ICHEP Preparations

In just three weeks time ICHEP 2012 will be underway with the biggest expected news to come from Higgs Searches presented on 9th July in Melbourne. Meanwhile closer to home a much more low-key meeting at CERN has given us an update on the running of the LHC. As far as I can tell from the images of the auditorium the only people who attend these meetings in person are the speakers, but there are high quality webcasts so nobody else has to.

The usual LHC Machine Status Report by Steve Myers is worth watching if you are interested in where they stand with beam operations. Tonight they will have a celebration for collecting 5/fb although they have already passed the 6/fb mark. This merged slide shows progress as we approach the next technical stop compared to his prediction from Chamonix. It is good news that they are almost on target and will decide not to use the two months of extra running that had been set aside just in case. They will need the extra time to do the growing pile of tasks scheduled for the long shutdown which could easily extend to nearly two years long if they are not careful. If you are observant you will also notice that the main goal is illustrated with a picture I took for this blog last year but Myres will have to nick a lot more of my stuff if he is to get even for all the ones I took from him :)

Myers also reported a scary story about a situation that nearly led to LHC armagedon last week when they discovered in testing that the beam dump system relied on a power supply that formed a single point of failure. A simple fault could have led to a situation where the beams could not be dumped even when a failure signal would normally abort the run. The beams would have kept circulating like an unstoppable train with the only possible outcome being the loss of 120 MJ of beam energy around the accelerator ring with the potential to destroy almost anything and everything in the collider.

The progress talk from ATLAS is also interesting in that they revealed three new versions of Higgs plots using 2011 data with improved analysis methods. From this I deduce that at ICHEP they will update only the critical digamma and Z to 4l channels with 2012 data and will use these new versions of the 2011 data for some of the other channels. These will be combined to form the new ATLAS plot. Although the cut-off for collecting data for ICHEP has passed I think there is a good chance they will continue collecting up to the technical stop because the collection rate is now very high. This may give them close to 6/fb of data in the two high-resolution channels.

In the ICHEP abstracts CMS indicate that they will update all their channels with 2012 data. This difference between the two experiments is similar to what was presented at the December council meeting.  As far as I know there is no technical reason why the two experiments should not combine all the 2011 data and 2012 data in the high-resolution channels in time for ICHEP, but this would risk arriving at the unfair situation where one of the two experiments gets the discovery level significance first. I think there is a good chance that they will compare preliminary results in the next few days and if it is clear that they can both reach the critical 5 sigma level they may go for full combinations and announce the joint discovery. Whether they can do this depends on how much data they use, how well they deal with pile-up, how well they control the background, how lucky they are with the fluctuations and even how big the cross-section is if the Higgs is seeing BSM enhancements. My prediction is that they wont quite get there this time round, however an unofficial discovery using ATLAS+CMS is much more likely.

Apart from these Higgs results there will be a lot of other new results presented at ICHEP including a few exotic searches (such as heavy gauge bosons) using 2012 data from both ATLAS and CMS. I expect ATLAS to hold their 2012 supersymmetry searches back for SUSY 2012 in August but the abstracts from CMS indicate that a few new SUSY at 8 TeV will be shown at ICHEP. LHCb, Tevatron and many others from the accelerator labs, neutrino experiments and astronomical observatories have the potential to produce new discoveries in particle physics and ICHEP 2012 is the place to grab the headlines so we should expect the unexpected.

If you have not yet voted in the 3 Quarks Daily science blog awards viXra log would appreciate your support. Update: voting is complete and we appear to have made it through to the next round in about 9th place with 68 votes. Thanks.

16 Responses to ICHEP Preparations

  1. BJ says:

    You say it’s unfair that one gets there first. Well, I thought it was a competition, to drive everyone forward? Does the loser have to get a prize too?

    • Philip Gibbs says:

      If one of them got there first because they had a better choice of detector technology or they handled the analysis better then it would be fair for them to get the credit, but they have been very evenly matched and if one gets there first it will be because of the luck of the statistical fluctuations. In that case I think it would be best if they both get equal credit.

  2. ondra says:

    Nice update Philip. Some nice presentation showing very good machine and experiment behaviour, which could bring us lower systematic uncertainties. Do you have any information if they plan to fix ALICE vacuum problem?
    Btw all experiment talked about presenting 8 TeV data at ICHEP, so i think we will see something.

