BSM with cosmic strings: heavy, up to EeV mass, unstable particles

Abstract

Unstable heavy particles well above the TeV scale are unaccessible experimentally. So far, Big-Bang Nucleosynthesis (BBN) provides the strongest limits on their mass and lifetime, the latter being shorter than 0.1 second. We show how these constraints could be potentially tremendously improved by the next generation of Gravitational-Wave (GW) interferometers, extending to lifetimes as short as 10 −16 second. The key point is that these particles may have dominated the energy density of the universe and have triggered a period of matter domination at early times, until their decay before BBN. The resulting modified cosmological history compared to the usually-assumed single radiation era would imprint observable signatures in stochastic gravitationalwave backgrounds of primordial origin. In particular, we show how the detection of the GW spectrum produced by long-lasting sources such as cosmic strings would provide a unique probe of particle physics parameters. When applied to specific particle production mechanisms in the early universe, these GW spectra could be used to derive new constraints on many UV extensions of the Standard Model. We illustrate this on a few examples, such as supersymmetric models where the mass scale of scalar moduli and gravitino can be constrained up to 10 10 GeV. Further bounds can be obtained on the reheating temperature of models with only-gravitationally-interacting particles as well as on the kinetic mixing of heavy dark photons at the level of 10 −18 .

The First Three Seconds: a Review of Possible Expansion Histories of the Early Universe

“…The key feature of these spectra is that a flat plateau develops, produced by the strings continuously emitting throughout the RD period. In the case of strings evolving in a nonstandard period of expansion [993,994,995,996] the spectra will change similarly to the case of an inflationary plateau discussed above. The modification will be visible above a characteristic frequency corresponding to the reheating temperature T reh [994] f…”

“…For example with w = 0, if the emission is dominated by cusps, the high frequency spectrum would follow f − 1 3 . More subtle modification such as a change in the number of degrees of freedom will also leave a distinguishable feature in the spectrum at frequency (86) [994,996]. A short period of inflation would leave an imprint on the spectrum similar to the case of EMD [999,995], however, strings produced close to the beginning of inflation can have a much more striking phenomenology, as the stochastic background can be severely diluted, leaving recently produced GW bursts as the main detection prospect [998].…”

Metastable strings and dumbbells in supersymmetric hybrid inflation

“…The possible connection of the NANOGrav results with GUT models and high-scale leptogenesis has also been studied in [36][37][38][39], and effects of low-scale leptogenesis on the SGWB were considered in [40]. Note that, independent of grand unification, a SGWB form a cosmic string network is a very interesting and well motivated signature of physics beyond the Standard Model [41][42][43][44].…”

Gravitational wave complementarity and impact of NANOGrav data on gravitational leptogenesis

“…Most distinguishable feature of GW emission from cosmic string is prediction of a strong signal across a wide range of frequency which has triggered a growing interest in this JHEP05(2021)211 field [76][77][78][79][80][81][82][83][84][85][86]. This also includes recent studies to probe GUT [87,88], high scale leptogenesis [89], low scale leptogenesis [90].…”