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LHC physicists embrace brute-force approach to particle hunt
- hinkley 8y agoNot a physicist, so maybe I'm misunderstanding... How is smashing protons into each other at relativistic speeds billions of times not a 'brute force approach'?
- ddavis 8y agoWe have models which provide predictions about the signatures we would see in the detector if that model is true. The "general search" doesn't target a particular model. The only model used is our Standard Model, treated as background. Traditional searches utilize one or more of many Beyond Standard Model (BSM) models to treat as potential signal.
- soqpupit 8y agoThis seems like a great place for the top machine learning folks.
- ddavis 8y agoYep, the field is rapidly adopting ML all over the place. The last paragraph in the article mentions a very hot topic right now.
- soqpupit 8y agoIt seems like an interesting problem. It has clearly defined requirements for success, lots of data with (one assumes) some hidden structure, and the structure is not yet known.
- jameskilton 8y agoIt's two parts. The smashing is just gathering raw data. Lots and lots of data. Then "brute force" approach has to do with what can be found in that enormous data set and how physicists have, until now, been looking for specific patterns from theories and expectations.
- stingraycharles 8y agoSo then the brute force approach could be an unsupervised pattern recognition algorithm?
- bonesss 8y agoThat's the AI part of the article. Basically, the LHC spits out data so your your Big Data looks small. The first pass was for data confirming/disconfirming some big theories where a specific peek at the data would give meaningful answers. So far the data shows that we had it right to start with. Now, for the next pass, they're expanding how they look at the data to find anything 'unusual'. "Pattern recognition" in this case is a bit harder than just checking for a recurring value, or a "true" in the "Unified theory of everything?" field. We're a bit closer to what we would generally call AI, and at very least some interesting techniques with more interesting followup experiments to weed out false positives.
- pasbesoin 8y agoI've yet to read the article, but I'll hazard a guess. At the time of LHC's design and instantiation, the amount of raw data it generated was vastly more than could be stored and arbitrarily processed. So, it was quickly filtered and shunted into processes designed to look for certain things. Communications and processing capabilities have increased substantially since then. One may now be able, with investment/expansion of those, to take a more "brute force" approach in mining closer to if not at the level of raw data and arbitrary -- or at least a broader range of -- associations.
- Analog24 8y agoIt's not quite that simple. The CMS detector (one of the two main detectors/experiments operating at the LHC) spits out about 10TB of raw data per second. This is more than any system can handle at the moment. To deal with this overwhelming flood of data there are layers of "triggers" that effectively filter out the collisions that aren't of any interest. The lowest level triggers are actually embedded in FPGAs on the detector itself, then there is a high-level trigger that runs on an on-site server farm that does minimal event processing to see if the even is interesting. All of this requires us to define what constituents an interesting event. The most basic trigger is called the "minimum bias trigger" because it requires us to make the fewest assumptions about what makes the event interesting. So even at the most general level a brute force approach will still have some bias because it will likely be using the minimum bias data. What makes it "brute force" is that they will no longer be looking for signals from specific new models, they will only be considering the Standard Model and essentially looking for outliers. The difficult part is that there is so much systematic uncertainty given the complexity of these detectors, which makes it hard to obtain statistical significance.
- hinkley 8y agoOh! So we are using the term brute force in the information theory sense of the word, not the scientific connotation?
- DoctorOetker 8y agocould you elaborate a bit on the "10 TB of raw data per second" ? If it's really raw how much room is there for domain specific lossless compression? How many seconds long has or will the experiment (CMS) normally run? How much did or will the CMS component of LHC cost from construction to its full lifespan? What fraction of that imaginary lump sum went to digital storage budget?
- trentlott 8y agoIt is physically, but not scientifically. Before they outlined what they were looking for. Now they're just sifting. Most science doesn't allow you to propose "We will expose A to X and see what happens", but rather expects a hypothesis: "We expect Z following X>A because of [rationale]."
