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

A2 Collaboration at MAMI, Stuart Fegan, A. Fix, C. Mullen, A. Neganov, A. Neiser, M. Ostrick, P. B. Otte, D. Paudyal, P. Pedroni, A Powell, S. N. Prakhov, G. Ron, A Sarty, C. Sfienti, V. Sokhoyan, K. Spieker, O Steffen, I.I. Strakovsky, T. StrubI Supek, A. Thiel, M Thiel, A. Thomas, Yu A. Usov, S Wagner, N.K. Walford, Dominik Werthmüller, J. Wettig, M. Wolfes, Nick Zachariou, L A Zana

Research output: Contribution to journalLetterpeer-review


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.
Original languageEnglish
Article number132001
Pages (from-to)1-6
Number of pages6
JournalPhysical Review Letters
Publication statusPublished - 31 Mar 2020

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© 2020, The Author(s).


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