Discussing the Future of CERN and Particle Physics in General

[voyager77]

Where do you see Particle Physics/CERN heading in the next 50-100 years?

What will come after the LHC? What research will come after the completion of the ATLAS, ALICE, CMS, and LHCb experiments?

How will the discovery of the Higgs Boson impact research in other areas of physics, both theoretical and experimental?

 

[JustinLevy]

This is a fairly pessimistic answer, but answering truthfully I'd guess:
With the energy crunch surely to arrive in the future, I think economies will be quite stressed during the transition and the public will not be interested in funded a yet larger collider.

Hopefully someone else believes something more optomistic, and will share to balance this out.

 

[humanino]

I believe we will have tabletop accelerators routinely used in medical applications, labs in school, border checkpoints, and the accelerator gigantism (not necessarily detectors !) will only be memories of the past.

Many people also think that very high energy is not the entire story anyway. There are already labs investing in intermediate energies, where non-perturbative QCD might still have some surprises for us in her pocket.

 

[vanesch]

Difficult to say ! In a way, this will probably depend on what's found at the LHC. I guess the worse would be that the LHC just finds some kind of vanilla Higgs, period. It would be hard to justify yet another big expense for a bigger machine then. The "it's just around the corner" argument will have been over used.

On the other hand, if the LHC comes up with new stuff, especially unexpected new stuff, and opens a totally new window on nature, then I guess it won't be so hard to convince the public sooner or later to build something bigger.

The funding of such machines is not as big a burden as one may think. There is ONE LHC, and it is the machine that will occupy particle physics for decades. If you take smaller-scale science but which is done in thousands of labs all over the world, then integrated over space and time, this is often more expensive than particle physics, but it doesn't show as much.

 

[ZapperZ]

As far as I know, the International Linear Collider (ILC) is the only proposed particle collider machine designed as the next logical step after the LHC. This facility has been estimated to cost roughly $10 billion in its initial Global Design.

Unfortunately, with the pullout of the UK, and the US cutting funding to it during the last fiscal year budget, its future is not looking too good for this project. Fermilab has proposed its "Project X", but this is more of a stop-gap measure (at least from the people that I've talked to) designed to keep the Main Injector going during the period after the shutdown of the Tevatron and the actual decision on when/where to build the ILC (which they hope will be there).

Zz.

 

[Vanadium 50]

First, vanesch is right. Particle physics appears expensive because there are a small number of large projects rather than the reverse. The total US HEP budget is something like $600M, and there are probably 6000 or so scientists in the US (that's the rough membership of DPF). So that's $100k/year/scientist.

NIH has a budget of around $30B, and claims to support ~300k scientists. That's again about $100k/year/scientist.

Second, it's hard to project a century out. If you had asked a physicist around 1900 what instruments would be used in a century, he might have said "better cathode ray tubes". And the LHC is in fact an offshoot of that technology. But I doubt it would have been recognizable as such in 1900.

Third, it's hard to see where you are going when you don't know where you are. The outcome of the LHC will clearly influence the direction of the field - one of the problems of the ILC was the decision to design it before LHC results, a decision the proponents are paying for now. If the LHC discovers some but not all of the particles of supersymmetry (or at least particles that look supersymmetric), the next step is a larger accelerator: whether it's a lepton or hadron collider would depend on what was seen and what could be inferred about the SUSY spectrum. If the LHC discovers a single scalar Higgs and nothing else, pushing up in energy becomes much less well motivated, and experiments doing precision physics, flavor physics and/or neutrino physics will become more appealing.

 

[ZapperZ]

First, vanesch is right. Particle physics appears expensive because there are a small number of large projects rather than the reverse. The total US HEP budget is something like $600M, and there are probably 6000 or so scientists in the US (that's the rough membership of DPF). So that's $100k/year/scientist.

NIH has a budget of around $30B, and claims to support ~300k scientists. That's again about $100k/year/scientist.

I think this hasn't been emphasized enough to many people, that the NIH budget towers over the budget of ALL of physics, not just HEP. So yes, while these are expensive machines to build, in the scheme of things and when looked at over how many years it is spread out, the cost does not even compare to the yearly budget of many areas of the US Govt (we won't even get into the amount spent on the military).

