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Physicists in Europe Find Tantalizing Hints of a New Particle
- jbattle 11y ago"Parked along the underground racetrack are a pair of mammoth six-story conglomerations of computers, crystals, wires and magnets: Atlas and C.M.S., each operated by 3,000 physicists who aim to catch and classify everything that comes out of those microscopic samples of primordial fire." Is that a typo? Are there really 6,000 physicists actively doing work on the large hadron collider?
- akrose 11y agoThere are far more, in fact. Each of these collaborations have around 3000 members, but there are also other experiments (LHCb, ALICE are the two big ones but there are some smaller ones too) and then there is also the team of accelerator physicists that operate the LHC. All in all I think it is closer to 10000.
- philippnagel 11y agoAccording to https://jobs.web.cern.ch/faq/all https://jobs.web.cern.ch/faq/all there "are over 2,250 staff members" "but there can be up to 13,000 people on site at any one time".
- cshimmin 11y agoThose are jobs for the CERN facility alone (which also probably includes services like HR, translation, janitorial, etc). But thousands more work essentially full time as "CERN users". These scientists and engineers are typically paid by member organizations around the world, i.e. universities (think professors, postdocs, grad students) and national labs (LBNL/Brookhaven/Fermilab etc in the US, in2p3 in France, DESY in Germany). The ATLAS and CMS author lists are about 3000 each (generally all physicists), but all told there are over 10,000 scientists, technicians, and engineers who basically work full time running the LHC and its associated detectors. That's not to mention all the people working on any of CERN's many other projects that have nothing to do with the LHC.
- arethuza 11y ago"nothing to do with the LHC" Or possibly nothing to do with physics - I went to a conference at CERN in '94 about one of their computing projects. I believe that project became quite popular.
- cottonseed 11y agoYes. The ATLAS Collaboration publications have around 3,000 authors: http://arxiv.org/find/hep-ex/1/au:+Collaboration_ATLAS/0/1/0/all/0/1 http://arxiv.org/find/hep-ex/1/au:+Collaboration_ATLAS/0/1/0...
- Gravityloss 11y agoMaybe it's the closest to the Manhattan project or Apollo program that Europe has had.
- aurhum 11y agoI respectfully disagree. 1) The Manhattan project is not comparable in scope: Both the UK and France developed nuclear weapons on their own. 2) This is not a European project per se. Most of the developed nations in the world contribute, and as such this is very much a project for and by humanity itself.
- peterwaller 11y agoOfficial ATLAS and CMS plots: https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2015-081/ https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATL... http://cms-results.web.cern.ch/cms-results/public-results/preliminary-results/EXO-15-004/index.html http://cms-results.web.cern.ch/cms-results/public-results/pr... This video shows how one of the plots evolves over time as you discover a particle (in this case, the Higgs, discovered in 2012): https://www.youtube.com/watch?v=zLZZOrpQFo4#t=3m https://www.youtube.com/watch?v=zLZZOrpQFo4#t=3m A nice blog post: http://resonaances.blogspot.co.uk/2015/12/a-new-boson-at-750-gev.html http://resonaances.blogspot.co.uk/2015/12/a-new-boson-at-750... While exciting, there are countless examples in history of such discoveries disappearing as more data is collected.
- cshimmin 11y ago> While exciting, there are countless examples in history of such discoveries disappearing as more data is collected. As someone who works on ATLAS and has been watching this result develop over the last several weeks (without knowing what was going on at CMS), my excitement has been very tempered by this fact. Especially given that the global p-value is quite modest (see also: Look Elsewhere Effect [1]). For sure it's too early to know anything. But I have to say, when I heard the CMS announcement yesterday that they were also seeing it, in almost exactly the same place, it's much more exciting! [1] https://en.wikipedia.org/wiki/Look-elsewhere_effect https://en.wikipedia.org/wiki/Look-elsewhere_effect
- idlewords 11y agoA domain expert on an Internet forum? Prepare to be corrected!
- jessriedel 11y agoOn the optimistic side: has anyone done an estimate of the global significance taking into account the fact that CMS and ATLAS both saw the excess at the same place (~740 GeV)? (Clearly, if the situation was a simple as each bin being "excess" or "no excess", then you would only correct for the look-elsewhere effect for one of the experiments. When you turned your attention to the second experiment, that bin would already be special. This is muddied by the fact that things are not so clean, and the small blip of CMS was just the largest of several blips, etc.) On the pessimistic side: has anyone done a "fully global" significance test, taking into account all the other bump hunts of similar a-priori interest?
- eli_gottlieb 11y agoSo they haven't rejected the null hypothesis yet, and they're still getting themselves written-up in the New York Times?
- jsprogrammer 11y agoThe null hypothesis is unrejectable. Heh. Downmod.
