LHC Discovers New Particle That Looks Like the Higgs Boson 396
The wait is over: new submitter Roger W Moore (among many, many other submitters) writes "The ATLAS and CMS experiments at CERN have just announced the discovery of a new particle which is consistent with a Standard Model Higgs boson. There is still a lot of work to do to confirm whether this really is the Higgs, and if so whether it is a Standard Model Higgs, but this is a major result."
Dr. Higgs himself said it best... (Score:5, Informative)
In the press conference, Dr. Higgs summed the findings up nicely: "This is an achievement in experimental methodology." To detect this signal has required a momentous effort, and the good people at CERN have had the good fortune of reaching results quicker than anticipated.
This isn't earth-shattering news or anything even unexpected, but it is still cause for celebration. Let us rejoice and then continue to push on towards new findings.
A good introducton to the Higgs mechanism (Score:5, Informative)
Re:Found at 125 GeV (Score:2, Informative)
Re:Found at 125 GeV (Score:5, Informative)
The Higgs particle is just the particle manifestation of the Higgs gauge field. Think of it as a huge block of jello through which all massive objects move. 125 GeV is the energy required to scoop out a bit of that jello and isolate it.
Re:Careful Announcement (Score:5, Informative)
That's because they're not in competition as such. The results are complimentary. The Tevatron was able to isolate the same signal, just to a lower degree of precision (2.9 sigma as opposed to 5.0 sigma).
Re:Found at 125 GeV (Score:5, Informative)
Possibly something else (Score:5, Informative)
http://www.reddit.com/r/science/comments/w0tty/higgs_boson_confirmed_at_5sigma_standard/c599ijb [reddit.com]
Actually, we observed a new state at 125 GeV and it seems consistent with a Standard Model Higgs boson. We have NOT discovered the SM Higgs boson because we simply haven't confirmed that this new particle is the SM Higgs because we're only looking at mass itself. It could be something else with a mass of 125 GeV. To actually claim it is the SM Higgs, we need to confirm that it has spin 0, the right coupling ratios, etc. And that's what I'm working on right now. But it is very exciting because we have discovered new physics. Source: Working at CMS
Re:Worth the waking hours (Score:4, Informative)
Did you see this character there with you (assuming you're not Jester posting on /.):
http://resonaances.blogspot.com/2012/07/h-day-live.html [blogspot.com]
My favorite line from the onsite report "10:46 Standing ovations, screams and shouts, the audience throwing bras and underwear at the stage."
Personally I like this image:
http://3.bp.blogspot.com/-Cmf9NdNvpWw/T_Pm8cpuljI/AAAAAAAAAww/LF-1GXkBNfM/s320/godparticle.jpg [blogspot.com]
Re:huh (Score:5, Informative)
Now we just need to solve gravity, dark matter, dark energy, unify quantum chromodynamics with relativity, and a ton of other stuff.
Party's not over, folks. :)
I suspect dark matter will be easiest. Wouldn't be surprised at all if the LHC solves that one. All you need to see is what looks like a clear violation of conservation of energy/momentum at a consistant, high energy in your results, and you've got evidence that something heavy that interacts weakly or not at all with normal matter is flying off in the opposite direction. That something would probably be dark matter.
The others... that's probably going to be a long, hard slog.
Re:Dr. Higgs himself said it best... (Score:5, Informative)
I'm in CMS and we pretty much released all the details now at the seminar. If ATLAS held back until publication, then either they didn't manage to get it approved or they cut corners and didn't feel presenting the results right now yet. In any case it's CMS that showed most thorough investigation here. Though I can understand delaying the lower priority channels until some time this/next week I don't understand why they didn't provide a mass fit at todays seminar which was to be a discovery seminar (or they didn't expect CMS to have 5 sigma).
It is the mass (Score:5, Informative)
Hence the mass of each type of particle depends on the zero energy value (vacuum expectation value) of the Higgs field and how strongly the particle couples to it while the mass of the Higgs boson depends on how the energy density of the Higgs field changes as the strength of the field varies.
Re:Found at 125 GeV (Score:4, Informative)
Photons are massless and don't interact with the Higgs field. In fact, it's the opposite of æther theory - almost everything *but* light (and a few other particles) interacts with it ;)
Re:Found at 125 GeV (Score:4, Informative)
Yes and no, photon has no mass at rest, but photon never rest. When moving they have the effective mass of their kinetic energy.
Re:Found at 125 GeV (Score:5, Informative)
The mass of helium is 4.002602 g/mol. Divide by Avogdro's number, and a single atom of helium weighs 6.646E-24 g. The difference in mass is what powers the sun. Parent is simply making the same argument on the scale of a proton split into its parts.
