MIT, the LHC and a royal wedding

It’s always a pleasure to pop over to MIT for the afternoon, and on Friday I attended a seminar titled ‘MIT and the World’s Largest Science Experiment: Hunting the Higgs Boson”, given by Markus Klute, Assitant Professor of Physics at MIT and member of the CMS (compact muon solenoid) collaboration at CERN. It seems MIT has quite a big involvement with the LHC, with a large group working at the CMS detector and a smaller group at ATLAS; about 40 researchers overall.

MIT and the World’s Largest Experiment: Hunting the Higgs Boson

The talk was aimed at a wide audience, and much of it was a fairly standard introduction to particle physics and the experiments at the Large Hadron Collider. I always try and attend such talks whenever I can, partly to pick up any new information but also to see how the real players present the story.

Starting with a review of the nucleus and its particles, Markus gave a succinct overview of the Standard Model. I liked the way he linked the theory to today’s news; in describing the way particles are believed acquire mass (the Higgs mechanism), he invited the audience to imagine Charles and Kate entering the auditorium, how people would interact (i.e. cluster around them) to different degrees, thus acquiring different masses. This is a nice twist to a common analogy and it never hurts to connect with current events. (Being Irish, I’d be a neutrino with almost zero interaction, though I wish the couple well).

Professor Klute then gave a nice overview of the four main detectors at the LHC, and then some details about his group’s contribution to the CMS experiment, particularly in the area of building the tracking system. I won’t repeat the details but you can find a good review of US involvement at the CMS detector here. I particularly enjoyed the emphasis on the ‘rediscovery’ of the particles of the Standard Model at CMS, beautifully summarized in the plot below. I think particle physicists should emphasize this chart more, it gives great confidence in the methods of particle physics (and shows how sociologists such as Shapin and Schaffer underestimate the reproducibility of big science experiments, see ‘Leviathan and the Air Pump’).

Summary chart of particles rediscovered at CMS

I liked the speaker’s simple description of particle detectors: a camera with a hundred million pixels and a shutter speed of 400 million times per second – not to mention the filtering. He also placed great emphasis on the computing challenges thrown up by the data, giving a nice overview of the Worldwide LHC Computing Grid. I also liked the way he described particle physics experiments  in terms of four components: accelerators, detectors,  computing and people!

Finally, there was a nice overview of the challenge of the hunt for the Higgs, explaining that

– it is rarely produced

– decays almost immediately

– its mass is not known, hence neither are the main production or decay channels

Professor Klute then gave a very quick review of the main production and decay channels for the Higgs and explained how CMS will look for them.

Higgs production via gluon fusion; a dominant process for a range of mass

The decay channel depends on the Higgs mass

Another nice plot was a summary slide showing the masses already ruled out by previous accelerator experiments.

The window is closing

Finally, the speaker gave a quick synopsis of the possibility of observing physics beyond the Standard Model, concentrating on the possibility of the detection of supersymmetric  particles, in particular the possibility of supersymmetric Higgses. After questions and answers, there was a poster session and reception, with some very impressive posters by MIT postgrads at CMS.

All in all, a very enjoyable LHC talk with a useful description of US participation in the project. If you want to more about this, the US LHC blog is well worth following.


Markus points out I said Charles and Kate instead of William! This is such a whopping error (of planetary magnitude) I think I’ll leave it. Re Higgs production and decay channels, there is an really nice overview here by a group at Imperial College also involved with the CMS experiment. This week there was a big meeting at Notre Dame concerning US participants in the CMS experiment, you can link to it here


Filed under Particle physics

8 responses to “MIT, the LHC and a royal wedding

  1. John

    LOL…. I liked your analogy…
    (Being Irish, I’d be a neutrino with almost zero interaction, though I wish the couple well).

    LOL…..Its a good one!


  2. cormac

    Thanks John.
    Actually, Markus points out that I said Charles and instead of William, which shows you how much attention I paid to the event.

  3. Cormac, have you ever written a blog explaining why the neutrino is no longer considered a good candidate to explain dark matter and how its very low mass value is ascertained. thanks for your blog though I wish that some video clips of your public presentations were available.

