Signal Injection Test: What, How, & Expectations

In summary, the "signal injection test" is a way to measure how close a simulated signal is to the Standard Model Higgs signal strength. If the signal is too weak, it is excluded at 95% confidence level.
  • #1
Alkass
20
0
hi

I would like to ask, what is all about a "signal injection test" ? How is it done and what one expects to see ? I ve read about it in some Higgs study/plots CERN has published

thanks

Alex
 
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  • #2
You can simulate what you expect without a Higgs, and then you can add a Higgs signal and see how the measurements change - is it possible to see the difference? As far as I know, "signal injection" is just that.
The same is possible for all other particle searches, of course.
 
  • #3
Ok, I get it - So what happens if you see the difference or not and how you quantify it ? Does it change the statistical significance of the null hypothesis in the case you can "see" a differnece? Or one should think about it, like a "biased" search, thus you should consider an H1 hypothesis in such a case instead of a null one ? At the end, why one would want to do such a test ?

thanks
-a
 
  • #4
So what happens if you see the difference or not and how you quantify it ?
If you do not see a difference between data and "simulation without signal", you can set an upper limit on the signal strength. If a simulated signal with some specific signal strength would lead to a significant deviation (usually: 10% or 5% probability that a downwards fluctuation gives fewer events), this signal strength is excluded at 90% (95%) confidence level.

That leads to those colorful plots like this one.

Consider a point at 150 GeV (just at the left edge of "LHC excluded"), for example, it is close to 1, and 1 is exactly the Standard Model signal strength. The point has the message "if there is a Standard Model Higgs at 150 GeV, we should have seen more events with a probability of 95%".

Actually, this is not true. Following my description, every point would have a probability of 5% to exclude everything, even if there is a Higgs and the data is not sufficient to see it yet. Therefore, the method is modified a bit to include the sensitivity of the search, but I think this is an irrelevant detail here.
 

What is a Signal Injection Test?

A Signal Injection Test is a method used in electrical engineering and physics to measure the response of a system to an injected signal. This is done to evaluate the performance and reliability of the system.

How is a Signal Injection Test performed?

A Signal Injection Test involves injecting a known signal into the system and then measuring the response. The signal can be in the form of a voltage, current, or frequency. The response is measured using various instruments such as oscilloscopes and spectrum analyzers.

What are the expectations of a Signal Injection Test?

The expectations of a Signal Injection Test are to identify any defects or malfunctions in the system, determine its frequency response, and evaluate its overall performance. It can also help in troubleshooting and identifying the source of any issues.

Why is a Signal Injection Test important?

A Signal Injection Test is important because it allows for the evaluation and validation of a system's performance. It can also help in detecting any potential issues before they can cause significant problems. This test is commonly used in industries such as telecommunications, aerospace, and automotive.

Are there any limitations to a Signal Injection Test?

Yes, there are some limitations to a Signal Injection Test. It may not be able to detect some types of faults or malfunctions, such as intermittent issues. It also requires specialized equipment and expertise to perform accurately. Additionally, the system needs to be powered and operational during the test, which may not be feasible in certain situations.

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