Large Hadron Collider Finishes 2011 Proton Run


The world’s largest and highest-energy particle accelerator has been busy. At 5:15 p.m. on October 30, 2011, the Large Hadron Collider in Geneva, Switzerland reached the end of its current proton run. It came after 180 consecutive days of operation and four hundred trillion proton collisions. For the second year, the LHC team has gone beyond its operational objectives – sending more experimental data at a higher rate. But just what has it done?

When this year’s project started, its goal was to produce a surplus of data known to physicists as one inverse femtobarn. While that might seem like a science fiction term, it’s a science fact. An inverse femtobarn is a measurement of particle collision events per femtobarn – which is equal to about 70 million million collisions. The first inverse femtobarn came on June 17th, and just in time to prepare the stage for major physics conferences requiring the data be moved up to five inverse femtobarns. The incredible number of collisions was reached on October 18, 2011 and then surpassed as almost six inverse femtobarns were delivered to each of the two general-purpose experiments – ATLAS and CMS.

“At the end of this year’s proton running, the LHC is reaching cruising speed,” said CERN’s Director for Accelerators and Technology, Steve Myers. “To put things in context, the present data production rate is a factor of 4 million higher than in the first run in 2010 and a factor of 30 higher than at the beginning of 2011.”

But that’s not all the LHC delivered this year. This year’s proton run also shut out the accessible hiding space for the highly prized Higgs boson and supersymmetric particles. This certainly put the Standard Model of particle physics and our understanding of the primordial Universe to the test!

“It has been a remarkable and exciting year for the whole LHC scientific community, in particular for our students and post-docs from all over the world. We have made a huge number of measurements of the Standard Model and accessed unexplored territory in searches for new physics. In particular, we have constrained the Higgs particle to the light end of its possible mass range, if it exists at all,” said ATLAS Spokesperson Fabiola Gianotti. “This is where both theory and experimental data expected it would be, but it’s the hardest mass range to study.”

“Looking back at this fantastic year I have the impression of living in a sort of a dream,” said CMS Spokesperson Guido Tonelli. “We have produced tens of new measurements and constrained significantly the space available for models of new physics and the best is still to come. As we speak hundreds of young scientists are still analysing the huge amount of data accumulated so far; we’ll soon have new results and, maybe, something important to say on the Standard Model Higgs Boson.”

“We’ve got from the LHC the amount of data we dreamt of at the beginning of the year and our results are putting the Standard Model of particle physics through a very tough test ” said LHCb Spokesperson Pierluigi Campana. “So far, it has come through with flying colours, but thanks to the great performance of the LHC, we are reaching levels of sensitivity where we can see beyond the Standard Model. The researchers, especially the young ones, are experiencing great excitement, looking forward to new physics.”

Over the next few weeks, the LHC will be further refining the 2011 data set with an eye to improving our understanding of physics. And, while it’s possible we’ll learn more from current findings, look for a leap to a full 10 inverse femtobarns which may yet be possible in 2011 and projected for 2012. Right now the LHC is being prepared for four weeks of lead-ion running… an “attempt to demonstrate that large can also be agile by colliding protons with lead ions in two dedicated periods of machine development.” If this new strand of LHC operation happens, science will soon be using protons to check out the internal machinations of much heftier structures – like lead ions. This directly relates to quark-gluon plasma, the surmised primordial conglomeration of ordinary matter particles from which the Universe evolved.

“Smashing lead ions together allows us to produce and study tiny pieces of primordial soup,” said ALICE Spokesperson Paolo Giubellino, “but as any good cook will tell you, to understand a recipe fully, it’s vital to understand the ingredients, and in the case of quark-gluon plasma, this is what proton-lead ion collisions could bring.”

Original Story Source: CERN Press Release.

8 Replies to “Large Hadron Collider Finishes 2011 Proton Run”

  1. It is actually very exciting that they did not discover it yet. It adds to the suspense. 🙂

  2. [IVAN]Should be “Higgs boson”, not “bosun”. I think the latter is some kind of naval term.[/IVAN]

  3. Sorry, Tammy, but I just had to beat Ivan to this one. “Right now the LHC is now being prepared.” Maybe you can fix it before he stops in. (As a former sailor, I do like the ‘bosun’ though.)
    The LHC continues to enthrall. Thanks.

    1. gotcha’. thanks, guys! one good case of the flu and i find i’m seeing doubledouble. but even not feeling the best and i couldn’t resist femtobarns! (i guess you’d have to be from rural ohio. “hey, sally… where be de’ cows? last time i saw ’em theys out by femtobarns…”

      ok, buckeyes… i we can’t laugh at ourselves, who can? 😀

      1. Hope you feel better soon, but don’t pass that flu my way. I had it two years ago and it took a month to get back to par.

  4. It should be pointed out that the unit barn is a cross section area of scatter equal to 10^{-24}cm^2. This is about the area a proton or nucleon presents. A femtobarn is 10^{-39}cm^2 or 10^{-15} of a barn. This is a pretty small length scale ~ 10^{-19}cm. The inverse femtobarn is then the number of collision per femtobarn.

    The term barn came from the early days of nuclear physics when uranium nuclei were described as “big as a barn.”


    1. Thank you for pointing this out.
      It is interesting also to compare the vast difference of the unit cross section resolution and energies presently obtainable with the LHC to that of the plank scale which is a very high energy of 1.22 x 10^19 GeV or a very small size of 1.616 x 10^-35 meters. Though it may seem we are on the way to a break-through, its amazing how far yet there is to go. It would take a cyclotron the size of the orbit of Mars to achieve these energies.

      1. Here is the problem we have with Planck scale physics in general. The Planck mass is m_p = sqrt{?c/G} or about 10^{-5}g. The energy equivalent is about 10^{15}erg, or the energy in 4 liters of petrol, or about a gallon of gasoline. So to do direct Planck scale physics would require that amount of energy per particle collision in order to generate a quantum unit of black hole. The LHC runs with a luminosity of around 10^{13} particles per bunch, where this would be larger for a Planck scale accelerator. For a Planck scale accelerator it would then require each bunch be accelerated with the energy equivalent of 100 trillion gallons of fuel, or the equivalent of over a trillion barrels of petroleum. This is about half the total global reserve of oil! The actual practical amount of energy is likely several orders of magnitude larger than this This is not to mention this accelerator would have the radius comparable to a galaxy. If you scale up the approximately 10km of the LHC to the scale required, 10^{16}, this machine would be around 10^{17}km or about 10,000 light years. That is far larger than the orbital radius of Mars. So clearly this is not going to happen.

        It may be possible to work with cosmic ray physics. The Earth’s atmosphere acts as a sort of scintillation device and an array of detectors lofted on heliostats (semi-permanently lofted balloon-dirigibles) could serve as a detection system for the path of exceedingly high energy particles up to 10^9 GeV. For various reasons I think that Calabi-Yau manifolds of compactification have larger scales at energy below the Planck scale, which involve these extra-large dimensions. There is then a chance to measure scattering amplitudes which have a correspondence to this sort of physics. Cosmic rays have abundant particles up to 10^4GeV and this might be one way to look at this very hight energy scattering.

        The ultimate scattering experiment is the universe itself. So we may be forced to look at very subtle signatures in the early universe. Neutrino detection could measure physics far earlier than the CMB surface of last photon scatter. LIGO detectors might also provide a way of looking into the very early cosmos as well.


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