WG2 STXS in Decay discussion
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LHCHWG2 meeting
- Zoom Meeting ID
- 69232720461
- Host
- Giacomo Ortona
- Useful links
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- Zoom URL
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Introduction (M. Duehrssen0
- This effort started ~10 years ago, but not much push for it until now
- This is a first case study of its feasibility with H->4l events from CMS and ATLAS
- We know STXS (in production) is affected by potentially large acceptance effects
- If we define Lorentz invariant fiducial regions in decay, we can mitigate them. Lorentz invariance is crucial to reduce DoFs.
- The goal is to have the same behaviour (or very close behaviour) between SM and BSM
- Detector effects are not completely removable, but we can mitigate them.
ATLAS presentation
- Fiducial selection close to Reco, but remove pT and eta dependance
- Close behaviour between SM and BSM
Action items:
- It would be nice to see the double ratio
- It would be nice to compare ZZ* vs gamma*gamma* vs Zgamma*
A: the eigenvectors shown are in any case taken among the most extreme cases - It would be nice to compare ttH and ggH
A: this was checked, the behaviour was the same
CMS presentation
- The agreement seems worst than in ATLAS case
A: it could be the CMS samples are more extreme, but most likely the fiducial volume was defined fine tuning it on the ATLAS selection and thus CMS pays a price for this. Some work is needed to adapt and compromise the fiducial selection across the 2 experiments.
Discussion / Action items
- The 2 experiments need to work a bit more on the definition of the fiducial selection
- Using the same samples should help making an apples-to-apples comparison
- Material could be shared on the WG2 twiki
- If the method works, the idea is to replace the decay defnition in STXS with the result of this study. To be noted: since the fiducial decay volume is not dependent on the production (Lorentz invariance), if we define M STXS production bins and N decay bins, the total number of bins is N+M (and not N*M). The (relative) number of events in each decay bin is the same for each production bin. So stage 0 would be to replace the definition of the decay final state, stage 1 we can introduce some binning (for example mZ2 which is sensitive to CP).
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