I would also like to point out that the NIH benefits from many of the spending and development done in basic physics. The clearest examples that I can give is the use of various synchrotron radiation centers, which is funded out of DoE Basic Energy Sciences division, and the use of proton therapy, which obviously came directly out of high energy physics/accelerator physics. These were not research that were funded out of NIH money, but they certainly reap the rewards for it after all the ground work had been done. It is why many in the NIH and in the medical industries are also urging the increase in funding for DOE and NSF. Advances in the basic physics areas DO trickle down into advances in medical/biological fields.

Second, it's hard to project a century out. If you had asked a physicist around 1900 what instruments would be used in a century, he might have said "better cathode ray tubes". And the LHC is in fact an offshoot of that technology. But I doubt it would have been recognizable as such in 1900.

Third, it's hard to see where you are going when you don't know where you are. The outcome of the LHC will clearly influence the direction of the field - one of the problems of the ILC was the decision to design it before LHC results, a decision the proponents are paying for now. If the LHC discovers some but not all of the particles of supersymmetry (or at least particles that look supersymmetric), the next step is a larger accelerator: whether it's a lepton or hadron collider would depend on what was seen and what could be inferred about the SUSY spectrum. If the LHC discovers a single scalar Higgs and nothing else, pushing up in energy becomes much less well motivated, and experiments doing precision physics, flavor physics and/or neutrino physics will become more appealing.

The problem right now is that, based on the history of the development of these huge facilities, there usually is the planning of the next facility after the commissioning of the newest one. After LEP went online, the HEP community planned on the Tevatron. When the the Tevatron went online, the HEP community then set out to plan for the LHC. Now, with the LHC about to go into operations, there's no clear project on the next HEP machine. The ILC is in critical condition based on what I've said earlier, with the burden being carried by Europe (sans the UK), Japan, and China.

The reason why HEP machines are usually planned as soon as the new one goes online is because of the extremely long and tedious planning stage. It can take a decade or more to really come up with the design, cost, etc for one of these monsters. So just as when the Tevatron has reached its limit, and we have squeezed as much as we can out of it, the LHC takes over. Eventually, the LHC will also reach its limit and the community will now have to go to the next step. Without advanced planning starting now, and with the cost and complexity being considered, it will take 10 to 15 years to plan on such a machine. That's a long lead time.

It is why the ILC planning is going done now, even before one actually sees a single result coming out of the LHC. But with the delay in a decision on whether to build such a thing by the DoE (postponed to at least 2025), we may have a gap where the ceiling will stay fixed for a long time.

Zz.

 

[Vanadium 50]

ZapperZ, while your timeline isn't quite right (LEP and the Tevatron ran at the same time) I understand the desire to get building the next machine right away. The problem with e+e- machines is that they have a hard limit on the mass of what they can produce, and if the physics you are interested in is above that, tough. A number of e+e- colliders were built to discover the top quark, but none had enough energy. It might be worth $100M to gamble this way, but $10B is, as they say, real money.

So, let me propose a scenario. A 500 GeV linear collider is built, expandable to 1 TeV, at a cost of $10B. The LHC discovers a Higgs boson at 750 GeV, and a gluino at 650 GeV, but no squarks or gauginos light enough to see. Now you have a clear path forward - you need a hadron collider with higher energy than the LHC, but you've just spent $10B on a white elephant: a linear collider that has nothing to see.

 

[ZapperZ]

ZapperZ, while your timeline isn't quite right (LEP and the Tevatron ran at the same time) I understand the desire to get building the next machine right away. The problem with e+e- machines is that they have a hard limit on the mass of what they can produce, and if the physics you are interested in is above that, tough. A number of e+e- colliders were built to discover the top quark, but none had enough energy. It might be worth $100M to gamble this way, but $10B is, as they say, real money.

So, let me propose a scenario. A 500 GeV linear collider is built, expandable to 1 TeV, at a cost of $10B. The LHC discovers a Higgs boson at 750 GeV, and a gluino at 650 GeV, but no squarks or gauginos light enough to see. Now you have a clear path forward - you need a hadron collider with higher energy than the LHC, but you've just spent $10B on a white elephant: a linear collider that has nothing to see.

