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Why the LHC May Mean the End of Experimental Particle Physics

Posted by Soulskill on from the until-we-get-that-dyson-sphere-built dept.

StartsWithABang writes: At the end of the 19th century, Lord Kelvin famously said, "There is nothing new to be discovered in physics now. All that remains is more and more precise measurement." He was talking about how Newtonian gravity and Maxwell's electromagnetism seemed to account for all the known phenomena in the Universe. Of course, nuclear physics, quantum mechanics, general relativity and more made that prediction look silly in hindsight. But in the 21st century, the physics of the Standard Model describes our Universe so well that there truly may be nothing else new to find not only at the LHC, but at any high-energy particle collider we could build here on Earth. If there are no new particles found below about 2–3 TeV in energy—particles that the LHC should detect if they’re present—it’s a reasonable assumption that there might not be anything new to find until energy scales of 100,000,000 TeV or more. And even if we build a particle accelerator to the fullest capacity of our technology around the equator of the Earth, we still couldn’t reach those energies.

24 of 191 comments (clear)

  1. Dark Matter and Energy by rockmuelle · · Score: 2

    Well, if we find a way to measure either of those using high-energy experiments, we'll get a few more decades out of the field.

    Just when we think we're done, we're usually just at the beginning...

    -Chris

    1. Re:Dark Matter and Energy by VernonNemitz · · Score: 4, Informative

      The original article clearly indicates that such particles need to be found first, within the abilities of the LHC. OR, we need something bigger than the Earth's circumference.

    2. Re:Dark Matter and Energy by dreamchaser · · Score: 2

      Except they are talking out of their ass. They don't know for certain, not at all. It's all supposition.

    3. Re:Dark Matter and Energy by tnk1 · · Score: 3, Informative

      While I agree with you to some extent, the fact is that it isn't going to be a matter of whether we're missing say 1% or 37% of the energy at the LHC we need to make a breakthrough. The theories and models in question provide only certain situations that you might find new particles, which is likely the basis for what this article is saying.

      In other words, its like having a road map that shows a freeway and all of its exits, but we otherwise have no idea where we are on that map. If the next exit is 2 miles from the previous exit, then chances are good we are in this one place on the map with lots of exits. However, if there are no exits even after 10 miles of driving, then the map shows us that we are most likely in this one rural area that doesn't have an exit for 100 miles.

      In this case, mathematics and theoretical physics provides us the map with all the possible places you could find particles. Now we have to determine where we are on that map by finding where the next particle is to be found. If it is at LHC energies, then our map says we're likely to find a some new particles with minimal increments of further energy use. If it isn't, then we know we've hit the "rural" area on the map and we won't be seeing another particle for a long, long time because we need an particle smasher the size of the solar system to hit those energies.

      Of course, brand spanking new physics could alter the "roadmap", but since the Standard Model does predict *just about* everything we have seen in experiments, then it means our physics is still incomplete, but has become accurate enough that we can predict what would happen down to the place we'd need the hundred million TeV to see anything new or to answer the specific items that the Standard Model does leave open.

    4. Re:Dark Matter and Energy by khallow · · Score: 2

      What if the research would require about 20% more energy than the LHC is capable of?

      It's not that simple. LHC can find such things, it just takes more time to do the statistics. You really would need an order of magnitude difference in energy to make a difference.

    5. Re:Dark Matter and Energy by rubycodez · · Score: 2

      False.

      The universe can produce ZeV range particles 10^21, already there are experiments in the works to detect dark matter decays from cosmic rays. Turns out we only need very sensitive detectors for expected decay products.

    6. Re:Dark Matter and Energy by Ramze · · Score: 4, Interesting

      Actually, you have that a bit backwards. The Standard Model says we're done finding new particles. The Higgs was the last one we expected to find, and it was so necessary to the theory that we could describe all of its attributes long before we actually found it. When we did, it matched the theory perfectly -- too perfectly. We knew its mass, spin, decay rate, and interaction with other particles just from the math before we even found it in the lab. Physicists were both relieved and saddened by the discovery as it meant the standard model was correct and there were no new physics to be found.