- cshimmin 11y agoNull hypothesis: There is so such thing as toast. Experiment: I had toast for breakfast. Null hypothesis rejected.
- jsprogrammer 11y agoI believe "There is no such thing as toast." is only a theorem. Theorems may be rejected all day long. Edit: A null hypothesis in this schema would be something like (a bit ridiculous, but not my example): If toast exists and I eat it for breakfast, I should be able to detect that I ate it for breakfast at a higher rate than the false positive rate of my ability to determine whether what I eat for breakfast is or is not toast. Keep downmodding. Or, you know, refute what I have said.
- oldmanjay 11y agoI didn't vote on your comment but I can't make enough sense out of it to write a refutation. There is a sort of "evolution is only a theory" flavor to the whole thing.
- krick 11y agoYou could just open the Wikipedia, you know: https://en.wikipedia.org/wiki/Null_hypothesis https://en.wikipedia.org/wiki/Null_hypothesis the term "null hypothesis" usually refers to a general statement or default position that there is no relationship between two measured phenomena, or no difference among groups Rejecting or disproving the null hypothesis — and thus concluding that there are grounds for believing that there is a relationship between two phenomena — is a central task in the modern practice of science, and gives a precise criterion for rejecting a hypothesis.
- SteveWatson 11y agoPaywall
- briggsly 11y agoSimple workaround. Copy the article title and paste it into a Google search. When Google is the referrer, they drop the paywall [1]. For NYTimes and WSJ articles, this works almost every time. [1] http://www.techtimes.com/articles/38718/20150310/7-ways-to-get-around-the-paywalls-of-wall-street-journal-new-york-times-and-more.htm http://www.techtimes.com/articles/38718/20150310/7-ways-to-g...
- euyyn 11y agoThanks!
- helly 11y agoSo to explain the world we see, we combine quantum theory, theory of relativity, dark matter, gravitation, electromagnetism, two types of nuclear force and a zoo of now 62 elementary particles? I often wish for some kind of "Physical Philosophy". That tries to make sense of the world independent from those theories. For example: what if the theories just keep growing indefinitely? If we keep "finding" more and more complex theories that explain some aspects of what we see better then the old ones and keep "finding" new particles? What would that tell us about reality? What if we found a very simple formula that explains everything with just one type of particle and one dimension? Would it matter?
- cshimmin 11y agoThat's pretty much exactly what theorists are trying to do. For example, we used to think that electricity and magnetism were different forces and subject to different equations/rules. Then we united them into a theory of electromagnetism and realized they're governed by the same equations. Next we discovered the weak nuclear force which seemed totally different, only to later realize that the weak and electromagnetic forces are actually both part of the same (electroweak) force, and both are governed by the same fundamental equations. It is suspected (and/or hoped) by physicists that this trend continues; that the other nuclear force can be united with the electroweak forces under a single theory; there are already hints that this is the case (see: Grand Unified Theories). So far not much progress on getting gravity to fit in with the picture though :/
- exch 11y agoHaving things be complex and messy is hardly ideal, but I think Neil deGrasse Tyson's sentiment is important to keep in mind: The universe is under no obligation to make sense to you. But as cshimmin mentioned, we already unified electricity and magnetism. I am reasonably confident we'll find something equally nice and elegant for the rest. Maybe not tomorrow, or in a hundred years, but it'll happen. If only because we're too stubborn a species to let it be.
- Udo 11y agoThe world is complex, but we haven't gotten to the stage yet where you should feel lost, even as a layman. It is absolutely possible to know enough classical physics, QM, and theory of relativity to have a decent understanding of our current models. You absolutely don't have to be able to recite a table of elementary particles in order to understand this. > I often wish for some kind of "Physical Philosophy". That tries to make sense of the world independent from those theories. If your sense-making framework can (or must?) be independent from the facts, there is an enormous multitude from all cultures available for you to choose from. But if facts are important to you, and you don't know where to start, watch some popular science documentaries. If you prefer a touch of philosophy, I can suggest the original Cosmos series by Carl Sagan. But on the whole, sense and meaning is not something that can be prescribed by scientific knowledge - it can, however, help inform your own decisions about sense and meaning. > For example: what if the theories just keep growing indefinitely? This does not describe the current state of physics research. In fact, we are almost struggling to discover new physics, and so far most particle physics experiments line up so well with theory it's almost frustrating. What we can see right now is not the bottomless fractal recursion into nothingness which you describe.
- andrewflnr 11y agoI'm confused about why they think it could be a graviton. Since gravity is an infinite-range force, wouldn't its carrier be massless like the photon?
- hasenj 11y agoIsn't the fabric of spacetime itself the carrier for gravity?