- badosu 8y agoI wonder if this is due to the success of the current models (less hidden corners), academic incentives for paper production as opposed to breakthrough work, the ever growing specificity and cost of experiments (making less sure experiments unviable) or some combination of these factors.
- jerf 8y ago"Most science doesn't allow you to propose "We will expose A to X and see what happens", but rather expects a hypothesis: "We expect Z following X>A because of [rationale]."" Which I consider one of the major flaws of the current scientific practice. There's absolutely nothing wrong with trawling over data looking for interesting things. You just have to be more statistically careful. Huge amounts of science have been done by just trawling over things or rapid-fire throwing theories at the wall and seeing what sticks. Having to always call your shots means you can only slightly push the frontier back. There's a place for that, which is probably "the vast majority of experiments". But we need that more exploratory stuff too. But somehow we got entrenched with a terrible oversimplification of science as "The Way Science Is Done", which hyperspecifies the parameters of the ways we can modify our confidence values in various theories. There's more valid choices than is currently considered valid, and we're missing out.
- godelski 8y agoThis is a good question! It really depends how you're smashing the protons together. Did you create a model and then smash them together and analyze them? So you are testing "I believe that if I smash protons at X energy level that they will cause y_0,...,y_n decays" This is standard hypothesis testing. You are looking in a specific place. A brute force method in this area is more like "Well... I'm not really sure. Why don't we just smash these protons together at uhhh... idk X energy?" And then you get "well that was interesting" or "okay, that was expected". This is overly simplified. Basically a brute force method is just doing and observing. Not really predicting things. You're searching a large solution space and so you just try random things and hope you get lucky. (they have some good guesses of areas too look, so it isn't completely in the dark)
- noobermin 8y agoCorrection, the group leaders have decided that their unwilling graduate students should embrace the brute-force approach.
- iainmerrick 8y agoIt’s the machine. The machine has to be configured. Yes, there are group leaders who have the final say on the configuration, and no, they aren’t grad students.
- Blackbeard_ 8y agoThe article is just discussing a type of data analysis. The machine runs the same way regardless.
- yk 8y agoSo the last hope collider people are getting desperate? To explain a bit, the well known trouble with today's physical theories is, that on one hand we know that general relativity and quantum field theories do not fit well together, on the other hand we don't have a good idea of the way forward. So the hope was, that LHC would show something interesting, like supersymmetry, or at least deviations from the standard model. So far it only shows precisely what one expected before, so the theoretical problems are precisely the same as before.
- elorant 8y agoCorrection: We don't have a testable idea of the way forward. As with current technology.
- wuliwong 8y agoI've been out of the theoretical physics game a little while, what are the leading "untestable" quantum-gravity theories out there today?
- meowface 8y agoString theory's one.
- Filligree 8y agoString theory's several trillion.
- meowface 8y agoTrue, I should say "a" string theory.
- orbifold 8y agoString Theory is a theory in the same sense that Quantum Field Theory is a theory. You need concrete phenomenological models to make predictions. While there some ways to do that starting from string theory there is no one known model to rule them all, the way the earlier attempts like Georgie‘s SU(5) GUT Model was. For some flavors like F-theory it is even a research questions how to make certain predictions of matter content etc at all. This is made more uncomfortable by te fact that the most natural susy extensions of the standard model have been all but ruled out. This also eliminates one of the main reasons for susy: as a solution to the fine tuning problem.
- brianberns 8y agoThe article never clearly describes the brute-force approach. Is it just a matter of looking for statistical outliers along all the different dimensions they can think of? How would they then distinguish the "interesting" outliers from random flukes?
- Blackbeard_ 8y agoThe gist is that you would roughly look for deviations from theory on one (probably small) dataset, you'd identify any regions of interest and then run a proper analysis of that region on a different dataset to see if the effect is real.
