LHC Q&A

Yet another LHC thread? Well, simply put, there are so many already that I couldn't pick one, so I figured I'd start anew.

I'm a physicist, currently not working in particle physics, but did my masters project at CERN, so I just wanted to address some of the misconceptions that seem to be flying around here to the best of my ability.

1. What exactly will happen later today (10 September)?
   
   A circular accelerator operates by circulating two beams, one clockwise and one counterclockwise. By focussing the beams at specific points, it is possible to control where collisions occur. Today, one beam will be put into the ring, which amounts to a final test of all the components that are used to control particle trajectories. If all goes well, the opposite beam will be input by as soon as the end of the week. This will result in the odd collision here and there, but no serious data will be produced. During the following weeks, the focussing systems will be "tuned" to achieve high collision rates at the detector sites. If I understand this correctly, there are maybe a dozen accelerator physicists worldwide who have specialized in tuning, and whenever a new collider goes online a few of these guys are flown in and treated like royalty by everyone - including directors and nobel laureates - while applying their arcane art (i.e. fiddling with controls).
   Substantial collision rates and serious data taking will begin either once tuning is complete or directly after the official inauguration (end of October), whichever is later.
   
   
2. Will the world end in October, then?
   
   Nobody really knows what we will be seeing, that's the whole point of building such a costly machine. There are a number of reasonable expectations, based on extrapolations and generalizations of current theories, based on data obtained from earlier, lower-energy experiments. So, nothing can be ruled out a priori either.
   However, as has been stated many times, nothing that happens at LHC doesn't happen in nature (in space) all the time, and at yet much higher energies (typical ultra-high-energy cosmic rays are a million times as energetic as LHC protons). The reason for recreating these events in a controlled fashion is simply to enable us to put the detector in the right place. So, all reason suggests that if something catastrophic could occur, it would have occured naturally long before now.
   
   Finally, one shouldn't lose sight of the fact that the thousands of people directly involved with the project are, well, people. They may be invested in the work, but they certainly don't want to die, let alone bring about the apocalypse. They are the ones with the best grasp of the subject matter, and if they had any serious misgivings, they would not go ahead. There surely are some nutty scientists among them (one of my favourite CERN-tales is about a Russian guy who routinely used to stick his head into the beamline to see if the beam was on, which works by virtue of the particles causing scintillation within the eyeball), but most of them are both sane and conservative in taking risks.
   
   
3. Are there any ulterior, or even sinister, motives at work?
   
   Not that I can discern. The project is the natural next step in the evolution of particle physics experiments, I'm not aware of anyone involved expressing surprise at any of the design features. The cost of the project, on the order of five billion euros, may seem excessive at first, but considering that this is a 25-year project with on the order of ten thousand scientists involved, this breaks down to twenty thousand euros per person per annum, which is not at all unusual.
   No immediate payoff in terms of useful technological results is expected, and while everyone expects payoff in terms of scientific progress, what direction this progress will take is uncertain, as mentioned above. Hence, suspicions of any sort of "advanced weapons research" agenda seem very far-fetched.
   
   
   [edit on 9-9-2008 by TeraBlight]

[continued in new post due to character limit]

If you have further questions, I'll do my best to answer them, just bear in mind that I'm neither a specialist in theoretical particle physics nor have been involved in the LHC project in the last five years.

And don't forget to be excited about all this, even if you have misgivings!

[edit on 9-9-2008 by TeraBlight]

reply to post by TeraBlight


Good thread, but because it's actually filled with facts and reason...most won't be interested.
You need to fill it with doom and gloom..and spruce up the title to "Death from the LHC" or something.

But in all seriousness, good thread.

[edit on 9/9/08 by blupblup]

I agree with Blupblup. Excellent thread, thanks for posting it.

Sorry for a question that has probably been asked a million times, but what, exactly, is the main goal of this project in your own words ?

What are the plans when (if) they don't find what they are looking for? Obviously to get the data necessa4ry to build new models they need to do many repeated collisions and the data collected will take years to process. But what then?

Oh yes, and thank you for not posting another end of the world thread. They are very annoying.

[edit on 9/9/08 by Shere Khaan]

if the LHC fails to work for some reason, whats plan B? [-if you have any inside scope-]

OP , was a great idea for getting rid of the "Doom-Gloom" scenarios!!

There are very many "Un" seen scenarios that are being dubbed into the catagory of "Possible failures of the LHC" and they do have many "Counter actions" for the LHC device, which also falls "Beyond the design cases" for explanation, and yet there is no direct explanation of the systems cooling deice (Cryo-chambers) and the event that there is not a possible explanation of the cryo-tanks being able to hold there basic objective of temp controls.

