid in spite of evidence because there is no means to produce contradictory evidence for the class. Even if higgs evidence were found to invalidate certain string theories, the class of string theories can, as a whole, not be invalidated by any experimental means feasible within hundreds of years.

Re:Higgs (1)

sconeu (64226) | about 6 years ago | (#24488211)

Isn't string theory dying?

No, it's just getting stained.

Re:Higgs (1)

Bandman (86149) | about 6 years ago | (#24489411)

This is what happens when you get your physics advice from XKCD

Re:Higgs (1)

rjhubs (929158) | about 6 years ago | (#24487963)

oh string theory would find a way to survive.. those people never go away.

Re:Higgs (4, Interesting)

RedOctober (10155) | about 6 years ago | (#24490745)

I remember reading somewhere that some astronomy students, out of perversity, decided to continue working on the Ptolomaic system, adding additional epicycles on top of the ones that were conventional at the time to improve on accuracy, and to add the new planets discovered since then. The end result was a complex system that fairly accurately predicted planetary positions. Of course, it was all done tongue in cheek, but it does demonstrate that certain systems can be tailored ad infinitum to greater levels of accuracy - even if they are wrong in principle.

I wish I could find a link to to this.

Re:Higgs (0)

Anonymous Coward | about 6 years ago | (#24487991)

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

Is that really the case? I thought super symmetry was not actually part of the standard model. Although it's usually included in all of the next-gen theories (like string theory), even the ones which aren't full Theories of Everything, I didn't think that it was strictly part of the standard model, which doesn't purport to be a Theory of Everything.

Granted, without the Higgs and super symmetry we're left scratching our heads as to why Fermions are different from Bosons, and why all the particles are such different masses, but I didn't think they were required for the standard model.

Re:Higgs (0)

Anonymous Coward | about 6 years ago | (#24488057)

"For example, a very large higgs would rule out huge branches of string theory..."

Great Scott! String theorists might have made a potentially falsifiable prediction? After 30+ years of mathematical masturbation, string theory might finally have earned its name and actually be...science?!

Oh wait. "...almost killing it." And only "huge" branches, whatever that means for something that has infinite ill-defined branches. Nothing to see here, move along.

Re:Higgs (0)

Anonymous Coward | about 6 years ago | (#24488063)

Apparently these results with 95% probability rule out the Higgs having a mass of 170 GeV. Which happens to be a major prediction in the Noncommutative Geometry [blogspot.com] interpretation of the Standard Model.

Re:Higgs (4, Insightful)

syousef (465911) | about 6 years ago | (#24488233)

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 (4, Insightful)

Nutria (679911) | about 6 years ago | (#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 (4, Insightful)

Minwee (522556) | about 6 years ago | (#24491353)

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!"

Re:Higgs (2, Interesting)

Joe Snipe (224958) | about 6 years ago | (#24489217)

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 (5, Insightful)

Xtifr (1323) | about 6 years ago | (#24489407)

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:Higgs (2, Funny)

Bloodoflethe (1058166) | about 6 years ago | (#24489821)

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.

Re:Higgs (0)

Captain Splendid (673276) | about 6 years ago | (#24490071)

the technocracy

Tinfoil hat on a little too tight? I bet you're one of those people who thinks the moon landing was faked.

Re:Higgs (1)

Bloodoflethe (1058166) | about 6 years ago | (#24490759)

Hah, play White Wolf's Mage sometime :D

Re:Higgs (1)

GrayNimic (1051532) | about 6 years ago | (#24491957)

A positive result says "we were right" - which isn't very useful as far as going forward and doing more theory development. A negative result implies we were wrong about *this* prediction, but (especially if the theory is well established) the theory 'correctly' predicts a multitude of other phenomena with a plethora of experiments to back it. Now theoreticians have a puzzle to solve, to find a theoretical description that still fits all the old experimental evidence but also fits the new one. Such impetus and pursuit tends to be viewed as doing more to refine our understanding of reality than a simple "we were right" result, which gives little direction for how to "move forward" (presuming our current theory is not the ultimate truth already, and thus needs refinement).

Presuming, of course, that the negative result is interpretted as an issue with the theory, rather than an issue with the experiment/equipment.

SUSY independent of Higgs (1)

Roger W Moore (538166) | about 6 years ago | (#24489085)

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 are others: Dark Matter, unification of forces etc.

