## Signatures of the $d^*(2380)$ hexaquark in d($γ$,$p\vec{n}$)

Research output: Contribution to journalLetterpeer-review

## Author(s)

• A2 Collaboration at MAMI

## Department/unit(s)

### Publication details

Journal Physical Review Letters Accepted/In press - 2 Mar 2020 Published (current) - 31 Mar 2020 124 6 1-6 English

### Abstract

We report a measurement of the spin polarisation of the recoiling neutron in deuterium photodisintegration, utilising a new large acceptance polarimeter within the Crystal Ball at MAMI. The measured photon energy range of 300~--~700~MeV provides the first measurement of recoil neutron polarisation at photon energies where the quark substructure of the deuteron plays a role, thereby providing important new constraints on photodisintegration mechanisms. A very high neutron polarisation in a narrow structure centred around $E_{\gamma}\sim$~570~MeV is observed, which is inconsistent with current theoretical predictions employing nucleon resonance degrees of freedom. A Legendre polynomial decomposition suggests this behaviour could be related to the excitation of the $d^*(2380)$ hexaquark.