1. II Hadron spectroscopy Paradigm change Mikhail Bashkanov
University of Edinburgh
UK Nuclear Physics Summer School

2. Outline Naïve quark model N* puzzle Molecular states Exotics
Tetraquarks
Pentaquarks
Hexaquarks
Hybrids
Glueballs

3. Types of particles/resonances
Meson
Baryon
white
color
anticolor

4. Quarks fermions 3 colors Parity +1 Constituent quarks: 𝑀 𝑢/𝑑 ~300 𝑀𝑒𝑉
𝑀 𝑠 ~500 𝑀𝑒𝑉

5. The early days Baryons are 3 quark systems
Murray Gell Mann 1964
“A schematic model of baryons and mesons”
Baryons are 3 quark systems
Mesons are quark-antiquark systems

6. Excited states?
Shell model

7. Nucleon excited states?
𝑃= −1 𝐿
P – parity
L – angular momentum

8. Excited states - expectation
1 𝑠 1/2
1 𝑝 3/2
1 𝑝 1/2 1𝑝 u d u
𝑵 𝟗𝟒𝟎 , 𝑱 𝑷 = 𝟏 𝟐 +

9. Excited states - expectation
1 𝑠 1/2
1 𝑝 3/2
1 𝑝 1/2 1𝑝
𝑵 ∗ (𝟏𝟓𝟐𝟎) ,𝑱 𝑷 = 𝟑 𝟐 − u u d
1 𝑠 1/2
1 𝑝 3/2
1 𝑝 1/2 1𝑝 u d u
𝑵 𝟗𝟒𝟎 , 𝑱 𝑷 = 𝟏 𝟐 +

10. Excited states - expectation
1 𝑠 1/2
1 𝑝 3/2
1 𝑝 1/2 1𝑝 u
𝑵 ∗ (𝟏𝟓𝟑𝟓) ,𝑱 𝑷 = 𝟏 𝟐 − u d
1 𝑠 1/2
1 𝑝 3/2
1 𝑝 1/2 1𝑝
𝑵 ∗ (𝟏𝟓𝟐𝟎) ,𝑱 𝑷 = 𝟑 𝟐 − u u d
1 𝑠 1/2
1 𝑝 3/2
1 𝑝 1/2 1𝑝 u d u
𝑵 𝟗𝟒𝟎 , 𝑱 𝑷 = 𝟏 𝟐 +

11. Excited states - expectation
1 𝑠 1/2
1 𝑝 3/2
1 𝑝 1/2
𝑵 ∗ ??? , 𝑱 𝑷 = 𝟏 𝟐 + 1𝑝 d u u
𝑵 ∗ (𝟏𝟓𝟑𝟓) ,𝑱 𝑷 = 𝟏 𝟐 − 1𝑝
𝑵 ∗ (𝟏𝟓𝟐𝟎) ,𝑱 𝑷 = 𝟑 𝟐 −
𝟓𝟗𝟎 𝑴𝒆𝑽 1𝑠
𝑵 𝟗𝟒𝟎 , 𝑱 𝑷 = 𝟏 𝟐 +

12. Excited states - expectation
1 𝑠 1/2
1 𝑝 3/2
1 𝑝 1/2
???𝑵 ∗ 𝟗𝟒𝟎+𝟐∗𝟓𝟗𝟎=𝟐𝟏𝟐𝟎 , 𝑱 𝑷 = 𝟏 𝟐 + 1𝑝 d u u
𝑵 ∗ (𝟏𝟓𝟑𝟓) ,𝑱 𝑷 = 𝟏 𝟐 − 1𝑝
𝑵 ∗ (𝟏𝟓𝟐𝟎) ,𝑱 𝑷 = 𝟑 𝟐 −
𝟓𝟗𝟎 𝑴𝒆𝑽 1𝑠
𝑵 𝟗𝟒𝟎 , 𝑱 𝑷 = 𝟏 𝟐 +

13. Excited states - reality
𝑵 ∗ (𝟏𝟓𝟑𝟓) ,𝑱 𝑷 = 𝟏 𝟐 − 1𝑝
1 𝑠 1/2
1 𝑝 3/2
1 𝑝 1/2
𝑵 ∗ (𝟏𝟓𝟐𝟎) ,𝑱 𝑷 = 𝟑 𝟐 − 1𝑝 d u
𝑵 ∗ 𝟏𝟒𝟒𝟎 , 𝑱 𝑷 = 𝟏 𝟐 + u 1𝑠
𝑵 𝟗𝟒𝟎 , 𝑱 𝑷 = 𝟏 𝟐 +

14. Hyperons 𝑵 ∗ (𝟏𝟓𝟑𝟓) ,𝑱 𝑷 = 𝟏 𝟐 − 𝑵 ∗ (𝟏𝟓𝟐𝟎) ,𝑱 𝑷 = 𝟑 𝟐 −
𝑵 ∗ (𝟏𝟓𝟑𝟓) ,𝑱 𝑷 = 𝟏 𝟐 −
𝑵 ∗ (𝟏𝟓𝟐𝟎) ,𝑱 𝑷 = 𝟑 𝟐 −
𝑵 ∗ 𝟏𝟒𝟒𝟎 , 𝑱 𝑷 = 𝟏 𝟐 +
1 𝑠 1/2
1 𝑝 3/2
1 𝑝 1/2 1𝑝 u d
𝚲 𝟏𝟏𝟏𝟔 , 𝑱 𝑷 = 𝟏 𝟐 + s
𝟏𝟕𝟔 𝑴𝒆𝑽
𝑵 𝟗𝟒𝟎 , 𝑱 𝑷 = 𝟏 𝟐 +

15. Excited hyperons? 1 𝑝 1/2 1𝑝 𝚲 ∗ 𝟏𝟕𝟎𝟎? , 𝑱 𝑷 = 𝟑 𝟐 − 𝟏𝟕𝟎𝟎=𝟏𝟓𝟐𝟎+𝟏𝟕𝟔 d
1 𝑠 1/2
1 𝑝 3/2
1 𝑝 1/2 1𝑝
𝚲 ∗ 𝟏𝟕𝟎𝟎? , 𝑱 𝑷 = 𝟑 𝟐 − 𝟏𝟕𝟎𝟎=𝟏𝟓𝟐𝟎+𝟏𝟕𝟔 d
𝑵 ∗ (𝟏𝟓𝟑𝟓) ,𝑱 𝑷 = 𝟏 𝟐 − u s
𝑵 ∗ (𝟏𝟓𝟐𝟎) ,𝑱 𝑷 = 𝟑 𝟐 −
𝑵 ∗ 𝟏𝟒𝟒𝟎 , 𝑱 𝑷 = 𝟏 𝟐 +
𝚲 𝟏𝟏𝟏𝟔 , 𝑱 𝑷 = 𝟏 𝟐 +
𝟏𝟕𝟔 𝑴𝒆𝑽
𝑵 𝟗𝟒𝟎 , 𝑱 𝑷 = 𝟏 𝟐 +

16. Excited hyperons - reality
𝑵 ∗ (𝟏𝟓𝟑𝟓) ,𝑱 𝑷 = 𝟏 𝟐 −
𝑵 ∗ (𝟏𝟓𝟐𝟎) ,𝑱 𝑷 = 𝟑 𝟐 −
𝚲 𝟏𝟓𝟐𝟎 , 𝑱 𝑷 = 𝟑 𝟐 −
𝑵 ∗ 𝟏𝟒𝟒𝟎 , 𝑱 𝑷 = 𝟏 𝟐 +
𝚲 𝟏𝟒𝟎𝟓 , 𝑱 𝑷 = 𝟏 𝟐 −
𝚲 𝟏𝟏𝟏𝟔 , 𝑱 𝑷 = 𝟏 𝟐 +
𝟏𝟕𝟔 𝑴𝒆𝑽
𝑵 𝟗𝟒𝟎 , 𝑱 𝑷 = 𝟏 𝟐 +

17. Lattice QCD

18. Lattice QCD Models Nature 𝑀 3/ 2 − > 𝑀 1/ 2 −
𝑀 3/ 2 − > 𝑀 1/ 2 −
𝑀 3/ 2 − < 𝑀 1/ 2 −
𝑀 1/ 2 + ≫ 𝑀 1/ 2 −
𝑀 1/ 2 + < 𝑀 1/ 2 −

19. Missing states- extra states

20. Ideas?
Di-quark degrees of freedom u d u d u u

21. Ideas? Di-quark degrees of freedom 𝑁 ∗ (1440) is a breathing mode u d

22. The Roper resonance: 𝑁 ∗ (1440)
Previous pion-nucleon resonances were discovered from observations on the qualitative behavior of experimental observables. The resonance suggested in this paper, however, is not associated with conspicuous features in the observables measured so far and has been inferred from a more quantitative analysis.
L. D. Roper, Phys. Rev. Lett. 12 (1964) 340

23. The Roper resonance 1077 1371 1379 1440 𝑁𝜋 Δ𝜋 N𝜎 N ∗ Mass [MeV]
Old days:
Mass=1440 MeV ( )
Width=350 MeV ( )
𝑩𝒓 𝑵 ∗ →𝑵𝝅 =𝟔𝟎−𝟕𝟎%
𝑩𝒓 𝑵 ∗ →𝚫𝝅 =𝟐𝟎−𝟑𝟎%
𝑩𝒓 𝑵 ∗ →𝑵𝝈 =𝟓−𝟏𝟎%
First radial excitation
1077
1371
1379
1440 𝑁𝜋 Δ𝜋 N𝜎
N ∗
Mass [MeV]

