1. Hexaquarks under the microscope
Mikhail Bashkanov

2. Baryon-Baryon molecule Meson-Baryon molecule
Possible particles
Tetraquark
Meson-Meson molecule
Hexaquark
Baryon-Baryon molecule
Pentaquark
Meson-Baryon molecule
𝑓 0 / 𝑎 0 (980)
deuteron
𝑍 + (4430)
Λ(1405)
d ∗ (2380)
𝑃 𝑐 + (4450)
Mikhail Bashkanov "Dibaryons"

3. 𝑑 ∗ (2380) hexaquark I(Jp) = 0(3+) Δ Δ 𝚪 𝒅 ∗ =𝟕𝟎 𝐌𝐞𝐕≪ 𝚪 𝚫𝚫 =𝟐𝟒𝟎 𝑴𝒆𝑽
𝚪 𝒅 ∗ =𝟕𝟎 𝐌𝐞𝐕≪ 𝚪 𝚫𝚫 =𝟐𝟒𝟎 𝑴𝒆𝑽 u u u d d d
Threshold
I(Jp) = 0(3+)
80 MeV d* Δ Δ
𝑴 𝒅 ∗ =𝟐.𝟑𝟖 𝑮𝒆𝑽≈𝟐 𝑴 𝚫 −𝟖𝟎 𝑴𝒆𝑽

4. Total cross section pn  d00
d*(2380) dibaryon
70 MeV
P. Adlarson et. al Phys. Rev. Lett. 106:242302, 2011

5. Dibaryon: hadronic decays
PRL 106 (2011)
PLB 721 (2013) 229
WASA data
𝑑 𝜋 0 𝜋 0
𝑑 𝜋 + 𝜋 −
pn  d*(2380) 𝑝𝑛
𝑝𝑝 𝜋 − 𝜋 0
𝑝𝑛 𝜋 0 𝜋 0
𝑝𝑛 𝜋 + 𝜋 −
PRL 112 (2014)
PRC 90, (2014) d*
PRC 88 (2013)
PLB 743 (2015) 325 d* d*

6. deuteron to d*(2380) transitions
0.15% 5%
Deuteron: |6𝑞 |𝑝 𝑛 𝑆−𝑤𝑎𝑣𝑒 |𝑝 𝑛 𝐷−𝑤𝑎𝑣𝑒 𝜸 𝜸
𝑑 ∗ (2380): |6𝑞 |Δ Δ 𝑆−𝑤𝑎𝑣𝑒 |Δ Δ 𝐷−𝑤𝑎𝑣𝑒
66%
30% 2% d
E2, ( 𝟐 + ) 𝜸
d*(2380) d
M3, ( 𝟑 + ) 𝜸
𝐸 𝛾 ~570 𝑀𝑒𝑉 d
E4, ( 𝟒 + ) 𝜸
deuteron

7. d*(2380) in photoproduction?
𝜋 0  p
𝜋 0 d*  d* d d d n
𝛾𝑑→𝑑 𝜋 0 𝜋 0
𝛾𝑑→𝑑 𝜋 0 𝜋 0
Conventional Background M. Egorov, A. Fix, Nucl.Phys. A933 (2015)
𝑑 ∗
M. Guenther, Hadron 2017
T. Ishikawa et al.  Phys.Lett. B772 (2017) 398

8. 𝛾𝑑→ 𝑑 ∗ →𝑝𝑛

9. Beam asymmetry Σ fit 𝜎 1 = 𝜎 ⊥ − 𝜎 ∥ =Σ𝜎 ~ 𝐽=2 𝐵 𝐽 𝑃 2 𝐽 (𝑐𝑜𝑠Θ)
𝜎 1 = 𝜎 ⊥ − 𝜎 ∥ =Σ𝜎 ~ 𝐽=2 𝐵 𝐽 𝑃 2 𝐽 (𝑐𝑜𝑠Θ)
𝜎 ⊥ − 𝜎 ∥ 𝜎 ⊥ + 𝜎 ∥ = 𝑃 𝛾 𝚺𝑐𝑜𝑠2𝜙
Σ Θ 𝜎 Θ 𝜎 0 ~ 𝐽=2 𝐵 𝐽 𝑃 2 𝐽 (𝑐𝑜𝑠Θ)
𝐵 𝐽 =𝑓(𝐸) – smooth function +BW for the d*
Phys. Lett B789, (2019), 7-12

10. Deuteron photodisintegration: beam asymmetry Σ
Σ Θ 𝜎 Θ 𝜎 0 ~ 𝐽=2 𝐵 𝐽 𝑃 𝐽 2 (𝑐𝑜𝑠Θ)
𝑑 ∗ M3 transition seems to be preferable