  3. algernon says:

    Nice post.
    When can we expect the first rumors about what has been found in the 2012 data? IIRC last year we got news about the 125GeV signal in advance of the conference…

  4. wl59 says:

    At the moment they can’t yet tell everybody, that now is established that Higgs don’t exist, for not to suffer government cuts

  5. Tony Smith says:

    Tommaso Dorigo (a member of CMS) said on his blog today (16 June 2012):
    “… the reconstruction of the data takes a while longer, so in fact right now there’s only about two thirds of the data already collected that is available for analysis …”.

    Unless I misunderstand, that means that the event data collected at the cutoff several days ago is just raw machine output and that it must undergo “reconstruction” before it can be put in the form of a histogram showing number of events in each energy region bin.

    Only 2/3 of the 5/fb, or about 3/fb, is now available in such a histogram form,
    so nobody now knows what a full 5/fb histogram would look like.

    Further, as Tommaso also said,
    the histogram stage is only a first stage:
    “… What takes longer is to validate all results, combine them, and approve them …”.

    Unless I misunderstand, the validation, approval, etc., is necessary to get things like Confidence Level determinations of discovery, evidence, exclusion, etc.

    Still further, even if a single Standard Model Higgs is excluded,
    there could be some peaks with lower cross-section that could
    combine to effectively act as a Standard Model Higgs,
    analysis of them would require changing cross-section criteria from that of the initial analysis and so would take somewhat longer
    might not even be done by ICHEP
    (although indications of such smaller peaks might appear at the histogram stage of analysis, now about 2/3 done).


  6. geert verhoeven says:

    A 4 sigma in the Gamma-Gamma channel with 2012 data? http://www.math.columbia.edu/~woit/wordpress/?p=4772

    • Philip Gibbs says:

      IF they end up with 4-sigma each in gamma-gamma and IF they are in exactly the same place as before and IF they decide to combine 7 TeV with 8 TeV data then they will be very close to 5-sigma from each experiment in this channel. In fact it would show again that the cross-section is about twice as high as expected with something like 2 to 3-sigma significance. However we will need to see exactly what they really have before we can really conclude anything like that. Update: Actually it was 4-sigma for the combination, not 2012 alone, see below, so there may not be such a big over-excess

      • JollyJoker says:

        Also means they have discoveries with 2012 data alone when combining different channels.

      • Francis Bursa says:

        Unless the 4 sigma is already after combining with the 7 TeV data – it is not clear if the rumour means 4 sigma just for this year’s data or together with last year’s. In the latter case the cross-section would be about right for the Standard Model, I think.

      • Philip Gibbs says:

        My interpretation of what he says (taking both his sentences together) is that they have seen 4-sigma in this years data alone. but yes it is possible that there is some such ambiguity and confusion.

      • Peter Woit says:

        I’ve updated my blog posting to clarify. The “4-sigma” refers to combined 2011 and 2012 data, not just 2012 data.

      • Philip Gibbs says:

        Ok I will rework my posts to correct for this thanks

  7. wl59 says:

    Yes, hope we that CMS and ATLAS shows both a signal at the same mass like last year, 124 and 126 resp., but that the significance in the whole area is now higher and the signal sharper, perhaps less than +/- 0,4 for its <95% width, then both experiments exclude mutually each other, and the people can claim the discovery of any completely new particle/process nor predicted by known physics … :)

  8. Philip Boucherat says:

    I know absolutely nothing about this, but I find it kind of funny that we keep getting announcements of an amazing discovery, see a room full of excited physicists somewhere in Switzerland, and then find out that after all the hype they’re still not sure if they’ve made a discovery or not. And I think I heard that they are going to shut down the LHC for a couple of years because it needs a service – so how can they rely on their experiment results if they’re not sure if their equipment is working properly? Anyway, very interesting blog even if I don’t really understand it! And your sister is very proud of you by the way!

    • Philip Gibbs says:

      Hi Phil, long time no see.

      They are finally sure that they have discovered something, a new particle. They are just not sure what it is. They are just being over-cautious. It is the Higgs boson.

      The LHC shutdown was planned from the beginning. It is not because it is not working properly. There will be routine maintenance like servicing a car, plus they are upgrading it to reach higher energy.

      The data they collect can normally be relied on, but you have to remember that this is a new machine pushing the boundaries of knowledge. It does not come with an instruction booklet and a warranty. They have to test how everyting is working and make sure it is all understood before they can claim any results. There are hundreds of papers they have written about just the operation and callibration.


Get every new post delivered to your Inbox.

Join 270 other followers

%d bloggers like this: