Of Particular Significance

Articles on Standard Model Higgs: #1 How it is Produced; #2 How It Decays

POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON 12/10/2011

To tell you what you need to know for the presentations on the Higgs particle search coming up on December 13th, I’m writing a sequence of three articles about the Standard Model Higgs particle, the simplest form of Higgs particle that might be present in nature, and the one that is the main target, during Phase 1 of the search for the Higgs particle, that the Large Hadron Collider (LHC) experiments are aiming to discover or rule out.

Click here for Article # 1, which is about how these particles are made. There are five major processes by which the Standard Model Higgs particle may be produced at the LHC.  In this article I’ll tell you what they are, and what we’d learn if we measured each of them precisely.

Click here for Article #2: how the Standard Model Higgs particle decays, and what we can learn by measuring those decays precisely.

Sunday or Monday, Article #3: how we search for the Standard Model Higgs particle, combining what we know about its production and decay with what we know about other processes that will mimic its presence in an LHC detector.  And also [probably to be extended later in the week] how we will go about making precise measurements of the properties of any candidate Higgs particle that we observe, to confirm that it really is a Standard Model Higgs particle, and not something more complicated.


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2 Responses

  1. Dear Matt, there has been some seriously heavy traffic on your site since the CERN Higgs presentation. I am a layman who tries to keep my cats and fellow humans informed. Would I be wrong to summarize the current state of play as follows:

    1. It has proven difficult to rule out signals between 115 and (about) 128 GEV.

    2. ATLAS and CMS both appear to have blips on both of two SM Higgs decay channels nearly ( but not exactly) about a Higgs mass of 125 GEV.

    3. Five sigma, one way or another, is about 2500 inverse femtobarns away. (or in baseball parlance — wait’l next year)

    Is there anything else I should tell my cats?

    1. Close.

      1. is right.
      2. is right (though in 2, CMS also claims to have not blips but small general excesses in three other channels that do not give a good mass measurement but do tell you something about rate — I cannot evaluate these claims yet; and ATLAS has a similar excess in the one channel, but I really don’t trust that one yet.) 3. 5 sigma for each experiment *separately* requires that much data. But 5 sigma for the two experiments together will come sooner. But still — wait’l next year.

      p.s. in baseball you say “wait till next year” when you lose. There were no losers here. It is a huge achievement by the LHC experiments and the accelerator to come this far during 2011.

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