How macroscopic limits on neutron-star baryon loss yield microscopic limits on non-standard-model baryon decay

Abstract

We investigate how our baryon-loss limits from anomalous binary-pulsar period lengthening can be interpreted microscopically to yield specific constraints on the particle physics of baryon number violation within a neutron star. We focus on the possibility of anomalous baryon disappearance via dark baryon processes and on scenarios in which the produced dark-sector particles do not survive to influence the response of the star to baryon-number-violating effects. We flesh out the conditions for which this may occur, as well as other key assumptions. We then turn to the analysis of particle processes in the dense nuclear medium found at the core of a neutron star, employing the techniques of relativistic mean-field theory. Using our study of in-medium effects and limits on macroscopic baryon number violation, we extract limits on in-vacuum baryon-number-violating processes, and we determine them for various equations of state. We conclude by noting the implications of our results for models of dark-sector-enabled baryogenesis. Published by the American Physical Society 2024

Pulsar timing anomalies: a window into baryon number violation

“…Under these assumptions, BNV is envisioned to steer a neutron star through a series of quasi-equilibrium states, each described by the fixed baryon-conserving EoS. Such a transformation impacts the binary orbital periods of pulsars and their spin-down rates [14,[22][23][24]. Our previous paper laid the groundwork by exploring how neutron stars can generically constrain ongoing BNV, leveraging effects on binary pulsars' orbital periods [22].…”

“…Our previous paper laid the groundwork by exploring how neutron stars can generically constrain ongoing BNV, leveraging effects on binary pulsars' orbital periods [22]. Subsequent research delved deeper into the specifics of particle physics models and the role of dense matter in BNV processes within neutron stars [14]. While these studies primarily focused on mechanisms affecting the orbital period of binary pulsars, the intricate details of BNV's influence on pulsar spin-down characteristics remained unexplored.…”

“…Despite the elusive nature of BNV in current terrestrial experiments, like those conducted at Super-Kamiokande [12] and KamLAND [13], the extreme conditions within neutron stars provide a starkly different environment that may facilitate BNV processes. The intense gravitational forces within these astrophysical bodies can result in highly repulsive interactions among baryons, potentially enabling decay channels that are kinematically inaccessible in vacuum or within the confines of atomic nuclei [14]. The dense cores of heavier neutron stars, possibly teeming with hyperons [15], offer a natural laboratory for probing BNV within the strange quark sector.…”

“…The dense cores of heavier neutron stars, possibly teeming with hyperons [15], offer a natural laboratory for probing BNV within the strange quark sector. In this context, observational data from binary pulsars have been used [14] to place constraints on hyperon decays to dark sectors [16], with implications that significantly extend beyond the reach of current terrestrial experiments [17]. These constraints are far more stringent, enhancing our understanding of BNV in these exotic environments.…”

“…The potential occurrence and rates of BNV across neutron stars, if they exist, are likely to be non-uniform and would be influenced by the complex interaction between particular particle physics models and the internal conditions of these stars. The composition of particles and their energy spectrum within a neutron star -factors critical to BNV rates [14]-are primarily dictated by the star's total mass and the chosen equation of state (EoS). For instance, in scenarios anticipating BNV in the strange quark sector [16,[18][19][20], BNV activity is contingent upon a critical mass threshold for hyperon presence in the core.…”