Speaker
Description
The dibaryon resonance d(2380) with I(JP) = 0(3+) -- first observed in the
double-pionic fusion to the deuteron [1] -- has meanwhile been detected in all
relevant two-pion production channels in incident neutron-proton collisions
[2]. In addition, its resonance pole has been revealed in neutron-proton
scattering [3].
Theoretical calculations describe this state either as a compact hexaquark [4]
or a dilute molecular-like object [5]. Whereas the d decay into two-pion
channels does not discriminate between these two scenarios, the decay into
single-pion channels is very discriminatory. In the hexaquark case this decay is
heavily suppressed with a branching less than 1% [4]. In the molecular-like
case a branching of as much as 18% is expected.
In order to clarify this situation we have measured the isoscalar single-pion
production in the energy region of d*(2380). As a result we find no evidence
for such a decay with an upper limit of smaller than 9%. This is in support of
the hexaquark interpretation -- at least as the dominant configuration,
possibly surrounded by a cloud of molecular-like configurations [6].
*) suported by DFG (CL214/3-2) and STFC (ST/L00478X/1)
[1] P. Adlarson et al., Phys. Rev. Lett. 106, 242302 (2011)
[2] M. Bashkanov et al., Eur. Phys. J. A 51, 87 (2015)
[3] P. Adlarson et al., Phys. Rev. Lett. 112, 202301 (2014)
[4] Y. Dong et al., Phys. Lett. B 769, 223 (2017)
[5] A. Gal and H. Garcilazo, Phys. Rev. Lett. 111, 172301 (2013)
[6] A. Gal, Phys. Lett. B 769 (2017) 436
