On-shell effective theory for higher-spin dark matter

Abstract

We apply the on-shell amplitude techniques in the domain of dark matter. Without evoking fields and Lagrangians, an effective theory for a massive spin-S particle is defined in terms of on-shell amplitudes, which are written down using the massive spinor formalism. This procedure greatly simplifies the study of theories with a higherspin dark matter particle. In particular, it provides an efficient way to calculate the rates of processes controlling dark matter production, and offers better physical insight into how different processes depend on the relevant scales in the theory. We demonstrate the applicability of these methods by exploring two scenarios where higher-spin DM is produced via the freeze-in mechanism. One scenario is minimal, involving only universal gravitational interactions, and is compatible with dark matter masses in a very broad range from sub-TeV to the GUT scale. The other scenario involves direct coupling of higher-spin DM to the Standard Model via the Higgs intermediary, and leads to a rich phenomenology, including dark matter decay signatures.

A complete Effective Field Theory for Dark Matter

“…Finally, the restriction to spin up to unity is also made for simplicity; DM with higher spins has been recently considered in Refs. [20,21].…”

“…It is typically assumed that the new state is either a scalar, a vector or a fermion, although higher spins have been also considered, see Refs. [20,21] for recent accounts. Among the simplest and most economical of these EFTs are the Higgs-portal models, in which a single DM particle is introduced in addition to the SM particles; it interacts in pairs only with the Higgs sector of the theory, which is assumed to be minimal [22] and, hence, involves only the unique Higgs boson observed at the LHC [23,24]; see Refs.…”

Constructing on-shell operator basis for all masses and spins

“…To formulate the massive EFT, the complete operator bases should be systematically constructed. However, so far there is no principle to construct the complete massive bases even there are some primary explorations done in [28][29][30][31]. In this paper, we first propose a method to systematically construct the on-shell amplitude bases involving massive particles with any spin based on group theory.…”

Confronting spin-3/2 and other new fermions with the muon g-2 measurement

“…Massive higher-spin particles, in particular spin-3/2 fermions in addition to spin-2 bosons are present in many supersymmetric extensions of gravity [8][9][10][11], and are also predicted in string-theoretical frameworks [12,13]. Furthermore, they are of interest on purely phenomenological grounds as, for instance, they may constitute dark matter (DM) [6,[14][15][16][17], or appear in the form of non-conventional experimental signatures at the LHC and future colliders [7]. As presently there is no well-motivated paradigm for searching for new phenomena beyond the SM, all possible directions must be pursued in the search for new physics and thus, considering the possibility of higher-spin fields is certainly worthwhile.…”