Exploring the Standard Model at the LHC

[dpackard]

So, what will we see at the LHC if the Standard Model is all that there is to physics at this energy scale? What if there is no supersymmetry, no strings, no loops (or at least no emergent behavior that would be seen here)? Are we going to be able to tell if those theories are false pretty immediately?

 

[Haelfix]

If they find a scalar higgs, that would complete the standard model. If they find nothing else it does falsify some models of supersymmetry, most technicolor models, some LeD models, but not all. What it does do is it removes the primary justification for things like 'low energy' supersymmetry in the first place. Namely as a mechanism to bypass the hierarchy problem.

In the words of a colleague, the hierarchy problem could become the hierarchy fact, and that could mean the end of particle physics as we know it (most people will assume we merely missed something due to experimental reasons). Theres not many 'simple' and elegant ways around that disaster scenario absent some really contrived scenarios that basically trade off undesirable attributes.

That scenario wouldn't say much at all about the state of string theory, or other theories of quantum gravity, but then again it wouldn't help clarify things either and we'll probably remain stuck in the hands of theorists.

 

[Poop-Loops]

So if the Higgs boson is found, then particle physicists can just go home?

Or is there a lot more to do? I mean, my professor is working on finding an Axion, so what would that do to the Standard Model if it were found?

 

[ZapperZ]

So if the Higgs boson is found, then particle physicists can just go home?

If only physics is that easy...

There's a huge amount of investigation to be done beyond just looking for the Higgs. http://www.nature.com/nature/journal/v448/n7151/full/nature06079.html" describes several of them, even if the Higgs isn't found. One should also consider that it is almost impossible to justify the building of a multi-billion dollar facility just to do ONE type experiment that we expect to yield just one result.

Besides, if all we care about is the finding of the Higgs, then why is Japan still committed in upgrading KEK and its B-factory? There's a lot more about elementary particles and the Standard Model that needs to be studied. The CP violation issue is still very much a hot topic, and the nature of the origin of the proton spin is still being debated. And then there's still a sector of QED that still needs to be studied and verified - the photon-photon collider.

If there's anything that I have seen in all the years that I've been involved in physics, as soon as you answer one question, a dozen more pop up. We will never run out of things to study.

Zz.

 

[malawi_glenn]

Also why the neutrino has mass, that is not a part of the standard model as far as I know..

 

[neu]

Obviously the LHC's purpose extends far beyond just proving/refuting Higgs theory, but would it not be somewhat "unfortunate" for the LHC developers if Higgs events where spotted at the Tevatron, which I believe is still possible if the Higgs mass is <130 GeV ?

 

[jtbell]

Also why the neutrino has mass, that is not a part of the standard model as far as I know..

As I recall, the Standard Model doesn't allow us to predict why quarks and leptons have their specific masses. The Higgs mechanism generates the masses, but with an arbitrary coupling constant which must be different for each particle in order to get different masses for each of them. (at least in the simplest version of the Higgs mechanism.)

So, originally we had the problem of why neutrinos should have exactly zero mass, i.e. why doesn't the Higgs interact with neutrinos? Now we merely have the problem of why neutrinos have so much smaller masses than the other fundamental fermions.

 

[Poop-Loops]

If only physics is that easy...

There's a huge amount of investigation to be done beyond just looking for the Higgs. http://www.nature.com/nature/journal/v448/n7151/full/nature06079.html" describes several of them, even if the Higgs isn't found. One should also consider that it is almost impossible to justify the building of a multi-billion dollar facility just to do ONE type experiment that we expect to yield just one result.

Well I knew LHC would be for more than just the Higgs, even if it was the main goal, but I wasn't aware that it was to find more particles or something.

the photon-photon collider.

I'm imagining two guys standing opposite each other in a hall-way holding flashlights.

If there's anything that I have seen in all the years that I've been involved in physics, as soon as you answer one question, a dozen more pop up. We will never run out of things to study.

Zz.

Yeah... but I guess I'm kind of worried that if they do find the Higgs boson and everything eventually turns out to be neat, it won't be as cool as if something like String Theory or something even more exotic were true, with like FTL travel, time travel, multiverses, etc.

I know I know, it's all far-fetched, but it's like your dad taking you to the dentist, and you hoping until you are sitting in his chair that at some point your dad will say "just kidding" and turn around and take you to Disney Land instead.

 

[ZapperZ]

Yeah... but I guess I'm kind of worried that if they do find the Higgs boson and everything eventually turns out to be neat, it won't be as cool as if something like String Theory or something even more exotic were true, with like FTL travel, time travel, multiverses, etc.

If they don't find the Higgs, String theory (or certainly flavors of it) might also be in deep doo doo.

