====== B2b: Operator analysis of New Physics in top quark observables ======

^Principal Investigators^^
|[[http://www.thphys.uni-heidelberg.de/~westhoff/ | Jun.-Prof. Susanne Westhoff ]] |Heidelberg University |

==== Subject ====

Top-quark interactions can be tested to high precision directly in resonant top production at the LHC, as well as indirectly in flavor and electroweak precision observables. We perform a model-independent global search for physics beyond the Standard Model in top-quark ob- servables in the framework of an effective field theory (EFT), described by $${\cal L}_{\rm eff} = \sum \limits_{i} \frac{C_i}{\Lambda^2} {\cal O}_i + {\cal O}(\Lambda^{-3}).$$
In this framework, effects of new physics in different observables are correlated in a predic- tive way. For example, the effective operator $${\cal O}_{tW} = 
\left (\bar Q_L \sigma^{\mu \nu} \tau^\alpha t_R \right ) \tilde H W_{\mu \nu}^{\alpha}$$ contributes to electroweak single top production at the LHC, but  also to rare  meson decays. 

In our global analysis, we connect top-quark and Higgs observables with flavor observa- bles by matching the EFT {Ci Oi} from Eq. (1) onto the weak effective theory {Ci Oi} and evolving the Wilson coefficients down to the energy scale of meson decays.

The EFT connection between flavor and high-energy observables depends on the flavor struc- ture of the Wilson coefficients Ci at high energies. We identify new search directions in high- energy processes that are compatible with a specific flavor structure and thus guide future searches for new physics with top-quarks.

==== Topics ====

  - Precise predictions of new physics effects  in top-quark observables 
     * Computation of top-quark LHC observables in the effective theory at NLO QCD.
     *  Monte-Carlo simulations of cross sections and kinematic distributions.
  - Global data analysis and interpretation
     * Global fit of top observables to LHC data, using analysis tool SFitter. ◦ Detailed analysis of systematic uncertainties and correlations.
     *  Interpretation of fit results in terms of Wilson coefficients.
  - Combination of high- and low-energy observables 
     * Include flavor observables with virtual top-quarks in global analysis.
     *  Connect observables at different energy scales through renormalization group evolution at LO QCD.
     * Impact of flavor observables on flavor structures of Wilson coefficients.
  - Future goals 
     * Include Higgs and electroweak observables in global fit.
     * Investigate effects of CP violation in top-quark interactions.
     * Interpret fit results in terms of complete models of new physics.