Just after 1 pm European time today, the LHC at CERN collided two beams of protons with a total center-of-mass energy of 7 TeV (seven trillion electron volts), three and a half times more energy than the proton-antiproton collisions at the Tevatron at Fermilab, and far greater than the 2.4 TeV achieved by the LHC in December 2009. This milestone clearly marks the beginning, at long last, of the first major physics run of the new accelerator.
We’ve been waiting a very long time for this. In the 1980s the field had its eyes fixed firmly on the SSC, the Superconducting Supercollider to be constructed in Waxahachie, Texas. After years of design, the go-ahead was given by President Bush in 1988 shortly after his election to construct the huge machine, which was to collide protons with 40 TeV energy. Alas, changes to the design sent costs rising, and, after spending over 2 billion dollars on tunnel boring and lab construction in Texas, the project was canceled by Congress in October 1993.
Those were dark days for particle physics. Any hope of pushing to higher energies seemed to lie in pushing ahead with the design of the LHC at CERN, which had been simmering along but was looking like it would be too little too late if the SSC came on line first. Nevertheless, the Tevatron was just starting to gather significant physics data, and the CDF and D0 experiments would soon discover the top quark, completing the picture of the standard model quarks.
With the SSC out of the picture work on the LHC really began in earnest. The magnet design was finalized and plans for constructing the machine began to gel. It would take many years to complete the engineering, prototyping, and industrialization of the magnet production, and a lot of money. In 1997 the US and CERN reached an agreement (brokered in part by Rep. Sensenbrenner of Wisconsin) whereby the US would contribute about $50 million per year over ten years to the machine itself. This was precedent-setting: never before had the cost of machine construction at CERN, or Fermilab, or SLAC been borne in such large part by a foreign entity. It was essentially the price of admission for the US community to participate in the large experiments ATLAS and CMS, to which the US has committed about half a billion dollars. So though the LHC and the experiments are in Europe, the US has a billion dollar investment in the projects. And now it is time to begin to reap the rewards.
In 1997 it was foreseen to have circulating beams in the LHC by 2005. Construction of the detectors was steady, and it is arguably the case that the experiments were ready before the accelerator. But the completion date of both sets of projects slipped, to 2006, then 2007, and then finally in 2008 all was ready. And, as we all know, in September 2008, after one week of beam commissioning, the LHC suffered a major magnet quench accident which damaged over a kilometer of the machine, necessitating a year-long repair campaign, and a reassessment of the path to the full design energy of 14 TeV.
A large portion if the machine has yet to be retrofit to prevent the type of accident experienced in 2008, but it was decided to operate the collider at 7 TeV and gather physics data in the next year. The energy will open up a new regime to explore for physics beyond the standard model, and we are ready and eager to do just that!
More on the physics in the next post…
March 30th, 2010 at 7:39 am
HELLO HUMANS!
March 30th, 2010 at 7:41 am
[...] can read more about this from someone who know his gluons from his gravitons at Cosmic Variance, or from the horses mouth at [...]
March 30th, 2010 at 7:59 am
Higgs! I was hoping you’d grace us with your appearance! The first person you should really get acquainted with is Alcuin of York, who can introduce you to lower case letters.
March 30th, 2010 at 8:13 am
Great fun watching the CERN Twitter feed:
http://twitter.com/CERN
And Ian Sample has a good live-blog in the Guardian:
http://www.guardian.co.uk/global/2010/mar/29/lhc-launch-live-large-hadron-collider
March 30th, 2010 at 8:43 am
Videos of real collisions in CMS:
http://tinyurl.com/CMScollision
http://tinyurl.com/CMScollisionGeom
More on: http://cms.web.cern.ch/cms/
March 30th, 2010 at 10:31 am
It is amazing how long and hard people have worked for today’s success – and all the physics that is to follow. The LHC experiments have honed their analysis strategies following examples from the Tevatron. Will those strategies work perfectly, or will they need adjustments? Now that we have real data, we will find out. The event displays, and first low-energy physics results are like the dawn before the sun rises. The results that we see this summer will put all this at a totally different level – finally.
March 30th, 2010 at 11:21 am
[...] For more about the long road to now and the future of LHC physics, follow DISCOVER blog Cosmic Variance. [...]
March 30th, 2010 at 1:11 pm
HELP me understand how the (putative) Higgs field offers no resistance to non-accelerating bodies, regardless of relative velocity, yet resists their acceleration; i.e. imparts “mass”?
March 30th, 2010 at 1:42 pm
trying to build the ssc in a remote location in texas instead of at fermilab was really stupid.
March 30th, 2010 at 2:26 pm
Thrilling.
March 30th, 2010 at 5:15 pm
“We’ve been waiting a very long time for this.”
….ummm… no we haven’t actually. What we’ve been waiting for are discoveries, which [if we are very lucky] are 2 or 3 years off. It’s rather funny that there can be so much ecstasy over the mere fact that the thing didn’t blow up when it was turned on….
March 31st, 2010 at 3:14 am
@ Helium Head: It’s difficult to explain properly without assuming a grounding in quantum field theory. The idea of the Higgs offering resistance or drag to moving particles is really pedagogical – the proper answer is that the Higgs couples to other fields such that in a low energy state, when the Higgs field has a non-zero value, a term appears in the electron’s equations of motion that corresponds to mass. How strongly the electron couples to the Higgs determines its mass.
Hope that helps a little.
March 31st, 2010 at 1:22 pm
John—I understand that the total integrated luminosity the first day was 0.01 inverse nanobarns, and that this was “more than expected”. At this rate, of course, it will take 300,000 years to hit an inverse femtobarn. What sort of luminosity increase is expected in the next few weeks?
March 31st, 2010 at 7:18 pm
New Physics already found, the following results were prematurely leaked.
http://nzscience.blogspot.com/2010/03/lhc-discovers-black-rings.html
[...]
However, a recent joiner with their PhD still fresh, emailed a friend with some exciting news about the discovery of Dark Rings – obviously not realizing that such would soon become public.
[...]
April 28th, 2010 at 2:33 pm
[...] March 30, when the LHC at CERN first collided protons at an unprecedented total energy of 7 TeV (7 trillion electron volts) the machine has been steadily moving from crawling to walking. Last [...]
April 28th, 2010 at 4:02 pm
[...] March 30, when the LHC at CERN first collided protons at an unprecedented total energy of 7 TeV (7 trillion electron volts) the machine has been steadily moving from crawling to walking. Last [...]
April 29th, 2010 at 3:57 pm
[...] March 30, when the LHC at CERN first collided protons at an unprecedented total energy of 7 TeV (7 trillion electron volts) the machine has been steadily moving from crawling to walking. Last [...]
April 29th, 2010 at 6:28 pm
[...] March 30, when the LHC at CERN first collided protons at an unprecedented total energy of 7 TeV (7 trillion electron volts) the machine has been steadily moving from crawling to walking. Last [...]
April 30th, 2010 at 8:35 am
[...] March 30, when the LHC at CERN first collided protons at an unprecedented total energy of 7 TeV (7 trillion electron volts) the machine has been steadily moving from crawling to walking. Last [...]