LHC To Start Back Up In November At Half Power

mcgrew writes to mention that the Large Hadron Collider, smasher of particles, will get another chance to prove itself this November. The restart will begin with tests at half power, a mere 7 trillion electron volts (TeV), and ramp up slowly to the designed goal of 14 TeV. "Measurements indicate that some of the electrical connections could not safely handle the amount of current needed to run at the full 14 TeV, so will need to be replaced before dialing up the energy that far. But even 7 TeV is much higher than physicists have ever probed in the laboratory before. The Tevatron accelerator at Fermilab in Batavia, Illinois, is the current record holder, with collisions at 2 TeV."

Temporary!

[Roger W Moore]

One thing missing from the summary is that 3.5 TeV/beam is only (hoïpefully) a very temporary setup. The ramp up to 5TeV/beam, or 10 TeV centre of mass energy should be quick rapid if everything works. Going to the full 7 TeV will take longer though.

Re:True, but...

[FrangoAssado]

There's an excellent video on YouTube of Ed Farhi explaining it in some detail: Why Physicists Need the Large Hadron Collider [youtube.com]

Basically, if all they find is the Higgs boson, that will be a huge disappointment. (Unfortunately, that's the expected outcome.)

Re:Only half

[TheRaven64]

Meh. You have to wait for someone to manually update that page. You'd be better off checking the status yourself with the internal and external webcams [cyriak.co.uk].

Re:How much is an electronvolt?

[Anonymous Coward]

One electron volt is equal to 1.60217653(14) x 10^19 joules.

And they are talking about 7 and 14 Trillion eV which is a bunch of joules! Pretty nice ;)

You missed by a factor of 10^38

1 eV = 1.6 x 10^MINUS19 Joules

Re:How much is an electronvolt?

[FrangoAssado]

Actually, 1 electron volt is closer to 10^(-19) Joules, so

14 TeV = 2.2 x 10^(-6) J

(When in doubt, ask google [google.com]! :-))

Re:True, but...

[Gromius]

Well when you find the Higgs, you want to measure its properties and see if you really have a Higgs and not some random new particle. And then if it is the Higgs, you want to see which Higgs it is. All this takes time and lots and lots of data.

And unless we are very unlucky, there should hopefully be lots of other werid and wonderful things to find. I'm personally not interested in the Higgs at all but much more exotic things. But for the media, its easier to say "we are looking for X" rather than we are looking for "X, Y, Z oh and dont forget about B but to be honest, we dont know what happens at these energies and would like to find out"

Re:Fun with units...

[BitterOak]

Your post is modded funny, but it is absolutely correct.

The key point, however, is that when you flick your finger, and end up hitting a huge number of protons, the energy is therefore distributed among all these protons, neutrons, electrons, etc., and so nothing very interesting happens. When all the energy is is concentrated in one collision between two subatomic particles, then very interesting things happen, the most important of which is the creation of a shower of short-lived particles which we don't see in ordinary matter. The most interesting of these particles don't live long enough to even propagate into the detectors, but their decay products do give clues to their existence. It is hoped that the current holy grail of particle physics, the Higgs boson, will be found this way.

The actual plan

[andre.david]

Hi,

We were just briefed at CERN of the plan. It is a plan. Plans can change. With that proviso:

0 - get the beams circulating at injection energy (from last year's experience, this happened in one week)

1 - take some collision data at injection energy (450 GeV/c per beam => 900 GeV at center-of-mass or half the Tevatron) (from last year's experience, this could be only another week)

2 - CERN will observe the annual closure from Dec 19 to Jan 3.

3 - ramp the energy up to 3.5 TeV/c per beam (7 TeV center-of-mass energy, 3.6x more than the Tevatron)

4 - take enough data to be competitive with 20 years of Tevatron in some topics

5 - ramps the energy to 5 TeV/c per beam (10 TeV center-of-mass energy, 5 times more than the Tevatron)

6 - inject lead-ions and have some Pb+Pb collisions at around 2.75 TeV center-of-mass energy? (that would be 13 times more energy than Brookhaven's RHIC Au+Au)

7 - shutdown and work on getting the machine ready for 7 TeV/c per beam

Thank you for your attention.

Re:Fun with units...

[burtosis]

http://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/beam.htm [web.cern.ch]

What you say is very misleading. While that is true on a proton basis, you are neglecting the 115 billion protons per packet, with 2808 packets per beam. This puts your calculation off by 15 orders of magnitude. Unless your finger can flick a typical scobie up to mach 2.

Re:True, but...

[The_Wilschon]

On the contrary. The Higgs is discoverable at a 5 sigma significance level (PhysRev standard for "discovery") with about 1 year's worth of data at design energy and luminosity.[1] Furthermore, since people have already worked on analyses, it will only take probably about 6 months to run the analyses on the data and get the results approved by the collaboration. So, with the current startup schedule, barring any more problems, we should expect to see a Higgs discovery paper from CMS and ATLAS in time for the Winter 2011-12 conference cycle.

[1] http://arxiv.org/abs/0812.1458 [arxiv.org]

Re:True, but...

[The_Wilschon]

Supersymmetry is a bigger deal than the Higgs, I would judge. The LHC is expected to find SUSY quite rapidly. Additionally, we will want to measure Higgs properties, perform precision measurements of various things such as the single top cross section, B_s mixing (and CP violation, and maaaaybe CPT violation), the top mass, the W and Z masses, etc. More exotic things include searching for (yes, really) black hole production, large extra dimensions, technicolor (an alternative model to the standard model Higgs mechanism), WIMPs, dark matter, excited states of the W and Z, a fourth fermion generation, glueballs, tetraquarks, pentaquarks, magnetic monopoles, leptoquarks, sterile neutrinos, etc, and other, completely unexpected, new physics.