Beyond the dark matter effective field theory and a simplified model approach at colliders

Seungwon Baek,Chaehyun Yu,P Ko,Myeonghun Park,Wan-Il Park

doi:10.1016/j.physletb.2016.03.026

Abstract

Direct detection of and LHC search for the singlet fermion dark matter (SFDM) model with Higgs portal interaction are considered in a renormalizable model where the full Standard Model (SM) gauge symmetry is imposed by introducing a singlet scalar messenger. In this model, direct detection is described by an effective operator m_q \bar{q} q \bar{\chi} \chi as usual, but the full amplitude for monojet + \not E_T involves two intermediate scalar propagators, which cannot be seen within the effective field theory (EFT) or in the simplified model without the full SM gauge symmetry. We derive the collider bounds from the ATLAS monojet + \not E_T as well as the CMS t\bar{t} + \not E_T data, finding out that the bounds and the interpretation of the results are completely different from those obtained within the EFT or simplified models. It is pointed out that it is important to respect unitarity, renormalizability and local gauge invariance of the SM.

Highlights

Dark matter effective field theory (DM EFT) has been widely used for analyzing the data from DMdirect detections, thermal relic density and collider searches for mono X + ET [1], based on crossing symmetry which is an exact symmetry of quantum field theory
We repeat the analysis on the ATLAS monojet + ET signature [11] and the CMS tt + ET [12] signatures and derive the bounds on the new physics scales, which are completely different from those obtained by ATLAS and CMS Collaborations [24]
In this letter, we discussed the DM search at LHC within a renormalizable theory for singlet Dirac fermion DM with Higgs portal and the full Standard Model (SM) gauge symmetry, and demonstrated how and why the EFT approach or DM simplified models without the full SM gauge symmetry can break down for collider searches, and why the complementarity based on crossing symmetry of quantum field theory can be misleading

Summary

Introduction

Dark matter effective field theory (DM EFT) has been widely used for analyzing the data from DM (in)direct detections, thermal relic density and collider searches for mono X + ET (with X = g, γ, W, Z etc.) [1], based on crossing symmetry which is an exact symmetry of quantum field theory. Assuming the complementarity among direct detection, collider search and indirect detection (or thermal relic density), the bound on the scale Λ, (or M∗) of above operators has been studied extensively in literature [1]. One can write down the SM gauge symmetry invariant effective operator as a dimension 7 operator form; L ydyχ Λ3. The simplest way to write down a renormalizable operator that is invariant under the full SM gauge group is to introduce a real singlet scalar field S [5, 9] and induce an operator sχχ × hqq. Note that there is a generic cancellation between two contributions from two neutral scalars, which cannot be seen within EFT approach [5, 9]

Renormalizable Model with the full SM gauge symmetry

Collider Studies

Relation between a mediator and an effective operator approach

Conclusion