      It's the idea of finding new particles that is all supposition. We know the standard model can't explain everything, but we don't know that missing particles are the solution. We also don't know how to detect those new particles if they do exist. Gravitons, sterile neutrinos, and black matter particles (whatever those may be) would be electrically neutral and barely interact with anything -- much less a particle detector. We suspect we will be able to detect them indirectly if they exist at all. There is a slim chance that there may be more than one type of Higgs, but other Higgs are not necessary for the theory to work and other Higgs would be at much higher energy levels.

      You are correct that no one knows for certain -- that's the whole reason they conduct the experiments. But, the very well known math and theory strongly suggest that we're done. It's the wild supposition arguments that hope there's something more.

      And that's not because they don't WANT to find new physics... it's just... quantum mechanics and particle physics are so well understood that it would be extremely surprising to find other fundamental particles -- b/c if they exist, they must be very very weakly interacting with all the known particles or at least very short lived to not cause chaos with the currently understood theory.

  2. Citation needed by belrick · · Score: 3, Insightful

    In the article this: "it’s a reasonable assumption that there might not be anything new to find until energy scales of 100,000,000 TeV or more. " is asserted without supporting evidence.

    1. Re:Citation needed by jfengel · · Score: 4, Interesting

      The idea is that if we don't find anything, the next most likely place to go looking is at the energy where the strong, weak, and electrical forces unify, around 10^13 TeV. The number they give is a few orders of magnitude below that; we probably wouldn't have to get all the way to the grand unification energy to see hints of new particles. I think that's the evidence you're looking for; it's justified by our present theory.

      It's a "reasonable assumption" in that those theories begin to break down at that scale. We expect our theories to hold quite well, which would mean that we wouldn't expect to find anything novel until we got close. And then we have every reason to expect to find new things, which is what you need to help drive a theory that's measurably different from our present one.

      Of course we never know what we'll find, but it would be hard to build any sort of intermediate-sized collider, which would cost insane amounts of money, and theory predicts that it wouldn't find anything of value unless it were even bigger. It could be even worse; they might not find anything for a few more orders of magnitude, at which point they'd be probing not just the strong, weak, and electrical forces, but also gravity. We know for certain that the theory breaks down there, but the amount of energy required to probe the breakdown is simply ludicrous.

  3. Re:Hubris by AchilleTalon · · Score: 2

    Well, the point is not there isn't anything else to discover, the point is at which energy levels we can expect to find something. His assumption is based on the current theories and at which energy levels we can hope to find something. There is no reason we should observe particles at all energies and an energy desert is very likely and plausible. So, should we invest ressources, money and energy into the business of searching new particles at all energy levels without at least some indication they exists? Given the amount of money needed here, I don't think so. We should go ahead if we have a strong enough indication it may pay off.

    In the mean time, we still have astronomical observations we can rely on and cosmic particles we can try to use given some are accelerated at energy levels much higher than what the LHC or any upcoming accelerator can reach. The problem being the luminosity, but in the case of cosmic particles, we have plenty of time to accumulate results on very long period of time to compensate for the infeasibility to build a large enough accelerator to reach these levels.

    --
    Achille Talon
    Hop!
  4. Neutrinos by Framboise · · Score: 4, Informative

    Has this guy never heard that the mere fact neutrinos have a mass does not fit in the Standard Model, and that plenty of good experimental physics can be made on these particles?

    1. Re:Neutrinos by Ramze · · Score: 2

      Neutrinos with mass certainly DO fit in the Standard Model. In fact, all 3 known left-handed neutrinos are a part of the standard model. Neutrinos are even known to oscillate between the 3 types. Originally, neutrinos were assumed to be massless as their mass is so incredibly tiny it couldn't be detected when the particles were first proposed and discovered. Their insignificant mass didn't alter any predictions the model made on particle physics at the time. That does not mean that they aren't more well understood today, nor that they have some magical capability that doesn't fit the framework of the standard model. They were just assumed to be massless because they moved at near light speed and there didn't seem to be any right-handed neutrinos detected that would show they interacted with the Higgs... also, every particle interaction that created them didn't have any missing mass that would need to be accounted for by the neutrino ejected from the collision.

