7 TeV per beam compared to 1 TeV per beam

[barnflakes]

If I've read this correctly, it seems the LHC will be colliding beams at 7 TeV each, producing a total collision energy of 14 TeV. The previous record was approximately 950 GeV at LEP/Tevatron producing a total collision energy of 1900 TeV. When the LHC starts colliding early next year (perhaps sooner), they want to use 3.5 TeV per beam. So does this mean physicists will be analysing this data for new discoveries, since collisions will have 3x more energy than any previous collision in a detector? Why is there such a rush to get to 7 TeV per beam? Is there some sort of physics that isn't predicted to happen until 14 TeV is reached? Do all the particles/events that happen at 14 TeV also happen at 2x3.5 TeV?

 

[Ben Niehoff]

Assuming there is some new particle in the 1.9 TeV to 7 TeV range, the 3.5 TeV beams have a chance of finding it, yes. But if the beam energy goes up to 14 TeV, then the new particle will be produced in larger amounts, generating more events which can be analyzed to determine its properties.

 

[Bob S]

Why is there such a rush to get to 7 TeV per beam?

The urgency in getting to 7 TeV per beam is the honor of claiming a Nobel Prize; nothing more, nothing less. The United States could save many millions of dollars by turning off the Tevatron now, and letting LHC make the next big discovery.

Bob S.

 

[barnflakes]

Yeh I understand a lot of it is to do with statistics and therefore high energies are better, but what physics, apart from the higgs boson, are people trying to find at specific energy levels? Are there other important energies that people will be keeping a close eye on for supersyemmtric particles say, or extra dimensions? Basically - what predictions have people made and what energies will those predictions be able to be tested? Apart from the Higgs of course.

 

[ansgar]

Yeh I understand a lot of it is to do with statistics and therefore high energies are better, but what physics, apart from the higgs boson, are people trying to find at specific energy levels? Are there other important energies that people will be keeping a close eye on for supersyemmtric particles say, or extra dimensions? Basically - what predictions have people made and what energies will those predictions be able to be tested? Apart from the Higgs of course.

You could pick up:

https://www.amazon.com/dp/9812833897/?tag=pfamazon01-20

https://www.amazon.com/dp/0750309865/?tag=pfamazon01-20

 

[ansgar]

If I've read this correctly, it seems the LHC will be colliding beams at 7 TeV each, producing a total collision energy of 14 TeV. The previous record was approximately 950 GeV at LEP/Tevatron producing a total collision energy of 1900 TeV.

WHAT? 1900 TeV :)

 

[mgb_phys]

WHAT? 1900 TeV :)

Typo, the tevatron reached 1900Gev or 1.9Tev

As to whether there is a specific expectation to fin a particle at 14Tev or that was just the highest you could reasonably afford to build / have a chance of making work?
You would have to ask the designers - in private, when drunk.

 

[Borek]

but what physics, apart from the higgs boson, are people trying to find at specific energy levels?

If they would know they would be not trying to find, but trying to prove. That's the beauty of each experiment - it may give something completely new.

Sure, It doesn't have to.

 

[humanino]

As to whether there is a specific expectation to fin a particle at 14Tev or that was just the highest you could reasonably afford to build / have a chance of making work?
You would have to ask the designers - in private, when drunk.

It is not as simple as size of the accelerator (tunnel already available) and total energy. Luminosity is also quite a factor in the game, since we do not want to design experiments supposed to run for decades, but years is acceptable. The product luminosity times energy gives you roughly the energy stored in the machine, hence the challenge.

 

[barnflakes]

If they would know they would be not trying to find, but trying to prove. That's the beauty of each experiment - it may give something completely new.

Sure, It doesn't have to.

A particle doesn't just show up out of nowhere though does it, you have to test it against a model, otherwise why make models in the first place?

 

[TMFKAN64]

A particle doesn't just show up out of nowhere though does it, you have to test it against a model, otherwise why make models in the first place?

Sure, why not? When the muon was first discovered, scientists didn't have a clue what it was and had no model for it.

Sometimes, you find the particle and *then* set about building a model, and sometimes the other way around.

 

[mgb_phys]

Sometimes, you find the particle and *then* set about building a model, and sometimes the other way around.

Though with the time and cost of an experiment like the LHC you want to be super-sure of finding something before you start winding magnets.

That was always my dislike of HEP - you have to be so sure before doing the experiment that there is almost no point in doing the experiment.

 

[humanino]

That was always my dislike of HEP - you have to be so sure before doing the experiment that there is almost no point in doing the experiment.

Because an experiment is cheap and fast, it does not matter if you loose your time doing it ?

Everything is scaled up in HEP, including the time and thinking it takes to design the experiment. As LHC exemplified beautifully, the design of the machine did not take nearly as long as the completion of the machine. A guesstimate, the design was negligible compared to the construction and commissioning.

It is quite possible that the LHC will see nearly zip, nada, even in several years. We call that "hidden sectors" and Franck Wilczek describes it nicely in section 5 of
Anticipating a New Golden Age
Of course, it would be disappointing at first. But we can not ignore the possibility,

Hidden sectors are entirely possible. They could complicate things in the short run, but would teach us even more in the long run.

 

[mgb_phys]

Everything is scaled up in HEP, including the time and thinking it takes to design the experiment. As LHC exemplified beautifully, the design of the machine did not take nearly as long as the completion of the machine.

It's more that there doesn't seem to be much room for finding the unknown.
With a telescope you obviously want as big as possible but the same instruments can be used for a range of observations and with new instruments the telescope will be in use for 50 years.

I suppose it's really a facility vs a single huge experiment thing.

 

[humanino]

the same instruments can [...] be in use for 50 years.

You chose an appropriate number : the Proton Synchrotron first accelerated protons on 24 November 1959 and is still quite in use.

 

[mgb_phys]

I never wanted to do HEP, there are too many high voltages and I wasn't tall enough.

(My prof once said that the only use of grad students on projects like LHC was to stand in front of detectors to give scale - and so the optimal student was 2.0m tall)

 

[humanino]

Once the experiment is in production, there is not so much to take care of anymore. The truth is that there is nothing as bad as cabling.

 

[Borek]

(My prof once said that the only use of grad students on projects like LHC was to stand in front of detectors to give scale - and so the optimal student was 2.0m tall)

Or 6' if your target audience is not metric.

 

[arivero]

Though with the time and cost of an experiment like the LHC you want to be super-sure of finding something before you start winding magnets.

There is the unitarity bound, it tells us that there is something in this energy scale, or that QFT (and any many particle relativistic quantum mechanics) is wrong.

 

[humanino]

There is the unitarity bound, it tells us that there is something in this energy scale, or that QFT (and any many particle relativistic quantum mechanics) is wrong.

That there is something is no proof we will see it, and playing the devil's advocate (?) I'll quote again

Anticipating a New Golden Age

 

[arivero]

Sure, why not? When the muon was first discovered, scientists didn't have a clue what it was and had no model for it.

Still, they were looking for something in that scale: the pion.