Will The LHC Be The End Of Experimental Particle Physics? (Synopsis)

“There is nothing new to be discovered in physics now. All that remains is more and more precise measurement.” -Lord Kelvin

When Kelvin said that over 100 years ago, 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.

Image credit: E. Siegel. Image credit: E. Siegel.

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.

Image credit: ILC collaboration. Image credit: ILC collaboration.

Come read why the LHC may well be the very end of experimental particle physics.


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No. Flat out no. The ILC is on the way and will be built. What it will find is anybody's guess.

By Richard Mitnick (not verified) on 10 Sep 2015 #permalink

The Standard Model has it's origin in Cosmic Ray detection, and it has brought order and understanding to the madness of particles. Knowing that there are Ultra-high-energy cosmic rays that are of some energy higher that what's being done at the LHC and we don't notice anything spectacular it makes little to no sense to keep building these accelerators to find something new.

The problem isn't so much the speed and energy of these particles but rather the detector itself, there is a threshold where we can't measure beyond. For the magnetic field we can do all kinds of experiments but for the Higgsfield there's nothing that we can influence it.

The biggest advancement in physics these days are done with computer simulations and it is here where there's still a large field for discoveries thanks to modern supercomputing maybe quantum one day.

By Paul Dekous (not verified) on 10 Sep 2015 #permalink

"The problem isn’t so much the speed and energy of these particles but rather the detector itself, there is a threshold where we can’t measure beyond"

Proof plz.

Einstein's box.

By Paul Dekous (not verified) on 11 Sep 2015 #permalink

He's dead. Einstein's box fell off within a couple of years being dead. It's well gone now.

I dunno, Ethan, you sound an awful lot like your own Kelvin quote. "Dark matter is a problem sure, but as best we can determine there is nothing beyond the standard model" is very analogous to "the blackbody radiation paradox is a problem, sure, but as best we can determine there is nothing beyond Newtonian mechanics and electromagnetism." The problem itself is a possible indication of something beyond your current model.

Or were you just making the pragmatic argument, that we've reached the limit of what current technology or even reasonably extrapolated future technology can discover? I would not even be too confident about that; technology development over the past century has been distinctly non-linear, I would bet dollars to donuts that a conservative extrapolation over what we can do in the next 50 years is going to miss *some* huge and impactful advance. Maybe it doesn't come in particle physics, but it'll come.

One thing we can be fairly sure of, though, is that the difference to what we can see and reach will be of approximately the same effect as the change from a simple oblate spheroid to a geoid with 12 axises to describe.

IOW it makes a lot of difference to people who want or need to be super accurate, but it's not making much difference otherwise.

A "Hey, isn't the earth round, not flat?" type change would be the result if we could find a way to make a wormhole or make a transporter or manipulate gravity.

That'll be a long time after a new paradigm arrives.

(see GPS that IS a concrete difference to society that totally relies on GR. and see how long it took between GR and GPS...)

@7: I agree, with a caveat. Yes any new physics will essentially be identical at human-level scales to what we have, and only differ from current theory mostly at the scale of the problems we can't currently solve. However, that doesn't mean that the new science will not practically impact the lives of laypeople. QM may only differ from NM on the approximate scale of atoms, but since we use it to help us build things like scanning electron microscopes, its still impactful. If quantum computing ever gets realized, it'll be even more impactful. Or as you mentioned, GR and a precise GPS system. An effect predicted by future science (but not by us today) doesn't have to be big or occur in standard human environmental conditions in order to be impactful on technology and human society.

Well, it's really more that any new thing will show the same as we see now, else it would not be concordant with reality as we know it now.

Only if found, raggie. Only if found, and with the predicted features.

@8: The Standard Model and QCD are 40 years old, since then no new theory has come out of particle physics and as Ethan points out nothing new will be found except some tiny details. This is a reality check.

We have UHECRs for reference, it's not like going the extra mile into the darkness and possibly bumping into something unique, (UHE)CRs are still way a head of the LHC and possible future colliders, and they're continuously smashing particles above us and there's nothing exceptional showing up.

If you wish you can keep on swinging the pendulum and make a bigger and bigger version but you won't find any new physics and theories by doing so ... we're not advancing here anymore ... just like people stopped flying to the Moon and NASA build instead the Space Shuttle and launched the Hubble telescope.

By Paul Dekous (not verified) on 11 Sep 2015 #permalink

"If you wish you can keep on swinging the pendulum and make a bigger and bigger version but you won’t find any new physics and theories by doing so"

Proof plz.

And no cryptic two word answer that conveys nothing other than you can google scientific names.

There are particles with any energy levels, up to their theoretical limits, already flying around in space.

What makes is impossible to send particle detectors to space and make observations there, instead of keep trying to build bigger and bigger particle accelerators on Earth?

Nothing. But the problem is detecting them enough times to know that they look a certain way as expected.

What makes is impossible to send particle detectors to space and make observations there, instead of keep trying to build bigger and bigger particle accelerators on Earth?

Off the top of my head? Low, uncontrollable, and varying flux, high background noise, and insufficient engineering expertise to keep the detection apparatus.up and running up there. Other than those problems, its a great idea! :)

I expect we'll try it at some point. You never really know if you're right until you do. But I think such efforts are low priority right now because our best scientific estimates are that they are endeavors that are considered to be more expensive and a higher risk of failure than the same experiment conducted down here on earth. That's just a guess though.

And of course things can change. If, for example, some gamma ray burst was to shoot through the solar system and coincidentally be close enough for us to get a satellite to it (but far enough away not to fry us), then yeah I bet we'd try to send something up there to study it.