Baloney: if 80+ orders-of-magnitude wrong can be (0)

Anonymous Coward | about 6 years ago | (#24491405)

...ignored ( one of the fundamental constants of the Standard Model ),
then it *doesn't matter* what evidence shows:
the Standard Model won't be replaced
until its successor has an infinite force of exceptionally-armed commandos.

This is the same as that scientists who dismiss the evidence of the fractal nature of universe
( galaxies are polarized, not just the light coming from some of 'em ),
because we haven't a model authorizing that circumstance:

--

Nor should they dismiss observations. I encountered such a situation when I was writing a story about the work of physicists Luciano Pietronero and Francesco Sylos Labini at the University of Rome. They argue that 3D maps of the galaxy distribution produced by the Sloan Digital Sky Survey (SDSS) show that the universe is not homogeneous, but fractal. This, too, challenges the Copernican Principle, and as such,
*most of the cosmologists I spoke to dismissed it outright.*

One cosmologist wrote to me in an email: "There is no fractal or inhomogeneous physical model of the universe of any kind. Therefore although there are particular observations that present a challenge to the standard model, there is no sense in which there is a preferred model that predicts or is explained by inhomogeneity . . . So the observations are interesting, but without a physical model to back them up, they are unlikely to have an impact on our thinking about cosmology."

I found this statement rather shocking. Cosmologists are willing to dismiss observations because they don't fit with theory? Isn't science supposed to work the other way round?

--

http://www.newscientist.com/blog/space/2008/07/are-we-living-in-giant-cosmic-void.html [newscientist.com]

one instance of infinitely many...

Newbie question (1)

DoofusOfDeath (636671) | about 6 years ago | (#24487711)

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

Re:Newbie question (4, Informative)

Free the Cowards (1280296) | about 6 years ago | (#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:Newbie question (2, Informative)

Dice (109560) | about 6 years ago | (#24487749)

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:Newbie question (0)

Anonymous Coward | about 6 years ago | (#24487783)

GeV is (G)iga (e)lectron (V)olts, which is technically a measure of energy. But since the masses involved are so darn small, and E=mc^2, it becomes a useful unit of measurement for subatomic particles :)

Re:Newbie question (1)

fractic (1178341) | about 6 years ago | (#24487787)

A GeV is an unit of energy and thus mass. But it's so little that expressing the mass in grams would lead to very small numbers. See wikipedia [wikipedia.org] for more information.

Re:Newbie question (1)

Delwin (599872) | about 6 years ago | (#24487789)

E = MC^2

Re:Newbie question (2, Insightful)

neurovish (315867) | about 6 years ago | (#24487819)

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.

Re:Newbie question (1)

mcelrath (8027) | about 6 years ago | (#24487849)

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 are appropriate) to get the unit of energy.

More generally, this is called "natural units". We set hbar=c=1 in quantum mechanics, leaving only one real unit, energy. At the end of any calculation, one can re-insert hbar and c in relevant units. General Relativists also set Newton's constant to 1, which removes units altogether. It's a neat trick. Try it. ;)

length = hbar/energy; momentum = energy/c; mass = energy/c^2; time = length/c; etc.

Re:Newbie question part deux (0)

Anonymous Coward | about 6 years ago | (#24487937)

How does the energy of the new CERN compare with what we might have expected from the 'Supercollider' that was scrapped under Texas?

Has detector technology improved sufficiently and recently as would have made it obsolete by now?

If the energies would have been comparable, and we would have had it online, say, 5 years ago,
how much further along might we be speculating?

Texas missed out on bragging rights... go figure.

Re:Newbie question part deux (5, Insightful)

mcelrath (8027) | about 6 years ago | (#24488597)

The SSC in Texas was 40 TeV, and the LHC at CERN will be 14 TeV when fully operational. They're about to turn on now, but will make their first run at the lower 10 TeV. Fermilab runs at 2 TeV.

Yes, we would have had the answers to all these questions and more 10 years ago, if the SSC hadn't been scrapped.

<soapbox>
The US is at a significant disadvantage when it comes to "big science". Every year, every project must come back to congress and beg for funding, justify their existence, rather than spend that time doing science. As a consequence, funding in the US is extremely volatile. Look at the budget crisis of DOE in December, the zeroing of the ITER budget, and the canceling of the SSC in 1993 for a few examples. Big science is worthwhile. We should figure out how to give scientists some measure of job security, so they can concentrate on science. This is a miniscule portion of the budget.
</soapbox>

Re:Newbie question part deux (1)

jandrese (485) | about 6 years ago | (#24488859)

The SSC being shut down still makes me mad. The politicians still consider it a win though, since they shut down that "wasteful government racetrack for microscopic particles".