- smueller1234 8y agoCaveat: Been a while since I studied this stuff. The problem with this approach that I see is that it's much more likely to pick up lingering detector issues than the regular test-a-theory. (The difference between looking for a specific thing in a specific place vs picking up anything unexpected.) I wouldn't worry do much about purely statistical artifacts because those can often be worked out with prescriptions and remeasuring. The systematic but not-understood biases are the ones that should plague this approach since in the extreme they would need an independent experiment. I wonder whether CMS and Atlas are sufficient for that.
- ThaJay 8y agoTesting for detector issues and those sort of things seems like very important groundwork for future experiments.
- supernovae 8y agoI wish we had finished the SSC :(
- pasbesoin 8y agohttps://en.wikipedia.org/wiki/Superconducting_Super_Collider https://en.wikipedia.org/wiki/Superconducting_Super_Collider A somewhat early harbinger of the U.S.'s decline in public funding of fundamental science -- and all the practical discoveries, engineering, and knowledge that derive from same. From random news stories I encounter, it appears that "they" keep trying to shut down FermiLab. However, despite being "older" and "smaller", FermiLab continues to make important contributions. And among other things, they contributed significantly to the Higgs Boson work. Not mentioned in the Wikipedia article, was the debate over whether the SSC should even have been located in Texas -- apparently, there were significant political factors in the decision. IIRC, there was counter-argument that it should be located as close as possible to FermiLab, for synergy and efficiency in continuing its work. There are the cited "costs". However, these project seem to invariably produce a lot more practical value than they consume. Cryogenics, superconducting technologies, data processing and communication, and on. As I've said before, if you appreciate your medical MRI... Not to mention NMR contributions to chemistry and biology... Etc. It all hangs together. And killing fundamental research is kind of like killing the goose that lays those golden eggs.
- bonesss 8y ago> apparently, there were significant political factors in the decision As I recall the history this project is a near-perfect example of how pork-oriented-spending is not congruent with R&D projects. Everything from site selection to subcontracting was divvied up to appeal to the relevant congressmen. These unnatural constraints caused delays, logistical issues, and massive cost overruns. Their ability to solve those issues was hamstrung by the projects organization. Thanks to the dependencies they were a ways in before this all blew up and the project had to be stopped. Building something like the SSC or LHC is fundamentally hard. Making someone do something that is hard while twirling a baton for political pleasure, much less getting critical components from two suppliers who can't integrate until construction, almost guarantees failure. The correct approach, ironically, is perfectly embodied by the post WW2 machinations of the US government... Make the goals clear, dump appropriate money in engineering and technology organizations, let the nerds figure out the devlish details, and enjoy your A-bomb blowing up on time and schedule.
- edw 8y agoThe article never outlines what the alluded-to downsides are (p-hacking, spurious correlations) which makes me wonder if the article’s sourcing leaned too heavily on advocates of this theory-free approach, which was the subject of a Wired cover story a few years ago, so it must be true, amirite? Reading the article makes me wonder what Woit (author of Not Even Wrong book and blog) thinks about this and how it dovetails with the epistemological morass the string theory people have gotten themselves into.
- est 8y agoso LHC is basically in 大力出奇迹 mode?
- abvr 8y agoBut it's always been a brute-force approach which is usually used at CERN, for detecting and analyzing the particles that may arise out of the various particle accelerator collisions. It is however a wiser approach to probably involve the current hardware capabilities to crunch the vast amounts of data through some statistical analysis or algorithms to sift through so much data without much human intervention and obtain results that have lesser false positives, as those are one of the drawbacks of using the brute force approach. Further research in these areas which could then help improve the accuracy of these models an then be reinforced into the chain and obtain only the required data to then manually observe.
- Blackbeard_ 8y agohttps://arxiv.org/abs/1710.07663 https://arxiv.org/abs/1710.07663 Those interested in a (somewhat) accessible view of where particle physics is at in a big sense could read this article from the head of our theory group at CERN.
- vectorEQ 8y agotime to stop learning to break things into even smaller pieces and do something useful with the trillions of investments.
- russdill 8y agoThe CERN cost is just a few billion. The only things we take apart that have budgets measured in trillions are middle eastern countries.