Orateur
Description
Rare top-quark processes, ttW,ttH,tH,ttZ,tttt, are traditionally measured in separate analyses, despite substantial overlap among their multilepton final states. However, this strongly limits the overall physics understanding, as the correlations between the various measurements are large and poorly known. We propose a new approach to tackle these limitations by simultaneously reconstructing and classifying these processes within a unified framework. The reconstruction of these processes in the multilepton final state is challenging due to undetected neutrinos and the combinatorial ambiguity arising from multiple decay products. For the reconstruction and classification, we plan to exploit both permutation symmetry among final-state objects and Lorentz symmetry of their kinematics. We will utilize Lorentz-Equivariant Geometric Algebra transformers (LGATr)[1], whose layers are Lorentz-equivariant by construction and operate on multivectors of spacetime algebra, with controlled symmetry breaking introduced to match LHC physics. We will also test Lorentz Local Canonicalization (LLoCa)[2], which achieves equivariance through per-particle local frames and can be applied to arbitrary architectures. These approaches will be compared with standard transformer architectures. As Lorentz-equivariant networks benefit from input features that respect the underlying Lorentz symmetry[3], a key challenge is determining how best to represent the available kinematic information. The talk will present our approach and discuss the challenges and open questions in constructing meaningful representations for Lorentz-equivariant transformers
References:
1.arXiv:2405.14806
2.arXiv:2505.20280
3.arXiv:2608.02735