Re:Newbie question part deux (1)

Antwerp Atom (1306775) | about 6 years ago | (#24490033)

<soapbox> The US is at a significant disadvantage when it comes to "big science". Every year, every project must come back to congress and beg for funding, justify their existence, rather than spend that time doing science. As a consequence, funding in the US is extremely volatile. Look at the budget crisis of DOE in December, the zeroing of the ITER budget, and the canceling of the SSC in 1993 for a few examples. Big science is worthwhile. We should figure out how to give scientists some measure of job security, so they can concentrate on science. This is a miniscule portion of the budget. </soapbox>

I fear that as long as the creationists are in power in the US science will always have low priority. The last thing they want is that scientists discover how the universe was created as this would be a huge blow to the credibility of their god. Very sad indeed.

Re:Newbie question part deux (2, Insightful)

mcelrath (8027) | about 6 years ago | (#24490989)

While religious nuts are an easy scapegoat, that's not the problem. As I understand it, it comes down to the fact that no congress can bind any future congress. So no congress can set budget policy in any future year. They can make recommendations (and do), but this isn't guaranteed.

I don't think this problem is insurmountable. I would think that the creation of a certain kind of "scientific trust fund" could enable the use of a pot of money over a long time span.

Mass actually measured in eV/c^2 (3, Interesting)

Roger W Moore (538166) | about 6 years ago | (#24489287)

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'.

Re:Mass actually measured in eV/c^2 (1)

RedOctober (10155) | about 6 years ago | (#24490849)

Read your comment again. Einstein showed that energy and mass are equivalent. Also, "c" is a universal constant that never changes. With these to premises, using GeV as a unit for mass is perfectly consistent, as it's also a unit of energy.

Your point may be significant to someone learning about dimensional analysis in high school, but it's not an insight into physics. It's an issue of semantics. Mass and energy are fundamentally the same.

GeV = mass? (1)

Mursk (928595) | about 6 years ago | (#24487761)

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]

Re:GeV = mass? (3, Informative)

Chris Burke (6130) | about 6 years ago | (#24488079)

And 1 GeV = 1.783×1027 kg

Slashdot ate your formatting it looks like. I'll write it as 1.783E-27 kg to get around it.

Re:GeV = mass? (1)

Mursk (928595) | about 6 years ago | (#24488115)

Oops. Thanks. And I even used the preview button, so I have no excuse...

Re:GeV = mass? (2, Informative)

jfengel (409917) | about 6 years ago | (#24488093)

That would be 10^-27 kg, a very small number, not 1027 kg.

Re:GeV = mass? (1)

Cacadril (866218) | about 6 years ago | (#24488929)

Please fix the typography; it is 1.783 x (ten-to-the-power-of-minus-twenty-seven), or if it works this time, 1.783 x 10^-27. A small amount by everday measures. (But surprisingly much for a moron like me. How can a particle this heavy be responsible for endowing electrons and neutrinos with their respective masses, that are mch smaller?)

Re:GeV = mass? (1)

kaos07 (1113443) | about 6 years ago | (#24489413)

Turn in your geek card. How could you be confused! Energy-mass equivalence is only described by the most well known formula in history.

E=mc^2

Re:GeV = mass? (1)

jadedoto (1242580) | about 6 years ago | (#24490475)

Uhh... wasn't that common sense? I agree. Geek card revoked.

Very misleading headline (4, Informative)

witte (681163) | about 6 years ago | (#24487767)

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

Re:Very misleading headline (1)

Nimey (114278) | about 6 years ago | (#24488879)

On Slashdot? Never!

Re:Very misleading headline (3, Funny)

Profane MuthaFucka (574406) | about 6 years ago | (#24491543)

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 Christ. That is now clearly established as metaphor. The case is still open on the wine though. I expect quite a few graduate students to get their PhD's publishing various studies on that topic.

Needless to say, at our church, almost nobody sleeps through the sermons. The progress of science these days pretty much ensures a steady stream through our doors and full pews of good particle-physics lovin' Christians.

