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2017:groups:higgs:lhsmeftroadmap [2017/06/22 18:43] fabio.maltoni created |
2017:groups:higgs:lhsmeftroadmap [2017/06/29 14:29] (current) kristin.lohwasser |
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====== Staged approach towards constraining the SMEFT at the LHC ====== | ====== Staged approach towards constraining the SMEFT at the LHC ====== | ||
- | **Motivation:** Fiducial cross section measurements and STXS in Higgs physics are being developed and will provide non-maximally sensitive input to global SMEFT fits. Direct experimental top-down SMEFT interpretations of LHC SM measurements in Higgs and top physics have not yet taken off, due mostly to a difficulty of handling the richness of possible theoretical approaches together with many technical complications. | + | Interested people: Fabio Maltoni, Kristin Lohwasser... |
- | **Aim:** Stimulate the implementation and development of SMEFT measurements at the LHC by devising a multi-staged approach. | + | **Motivation:** Fiducial cross section measurements and STXS in Higgs physics are being developed and will provide non-maximally sensitive input to global SMEFT fits. Direct experimental top-down SMEFT interpretations of LHC SM measurements in Higgs and top physics have not yet taken off, due mostly to a difficulty of handling the richness and diversity of the many theoretical approaches together with the intrinsic technical complications. |
- | ** Stage 1 (proposal)**: Provide the strongest (even MVA based) constrains from (one or more) processes/observables on one operator at the time. | + | **Aim** : Stimulate the implementation and development of SMEFT measurements at the LHC by devising a multi-staged approach. |
- | ** Some advantages: ** | + | ** Stage 1 (proposal)** : Provide the strongest (even MVA based) constrains from (one or more) processes/observables on one operator at the time. |
+ | |||
+ | ** Some advantages ** : | ||
- A necessary step before achieving a global fit | - A necessary step before achieving a global fit | ||
- | - Way easier than a global and feasible today | + | - Way easier than a global fit and feasible today |
- Scales (less than) linearly with the number of operators | - Scales (less than) linearly with the number of operators | ||
- Basis agnostic (any operator can be added to the list) | - Basis agnostic (any operator can be added to the list) | ||
- Provides reference information to fits based on model independent bottom up approaches (fiducial or simplified XS) | - Provides reference information to fits based on model independent bottom up approaches (fiducial or simplified XS) | ||
- | - Educational purposes, i.e. learning about how each operator behaves, | + | - Educational purposes, i.e. learning about how each operator behaves |
- Provides benchmarking of sensitivities between different analyses and/or different experiments | - Provides benchmarking of sensitivities between different analyses and/or different experiments | ||
+ | - It offers a simple way to quantify the loss of sensitivity of STXS or FXS with respect to a top-down approach | ||
- Known issues such as interference vs squared dominance, validity studies, and others can be easily studied | - Known issues such as interference vs squared dominance, validity studies, and others can be easily studied | ||
- It can be automatised at the analysis level (basically one or few types of analysis really necessary) | - It can be automatised at the analysis level (basically one or few types of analysis really necessary) | ||
- | - Other? | + | - Other? Please add here... |
- | ** Drawbacks/Limitations: ** | + | **Drawbacks/Limitations** : |
- | - Results are not constraints on the coefficients and therefore should not be used to establish that operators coefficients are small. | + | - Results are not constraints on the coefficients and therefore should not be used as such. |
- | - Other? | + | - Other? Please add here... |
+ | |||
+ | ** Les Houches Project** : | ||
- | ** Les Houches Project: ** | ||
- Provide comprehensive list of operators (with simple normalisation) and implementation | - Provide comprehensive list of operators (with simple normalisation) and implementation | ||
- Provide minimal list of recommendations (sanity checks, int vs square treatments, perturbative orders, EFT validity,…) | - Provide minimal list of recommendations (sanity checks, int vs square treatments, perturbative orders, EFT validity,…) | ||
- Fully Work out a few examples in Higgs, Top and EW physics. | - Fully Work out a few examples in Higgs, Top and EW physics. | ||
+ | - More? | ||
+ | |||
+ | ** Examples of LHC analyses following the SMEFT-one-operator-at-the-time approach ** | ||
+ | |||
+ | - [[http://cms-results.web.cern.ch/cms-results/public-results/preliminary-results/TOP-17-005/index.html|CMS SM measurement of ttW and ttZ]] | ||
+ | - [[? |Diboson ]] | ||