  4. cormac

    Hi Thomas, it’a a fascinating subject but I think it would take more than a single post (I presume you meant a blog post). There are to main points here that I intend to write about soon
    1. the story of neutrino oscillation
    2. candidates for DM.
    In the meantime, Frank Close has just published a book on neutrinos, you can be surely it’s highly readable

  5. Hi Cormac,

    I’m glad you liked Markus’ talk. He is a top physicist on CMS and the MIT group overall are very strong and contribute in many areas. If you had to pick a talk to listen to, for the sake of getting a good overview of Higgs searches at the LHC, this would be the one. :)

    BTW, a word of caution: the indirectly excluded region in Markus’ plot obtains only for the standard model – CMS & the other LHC experiments do look at higher mass Higgs.


  6. cormac

    Thanks for that Micheal! Actually, I had wondered. One hears about the higher mass searches and then that plot is always shown!

  7. RSS feed request to Before It’s News

    Hi Mr. Cormac O’ Rafferty,

    My name is Ben Chasteen and I’m the Science editor at Before It’s News Our site is a People Powered news platform with over  2,500,000 visits a month and growing fast.

    We would be honored if we could republish your blog RSS feed in our Science category. Our readers need to read what your Antimatter blog has to say.

    Syndicating to Before It’s News is a terrific way spread the word and grow your audience. Many other organizations are using Before It’s News to do just that. We can have your feed up and running in 24 hours. I just need you to reply with your permission to do so. Please include the full name and email of the person who will be attached to the account, and let me know the name you want on the account (most people have their name or their blog name).

    You can also have any text and/or links you wish appended to the end or prepended to the beginning of each of your posts on Before It’s News. Just email me the text and links that you want at the beginning and/or ending of each post. If you know html you can send me that. If not, just send me the text and a link to your site. It should be around 200 characters or less (not including links).

    You can, if you like, create a custom feed for Before It’s News that includes multiple links back to your blog or web site. We only require that RSS feeds include full stories, not partial stories. We don’t censor or edit work.
    Thank you,

    Ben Chasteen
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  8. Mario E. de Souza

    Sorry, guys, but the Higgs is just a chimera because quarks are composite. You may say now ‘come on, we haven’t seen it’, and the truth is that we have seen several indications of it. The first one was found in 1956 by Hofstadter when he determined the charge distributions of both nucleons. (one can see them around p. 450 (depending on edition) of the Berkeley Physics Course, vol. 1 (Mechanics)). We clearly see that both nucleons have two layers of internal constituents. Unfortunately these results were put aside from 1964 on due to the success of the quark model and of QCD later on. From 1985 on we began to see more indications of compositeness, but we were so enthusiastic with the SM that we didn’t pay much attention to them. A partial list of them: 1) in 1983 the European Muon Collaboration (EMC) at CERN found that the quarks of nucleons are slower when the nucleons are inside nuclei; 2) in 1988 the SLAC E143 Collaboration and the Spin Muon Collaboration found that the three quarks of the proton account for only half of its total spin (other subsequent collaborations (EMC in 1989 and Hermes in 2007) have confirmed this result which is called the proton spin puzzle); 3) in 1995 CDF at Fermilab found hard collisions among quarks indicating that they have constituents (this was not published because CDF didn’t reach a final consensus); 4) Gerald Miller at Argonne (Phys. Rev. Lett. 99, 112001 (2007)) found that close to its center the neutron has a negative charge equal to -1/3e (inside the positive region with +1/2e); 5) new measurements of the EMC effect have been carried out by J. Arrington et al. at Jefferson Lab and they have shown that the effect is much stronger than was previously observed; etc.
    Gerald Miller wrongly attibuted to d quarks the -1/3 charge at the neutron center, but as the neutron ia a udd system we know (even from QCD) that none of the 3 quarks spends much time at the center.
    The relevant paper on this subject is Weak decays of hadrons reveal compositeness of quarks which can be accessed from Google (it is at the top on the subjects Weak decays of hadrons, Decays of Hadrons and Weak decays).

    Therefore, we should go back and probe further the nucleons in the low energy scale, and carry on Miller’s experiment with the proton.