135 GeV seems very high... (3, Interesting)

Dice (109560) | about 6 years ago | (#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:135 GeV seems very high... (1, Informative)

digitrev (989335) | about 6 years ago | (#24488005)

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 unreasonable. While it may not intuitively make sense, what about modern physics (i.e. quantum, relativistic, etc...) does these days?

Re:135 GeV seems very high... (2, Insightful)

Dice (109560) | about 6 years ago | (#24488099)

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:135 GeV seems very high... (2, Insightful)

EvolutionsPeak (913411) | about 6 years ago | (#24488159)

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?

Re:135 GeV seems very high... (1)

dAzED1 (33635) | about 6 years ago | (#24488519)

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 :)

Re:135 GeV seems very high... (1)

sconeu (64226) | about 6 years ago | (#24488225)

Isn't the proton a hadron?

Re:135 GeV seems very high... (4, Informative)

inertialFrame (259221) | about 6 years ago | (#24488299)

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.

Re:135 GeV seems very high... (1)

mcelrath (8027) | about 6 years ago | (#24488665)

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 energies, and the lower bound is about 114 GeV, coming from the LEP experiment.

Re:135 GeV seems very high... (5, Informative)

Jazzer_Techie (800432) | about 6 years ago | (#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:135 GeV seems very high... (3, Informative)

Dice (109560) | about 6 years ago | (#24488191)

In these theories, mass arises of interactions with the Higgs boson. Thus, the Higgs being massive doesn't exclude less massive particles.

Thanks for that hint, I've now found the Higgs mechanism [wikipedia.org] which is currently in the process of giving me a headache.

Re:135 GeV seems very high... (1)

antic (29198) | about 6 years ago | (#24488683)

Thanks also - helped me follow what's going on here!

Re:135 GeV seems very high... (3, Informative)

dougr650 (1115217) | about 6 years ago | (#24488183)

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 predict what mass(es) they should have.

If particle masses were an additive quantity based on the mass of the Higgs, as your intuition seems to tell you, then as long as there are massless particles like the photon, then the Higgs would also have to be massless and, by induction, so would every other particle we observe.

Re:135 GeV seems very high... (1)

mdenham (747985) | about 6 years ago | (#24490345)

If particle masses were an additive quantity based on the mass of the Higgs, as your intuition seems to tell you, then as long as there are massless particles like the photon, then the Higgs would also have to be massless and, by induction, so would every other particle we observe.

Not necessarily. It's entirely possible for the Higgs particle to be massless and still provide mass for any particle with mass. For example, the mass of any hadron, based solely on adding the component real particles, is around 1.2% of the observed mass - indicating that massless particles (or non-real ones, which should effectively cancel out with sub-vacuum, negative-mass states under any conditions that actually make sense - yeah, yeah, I know, man was not meant to understand quantum mechanics) are thereby providing 98.8% of the mass somehow.

Re:135 GeV seems very high... (1)

dwye (1127395) | about 6 years ago | (#24488281)

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, it would make more sense (in quantum mechanics? Boy, have I not been paying attention) for it to out-mass any other particle, then light things like massy neutrinos can barely interact, normal quarks and such interact more, and real Higgs particles, obviously, a lot.

As it turns out, the Higgs is almost the heaviest particle. I do not know how an intermediate vector baseball (which was the nickname for the meson which mediates proton-to-positron decay, at least back when I was in school) gets its much larger mass, though. Interact with a lot of virtuals at a time, obviously.

Re:135 GeV seems very high... (1)

RedOctober (10155) | about 6 years ago | (#24490877)

Unfortunatly, it's not common practice to teach QFT to undergraduates.

In any case, the Higgs boson is the particle associated with the Higgs field, much like the photon is the particle associated with the EM field. It's the Higgs field that gives massive particles their mass - and this is determined by a coupling constant in the field equations. There is no reason for the Higgs boson to be lighter than the lightest particle.

Fermilab is just trying to show up CERN (0)

Anonymous Coward | about 6 years ago | (#24487847)

And bless them for it, CERN is how long away from opening and is the newest and greatest hope for finding the god particle? I'm glad that stateside research, although smaller (and despite what they say, its NOT the motion of the ocean, its the size of the dinghy), it is not obsolete.

damn (-1, Troll)

Anonymous Coward | about 6 years ago | (#24487887)

I just took a monster shit. long and fat, like a nigger cock, though much lighter in color. The thing wasn't completely submerged -- and this isn't one of those fucking EPA low-water toilets, either. It went down in one flush, but there are residual shit stains all over the bowl.

