Flavourful Production at Hadron Colliders

TL;DR

This paper explores the potential existence of new scalar particles with flavour-dependent couplings at TeV-scale hadron colliders, emphasizing diquark scalars as promising candidates that could shed light on the Standard Model's flavour structure.

Contribution

It identifies diquark scalars as viable, unconstrained new particles with hierarchical flavour couplings, proposing them as key targets for collider searches to understand flavour physics.

Findings

Diquark scalars can have substantial couplings to light and heavy quarks.

Such scalars are compatible with existing flavour constraints.

Their discovery could provide insights into the Standard Model's flavour puzzle.

Abstract

We ask what new states may lie at or below the TeV scale, with sizable flavour-dependent couplings to light quarks, putting them within reach of hadron colliders via resonant production, or in association with Standard Model states. In particular, we focus on the compatibility of such states with stringent flavour-changing neutral current and electric-dipole moment constraints. We argue that the broadest and most theoretically plausible flavour structure of the new couplings is that they are hierarchical, as are Standard Model Yukawa couplings, although the hierarchical pattern may well be different. We point out that, without the need for any more elaborate or restrictive structure, new scalars with "diquark" couplings to standard quarks are particularly immune to existing constraints, and that such scalars may arise within a variety of theoretical paradigms. In particular, there can be substantial couplings to a pair of light quarks or to one light and one heavy quark. For example, the latter possibility may provide a flavour-safe interpretation of the asymmetry in top quark production observed at the Tevatron. We thereby motivate searches for diquark scalars at the Tevatron and LHC, and argue that their discovery represents one of our best chances for new insight into the Flavour Puzzle of the Standard Model.