Hexaquarks under the microscope Mikhail Bashkanov

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"

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

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

Dibaryon: hadronic decays PRL 106 (2011) 242302 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) 202301 PRC 90, (2014) 035204 d* PRC 88 (2013) 055208 PLB 743 (2015) 325 d* d*

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

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) 104-113 𝑑 ∗ M. Guenther, Hadron 2017 T. Ishikawa et al.  Phys.Lett. B772 (2017) 398

𝛾𝑑→ 𝑑 ∗ →𝑝𝑛

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

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

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, 114002

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

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

Recoil polarization at 90 degree Conventional background, Kang et al

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

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

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

Recoil polarization 𝑃(Θ) ~ 𝐽=1 𝐵 𝐽 𝑃 1 𝐽 (𝑐𝑜𝑠Θ) 𝑃(Θ) ~ 𝐽=1 𝐵 𝐽 𝑃 1 𝐽 (𝑐𝑜𝑠Θ) 𝑑 ∗ 2380 :𝐽=3 → 𝑃 1 3 (𝑐𝑜𝑠Θ)

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

Nuclear matter at high density p d* n Mikhail Bashkanov "Dibaryons"

The d*(2380) in neutron stars a new degree of freedom? I. Vidaña, M. Bashkanov, D.P. Watts, A. Pastore Phys.Lett. B781 (2018) 112-116

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)

 * * 𝑑 ∗ (2380) Thank you 

Recoil polarization at 90 degree

d*(2380) in photoproduction? R. Gilman and F. Gross nucl-th/0111015 (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

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”

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 9502244 R. Beck et al. (MAMI-A2) Phys.Rev. C61 (2000) 035204 Analysis of beam asymmetry 𝐸2 𝑀1 =2.5%

Recoil polarization