- andrewflnr 11y agoIn relativity, yes. But quantum mechanics people have hypothesized a graviton anyway, presumably with the goal of unifying the two theories.
- XorNot 11y agoNo that's a convenient metaphor for gravity at large scales.
- hasenj 11y agoor maybe particles are a convenient metaphor for small scales
- splat 11y agoThe graviton is expected to be massless, but I don't think there's any information about the particle's rest mass.
- T-A 11y agoYes. The graviton in question would be a massive partner to the ordinary, massless one. You get those in Kaluza-Klein style theories with extra dimensions [1], so they are often referred to as "KK gravitons". [1] https://en.wikipedia.org/wiki/Kaluza%E2%80%93Klein_theory https://en.wikipedia.org/wiki/Kaluza%E2%80%93Klein_theory
- yk 11y agoThe most interesting paragraph of the article is: A coincidence is the most probable explanation for the surprising bumps in data from the collider, physicists from the experiments cautioned, saying that a lot more data was needed and would in fact soon be available. So the data analysis is extremely complicated, in part because the number of tries depends on the correlation of datapoints. So if you look at 2 sigma signal in one hundred datapoints you expect to find 5 and even worse, if you try one hundred different measures then you expect 5 two-sigma events, if the measures are independent, which they are not in practice. So to calculate the number of tries is a highly non trivial business, which depends on exact knowledge what each desperate grad student did on his weekend. So the nice thing about data from both CMS and ATLAS is, that we can fix this by asking, what is the probability that CMS sees something at the same energy and in the same channel as the most interesting ATLAS result. And as it turns out, it is a 2-sigma event. So there is just a one in twenty chance that this occurs by random chance. However one in twenty is not exactly a discovery, just the probability that the Niners win on Sunday. Edit: Two things, first that analysis is of course very conservative and second even if it is a real effect, it may be just a presently badly understood background effect.
- irascible 11y agoFirst I read "heavy boson" and thought that sounded kinda metal, so it would be cool if they named it that, but then I misread "whale boy", which is even better, so I'm calling it now. Next heavy higgs boson will be called Whale Boy.
- skykooler 11y agoI like it.
- jgord 11y agoDumb question from non-physicist - if the 'Standard Model' is a good theory, why don't we have a good idea of where to find particles [ ie. predict their mass and other properties ]? Is the problem that its just hard to compute these values ? Or does the theory not predict particle masses ? Or do we need a fully unified theory of all fundamental forces, before we can predict particle properties from first principles ?
- toth 11y agoWell, we have found all the particles predicted by the Standard Model, last one missing was the Higgs boson. However, no-one really believes that the Standard Model is the ultimate theory. There must be other stuff out there that we have found yet. What people are looking for now are deviations from the standard model.
- Someone1234 11y agoDoes the standard model explain quantum entanglement? edit: Nevermind, read this article: https://en.wikipedia.org/wiki/Physics_beyond_the_Standard_Model https://en.wikipedia.org/wiki/Physics_beyond_the_Standard_Mo...
- aurhum 11y agoAt the moment the limiting factor is energy -- The energies required to create these collisions (and hence, the possibility of these new particles) is enormous. In a way that's the only way the LHC exisists; to create higher energy collisions than before. As for computing values: It's nice to have a theory, but it's nicer still to have it confirmed/falsified by expermiment.
- InclinedPlane 11y agoWhat do you mean? It predicted the Top and Charm quarks, the W and Z bosons (and their masses), and many other phenomena. We know the Standard Model isn't a complete theory or a "grand unified theory" though because there are too many empirically determined constants in it, and because it doesn't adequately explain all known particle physics.
- Jerry2 11y agoLubos Motl has a really good post that cuts through a lot of journalistic hype and explains possibilities: http://motls.blogspot.com/2015/12/first-batch-of-9-pheno-papers-on-new.html http://motls.blogspot.com/2015/12/first-batch-of-9-pheno-pap... I'll just quote the summary: > You see that the diversity of the explanations is huge – it's a landscape of possibilities. Whether you like it or not, whenever certain things are uncertain, the possible answers are diverse. String theory's landscape reflects the same principle in another, more consistent and more constrained, formalism. And the purpose of this new particle is simply mysterious at this moment. > It seems very likely that the new particle is a j=0 scalar particle. And it seems guaranteed that it can't be the only new particle that has to be added relatively to the Standard Model. But who are the friends of SS and what is their relationship and purpose? Nobody knows. If this extra knowledge about the particle emerges, we may start to call it a heavy axion, a technicolor or composite scalar, a pseudo-Nambu-Goldstone boson, or – which I find more likely – a new Higgs boson analogous to the (three-year) old one.
- termain 11y agoHow is 1+1=1 easy to achieve?