Now that the Higgs boson has probably been found at the LHC, what do you all think will be the future of high energy physics? Do you think LHC will find hints of post-Higgs physics at reachable energy scales? Do you think the International Linear Collider will ever get off the ground? Do you think there will be new large scale particle colliders that will replace the LHC, or will HEP focus on different fields, such as neutrino experiments?
The future of particle colliders
- Thread starter dutchfire
- Start date
It really depends on if the LHC is going to find anything new. The ILC only has a high chance of being built, if the LHC hints at anything interesting at high energy scales. The discovery of a supersymmetric particle with the promise for many more to be accessible at ILC energies would be a strong selling point for such a collider. But if the LHC finds nothing at high energies, it is going to be very hard to come up with funding for it. It might still be built, but only if there is a country that really wants a large prestige science project and is willing to spend a lot of money on it. At the moment Japan seems to be the only realistic chance for the project.
If there is no evidence of anything new at high energy, the most realistic proposal would be LEP3, which would use the LHC tunnel to build another electron-positron collider for precision measurements of the Higgs and other particles with less background. This could be built (comparably) cheaply and could reuse the existing detectors, but would not be very exciting. Still, it would probably result in good physics on a tight budget.
I am quite doubtful on the existence of supersymmetry, so my gut feeling is that the golden age of collider physics is over and HEP colliders might reach a dead end for now. This is a bold statement and in the past when people claimed that physics was mostly understood there was a huge mess waiting just around the corner. But it might be that there is nothing interesting in the energy range we can reasonably access right now. So going into other directions seems to be more promising. Neutrinos are still quite mysterious and measurements on antimatter are very basic at the moment.
If I had to bet, I'd say that precision measurements for example of the size of the proton are a better bet for physics beyond the standard model than ramping up the energy. But that is the part of the field I have most contact with and I am an experimentalist, so I am not convinced of theorists postulating doubling the particle number because of a hypothetical symmetry.
If there is no evidence of anything new at high energy, the most realistic proposal would be LEP3, which would use the LHC tunnel to build another electron-positron collider for precision measurements of the Higgs and other particles with less background. This could be built (comparably) cheaply and could reuse the existing detectors, but would not be very exciting. Still, it would probably result in good physics on a tight budget.
I am quite doubtful on the existence of supersymmetry, so my gut feeling is that the golden age of collider physics is over and HEP colliders might reach a dead end for now. This is a bold statement and in the past when people claimed that physics was mostly understood there was a huge mess waiting just around the corner. But it might be that there is nothing interesting in the energy range we can reasonably access right now. So going into other directions seems to be more promising. Neutrinos are still quite mysterious and measurements on antimatter are very basic at the moment.
If I had to bet, I'd say that precision measurements for example of the size of the proton are a better bet for physics beyond the standard model than ramping up the energy. But that is the part of the field I have most contact with and I am an experimentalist, so I am not convinced of theorists postulating doubling the particle number because of a hypothetical symmetry.
Like the late 19th century, we'll soon be looking at a field whose major problems have all been solved. I suggest physists consider switching majors:
@Uppi - why are you skeptical of supersymmetry? I thought that the observation of anti particles pretty much confirmed a lot of it.
Are there specific predictions that haven't worked out even though the experiments were well-designed?
Are there specific predictions that haven't worked out even though the experiments were well-designed?
Yeah, I also think that general budget constraints in Europe and the US at the moment will make a new large thing even less probable. Also, building a whopping big machine which doesn't find a new particle, but only adds a couple of digits to some parameters is going to be hard to sell to the public/politics/science community.
That sounds like a decent enough plan.
I also think we could be seeing more heavy-ion colliders, these are rather new and have been surprisingly succesful as far as I have heard. (Of course, I heard so from heavy-ion-collider physicists...)
uppi said:
douglas adams said:
I agree that it looks like there is no new knowledge to be found in the immediate vicinity of our capabilities, but I also know that the people who have said that before were proven wrong every time.
No, supersymmetry and antiparticles are not really related. We have known since the thirties (positron) that particles (can) have anti-particles. An anti-particle will have the same properties as the particle, but sometimes with a different sign (let's ignore CP violation for a moment). E.g. a positron has the same mass as the electron, and the same charge, but with an opposite sign. Importantly, the positron also has the same spin (1/2) as the electron. This makes the positron and the electron so much the same that they are actually described by a single field in Quantum Field Theory, and one generally considers them to be just different manifestations of the same particle. The anti-particles of other elementary particles usually don't even have their own name, and for some of them the distinction between particle and antiparticle is rather arbitrary. (You will also sometimes hear people say that an anti-particle is just a particle travelling backwards in time. This is a way you can interpret anti-particles, but it is little more than an interpretation.)
Now, as you might know, there are two types of particles in nature. Particles with integer (0,1,2...) spin, which are called bosons and particles with half-integer (1/2, 3/2,...) spin, called fermions. These types of particles behave radically different. Supersymmetry predicts that every fermion has a supersymmetric bosonic partner and vice versa, but that these partners just have not been discovered yet.
Such a theory is somewhat appealing, since it unifies our view of nation even more (and unification is good!) and I believe it also might explain some aspects of the Higgsmechanism. However, the only real prediction it does is the existence of these supersymmetric partners (or effects that could be explained by interaction with supersymmetric partners). These haven't been found. When supersymmetry appeared, they predicted that the lightest supersymmetric particle was just out of range for the best colliders at that moment. They have stayed with this prediction, the lightest supersymmetic particle is supposed to be just out of range of our current colliders.
Some (Many?) believe that the supersymmetric community has been busy moving the goalposts, to keep supersymmetry on the horizon, instead of admitting that it just hasn't worked out.The existence of antiparticles was already predicted by the relativistic theory of quantum mechanics as proposed by Dirac. Supersymmetry was a much later development.
As dutchfire said, it predicts a bunch of particles that we have no evidence for. There are at least a dozen versions of it and all of them have free parameters, so in principle there is a huge parameter space left for them to hide. But supersymmetry was originally developed to solve a fine-tuning problem in the standard model (i.e. the free parameters must have a precise value for the model to work, but there is no reason for them to have that value). To solve that problem the masses of the new particles must be quite low so that supersymmetry does not have its own fine-tuning problem. However, if the masses of the particles were low enough the LHC should have detected them already.
So although the parameter space is still huge, the parameter space where supersymmetry is attractive because it actually solves anything is getting very small.
But there are a lot of people, especially in the HEP community that believe we will detect supersymmetric particles very soon. Even if the LHC doesn't find anything it will take a long time until its supporters die out. But funding a new huge machine will require more reasons than belief in supersymmetry.
Selling it to the public or to politicians might be possible if you promise them enough. But backing those promises up enough to satisfy the scientists (who all want funding for their own pet projects) is going to be hard.
I haven't heard much about that, so it cannot be that revolutionary
But I agree that smaller, special-purpose colliders might be the future.
Most of the time they were proven physics took a totally unexpected turn. If there is a lot of new knowledge just beyond the edge of our theories, it might require something else than particle colliders.
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