Abstract
We investigate the bounds which can be placed on generic new-physics contributions to dijet production at the LHC using the framework of the Standard Model Effective Field Theory, deriving the first consistently-treated EFT bounds from non-resonant high-energy data. We recast an analysis searching for quark compositeness, equivalent to treating the SM with one higher-dimensional operator as a complete UV model. In order to reach consistent, model-independent EFT conclusions, it is necessary to truncate the EFT effects consistently at order 1/Λ2 and to include the possibility of multiple operators simultaneously contributing to the observables, neither of which has been done in previous searches of this nature. Furthermore, it is important to give consistent error estimates for the theoretical predictions of the signal model, particularly in the region of phase space where the probed energy is approaching the cutoff scale of the EFT. There are two linear combinations of operators which contribute to dijet production in the SMEFT with distinct angular behavior; we identify those linear combinations and determine the ability of LHC searches to constrain them simultaneously. Consistently treating the EFT generically leads to weakened bounds on new-physics parameters. These constraints will be a useful input to future global analyses in the SMEFT framework, and the techniques used here to consistently search for EFT effects are directly applicable to other off-resonance signals.
Highlights
Other particles in the SM) [1]
We investigate the bounds which can be placed on generic new-physics contributions to dijet production at the LHC using the framework of the Standard Model Effective Field Theory, deriving the first consistently-treated EFT bounds from non-resonant high-energy data
There are two linear combinations of operators which contribute to dijet production in the SMEFT with distinct angular behavior; we identify those linear combinations and determine the ability of LHC searches to constrain them simultaneously
Summary
In the SMEFT, the SM Lagrangian is systematically supplemented by higher-dimensional operators built out of SM fields which are invariant under SU(3)C × SU(2)L × U(1)Y. Note that the color-singlet four-quark operators composed of bilinears of distinctly-charged quarks cannot interfere with the QCD amplitude; this is due to the need for there to be quarks with identical weak charges and distinct color for a gluon to couple to These non-interfering operators are marked with an asterisk in table 1. The χ variable is constructed such that the SM contribution is largely independent of χ, whereas the contribution from the four-fermion contact operator considered in these analyses, notably Q(q1q) from table 1, is generally largest for small values of χ This difference in angular behaviors of the signal and background allows various experimental techniques to be used, including the consideration of normalized distributions, where higher-order QCD and experimental jet energy scale uncertainties can be partially removed. While these are equivalent statements for the signal strength predicted, they require distinct treatment when it comes to considering the theoretical errors inherent in the signal prediction
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