So, I guess you could say I am asking "What if the cooling systems fail and the entire 17 mi. of conductive area is unable to 'chill' itself for containment?"

Sorry about some sp?

what could finding the god particle lead to?
any possible practical applications for it?

Originally posted by Alora
what, exactly, is the main goal of this project in your own words ?

Hmmm... I'll try and make it as general as possible:

Matter is by far the most interesting subject of study in the natural sciences, because, unlike say energy and spacetime, it has structure. To date, all experiments suggest that all characteristics of material objects can be understood by understanding how the basic constituents of an object function. To paraphrase the saying, it seems that matter is precisely the sum of its parts, and no more. Thus, the study of these constituents, the elementary particles, called particle physics, is the most important foundation block of all natural science.

Now, study of elementary particles requires high energies, for three principal reasons:

• At terrestrial conditions, matter mostly occurs in the form of molecules, which are annoyingly complex objects. But, as well all know from everyday experience, we can break objects into fragments by smashing them together. Smash two molecules together with sufficient energy, they break down into atoms. More energy, the electrons come off and we get to see the stripped nucleus. More energy, the nucleus disintegrates into protons and neutrons.
  
  
• Now, it turns out that by increasing the energy further, we don't manage to break up protons. But, eventually, we observe something that we're not familiar with from everyday experience, namely that if we smash hard enough, things come out of the collision that didn't go in. Basically, this would be equivalent to crashing two cars into each other with enough speed, resulting in two crunched-up cars and two motorcycles. The reason this happens is that at a microscopic scale, energy and matter can be converted back and forth, famously expressed as E=mc^2. So, by smashing two protons into each other hard enough, you can end up with two protons and one (or many) extra particle pairs. These particle pairs occasionally turn out to be things that we don't ordinarily find in nature. By observing these, we can build a more comprehensive theory of elementary particles and their interactions than based on observing just naturally occuring ones. One of the things that people are excited about when it comes to LHC is that for the first time, the collisions will be energetic enough to produce the predicted Higgs-particle.
  
  
• The last aspect is much less tangible than the two previous ones, but is also the most fascinating for many. At everyday energies, we observe four forces which all behave quite differently: Gravity, electromagnetism, and two nuclear forces that have no large-scale effects. The way in which particles react to these forces depends on their charges. The electrical charge is well-known, the two nuclear forces have similar charges (one of them is called "colour charge", because whereas the electrical charge has two aspects, labelled positive and negative, this one seems to have three, labelled "red", "green" and "blue". Mass can be thought of as a particle's gravitational charge.
  The fascinating thing is that the forces suddenly begin to exhibit parallels and eventually become indistinguishable from one another as the particles subject to them become more energetic. As it is assumed that the universe was initially at a high-energy state, from which it expanded and "cooled down" to its current state, it follows that in this initial state there was just one unified force. As certain threshold energy levels were reached, the forces separated one after the other in a process called "symmetry breaking". It is thought likely that once we manage to recreate and fully understand this process, we will have a much better handle on not only particle physics but also many cosmological puzzles which stem from this early period of the universe.
  

Sorry, didn't mean for this to get this long, hit the character limit again.

Originally posted by Shere Khaan
What are the plans when (if) they don't find what they are looking for?

It's not really that sort of search. It's not like looking for a treasure chest, and if it's not there, you've failed. Instead, it's like climbing up to a ridge to get a look at the valley beyond. There are certain expectations of what will be found, but not finding it is just as valuable information, to an extent.
That being said, I daresay that there are a number of scenarios that would qualify as disappointments for most physicists. Observing just Higgs and nothing else, for instance, would be extremely boring. Observing nothing new at all would be extremely puzzling, but without giving one much to go on. What most people are hoping for is a diverse "zoo" (favourite word in particle physics) of new stuff to analyze.

Originally posted by CzErased
if the LHC fails to work for some reason, whats plan B? [-if you have any inside scope-]

Not sure I understand the question... if it fails to work, they'll fix it, I expect.

Originally posted by Allred5923
So, I guess you could say I am asking "What if the cooling systems fail and the entire 17 mi. of conductive area is unable to 'chill' itself for containment?"

I'm not much into the technical details, so I don't really know. As I understand it, a failure of the cooling system would just mean that they have to perform an emergency-shutdown, which would probably cause some fried components here and there which would have to be replaced, followed by an investigation into the cause of the problem and the design of a better cooling system. *shrug*

Originally posted by Fibonacci11235
what could finding the god particle lead to?
any possible practical applications for it?

