25–29 Sept 2017
Salamanca, Spain
Europe/Zurich timezone

Study of non-strange dibaryon resonances via coherent double neutral-pion photoproduction on the deuteron

28 Sept 2017, 15:35
20m
Sala Menor

Sala Menor

Talk Spectroscopy of baryons Spectroscopy of baryons

Speaker

Dr Takatsugu Ishikawa (Research Center for Electron Photon Science, Tohoku University)

Description

The search for non-strange dibaryon bound/resonance states has a long history.
A dibaryon state is of interest, which can be a molecule consisting of
two baryons or a spatially compact hexaquark object. The d*(2380) resonance
observed in the $pn$-collision reactions by the CELESIUS/WASA and WASA-at-COSY [1,2]
collaborations may be attributed to an isoscalar $\Delta\Delta$ quasi-bound state
$\mathcal{D}_{03}$, predicted by Dyson and Xuong [3]. The $\gamma d\to \pi^0\pi^0d$
reaction has been experimentally investigated using energy-tagged bremsstrahlung photon beams at the Research Center for Electron Photon Science (ELPH), Tohoku University, Japan [4]. The $\gamma d$ center of mass
energy $W_{\gamma d}$ is covered from 2.38 to 2.80 GeV.
All the final-state particles are detected with an electromagnetic calorimeter FOREST [5].
No clear resonance-like
behavior is observed in the excitation function near $W_{\gamma d}=2.38$ GeV [6],
where the $d^*(2380)$ dibaryon resonance is expected to appear. The measured
excitation function is consistent with the existing theoretical calculation for
this reaction. At high incident energies, $\pi^0d$ invariant-mass distributions
show a peak at approximately 2.15 GeV, which can be attributed to a $N\Delta$
quasi-bound state $\mathcal{D}_{12}$. We also discuss the properties of the peak
observed in the $\pi^0d$ channel.

[1] M. Bashkanov et al. (CELSIUS/WASA collaboration), Phys. Rev. Lett. 102, 052301 (2009).

[2] P. Adlarson et al. (WASA-at-COSY collaboration), Phys. Rev. Lett. 106, 242302 (2011).

[3] F.J. Dyson and N.-H. Xuong, Phys. Rev. Lett. 13, 815 (1964).

[4] T. Ishikawa et al., Nucl. Instrum. Meth. A 622, 1 (2010)

[5] T. Ishikawa et al., Nucl. Instrum. Meth. A 832, 108 (2016).

[6] T. Ishikawa et al., Phys. Lett. B, in press (doi:10.1016/j.physletb.2017.04.010).

Primary author

Dr Takatsugu Ishikawa (Research Center for Electron Photon Science, Tohoku University)

Presentation materials