Exploring properties of long-lived particles in inelastic dark matter models at Belle II

Abstract

The inelastic dark matter model is one kind of popular models for the light dark matter (DM) below O(1) GeV. If the mass splitting between DM excited and ground states is small enough, the co-annihilation becomes the dominant channel for thermal relic density and the DM excited state can be long-lived at the collider scale. We study scalar and fermion inelastic dark matter models for $$ \mathcal{O} $$ O (1) GeV DM at Belle II with U(1)D dark gauge symmetry broken into its Z2 subgroup. We focus on dilepton displaced vertex signatures from decays of the DM excited state. With the help of precise displaced vertex detection ability at Belle II, we can explore the DM spin, mass and mass splitting between DM excited and ground states. Especially, we show scalar and fermion DM candidates can be discriminated and the mass and mass splitting of DM sector can be determined within the percentage of deviation for some benchmark points. Furthermore, the allowed parameter space to explain the excess of muon (g− 2)μ is also studied and it can be covered in our displaced vertex analysis during the early stage of Belle II experiment.

Crossing two-component dark matter models and implications for 511 keV $γ$-ray and XENON1T excesses

“…We assume q X is a real number and q X = 0, 1 such that all X 1 , X 2 and Φ are charged under U (1) X . On the other hand, in order to simplify our discussion, we don't [19,35,69,70]. These operators need special treatments or care.…”

Multi-track displaced vertices at B-factories

“…• Dark-flavour non-diagonal production: as an example, consider inelastic dark matter coupled to a dark photon, e + e − → γA , A → χ 2 χ 1 , where χ 1 is a stable invisible particle and χ 2 is the LLP [24][25][26][27][28][29][30][31]77]. This example is an illustrative model that predicts only a single LLP, showing the importance of single-LLP searches (N dv = 1) where possible.…”

“…For example, if we consider the case of a dark photon that is kinetically mixed with the SM photon, there are strong constraints on the model if the dark photon decays either exclusively through its coupling to the SM [14][15][16][17][18], or invisibly to unseen hidden-sector states [19][20][21]. If, however, the dark photon decays to hidden-sector states that partially decay back to the SM (for example, in the case of inelastic DM [22][23][24][25][26][27][28][29][30][31]), then neither search strategy applies, and the parameter space can be relatively unconstrained. Indeed, truly model-independent constraints from electroweak precision tests [32] and deep inelastic scattering [33] are sufficiently weak that they do not completely exclude dark photons as an explanation for the 4σ discrepancy between theory and experiment in (g − 2) µ [34,35].…”

Probing charged lepton flavor violation with axion-like particles at Belle II

“…For past studies of LLPs at Belle II, see, e.g., refs. [63][64][65][66][67][68][69][70][71][72][73]. Experimental LLP searches conducted at BaBar and Belle appear in refs.…”