New Physics in LHC data

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  • Thread starter Malamala
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  • #1
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Main Question or Discussion Point

Hello! The attached pic is from this paper. So on the y you have counts and on the x you have a certain parameter used to search for a certain resonance. The colored part is the Standard Model (SM) prediction and the black dots are the obtained data while the dashed lines are the simulated prediction for the contribution of this new resonance. Obviously no deviation is observed in the region of interest. However if you look in the last 5-7 bins (maybe except the last 2), especially in the bottom plot, the data points deviate significantly from the predicted background. Is it because the simulation didn't focus much there (as it is outside the region of interest for the specific resonance) or it can be something deeper (the points seems to be quite a few sigma below the predicted model)? If the simulations are correct over the whole presented range, shouldn't these points be closer (within the error bars) to the predicted model? Thank you!
 

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  • #2
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Probably an issue with the theoretical prediction for the QCD contribution. If you would have systematic uncertainties shown in this plot they would probably cover the observed deviation.
 
  • #3
71
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Probably an issue with the theoretical prediction for the QCD contribution. If you would have systematic uncertainties shown in this plot they would probably cover the observed deviation.
Thank you for your reply! I am still a bit confused. An issue with the theoretical prediction doesn't mean there is something we don't understand about that particular region of phase space?
 
  • #4
34,065
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It means QCD is complicated. Predictions often have to rely on some assumptions, approximations, experimental data as input and so on. I'm more surprised that most of the region is so well-described. Some deviation at the edge of the phase space with such a steep distribution is perfectly plausible.
 

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