Finding it would be just a confirmation of a currently held theory, so in itself it wouldn't lead to much. Studying it will hopefully lead to advances in our understanding of gravity, which I'm sure will have enormous significance in the long run. Any sort of hyperspace drive/wormhole technology/time machine would require such an understanding, for example. It seems an essential step for any cool sci-fi tech. If you were looking for something closer to home, I'm drawing a blank, but that doesn't mean that there isn't anything... history shows how quickly new science can lead to new technology, even in areas in which it isn't expected.

Thanks for this thread TerraBlight....... long overdue.

By odd coincidence, I just tuned into the new TV series "Fringe"

I'm very interested in the interactions that might be indicative or produce evidence toward gravitational energies being translated into other dimensions. I kind of think of this as akin to higher levels of orbital energies, but not certain that's a proper analogy. What are your thoughts on this aspect of the experiments?

I don't have any fears of micro-singularities, but would also like to know if the theorized situations that might occur to produce strangelets are random, or are steps being taken to avoid formation of them?

I have an Avogadro's number worth of questions..... okay, slight exaggeration. Welcome to ATS and thank you!

Originally posted by TeraBlight
It's not really that sort of search. It's not like looking for a treasure chest, and if it's not there, you've failed. Instead, it's like climbing up to a ridge to get a look at the valley beyond. There are certain expectations of what will be found, but not finding it is just as valuable information, to an extent.

I agree it will give them a lot of hard minute data to test new theories with, which is why I am fully behind the LHC 100%. That and it's almost worth it for the Grid.

I guess my point is that currently science's best guess about gravity at the moment is the higg's boson. When they presumably don't find what they are looking for (I'm with Hawkings on this one) they pretty much have to go back to the drawing board. Personally I think they're going to find the answer in waves and not particles; I would be looking in exotic matter like the Bose-Einstein condensate.

RIGHT ON!!!

Thankyou, for bringing yourself forward in this matter to tell it like it is in a simple to understand an down to earth manner.

Yes I totally agree this is an exciting time in our shared history and it is because we have the courage to step outside the box and begin to work together financially to make things happen like LHC.

What a great time you must have had working there can you tell us more of your personal experiences ?

reply to post by antar



I would be fascinated to hear more and in more detail...

Excellent post!!!!

Semper

Hopefully some of the experiment that happen at the LHC will bring to light some theories on physics and weed out the crackpot versions. One can only hope that the benefits will outweigh the cost of this expensive machine in the end. maybe we will find the higgs boson particle. I am interested if they catch a glimpse of the glue holding the universe together.


-Aza

A couple of links, since the webcast seems to be down:

• Live-Blogging the LHC Startup! @ Cosmic Variance
  
  
• liveblogging startup from ATLAS control room @ US/LHC
  
  
• SPS Teletext (don't ask me to interpret the graph, I haven't a clue, but it's live beam data
  )
  
  
• hasthelargehadroncolliderdestroyedtheworldyet.com
  

[edit on 10-9-2008 by TeraBlight]

Trying to watch the live webcast of it, but it appears it's already swamped with users and not working.

You can see if you can get it going here:

webcast.cern.ch...

Guess I'll wake up tomorrow and see what all the fuss wasn't about.

Well, everything seems to be going according to plan and as smoothly as one could have hoped. The beam completed its first successful cycle at 10:28, and all the detectors registered the passage. Official press release.

One of the blogs had an interesting bit about the predicted "discovery schedule", once data taking begins in earnest:

• wibbler on Sep 9th, 2008 at 1:31 pm
  
  Surely we can at least approximately predict when the various components of the standard model will be rediscovered?
  
  
• JoAnne on Sep 9th, 2008 at 1:40 pm
  
  Wibbler: The plan is to have a short physics run later this Fall at 10 TeV center of mass energy (collison energy of the protons). This will give the detectors a chance to calibrate themselves by observing the Standard Model particles.
  
  
• graviton383 on Sep 9th, 2008 at 2:03 pm
  
  As JoA said it’s pretty clear that the SM particles will all be `rediscovered’ with only a (very) [f]ew inverse picobarns…so maybe with only a month of running at 10 TeV.
  

[edit on 10-9-2008 by TeraBlight]

reply to post by Teralight


I loved your choice of blogs, End of the World Party music was great, and lucky Caltek getting pizza and beer for the event.

Again I thankyou for coming on board with us, how did you find us and how long have you been reading the forum?