Neutrino measurements probe in-medium hyperon potentials for neutron-star equation of state

Neutrino-induced hyperon final-state interactions as constraints on the in-medium hyperon potential

arXiv:2607.09273v1 Announce Type: cross Abstract: Hyperon single-particle potentials $U_Y(\rho)$ control propagation in nuclei and hyperon onset in dense matter, where they soften the neutron-star equation of state and reduce the maximum mass -- the ``hyperon puzzle''. We show that charged-current accelerator (anti)neutrino interactions on $^{40}$Ar, producing $\Lambda$ and $\Sigma$ inside the nucleus, can constrain these potentials. At SBND and DUNE energies, the trapped-$\Lambda$ fraction and escaping-hyperon momenta vary monotonically with $U_\Lambda$ and $U_\Sigma$, with a kaon-vetoed FSI-$\Sigma^+$ tag adding sensitivity. Inserted in a GM1 relativistic mean-field equation of state at established hypernuclear/$\Sigma$-atom depths, the same potentials give $M_{\rm max} = 1.94\,M_\odot$ and $\Lambda_{1.4}=1034$, below the heaviest pulsars and above the GW170817 bound typical of GM1-class mean fields. A detector-level Fisher forecast yields $\delta U_\Lambda \simeq 0.3\,$MeV and $\delta U_\Sigma \simeq 3$-$4\,$MeV for fixed low-density exponent $\gamma$. Since hyperons are produced below saturation, $U_\Lambda(\rho_0)$ and $\gamma$ are 99.8\% anti-correlated; marginalising over $\gamma$ degrades the anchor to $\delta U_\Lambda \simeq 5.6\,$MeV ($1.3\,$MeV with a $\pm 0.2$ prior), while $\delta U_\Sigma$ is unchanged. For $U_\Lambda$, comparable systematics arise from hyperon-nucleon final-state cross sections ($-5/{+}2\,$MeV) and the exit-shift/gradient transport prescription ($-6\,$MeV). For $U_\Sigma$, the same $YN$ uncertainty biases the fit by $\mathcal{O}(150)\,$MeV; removing the $\Sigma^+$ tag does not cure this, because the $\Lambda$ momentum spectrum carries most $U_\Sigma$ information and is itself $YN$-sensitive. The low-density $U_\Lambda$ anchor is a robust handle, at several-MeV rather than sub-MeV precision. A joint fit with terrestrial and heavy-ion priors gives $M_{\rm max} = 2.21^{+0.04}_{-0.15}\,\,$Msun, set mainly by the external $c_\Lambda$ prior.

2 hours ago

In-medium hyperon potentials and the quarkyonic hyperon onset: charged $\Sigma$'s in $\beta$-equilibrium and the neutrino connection

arXiv:2607.09280v1 Announce Type: cross Abstract: Quarkyonic matter resolves the neutron-star hyperon puzzle statistically: neutrons fill low-momentum $d$-quark phase space, shifting the $S=-1$ threshold from $\muB=M_Y$ to $2M_Y-M_N$ and suppressing residual softening by $1/\Nc^3$ in the Fujimoto--Kojo--McLerran (FKM) mechanism. We dress FKM's IdylliQ model with in-medium potentials, constrained by hypernuclear data and neutrino-induced hyperon FSI, and find: (i) the dressed onset, $\muB^{\rm onset}=(2M_Y{-}M_N)+2U_Y-\UN$, carries $U_Y$ at weight 2, with $dn_{\rm onset}/dU_Y\simeq0.3\,\nz$ per $10\MeV$, twice the leverage. (ii) A self-consistent neutron potential enters at weight $-2$, so protection needs $\UN(n_{\rm onset})\lesssim+96\MeV$. (iii) With leptons in $\beta$ equilibrium, the $\Sigma^-$ ($dds$) onset becomes $\mue\ge258\MeV+\US-\UN$, never reached inside a $2\,\Msun$ core: $\Sigma^-$ switches from first hyperon to forbidden and the $\Sigma$ ordering inverts. (iv) The $\kY\ge\kbu$ continuation gives TOV softening below $0.05\,\Msun$ in the FKM ansatz family and below $0.025\,\Msun$ for the realistic interacting star, $4$--$8$ below hadronic models. In the family this is a ceiling; generally it is a floor, since hyperons above $\kbu$ are omitted. (v) In an interacting low-density sector calibrated to $\Mmax=2.12\,\Msun$, core strangeness is controlled by $(\UL(\nz),c_\Lambda)$: at $\UL(\nz)=-28\MeV$, the maximum-mass star is hyperon-free once the supra-saturation $YNN$ turn-over exceeds a few-MeV threshold $c^*_\Lambda$. Projected SBND+DUNE FSI precision pins $\UL(\nz)$ but leaves $c_\Lambda$ -- to which neutrino data are blind -- decisive: with the heavy-ion prior, $P({\rm hyperon\mbox{-}free\ core})=0.90$, versus $0.89$ from priors alone, prior-dominated rather than measured. The sharpest observable is differential: $d\Mmax/dU_Y$ is an order of magnitude smaller than in mean-field models, discriminating the two resolutions.

2 hours ago

Accelerator neutrinos as a probe of in-medium hyperon potentials

arXiv:2607.09255v1 Announce Type: cross Abstract: Charged-current (anti)neutrino interactions create $\Lambda$ and $\Sigma$ hyperons \emph{inside} the nucleus, making hyperon final-state interactions a terrestrial probe of the in-medium potentials that govern hyperon onset in neutron stars. In the StrangeMC simulation the trapped-$\Lambda$ fraction, escaping hyperon momenta, and a kaon-vetoed $\Sigma^+$ tag respond monotonically to $U_\Lambda$ and $U_\Sigma$ at SBND and DUNE. Marginalised over the low-density slope, a forecast gives $\delta U_\Lambda\approx6\MeV$ with systematics distinct from hypernuclear data; $U_\Sigma$ is limited by hyperon--nucleon cross sections.

2 hours ago