(disclaimer: I know, blabla deuterium, not protons and neutrons. However, see the definition of a state function.)
No, not really (Score:5, Informative)
The field is everywhere, not just around us but also inside us. Everywhere and anywhere. Comparable to electromagnetic fields, except you can't shield them.
What holds the galaxy (-ies) together is something else, that's gravity. Also a field, extending to fill the universe.
The Higgs particle (or field, can't talk about one without thinking about the other) gives the universe mass (well, it's one of the things that do that) so perhaps some clever brainiacs might be able to think something up connecting the Higgs and gravity in such a way that it unites all the forces. That would be a garuanteed ticket to Stockholm and a place in history as the greatest discovery (or theory, if you like) since the discovery of fire itself.
Rest mass versus relativistic mass (Score:0, Informative)
Photons are massless in rest. Which they normally aren't as they're zipping about with the speed of light. Then they exhibit relativistic mass (mass because of the energy they carry, as E=mc^2, remember?). This mass interacts with gravity, allowing light to bend around stars and light to be trapped inside black holes.
But, this mass has nothing to do with the mass that originates in the Higgs field. Complicated? Yes, but that's physics... :-)
Re:No, not really (Score:4, Informative)
Just in case you, or someone else, didn't get the reference:
The Force [wikia.com]
Re:Found at 125 GeV (Score:5, Informative)
Because of electromagnetic interactions with the atoms on the surface of the mirror
Because, as Einstein's famous General Theory of Relativity explained, gravity is not just a force between two masses like you were taught at school, it's actually a curvature of the geometry of space-time. The maths gets really complex really quickly, hence the web is full of analogies like the rubber-sheet model that can lead laymen to appealing [wikipedia.org] but incorrect conclusions [livejournal.com]. But when you do do the maths, it works astonishingly well [wikipedia.org] - and it's the simplest explanation we have that fits all the observed data.
See the previous answer - no, they wouldn't, because it would need an infinite amount of energy to do so. When you do the math (one example chosen at random is here [jimhaldenwang.com], there are many others) it turns out that the curvature of space-time becomes so strong near a black hole that inside the event horizon, space and time kind of switch roles - to move further away from the centre would mean moving backwards in time.
Sounds a bit kooky in words, true, but makes perfect sense in mathematical terms - and again, GR's predictions have been experimentally verified time and time again.
Re:Found at 125 GeV (Score:5, Informative)
Re:Found at 125 GeV (Score:5, Informative)
Re:Found at 125 GeV (Score:5, Informative)
That's shorthand, it's GeV/c^2, which is in fact a mass.
Re:Dr. Higgs himself said it best... (Score:4, Informative)
Re:explanatory update please? (Score:5, Informative)
Ok, this is going to be pretty rough, but here it goes:
The Standard Model describes all the "point particles" which can't be subdivided. Each of these particles has a few constant parameters like electric charge, color charge, mass, and spin. Electrons are one of them (-1e charge, 0.51MeV mass, spin 1/2) as are neutrinos (0 charge, some...mass, spin 1/2) and quarks (+2/3 or -1/3 charge, a few different masses, spin 1/2). Quarks come together in groups of 2 or 3 to build particles like protons and neutrons (and a whole bunch more). These are what you'd consider matter (Fermions). There are also particles that serve as "force carriers" - all the fundamental forces like electromagnetism and the nuclear forces can be thought of as exchanges of these other particles. They have integer spin, and we call them Bosons. The photon for instance represents the electric field (it's massless), the W and Z bosons represent the weak nuclear force (they have mass), and Gluons represent the strong nuclear force (they have color charge, like quarks).
The problem is that gravity isn't really mentioned anywhere in here, and unlike all the other particle parameters, "mass" seems pretty arbitrary. It's not a nice round number, so there has to be something else there behind the scenes. The solution to this is that we think there's another "field", which we call the Higgs field, and another force-carrying particle called the Higgs Boson. In the same way that particles with charge can interchange photons to "feel" the electric field, particles with mass can exchange Higgs bosons to "feel" the Higgs field. Particles that interact that way essentially tie up a bunch of energy in that reaction, and that extra bottled up energy is what we experience as mass. So the degree to which particles couple to the higgs field (you could think of it as their "mass charge" parameter) determines how much mass they have. And people way smarter than you and me have found equations that do, in fact, predict the right masses for various particles when you crunch the numbers.
The problem with finding bosons is that they're really just intermediary particles - photons are obvious enough only because they travel at the speed of light. Bosons with mass go much slower, and wind up decaying or interacting before we can directly observe them. So this find by the LHC is *indirect* evidence of the Higgs, based on how much energy they're missing from various collision interactions. But it matches the predictions to a very high degree so far, so they're calling it good.