Re:damn (-1, Troll)

Anonymous Coward | about 6 years ago | (#24488965)

TELL ME MORE!

In other news... (3, Insightful)

Pictish Prince (988570) | about 6 years ago | (#24488085)

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!"

Re:In other news... (1)

Eli Gottlieb (917758) | about 6 years ago | (#24490019)

But have they raised Cthulhu?

there there... (0, Troll)

curious.corn (167387) | about 6 years ago | (#24488279)

... those convenient epicycles are still eluding observation, isn't that strange

(ducks and crawls back to the cave, wondering about plasma instabilities)

IMHO, there is no spoon. (0)

Anonymous Coward | about 6 years ago | (#24488395)

Why do we need particles and mass when the ray-tracing techniques are so advanced within the holo-verse.

Move along, folks. (1)

Chappster (1169005) | about 6 years ago | (#24489015)

The short answer is this: according to the standard model, there are several different energy ranges that the higgs boson could possibly be in. I can't remember what the numbers are off hand, but I know that the Higg's boson energy is either small (from what they're trying to prove here), large - what LHC is trying to get at, and the holy-mother-of-god high. The latter would take an accelerator about the size of the Milky Way Galaxy to get to those energies using the same methods that we use in modern accelerators. Like the first post said; nothing to see here, move along.

Horribly Inelegant (1)

PakProtector (115173) | about 6 years ago | (#24489985)

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:Horribly Inelegant (2, Informative)

RedOctober (10155) | about 6 years ago | (#24490959)

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.

Re:Horribly Inelegant (1)

PakProtector (115173) | about 6 years ago | (#24491365)

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?

Re:Horribly Inelegant (1)

dougr650 (1115217) | about 6 years ago | (#24491379)

Unfortunately, just by postulating that matter "warps space-time" doesn't reduce or simplify the problem at all. That doesn't explain anything, it's just an observation of a phenomenon. What would the mechanism be for why it would warp space-time? Why would some particles warp it more or less than others? Can you predict or calculate the magnitude of the warping effect?

I don't see how Occam's Razor applies here. We already have a remarkably successful theory which has both explanatory and predictive power and this theory has been tested and borne out by experiment to an astonishing degree. This same theory accounts for the Higgs, so if it doesn't exist, that will make things vastly more complicated and confusing than they are now, not less so.

Re:Horribly Inelegant (1)

PakProtector (115173) | about 6 years ago | (#24491591)

I'm not saying I have the answer. I'm just trying to get someone explain to me why one makes more sense than the other. And as to why things mass more than others, I already gave an off the top of my head explanation -- mass is based upon total energy bound up in the matter. This would be why things become more massive as they accelerate.

Re:Horribly Inelegant (1)

dougr650 (1115217) | about 6 years ago | (#24491995)

I understand. And nobody has the answers, just theories and experiments to attempt to refine the theories. The Higgs makes more sense because it fits with what we already observe. If, by "the other," you mean a hand-wavy "space-time warp," then I guess that could make sense if there were some underlying principle that explained why that occurred. I think perhaps you're confusing general relativity, which deals with the curvature of space-time, with the quantum mechanics of the Standard Model, which is a distinct theory from GR. There are attempts to unify both theories, but one will not suffice to replace the other.

I think you're also somewhat confused about equating mass and energy. Things do not become more massive as they accelerate. You're thinking of "relativistic mass" which is the increase in mass due to a frame of reference which is moving relative to the particle. Also, what kind of energy is bound up in a single electron or W or Z to give it mass, following your line of reasoning? Again, there's no explanatory power there, all you can do is observe that they have mass for no particular reason. At least the standard model makes it possible to explain what the origin of these particles' mass is versus the Star Trek-y argument that they have mass because they have some kind of unknown intrinsic "energy" that warps space and time.

A Type-13 planet in it's last phase of development (0)

Anonymous Coward | about 6 years ago | (#24490251)

So long and thanks for all the fish.
Load More Comments
Slashdot Login

Need an Account?

Forgot your password?

Submission Text Formatting Tips

We support a small subset of HTML, namely these tags:

  • b
  • i
  • p
  • br
  • a
  • ol
  • ul
  • li
  • dl
  • dt
  • dd
  • em
  • strong
  • tt
  • blockquote
  • div
  • quote
  • ecode

"ecode" can be used for code snippets, for example:

<ecode>    while(1) { do_something(); } </ecode>