# Why was confirming Higgs mechanism worth it?

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1. May 16, 2014

### jon4444

I'm just looking for a layman's explanation of why the efforts to confirm Higgs was truly necessary and worth the expense. The counter-argument is that theoretical physics seem to be going along just fine assuming something like the Higgs mechanism existed without validating it. Also, nothing seems to have been actually "discovered"--this wasn't pure research in the sense of let's do this experiment and we're really not sure what we'll find. Most people seemed to expect the results that came out.

So without an answer resorting to waxing philosophical about pure science (or, more likely on the internet, how mortals can't understand these things), I'd appreciate a reasoned argument about why it was worth it (compared to, say, using the resources to further fusion research to address global warming.)

2. May 16, 2014

### Bill_K

No, on the contrary, there was a great deal of speculation what might turn up. The Higgs mechanism is a radically different idea, and there were many alternatives proposed, in which there were several Higgs particles, or none at all. We are still somewhat surprised at the value of the Higgs mass, which lies on the borderline of the range that's predicted to be metastable.

Most importantly, although the search for the Higgs boson gets most of the press, the LHC is really about looking for any other particles that might exist in that energy range.

3. May 16, 2014

### phyzguy

I don't think it is an either/or proposition. Fusion research is ongoing, both magnetic confinement (look up ITER) and inertial confinement (look up the NIF). It's not clear to me that spending more money on these programs would make them go much faster.

4. May 16, 2014

### ZapperZ

Staff Emeritus
The thing about science is that, until there is a clear experimental verification, ALL theory is just a "hypothesis"! Just because someone famous, clever, and well-known proposes it, scientists won't consider it to be valid until there is experimental validation.

The Higgs mechanism is an essential aspect of the Standard Model of particle physics. If it is not verified, then there's something fundamentally wrong with the Standard Model. This is crucial either way because the Standard Model is how we describe all fundamental particles so far.

Secondly, a large part of doing the experiment is in determining the mass of the Higgs. This is NOT KNOWN precisely because the theory itself allows for a huge range of possible mass. Earlier experiments at the Tevatron and other facilities have ruled out large ranges of mass where it could be found, so by the time the LHC was operational, they have a narrower range to look for. Determining the mass of the Higgs is crucial because a lot of other theories (including Supersymmetry) builds on top of the knowledge of this mass, the same way the Higgs other others are more easily studied because we know more precisely the mass of the Top, Strange, W, etc... So there is a quantitative aspect that can only be answered by experiment. This is an important discovery!

Finally, you seem to have a dismissive attitude about experiment in general, which is sad because this is what makes science, SCIENCE. While a large part of the general public seem to accept things just because they are told of something without seeking any evidence for their validity, science can't do it that way. Before something is accepted, it must be verified experimentally. I suggest you read this:

http://blogs.scientificamerican.com...ics-is-there-an-experimentalist-in-the-house/

Zz.

5. May 16, 2014

### George Jones

Staff Emeritus
As a mild example of what Bill said, David Griffiths in his much-used text "Introduction to Elementary Particle Physics" wrote

Here, MSM stands for Minimal Standard Model, branching ratios give the probabilities of various decay modes for Higgs.

Without experiment, how would we know which Higgs, if any?

6. May 16, 2014

### Staff: Mentor

The search for the Higgs was a major goal of the LHC, but it was just one of many interesting points. Some more:
• Do precision measurements with the new particle to verify it behaves like the standard model Higgs boson
• Look for other Higgs-like particles
• Search for supersymmetry and a large collection of other models of new physics
• Do precision measurements with existing particles to check the standard model, and to look for possible deviations there (those are indirect searches for new physics)
• Study heavy-ion collisions
• ...

7. May 16, 2014

### ChrisVer

First of all, CERN LHC is not all about Higgs. There are a lot of other stuff going on in there, which seek for different answers.
But my main problem is that I don't understand your question. A theory always seems to work fine, this doesn't mean it's true - not until it's verified by experiment...Unfortunately the seek for Higgs wasn't fruitful in previous accelerators, although there have been a lot of work which cannot be denied. Also, the Higgs mass was important for the theory for standard model as well as the theories beyond the Standard Model (eg Minimal Supersymmetric Standard Model)... but let's stay in the SM- there you have some parameters, one of which was the $λ$ for the $\phi^{4}$ interaction of the Higgs as well as the $\mu$ of the $\phi^{2}$ interaction- these parameters were free- before knowing the Higg's mass we couldn't work explicitly their values.... Now because of knowing the Higgs mass and the electroweak scale we can find $λ$ and try to give some answers about its evolution. One reason Standard Model is not considered a complete theory is because of its many free parameters which need experiments to be determined...
Nevertheless, the CERN is not only about the Higgs- apart from ATLAS there are also 3 other major programs each searching its own stuff....

