LHC end of proton-proton physics for 2010

Today the LHC is ending proton on proton physics for 2010 as planned and moving on to heavy-ion physics.

The pp runs that started back in February have been outstandingly successful. A peak luminosity of 201/ub/s was reached on one run, and that’s twice the set target. This means that collecting 1/fb of data during 2011 as planned should be possible.

The really good news is that the stability of the systems and the proton beams proved to be better than hoped. This meant they were able to surpass the target luminosity without having to take the collider to the limits it is capable of. Next year they have the option to increase the luminosity even further .

The experiments collected about 45/pb of data each and that might be enough to find some new physics. We may hear something about that at conferences scheduled for the winter months. They could easily have collected more data this year but the higher priority was to understand the running of the collider with closer bunch spacings so that they can make a well-informed plan for the early part of 2011 when they will set the run parameters for next year.

The commissioning has not been without its hitches. That would be too much to expect from such a large and complex machine pushing well beyond known boundaries. Most of the problems that have cropped up have been solved. However, they have still not traced the source of “The Hump” which still sometimes plagues the stability of the beams. Then there were UFOs and Ufions which are though to be dust particles in the beam pipe that trigger the protection systems and dump the beams. They also have problems with an electron cloud which is producing high unwanted backgrounds in ATLAS. The recent runs at 50ns also turned out to need “scrubbing” to clean up the beams. The last few days were spent trying to understand these issues so that they can implement fixes during the shutdown, or at least understand how to work round them and plan accordingly.

None of these problems are show stoppers and overall there is no doubt that the LHC has performed very well this year. This is surely down to some good decisions from the management together with the hard work of the thousands of dedicated individuals who have been looking after the many components of the experiment.

Update: Ion beams have already been circulating in the LHC today!


8 Responses to LHC end of proton-proton physics for 2010

  1. Ulla says:

    Lubos has an interesting note on dimuons
    http://motls.blogspot.com/2010/11/cms-sees-excess-of-15-gev-dimuon-events.html

    the antimatter-question. He says:
    Recall that neutralinos are Majorana fermions, identical with their antiparticles. In supersymmetric theories, they’re the superpartners of neutral bosons such as photons, Z-bosons (or W_3 and B gauge bosons, to choose the high-energy symmetric basis), and the three neutral Higgs bosons – or their proper superpositions that are mass eigenstates. In the low-energy basis, note that there are 2 polarizations of massless photons, 3 polarizations of massive Z-bosons, and 3 neutral Higgs bosons – which adds up to 8 polarizations, correct for 4 massive Majorana fermions.

    I would like to have comments on this, if it interests someone.

    • Philip Gibbs says:

      It’s a good spot from Lubos and a nice explanation. Of course if you plot enough statistical points you will find some outliers which is one reason why we require more significance here. We will need to look out for this plot when they include all the data collected so far.

    • Philip Gibbs says:

      Apparently Motl has removed his post because the author of the paper claimed that the excess was a mistake.

    • Bill K says:

      I think more than anything, this episode illustrates the hair-trigger dynamics that has resulted from use of the internet. It serves as a caution for all of us to be more careful, and think before we type. It took place in three stages, a) public exposure of very preliminary data, b) overoptimistic interpretation of that data by someone with a well-advertised interest in finding supersymmetry, and c) an almost instantaneous spread of the interpretation. All that started this chain of events and was ever in evidence was a single data point with a very large error bar.

      Don’t you think: if the original author had *any* suspicion that his data contained such a revolutionary discovery – the first evidence of supersymmetry – he would have held the information close until he was completely sure, and ready to make the claim himself!

  2. Ulla says:

    It is a bit surprising he clings to this when I remember his hostily attitude against Tommaso last year, about a 3 sigma evidence :)

    Look for instance this http://www.science20.com/quantum_diaries_survivor/rumors_about_light_higgs

    I also thought of Keas asymmetry.

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