From everyone that I've chatted with who happened to work at ATLAS, they all seem to think that a lepton collider is definitely needed to figure out some of the stuff that came out of the LHC. Many people expect that while they can resolve some things, there will be other aspect that cannot be resolved until one get a "cleaner" signal coming out of such a lepton collider. That was one of the major selling points of the ILC.

I'm ambivalent about the whole thing. While I do work in accelerator physics (and not HEP), the technology that I'm working on isn't ready to be used by the ILC even if gets built. So I really have no desire one way or the other to see it built now. Who knows, if we get lucky, one of the new acceleration mechanism that many of us are working on right now may be mature enough to be implemented by 2025 if it gets built then.

Zz.

 

[hamster143]

So, let me propose a scenario. A 500 GeV linear collider is built, expandable to 1 TeV, at a cost of $10B. The LHC discovers a Higgs boson at 750 GeV, and a gluino at 650 GeV, but no squarks or gauginos light enough to see. Now you have a clear path forward - you need a hadron collider with higher energy than the LHC, but you've just spent $10B on a white elephant: a linear collider that has nothing to see.

Firstly, if I'm not mistaken, 750 GeV Higgs would require nontrivial physics, b.c. for example SM Higgs above 250-300 GeV is excluded by precision measurements of electroweak parameters and t mass.

Secondly, how can you ever be sure that there's no squarks or gauginos left to see below 1 TeV? Maybe there's some stuff left but it's too weakly coupled to ordinary matter to see.

 

[Haelfix]

Yea there is an argument to be made that the ILC's design is premature by about 6 years. Its worth waiting to see what the LHC sees, and then tailor the next accelerator at figuring out what to make of it. 30 years is a long time, and that's not even counting any advances made in that time.

 

[Vanadium 50]

ZapperZ, I deliberately cooked up a scenario where the lepton collider in question was not the ILC, and indeed, there is no way to tell exactly what you would need. A lepton collider is fine for producing charged particle pairs, but note that everything that will have been seen in my scenario was neutral.

Hamster, the electroweak radiative correction limits are assuming no other particles. The scenario I cooked up has supersymmetry, so you have other particles. It's true that under minimal supersymmetry, you get a lighter Higgs, not a heavier one, but all this means is that if the data turned out as I described, reality would be more complicated than our simplest theories. I would even suggest that would make things more interesting rather than less.

In the scenario I described, you would know you were missing squarks by failure to see them in gluino decays: \tilde{g} \rightarrow \tilde{q} + \overline{q} and missing charginos by failure to see them in direct searches. You would see neutralinos, or at least the LSP, but that doesn't help you motivate a lepton collider of a particular energy.

 

[jal]

It’s only +800 pages.
http://arxiv.org/abs/0809.1869
Physics at BES-III
This physics book provides detailed discussions on important topics in $\tau$-charm physics that will be explored during the next few years at BES-III.

 

[Coin]

I believe we will have tabletop accelerators routinely used in medical applications, labs in school, border checkpoints, and the accelerator gigantism (not necessarily detectors !) will only be memories of the past.

Many people also think that very high energy is not the entire story anyway. There are already labs investing in intermediate energies, where non-perturbative QCD might still have some surprises for us in her pocket.

How would the requisite energies be reached with "tabletop" style accelerators, without the large tracks the current particle accelerators use?

Or are you suggesting that if "intermediate" energy is all that's needed then tabletop tech is enough?

 

[vanesch]

How would the requisite energies be reached with "tabletop" style accelerators, without the large tracks the current particle accelerators use?

The large size of current accelerators comes from the fact that the E (and B) fields are, due to material constraints, limited to certain values. In plasmas it is in principle possible to reach much much higher field values (especially E). There have been experiments where lasers make plasmas which accelerate particles on scales much smaller than a conventional accelerator would need.

See http://en.wikipedia.org/wiki/Plasma_acceleration

"tabletop" is maybe a bit ambitious for a multi-TeV accelerator though