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LHC and constrains on heavier Higgs bosons

  1. Aug 5, 2014 #1
    Hi all,

    I wonder if I study new Higgs scalars, How the data of the LHC for searching for heavier scalars
    in h-> WW->lvlv and h -> ZZ-> 4 l channels like in [arXiv:1304.0213] can make constrain on my
    study for the new Higgs?

    How a figure like figure 2 can give constrains on my model free parameters ..

  2. jcsd
  3. Aug 5, 2014 #2
    Well that figure is showing the constraints on the ratio of the cross section for h->WW->lvlv to the value predicted by the Standard Model, if the usual Higgs had each of the masses on the x axis. So anywhere the black line (observed 95% CLs limit) drops below 1 means a scalar behaving like a SM Higgs with that mass is excluded at that confidence level.

    So if you have a model which predicts a new scalar that has the same couplings as a SM Higgs then you can use the plot to say what masses it is excluded for. If the production cross section and branching ratio to WW is different to a SM Higgs then it is more complicated how that plot constrains the model. It can still be done but there is more work to do figuring out how the exclusion limits need to be scaled.

    edit: actually it is not so hard; once you predict the appropriate cross section in your model you divide it by the cross section according to the SM and you get a point on the y axis on that graph, for some given boson mass. If your model point falls above the black line, it is excluded.
    Last edited: Aug 5, 2014
  4. Aug 6, 2014 #3
    # If your model point falls above the black line, it is excluded.

    I think you mean below ?
  5. Aug 6, 2014 #4
    Hmm, no above. Downwards means lower cross-section relative to the SM Higgs, so less detectable. The graph excludes scalars with cross section equal to the SM Higgs for this process (the red line) from something like 150 GeV to about 600 GeV.
  6. Aug 6, 2014 #5


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    As the figure captions say: "95% CL upper limit". This means that larger values are excluded, since they are above the upper limit.
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