@Frank #14 (and others): You wrote, "What makes is impossible to send particle detectors to space and make observations there, instead of keep trying to build bigger and bigger particle accelerators on Earth?"

What makes you think it's impossible? We have had many such detectors! An early one from the 1960's, the Vela satellites discovered gamma-ray bursts (GRBs). The Compton Gamma Ray Observatory (GRO). It's successor, the Fermi Gamma-ray Large Area Telescope is still flying. The AMS detector is installed and running on the International Space Station.

None of these are useful for looking at the highest energy cosmic rays. Why not? Because the amount of material needed to absorb, and thereby record, that energy is prohibitive. Instead, what we really do is use the whole planet (well, really the whole thickness of atmosphere) as our detector. Look up Fly's Eye, AGASA, and the Pierre Auger Observatory for existing examples, and CTA (Cherenkov Telescope Array) for a future proposal.

By Michael Kelsey (not verified) on 11 Sep 2015 #permalink

You may also want to Google 'Turning the Moon into a cosmic ray detector' and the SKA project.

"As the (UHE) rays hit the surface of the 19 million square kilometres near side of the Moon, they will give off bursts of radio waves which will be detected by the 33,0000 square kilometre giant Square Kilometre Array (SKA) spread across South Africa and Australia. In effect, this turns the Moon into the largest-ever reflecting telescope with the SKA array acting as the eyepiece."

By Paul Dekous (not verified) on 11 Sep 2015 #permalink

Thanks Paul for the "Turning the Moon into a cosmic ray detector" info, interesting.

By Ragtag Media (not verified) on 12 Sep 2015 #permalink

What I meant was a space-based detector designed for detecting new and unknown particles, just like LHC is designed for.
" Because the amount of material needed to absorb, and thereby record, that energy is prohibitive"
I think that would be the answer though.

If a new particle is discovered will it be called the "Jesus particle"
Ya know the Son Of God (Higgs) particle.. Rimshot...
Did ya here this one?
A Higgs boson goes into a church and the priest says, ‘We don’t allow Higgs bosons here.’ And the Higgs boson says, ‘But without me there is no mass.. Dadumdump..

Actually, should we be spending more on detectors instead of colliders since the Universe is pumping out some extremely energetic particles?

By Ragtag Media (not verified) on 12 Sep 2015 #permalink

We may have reached the practical limit of current accelerators but there's research into boosting particles with lasers or plasma instead of microwaves. Some experiments already have shown accelerations that if they could be extended would match the energy of the LHC over just a few tens of meters(!) There's hope that we can explore far enough into the "Energy Desert" to see if it's really empty.

By Michael Hutson (not verified) on 13 Sep 2015 #permalink

What's with that log-scale plot of the mass/energy scale? It's weird enough to show atoms as less massive than electrons, and molecules as less massive than atoms; it's just plain wrong to show "0" as an identifiable point on a log scale.

@Michael Hutson: That's an interesting lead, thanks! I found this after a quick search on the 'Plasma acceleration' wiki page:

"The Texas Petawatt laser facility at the University of Texas at Austin accelerated electrons to 2 GeV over about 2 cm. This record was broken (by more than 2x) in 2014 by the scientists at the BELLA (laser) Center at the Lawrence Berkeley National Laboratory, when they produced electron beams up to 4.25 GeV."

Curious if something like the 13 TeV from the LHC would be possible ... and if there would be something like a Moore's Law prediction graph for this kind of research with a doubling in speed every couple of years : )

By Paul Dekous (not verified) on 14 Sep 2015 #permalink

@Michael Hutson: Oh but than again with this method you probably can't create the large bulk of collisions with billions of particles colliding that is needed to create sufficient data/statistics.

By Paul Dekous (not verified) on 14 Sep 2015 #permalink

@Paul Dekous: I was under the impression that electron-positron collisions are "cleaner" than proton-antiproton, especially if the collision energy precisely matches the mass-energy of the particle you want to produce.If linear accelerators can produce PeV range collisions, it might be possible to trade quantity for quality.

By Michael Hutson (not verified) on 14 Sep 2015 #permalink

@Michael Hutson #27: e+/e- collision _are_ cleaner than p-p or p-pbar (I worked on the BaBar experiment at SLAC from 1996 to 2008).

The backgrounds are much, much lower; the events are "pure" in that every track comes directly from the interaction of interest and not from extraneous low-energy stuff; and the beamline components mostly develop short-term activation, not long-lived radioactive contamination.

There are two real downsides. As you go up in energy, you can't use storage rings for electrons. The synchrotron radiation goes like E^4, so past a few hundred GeV (the beam energy at LEP before it was converted to the LHC) your beams lose more energy than you can pump into them with RF. That means you're stuck with linear colliders, which means one collision per bunch (maybe more with energy recyclers), which is horribly inefficient.

Second, the cross-section falls logarithmically with energy, so as you push up to ILC energies (Higgs production) you need staggeringly small beams and precise steering and focussing optics to get anything at all. We had micron-diameter beams at SLAC (the PEP-II B Factory, at 10 GeV); I understand the ILC (half a TeV) expects to produce and collide _nanometer_ bunches.

By Michael Kelsey (not verified) on 14 Sep 2015 #permalink

Well, at least there are different proposals, such as Lee Smolin's and Roberto Mangabeira's concepts that differ from String Theory and it even looks like they can propose experiments that can be done with real, current science! So the news about the End of Physics seem to be premature!

By Rafael A Bernal (not verified) on 22 Oct 2015 #permalink