If CERN could not find at least the standard model higgs, things would have to change a lot...But when you are searching for something, you are going on a travel on a terra incognita...the only guide you have, are the hypothesis/theory some people proposed behind... I am not sure if the researchers were sure they'd find Higgs, but they were pretty comfortable when they got a signal to publish a paper (2 papers) speaking of a new particle which seemed to be the Higgs particle.

Now was it worth the expenses? The whole idea is not just looking for the Higgs particle so that a bunch of physicist would fulfill their curiosity ... you know, nobody will give you money as a sponsor to see you happy with finding, a useless to him, particle... The whole program has offered a lot of new technology... From how to construct the facility (building underground, superconducting technology at a large scale etc etc) up to saving the data on the computers.... Never forgetting that "www." was invented at CERN, so the internet we've been using is a result of the experiment's needs.... and many other things I might be forgetting....

Last edited: May 16, 2014
8. May 19, 2014

### nikkkom

We know from the past that better scientific knowledge has real-world benefits.

Another thing we know from the past is that it's not untypical for those benefits to be the result of unexpected branches of sciense. Say, a discovery in chemistry can help to make computers faster by x10 (or x1000).

That's why governments and corporations are giving big money for research even in some cases where there is no obvious practical benefit for that particular research area.

Finding (or disproving) Higgs per se is very interesting only for physicists. The rest of society agrees to spend \$ on this because better understanding of particle physics *may* bring some unexpected practical benefit. Do you want humans to discover, say, faster-than-light travel or at least FTL comm? Or a way to convert any matter to energy (the ultimate solution to energy needs)? Maybe something like that *is* possible, we need to know more to find that out.

Of course, it may happen that at some point new experiments needed for further advances in particle physics will become so outrageously expensive (e.g. "a collider as big as Moon orbit") that humanity will decide not to finance them. We are not there yet.

9. May 19, 2014

### Staff: Mentor

I would say "we don't know". In the worst case, we found all particles below something like 10^16 GeV now - and we have no way to reach this energy with current technologies. There could be new particles at lower energies, but current measurements can't make a clear prediction.

There is a concept of an even larger accelerator at CERN to achieve an energy of roughly 100 TeV, but if the LHC and the planned ILC don't find anything really new I doubt it will get funded.
This was different for the LHC, where either the Higgs or something else had to be there.

10. May 19, 2014

### ChrisVer

Well the dessert between ~103 GeV and 1016 GeV is an assumption, the experiment may prove that somewhere we did wrong, and something else exists (leaving aside the rest of searches that go on).... Also in general, we still need to search for supersymmetric particles at those energies...indeed the measurements don't show anything so far, but there should be a more sophisticated approach in the analysis.

In my opinion, before LHC gets enough data and reaches its "endpoint" there won't be a new/larger accelerator. Propositions are accepted on the table, and there will certainly be more to come. However, when there is a worldwide colaboration taking place, someone has the right to make something bigger but cannot operate it, not until the first stops... (wasn't that the reason Fermilab closed? -maybe I'm wrong in this one)... Everything else that can be built, will have to propose some reason of existing/ a plan of research.

11. May 19, 2014

### Staff: Mentor

There could be new particles, sure, but building an accelerator for 105 GeV just covers a tiny fraction of the range between 104 GeV (=LHC next year) and 1016 GeV (inflation/GUT/?).

The ILC maybe. Assuming ~10 years construction time starting in ~3-5 years, it could start in the late 2020th, a bit after the HL-LHC starts to take data.
Even if it starts after the LHC gets shut down, there will be an overlap in terms of physicists, as planning and building the detectors needs years in advance (they are working on it already) and analyses always need some years after the running periods. As an example, the analysis of HERA data is still ongoing, and it shut down in 2007.

Fermilab is still open, just the large accelerator here (Tevatron) was shut down as it did not get enough funding (and it was clear that the LHC will produce much better results in most analyses).

12. May 20, 2014

### Bill_K

The Résonaances blog once reported on the shutdown:

I'm sure this account is totally unfounded - at least the part about the rolls of paper.

But what has happened to the Tevatron physically? Has it actually been dismantled and sold for scrap? Are there any plans to reuse the site?

13. May 20, 2014

### Staff: Mentor

Sure
The long baseline neutrino experiment seems to get the most attention, at least according to what I see.

14. May 21, 2014

### Bill_K

The FCC ("Future Circular Collider"), as seen here and here.

There are three ideas under study:

FCC-hh -- an 80-100 TeV pp collider, operational 2035-2040, using 16-20 T Nb3Sn magnets
FCC-ee -- electron-positron two-ring collider, energy tunable to Z pole, WW, H or ttbar
FCC- he -- electron-proton collisions