What Are Control and Signal Regions in Particle Physics Experiments?

[sandiego137]

I am recently reading the articles "Search for squarks and gluinos using final states with jets and missing transverse momentum with the ATLAS detector in sqrt s=7 TeV proton-proton collisions". However, as my limited knowledge, many technical terms that I am understanding as a result I am now struggling with it. By the way, I am second year undergraduate.

I will so appreciate if someone can help me to explain the following:
-what is the purpose of 'control region' and 'signal region'? e.g QCD control region.
-true/fake missing transverse energy.
-Monte Carlo simulation, I often came across the term' QCD Monte Carlo'.
-reversed delta phi cut.
-(jet)response function.
-seed events, smearing. eg. smeared the seed events.(really need explain for this)
-(jet)triggers.
-pseudo-data
-pt balance
-and finally, 'cut' etmiss cut, pt leading jet cut, etc...

I am not very good in English. Hope someone can help me, Thankssss!

 

[mitchell porter]

It would be better if a real experimental physicist answered your question. However, I do at least speak English, so...

-what is the purpose of 'control region' and 'signal region'? e.g QCD control region.

These might be regions of experimental parameter space. Observations in the signal region would be directly testing the hypothesis, observations in the control region might be controls in the sense of experimental design.

-true/fake missing transverse energy.

"Fake" = wrong, wrongly reconstructed.

-Monte Carlo simulation, I often came across the term' QCD Monte Carlo'.

http://en.wikipedia.org/wiki/Monte_Carlo_method#Physical_sciences"

-reversed delta phi cut.

A cut https://www.physicsforums.com/showthread.php?t=284486#2" a method of choosing which observations to keep and which to discard. phi might be the angle between jets, delta phi the change in phi. I don't know what the reverse delta phi cut is and couldn't find that phrase in the paper.

-(jet)response function.

A response function describes how one thing responds to another. So this describes how some property of the jet changes in response to another variable.

-seed events, smearing. eg. smeared the seed events.(really need explain for this)

I think seed events are sample observations used to set phenomenological parameters in the Monte Carlo simulation. Smearing http://plhc2010.desy.de/e43826/e89919/e89941/PLHC2010_poster_Owen.pdf" it's a correction to the raw data from the seed events.

-(jet)triggers.

The trigger is http://aliceinfo.cern.ch/Public/en/Chapter2/Chap2_HLT.html" the neural network which decides whether a particular observation gets recorded.

-pseudo-data

Simulated experimental data (not from real experiments), used to test the information-processing system.

-pt balance

p is momentum, p_T is transverse momentum, p_T balance is probably a measure of how lopsided p_T is.

-and finally, 'cut' etmiss cut, pt leading jet cut, etc...

Explained above.

P.S. For curious readers, http://arxiv.org/abs/1102.5290" .