The INTEGRAL/SPI 511 keV Signal from Hidden Valleys in Type Ia and Core Collapse Supernova Explosions

TL;DR

This paper explores how hidden valley models with long-lived composite states from supernovae could explain the INTEGRAL/SPI 511 keV gamma-ray signal, proposing new particle physics mechanisms and their astrophysical implications.

Contribution

It introduces hidden valley scenarios for supernova-produced states that could account for the 511 keV signal and discusses their potential effects on supernova dynamics and dark matter.

Findings

Hidden valley models can produce long-lived states explaining the 511 keV signal.

Type Ia supernova dynamics may be affected by these new states.

Mediator masses range from hundreds of GeV to TeV, with collider and cosmological implications.

Abstract

We examine under what circumstances the INTEGRAL/SPI 511 keV signal can originate from decays of MeV-scale composite states produced by: (A) thermonuclear (type Ia) or (B) core collapse supernovae (SNe). The requisite dynamical properties that would account for the observed data are quite distinct, for cases (A) and (B). We determine these requirements in simple hidden valley models, where the escape fraction problem is naturally addressed, due to the long lifetime of the new composite states. A novel feature of scenario (A) is that the dynamics of type Ia SNe, standard candles for cosmological measurements, might be affected by our mechanism. In case (A), the mass of the state mediating between the hidden sector and the SM $\ee$ could be a few hundred GeV and within the reach of a 500 GeV $\ee$ linear collider. We also note that kinetic mixing of the photon with a light vector state may provide an interesting alternate mediation mechanism in this case. Scenarios based on case (B) are challenged by the need for a mechanism to transport some of the produced positrons toward the Galactic bulge, due to the inferred distribution of core collapse sources. The mass of the mediator in case (B) is typically hundreds of TeV, leading to long-lived particles that could, under certain circumstances, include a viable dark matter candidate. The appearance of long-lived particles in typical models leads to cosmological constraints and we address how a consistent cosmic history may be achieved.