      There are theories on how and why the neutrinos oscillate between the 3 mass states and on how they interact with the Higgs to generate those masses. There are even theories that include right-handed "sterile" neutrinos that we haven't yet detected (and possibly can't ever hope to detect based on theories of their properties.) The fact that we can't prove it and don't have any good experiments in progress to figure it out doesn't mean the 3 flavors of neutrinos with their various masses don't fit perfectly well into the standard model as-is. These tiny, fast, ghostly particles just don't interact with regular matter very often, nor do they interact with electro-magnetic fields... so, it's very difficult if not impossible to devise experiments to definitively tell us much about how they generate their masses from the Higgs (or some unknown source) or why there are no detectable right-handed neutrinos (assuming they even exist... and if they do, that they exist for long enough to be detected before flipping back to left-handed ones).

       

    2. Re:Neutrinos by Framboise · · Score: 2

      Sorry, but the Standard Model predicts *massless neutrinos*, while oscillations found in experiments prove non-zero masses.
      See: https://en.wikipedia.org/wiki/Standard_Model_(mathematical_formulation)#Neutrino_masses/
      The extensions to the Standard Model that you mention could accommodate positive masses, but none of these is standard or unambiguously supported by experimental evidences yet.

  5. Re:breakaway science/civilizaiton by Anonymous Coward · · Score: 5, Insightful

    So, StartsWithABang starts by telling us that Lord Kelvin was a fool for thinking there was nothing left to discover and then he goes on to say practically the same thing.

    I see.

  6. How many coin toss heads in a row is natural? by Roger+W+Moore · · Score: 5, Interesting

    There is a good reason for that - there is no supporting evidence and, in fact, very strong evidence suggesting that it is completely wrong...but that's what you get with 'startswithabang', it usually ends with a whimper. The one of the most damning bits of evidence that there is something well before 10^19 GeV (no clue where he gets the 1^8 TeV figure from) is that the Higgs mass 125 GeV/c^2.

    Unlike every other fundamental particle the Higgs has no spin, which means it has no intrinsic angular momentum like electrons, quarks, photons etc. This has the effect that quantum corrections very strongly affect its mass. In fact these corrections apply to the square of the Higgs mass and grow as the square of the energy scale so if the Standard Model is good up to the Planck scale at 10^19 GeV these corrections are of the order of 10^38 in size. Each Standard Model particle has its own correction to the Higgs mass with fermions and bosons providing opposite sign corrections.

    Here is the problem though. In the Standard Model there is no symmetry between fermions and bosons and the coupling to the Higgs field, which determines these corrections, are all free parameters. So if we believe that there is nothing but the Standard Model before the Planck scale then we have an amazing co-incidence that a series of essentially random terms each of order 10^38 cancel so precisely that the remainder is of order 10^4.

    To put that in context it would be like tossing a coin about 100 billion times and getting heads every single time. I don't know about you but personally I would start getting suspicious that something was fixing the result sometime around toss 100.

    This is the issue with the Standard Model: the fact that there is a Higgs at 125 GeV is like the 100 billion coin tosses all coming up heads. The problem is that we do not yet know how nature is fixing the result but it does mean that the new physics required to fix it most likely occurs below ~10 TeV. While this is not a hard limit the higher in energy you go the less natural any accidental cancellation will be so really the energy limit where you expect new physics depends on how many times you can toss a coin and get heads before you believe that something is fixing the result.

    1. Re:How many coin toss heads in a row is natural? by Compuser · · Score: 2

      I think the limiting factor is going to be financial. Nobody will be building single purpose science facilities at a cost which is a significant fraction of the GDP. My guess is that something on the scale of $10-20B is imaginable (i.e. something like the failed SSC) but much bigger is not. Now, couple this with the fact that CERN was only able to sell their expansion due to the hunt for Higgs. This was not some nebulous cancellation of perturbative corrections but a very real prize which could then for years validate the technical prowess of a entity like EU. So unless there is something truly fundamental, firmly expected and magically marketable to politicians beyond CERN LHC scale, then it is unlikely to happen.
      Frankly, it is just as well. If I were a politician, I would allocate any new funding for identifying ways to reach higher energy scales cheaper. We need to shrink things like the ATLAS experiment down to lab-on-chip level. We need hard drives which can fit all data from CERN for a year on one platter. Give it a few hundred years of progress, shrink technology as much as possible, then scale up as need be.

