Signal strength parameter (interpretation)

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ChrisVer
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How can in general the signal strength parameter ##\mu## be interpreted?

I am talking for the parameter defined in Eq.1 here and plots like the Fig.1 here:
http://arxiv.org/abs/1507.04548

It says that it's the ratio of the i->H->f of the observed over what's expected by the SM... is the last the cross section prediction of the Higgs or for any other background?
Then what would the <1 or >1 indicate? I think the >1 indicate a signal excess, while the <1 indicate a signal underestimation(????)
 

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  • #2
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is the last the cross section prediction of the Higgs or for any other background?
Only Higgs. The background in data is subtracted before μ is calculated.
Then what would the <1 or >1 indicate?
A deviation from the standard model. If μ=1 gets ruled out in some channel, things get interesting.
 
  • #3
ChrisVer
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Only Higgs. The background in data is subtracted before μ is calculated.
Is that the case even if you have background overestimation compared to data?
 
  • #4
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I'm not sure if I understand your question. If you overestimate something, you are doing something wrong and should fix it, or not use what you cannot get right.
 
  • #6
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That is (hopefully) not an overestimate, just a statistical fluctuation. Yes, estimated signal strengths can be negative. As a random example, this ATLAS note has -0.4 +- 1.1 for VH -> Vbb in table 2. Note that it is consistent with 1, the uncertainties were just very large in 2012.
 

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