Invisible decay modes in nuclear gamma cascades

Abstract

We propose a high statistics experiment to search for invisible decay modes in nuclear gamma cascades. A radioactive source (such as 60 Co or 24 Na) that triggers gamma cascades is placed in the middle of a large, hermetically sealed scintillation detector, enabling photon identification with high accuracy. Invisible modes are identified by establishing the absence of a photon in a well-identified gamma cascade. We propose the use of fast scintillators with nanosecond timing resolution, permitting event rates as high as 10 7 Hz. Our analysis of the feasibility of this setup indicates that branching fractions as small as 10 −12 − 10 −14 can be probed. This experimental protocol benefits from the fact that a search for invisible modes is penalized for weak coupling only in the production of the new particle. If successfully implemented, this experiment is an exquisite probe of particles with mass below approximately 4 MeV that lie in the poorly constrained supernova "trapping window" that exists between 100 keV and 30 MeV. Such particles have been invoked as mediators between dark matter and nucleons, explain the proton radius and ðg − 2Þ μ anomalies, and potentially power the shock wave in type II supernovae. The hadronic axion could also be probed with modifications to the proposed setup.

Axion-Like Particles at Coherent CAPTAIN-Mills

“…These include ongoing and proposed experiments such as haloscopes (ADMX [5,6], ABRA-CADABRA [7,8], HAYSTAC [9,10], CASPEr [11]), helioscopes (CAST [12,13], IAXO [14,15]), interferometry [16][17][18][19], light-shining-through-wall experiments [20], ongoing and future accelerator-based experiments (NA62 [21], NA64 [22,23], FASER [24], LDMX [25,26], SeaQuest [27], SHiP [28], PASSAT [29]), reactor experiments (e.g., MINER, CONUS, TEXONO etc. [30][31][32]), dark matter experiments (DAMA [33], XMASS [34], EDELWEISS [35,36], SuperCDMS [37], XENON [38,39], Pan-daX [40]), resonant absorption by nuclei [41][42][43][44][45][46][47][48][49][50], astrophysical observations [51]…”

Exploring the robustness of stellar cooling constraints on light particles

“…Additionally, for judicious choices of parameters, our mechanism allows models that would otherwise be constrained by stellar cooling to explain anomalous observations such as the EDGES signal and the recent Xenon1T excess. This mechanism demonstrates the need for laboratory experiments (such as [42,43]) to robustly search for light particles as opposed to relying on bounds from extreme astrophysical environments. TABLE V. Core temperatures, densities, and radii for the various astrophysical bodies used to constrain axions.…”

Recent Progress in the Physics of Axions and Axion-Like Particles

“…For axions lighter than the megaelectronvolt scale, the constraints are from the axion-mediated fifth force induced by ḡaN , stellar cooling by ḡae (93), and supernova (SN1987A) cooling by ḡaN . The currently unconstrained supernova trapping window between 100 keV and 30 MeV may be explored by the GANDHI experiment (94). Ultralight axion DM can be tested by a future nuclear clock experiment (20), torsion balances (95), and atom interferometers such as AION (96) and AEDGE (97) through axion DM's CP-violating couplings.…”