  7. Re:Not a physicist but... by toonces33 · · Score: 2

    The article only talks about experimental particle physics.

  8. Would you pay a 100% income tax? by tepples · · Score: 2

    There is no price too high for knowledge.

    Sure, when you're spending Other People's Money. But would you be willing to contribute 100% of your income to a new collider?

  9. Re:breakaway science/civilizaiton by vux984 · · Score: 4, Insightful

    Not quite, he's saying there's lots left to discover. There just might not be anything left for the LHC to discover.

    I suspect even that is false, that there will be all kinds of science to be done with it. But it may be true we don't discover any new particles with it by smashing things together, which is the thing it was built for.

  10. Re:Stop thinking so small by MightyMartian · · Score: 4, Interesting

    No application we can think of. That's like someone mocking the guys making frogs' legs jump with electrical current in the 18th century. "Oh yes, very interesting, but so what?" And yet, within a half a century or so of those first gimmicky experiments with electricity, we had built the first high speed data network in history, revolutionizing, well, just about everything, and within a few decades of that we were replacing gas lights with light bulbs, people were using welding machines to build large steel structures and that changed, well, everything.

    There really is no way you can stick a long term price tag on basic research. Right now, figuring out what lies beyond the Standard Model is an interesting abstraction. But in fifty years, or a hundred years of us cracking that code, who the hell knows what we'll be building? Exotic materials, new propulsion systems, new communications systems, who knows? If the last five hundred years of scientific research has taught us anything, it's that science is the field out of which technical innovation is grows, and basic research is the fertilizer.

    --
    The world's burning. Moped Jesus spotted on I50. Details at 11.
  11. Re:breakaway science/civilizaiton by CreatureComfort · · Score: 2

    There are collisions happening at energies MUCH higher than any man-made collider will ever achieve right above our heads, in the upper atmosphere, every second. It's just still much cheaper to build giant colliders than a reasonable detection system to gain new information from those collisions.

    Once we've milked the LHC for all it can give, if it doesn't provide clues to it's successor, then we can start trying to catch cosmic rays in a controlled manner.

    --
    "Unheard of means only it's undreamed of yet,
    Impossible means not yet done." ~~ Julia Ecklar
  12. Neutrino Radiation by Roger+W+Moore · · Score: 3, Interesting

    but the short lifetime of the muon has kept anyone from coming up with a workable proposal so far.

    The other problem they had with the muon accelerator proposals which Fermilab looked at a while ago was the lethal amounts of neutrino radiation from muons decaying. While neutrinos rarely interact at energies below a PeV if you get enough of them there can be enough interactions to be dangerous if a human stood in the beam and unfortunately shielding really isn't an option with neutrinos.

  13. Re:"we still couldn’t reach those energies" by tlambert · · Score: 2

    "I don't believe you know X! Prove it by disclosing X to me! You will do this because you are as stupid as I am assuming you to be!"

    Is this how you got your first information that VAX/VMS error logs were world-readable, and thus disclosed failed login credentials and password typos that made it easy to log in as someone else? You tricked someone into telling you about the log file by appealing to their hubris?

    Nice troll, though...

  14. Re:"we still couldn’t reach those energies" by Anonymous Coward · · Score: 2, Insightful

    If you wanted to refer to FACET, you could have at least mentioned the name so that others who are curious can look it up, instead of just assuming you're a troll (and those that know about it can still view you as troll/naive because of your awkward wording...). However, everything I said in the previous post still applies. Nothing about the work at SLAC will bring a trivial replacement for LHC in the next decade. In a long time scale it will yield improvements, but they are going to be much more difficult than anything done before. As already said, plasma accelerators still have scaling issues. Just because you can achieve some amazing acceleration gradient doesn't mean you can just carbon copy it ten times and get ten times the energy.