Re:"Discovers"? (Score:4, Informative)
This is the mistake I fear CERN is going to make.
All particle physics experiments have two aspects: they are designed with some very specific target in mind, and once that target is found or excluded they are then run for as long as humanly possible searching for new stuff, both by going to higher energies and making more precise measurements on things already known (different decay channels, etc.)
Sometimes--as in the case of the Kamiokande detector, which was originally aimed at proton decay--we repurpose the system for different particles entirely (solar neutrinos, say.)
So your "fear" is that the LHC teams will behave completely differently from every particle physics team ever anywhere. Good luck with that.
Re:Found at 125 GeV (Score:5, Informative)
Because, as Einstein's famous General Theory of Relativity explained, gravity is not just a force between two masses like you were taught at school, it's actually a curvature of the geometry of space-time.
That's ... debatable. Modeling it as the curvature of the geometry of space-time has worked remarkably well--better than any other model anyone has come up with--but so far, nobody has been able to integrate that model with the Standard Model of QM. We still lack a solid model of quantum gravity. There are several as-yet-unproved models around, some of which are more consistent with the notion of curved space-time than others, but we don't know which is correct.
Quantum gravity is technically outside the domain of both GR and the Standard Model, and we're going to need a modified something to explain everything. Even if that modified something turns out to be some intermediate effect that allows the Standard Model and GR to both be correct in their respective domains. Which is possible, but I think most physicists expect us to find that either the SM of QM or GR will eventually be shown to be no more than a reasonable approximation, much as Newtonian gravity was in its day. What sort of appoximation is a completely open question, though.
Anyway, this latest discovery is a triumph for the Standard Model, not GR. Resolving the differences between SM & GR is a battle for another day. But it's important to remember that we're dealing with models here, and the actual universe is what it is, whether or not it perfectly fits our models. Well ... when I say important, I mean, possibly worth keeping in the back of your mind. Most physicists find it more useful to ignore the quandry, accepting that there eventually will be a resolution, and take both SM and GR at face value, since they've both proven correct in every test we've been able to devise. :)
Re:explanatory update please? (Score:3, Informative)
Quarks come together in groups of 2 or 3 to build particles like protons and neutrons (and a whole bunch more). These are what you'd consider matter (Fermions).
You probably meant hadrons (particles made of quarks), not fermions (particles with half-integer spin, in contrast to bosons with integer spin). In particular, there are both fermionic and bosonic hadrons.
There are also particles that serve as "force carriers" - all the fundamental forces like electromagnetism and the nuclear forces can be thought of as exchanges of these other particles. They have integer spin, and we call them Bosons.
All force carriers are bosons, but not all bosons are force carriers. Force carriers are also called gauge bosons, as they are bosonic excitations of gauge fields.
The problem with finding bosons is that they're really just intermediary particles - photons are obvious enough only because they travel at the speed of light. Bosons with mass go much slower, and wind up decaying or interacting before we can directly observe them. So this find by the LHC is *indirect* evidence of the Higgs, based on how much energy they're missing from various collision interactions. But it matches the predictions to a very high degree so far, so they're calling it good.
The problem isn't the bosonic nature of the particle, but rather its mass and strength of interaction with other particles, which affect the energy needed for its production, its lifetime and the possible channels of decay.
Re:Found at 125 GeV (Score:5, Informative)
Where does a wave on the ocean go? The "particles" are manifestation of a particle(or force) field, which is like an ocean with waves on it. These waves are called particles when they collide and collapse with something else, but are otherwise waves when they move around on the ocean. There is always some waves on the ocean but not always high enough waves to break over the sea-barrier. The sea barrier in this case is 125GeV.
Re:Objection: Assumes facts not in evidence (Score:5, Informative)
And we have a very good idea of what causes gravity, or rather, what gravity _is_. Gravity is the tendency of spacetime to curve in the presence of objects with mass (and/or energy). This curving of spacetime causes other objects to travel not in straight (relative to our local Minkowski space) line paths, but in curves, when they are close to the first object (and vice versa). Since you can't see the external dimension that spacetime is embedded in where it curves (google "de Sitter-space" if you are interested), you see gravity as a force between massive objects.
Re:Objection: Assumes facts not in evidence (Score:4, Informative)
Peter Higgs didn't name the mechanism. He only theorised about the family of "Lorentz-covariant field theories in which spontaneous breakdown of symmetry under an internal Lie group occurs".
(Yes, that's a direct quote from his second paper.)