If they do find the Higgs, I can almost guarantee that they'll find a lot more things they don't understand. Why do you think the ILC was proposed under the assumption that the LHC would have found the Higgs? Don't you think it is kinda strange to propose to build a $8 billion facility AFTER we have found the Higgs if there's nothing significant left to know and investigate?

Zz.

 

[Poop-Loops]

Gah, will this EVER end? Everything is just getting so complicated. Such and such particles, so many formulas, etc. Bleah.

But yeah, I can see what you are saying. Like the article you posted said, trying to persuade politicians to spend billions on a collider just to find one particle and then go home would not have worked.

So even if they find the Higgs, will other theories keep on chugging? Obviously the ones that depend on there not being a Higgs (if there are any) will die, but other theories will keep being worked on?

 

[malawi_glenn]

Gah, will this EVER end? Everything is just getting so complicated. Such and such particles, so many formulas, etc. Bleah.

ok, so you don't like the progress of science?

 

[Poop-Loops]

How did you extrapolate that from my comment?

I don't like how it's all getting complicated and seemingly unrelated. I guess I'd like some sort of easy to use formula or something. Thinking you are about to figure something out, only to find out you opened up 5 more questions is a bit disenheartening, you know?

 

[malawi_glenn]

How did you extrapolate that from my comment?

I don't like how it's all getting complicated and seemingly unrelated. I guess I'd like some sort of easy to use formula or something. Thinking you are about to figure something out, only to find out you opened up 5 more questions is a bit disenheartening, you know?

I think your sentence speaks for itself.

Why is it not good that things are complicated? By the way, Physics is about finding the symmetries. So in one way, elementary particle physics is the most naked thing you can study. If everythings was only "one simple formula" then things would probably been found today.

How many years have you studied physics?

 

[Poop-Loops]

Why is it not good that things are complicated?

What is this, a joke? Are you honestly asking why it's bad for something to be complicated?

By the way, Physics is about finding the symmetries. So in one way, elementary particle physics is the most naked thing you can study. If everythings was only "one simple formula" then things would probably been found today.

I thought the "one simple formula" has always been the goal.

How many years have you studied physics?

I'm a Junior now.

 

[malawi_glenn]

What is this, a joke? Are you honestly asking why it's bad for something to be complicated?



I thought the "one simple formula" has always been the goal.



I'm a Junior now.

One UNIFIED theory is the goal.

But it does not imply its going to be an easy one, and that not alots of formulas etc are given.

For example the standard model of Elementary particles as it is today, isn't something you can grasp until graduate studies etc. Very diffcult math and so on. (I mean, try study a book called "Introduction to the standard model och particle physics", and then you'll see that a lots of thins are needed to just understand the very first pages). And depending on which particles you are looking at etc, you have different equations. But the theory is based on one simple symmetry argument.

Of course the more elegant a solution is, the better there is. But don't mix "elegant" with simple.

 

[Poop-Loops]

So it doesn't bother you at all that there is more and more stuff you have to memorize, understand, etc, about a given field before you can add anything to it?

I picked up "Intro to Particle Physics" by Griffiths and quickly put it back down. It's beyond me at this point.

 

[malawi_glenn]

So it doesn't bother you at all that there is more and more stuff you have to memorize, understand, etc, about a given field before you can add anything to it?

I picked up "Intro to Particle Physics" by Griffiths and quickly put it back down. It's beyond me at this point.

Nope, that's why I think it is so fun with modern physics=)

Intro to particle physics by griffiths is also perhaps the easiest book you can study, it is written for undergraduates.. so Iam at that level now.

My approach is, the more I learn, the more I also realize that there is more to be learned. And that nature is so exciting and wonderful. Thats why I enjoy modern physics, it is very demanding on the same time as it is very symmetric and beatiful.

As Zapper said, when we find something new in our experiments, we find also new things that we had no idea that they should exist. So this is the way science goes, it is about exploring the universe: both large scales and on small scales. And something that we find might be useful in a technological sense, and the other things adds new things in our culture and world view.

 

[MadScientist 1000]

Nope, that's why I think it is so fun with modern physics=)

Intro to particle physics by griffiths is also perhaps the easiest book you can study, it is written for undergraduates.. so Iam at that level now.

My approach is, the more I learn, the more I also realize that there is more to be learned. And that nature is so exciting and wonderful. Thats why I enjoy modern physics, it is very demanding on the same time as it is very symmetric and beatiful.

As Zapper said, when we find something new in our experiments, we find also new things that we had no idea that they should exist. So this is the way science goes, it is about exploring the universe: both large scales and on small scales. And something that we find might be useful in a technological sense, and the other things adds new things in our culture and world view.