11. 𝑑 ∗ (2380) multipole expansion
𝑀3 𝐸2 ~ Ω d→ 𝑑 ∗ 𝑄 d→ 𝑑 ∗ ~ 𝑄 d→ 𝑑 ∗ 𝜇 d→ 𝑑 ∗ 𝑄 d→ 𝑑 ∗ ~ 𝑀 𝑑 𝜔 𝛾 2 𝜇 d→ 𝑑 ∗
If 𝜇 d→ 𝑑 ∗ is large the 𝑑→𝑑 ∗ M3 transition might be dominant
𝜇 𝑑 ∗ ∼7.6 𝜇 𝑁
Yubing Dong, Pengnian Shen, Zongye Zhang Phys.Rev. D 97, (2018), no.11,

12. The benchmark measurementd* p 𝛾 d n
Measure polarization of both
proton and neutron !
Mikhail Bashkanov "Dibaryons"

13. Experiment
𝛾 𝑑→𝑝 𝑛
Target 𝜸 p 𝒏
Θ,𝜙,𝐸 p
𝚯 ′ ,𝝓′
Polarimeter

14. Recoil polarization at 90 degree
Conventional background, Kang et al

15. Recoil polarization at 90 degree
proton
Conventional background, Kang et al
H. Ikeda et al., Phys. Rev. Lett. 42, May 1979, 1321

16. Recoil polarization at 90 degree
proton
background+ d*
Conventional background, Kang et al
H. Ikeda et al., Phys. Rev. Lett. 42, May 1979, 1321

17. Recoil polarization at 90 degree
neutron
proton
background+ d*
Conventional background, Kang et al
H. Ikeda et al., Phys. Rev. Lett. 42, May 1979, 1321

18. Recoil polarization 𝑃(Θ) ~ 𝐽=1 𝐵 𝐽 𝑃 1 𝐽 (𝑐𝑜𝑠Θ)
𝑃(Θ) ~ 𝐽=1 𝐵 𝐽 𝑃 1 𝐽 (𝑐𝑜𝑠Θ)
𝑑 ∗ :𝐽=3 → 𝑃 1 3 (𝑐𝑜𝑠Θ)

19. 𝑑 ∗ size d*(2380) Transition form factor Charge distribution*
d*(2380) d
Transition form factor
Charge distribution
Internal structure

20. Nuclear matter at high densityp d* n
Mikhail Bashkanov "Dibaryons"

21. The d*(2380) in neutron stars a new degree of freedom?
I. Vidaña, M. Bashkanov, D.P. Watts, A. Pastore
Phys.Lett. B781 (2018)

22. Conclusion The very first hexaquark d*(2380) is established
Mass, Width, Quantum numbers
Main decay branches
Structure: Hexaquark vs Molecule?
d*(2380) electro-magnetic coupling
Size, 𝜇, 𝑄,Ω
Neutron Stars? ( 𝑑 ∗ in medium)

23. 
*
*
𝑑 ∗ (2380)
Thank you 

24. Recoil polarization at 90 degree

25. d*(2380) in photoproduction?
R. Gilman and F. Gross nucl-th/ (2001) d*  p
T. Kamae, T. Fujita Phys. Rev. Lett. 38, Feb 1977, 471 d n
H. Ikeda et al., Phys. Rev. Lett. 42, May 1979, 1321
I(Jp) = 0(3+)
𝐌=𝟐.𝟑𝟖 𝐆𝐞𝐕

26. 𝑑 ∗ and beam asymmetry Σ 𝟑 𝑫 𝟑 & 𝟑 𝑮 𝟑 𝑑 ∗
E2 transition ( 𝟐 + )
M3 transition ( 𝟑 + )
E4 transition ( 𝟒 + ) p 
𝑑 ∗
𝟑 𝑫 𝟑 &
𝟑 𝑮 𝟑 d n
90% 10%
𝜎 ⊥ − 𝜎 ∥ 𝜎 ⊥ + 𝜎 ∥ = 𝑃 𝛾 𝚺𝑐𝑜𝑠2𝜙
H. Arenhoevel, M. Sanzone “Photodisintegration of the deuteron”

27. Beam asymmetry Σ 𝜎 ⊥ − 𝜎 ∥ 𝜎 ⊥ + 𝜎 ∥ = 𝑃 𝛾 𝚺𝑐𝑜𝑠2𝜙  Δ 𝜋
M1 transition ( 𝟏 + ) or
E2 transition ( 𝟐 + ) p N
𝜎 ⊥ − 𝜎 ∥ 𝜎 ⊥ + 𝜎 ∥ = 𝑃 𝛾 𝚺𝑐𝑜𝑠2𝜙
E2/M1 ratio for the 𝛾𝑁→Δ
𝐸2 𝑀1 = 1 2 𝑘 𝑀 𝑁 𝑄 𝑧𝑧 𝑁Δ 𝜇 𝑁Δ
T. Watabe et al. hep-ph
R. Beck et al. (MAMI-A2) Phys.Rev. C61 (2000)
Analysis of beam asymmetry
𝐸2 𝑀1 =2.5%

28. Recoil polarization