Yeah, but wouldn't it have been nice to find an easy way without a lot of complexities?

Well, hopefully the LHC will start firing in May without any more structural issues.

 

[malawi_glenn]

Yeah, but wouldn't it have been nice to find an easy way without a lot of complexities?

Well, hopefully the LHC will start firing in May without any more structural issues.

It depends on how you define "complexites".

 

[Poop-Loops]

The whole field of particle physics is complex. How many particles are there, exactly? There are 6 quarks alone, with things like flavor, strangeness, color, etc.

If you don't think all of that makes the field complicated, then you simply don't understand the meaning of the word "complex".

 

[malawi_glenn]

The whole field of particle physics is complex. How many particles are there, exactly? There are 6 quarks alone, with things like flavor, strangeness, color, etc.

If you don't think all of that makes the field complicated, then you simply don't understand the meaning of the word "complex".

All those attributes are due to very elegant symmetries, so in my opinion it is not complex.

I mean, are you asking for an equation like F = m*a, then you are not even close.

Symmetries are not complex, they are probably diffucult to understand but not complex.

This is perhaps what scares people of physics, that the theories are really hard to understand and one needs lots of math.

My field is many body systems, as atomic nuclei and hadrons, THERE we can start talking about complexities ;)

 

[Barmecides]

Obviously the LHC's purpose extends far beyond just proving/refuting Higgs theory, but would it not be somewhat "unfortunate" for the LHC developers if Higgs events where spotted at the Tevatron, which I believe is still possible if the Higgs mass is <130 GeV ?

Yes Tevatron is close to start excluding part of SM Higgs mass range, but mainly around 160 GeV/c2 first (due to H->WW* decay in that region).

 

[vanesch]

If only physics is that easy...

There's a huge amount of investigation to be done beyond just looking for the Higgs. http://www.nature.com/nature/journal/v448/n7151/full/nature06079.html" describes several of them, even if the Higgs isn't found.

Now, that's a very very good article! So it seems that 2008 is the year ! Finally some experimental data on 30 years of speculation...

 

[vanesch]

If they don't find the Higgs, String theory (or certainly flavors of it) might also be in deep doo doo.

In as much as I understand anything of this, String theory needs supersymmetry. So even if a higgs turns up, if no supersymmetry turns up, then this will be a problem for string theory. And if supersymmetry is observed, then this will probably be a boom comparable to the "hadronic explosion" of the 60ies!

This is why this LHC is so important: finally some experimental constraints!

 

[malawi_glenn]

Now, that's a very very good article! So it seems that 2008 is the year ! Finally some experimental data on 30 years of speculation...

when does the data analysis beging?

 

[Barmecides]

Now, that's a very very good article! So it seems that 2008 is the year ! Finally some experimental data on 30 years of speculation...

Tou look very optimistic...
2008 is LHC startup (and not more !). Remember the first years of Tevatron run 2 startup...
2009 and 2010 might be much more interesting if startup succeeds.

 

[staf9]

One UNIFIED theory is the goal.

But it does not imply its going to be an easy one, and that not alots of formulas etc are given.

For example the standard model of Elementary particles as it is today, isn't something you can grasp until graduate studies etc. Very diffcult math and so on. (I mean, try study a book called "Introduction to the standard model och particle physics", and then you'll see that a lots of thins are needed to just understand the very first pages). And depending on which particles you are looking at etc, you have different equations. But the theory is based on one simple symmetry argument.

Of course the more elegant a solution is, the better there is. But don't mix "elegant" with simple.

And even when we find that one unified theory, it will definitely pose many, many more questions than we already have.

With every question answered, we find more and more things that we don't know about

As for string theory: if we don't find the higgs, bosonic string theory will be up the creek without a paddle. Still, string theory comes in a variety of flavors and it seems like a near-impossible task to prove or disprove all of them.

Got another LHC question though that I'm sure someone here can answer: with the LHC will we be able to find/prove spin direction in fermions? And speaking of string theory, would we be able to prove the existence of tachyons with the LHC? Since they are supposedly FTL I can't think of any way of proving or disproving them.

 

[EL]

In as much as I understand anything of this, String theory needs supersymmetry. So even if a higgs turns up, if no supersymmetry turns up, then this will be a problem for string theory.

Even though string theory requires supersymmetry, it does not need low energy supersymmetry. It could as well be at much higher scales.
Low energy supersymmetry is mainly motivated by the hierarchy problem, the dark matter problem, and unification of gauge couplings at the GUT scale.

 

[CJames]

At this point it is my understanding that their is nothing that can disprove string "theory."

 

[Rade]

Here is a video on the LHC:
http://www.youtube.com/watch?v=67q_...sics-mathematics/13393-lets-talk-higgs-2.html