24. The Roper resonance 1077 1371 1379 1370 𝑁𝜋 Δ𝜋 N𝜎 N ∗ Mass [MeV] Now:
Width=190 MeV
𝑩𝒓 𝑵 ∗ →𝑵𝝅 =𝟒𝟎−𝟓𝟎%
𝑩𝒓 𝑵 ∗ →𝚫𝝅 =𝟏𝟎−𝟐𝟎%
𝑩𝒓 𝑵 ∗ →𝑵𝝈 =𝟐𝟎−𝟑𝟎%
𝒈 𝑵 ∗ →𝑵𝝅 =𝟎.𝟐
𝒈 𝑵 ∗ →𝑵𝝈 =𝟐.𝟓
𝑵𝝈 molecule
1077
1371
1379
1370 𝑁𝜋 Δ𝜋 N𝜎
N ∗
Mass [MeV]

25. Structure of the resonance. Transition form factor
𝒆 +
𝜸 ∗
𝒆 −
𝑵 ∗ 𝑵

26. Structure of the resonance. Transition form factor
𝒆 +
𝜸 ∗
𝒆 −
𝑵 ∗ 𝑵
𝒆 −
JLab
𝜸 ∗
𝒆 − 𝑵
𝑵 ∗

27. The Roper resonance = 𝑵𝝈 molecule

28. Excited hyperons - reality
𝑵 ∗ (𝟏𝟓𝟑𝟓) ,𝑱 𝑷 = 𝟏 𝟐 −
𝑵 ∗ (𝟏𝟓𝟐𝟎) ,𝑱 𝑷 = 𝟑 𝟐 −
𝚲 𝟏𝟓𝟐𝟎 , 𝑱 𝑷 = 𝟑 𝟐 −
𝑵 ∗ 𝟏𝟒𝟒𝟎 , 𝑱 𝑷 = 𝟏 𝟐 +
𝚲 𝟏𝟒𝟎𝟓 , 𝑱 𝑷 = 𝟏 𝟐 −
𝚲 𝟏𝟏𝟏𝟔 , 𝑱 𝑷 = 𝟏 𝟐 +
𝟏𝟕𝟔 𝑴𝒆𝑽
𝑵 𝟗𝟒𝟎 , 𝑱 𝑷 = 𝟏 𝟐 +

29. 𝚲(𝟏𝟒𝟎𝟓)
𝑁 𝐾 −Σ𝜋 molecule
𝑀 𝑁+ 𝐾 =1432 𝑀𝑒𝑉
𝑀 Σ+𝜋 =1328 𝑀𝑒𝑉

30. 𝚲 𝟏𝟒𝟎𝟓 from Lattice QCD

31. Molecular states. Mesons
𝜎 500 : 𝜋−𝜋 molecule
𝑓 0 / 𝑎 : 𝐾−𝐾 molecule
𝜅 700 : 𝐾−𝜋 molecule

32. Molecular states. Baryons
𝑁 ∗ : 𝑁−𝜎 molecule: |𝑢𝑢𝑑+ 𝑢 𝑑+ 𝑢 𝑑
Λ 1405 : 𝑁− 𝐾 molecule: | 𝑢𝑑𝑑+𝑠 𝑑
N ∗ : Σ−𝐾 molecule: | 𝑢𝑑𝑠+𝑑 𝑠

33. 𝐍 ∗ (𝟏𝟓𝟑𝟓) N ∗ 1535 : Σ−𝐾 molecule: | 𝑢𝑑𝑠+𝑑 𝑠
𝑀 Σ − + 𝐾 + = =1691 𝑀𝑒𝑉
T. Inoue,* E. Oset, and M. J. Vicente Vacas, Phys. Rev. C 65, (2002)

34. Dynamically generated resonances
Λ 1405

35. Types of particles/resonances
Meson
Baryon
white
color
anticolor

36. Baryon-Baryon molecule Meson-Baryon molecule
Possible particles
Tetraquark
Meson-Meson molecule
Hexaquark
Baryon-Baryon molecule
Pentaquark
Meson-Baryon molecule

37. Multiquark vs Molecule
Tetraquark
Meson-Meson molecule 𝑞 𝑞 𝑞 𝜋 𝑞
XYZ states in charm sector 𝑞 𝑞 𝑞 𝑞
𝑍 𝑐 𝑐 𝑢 𝑑 𝑔
𝑍 → 𝐽 𝜓 + 𝜋 + 𝑞 𝑞 𝑔

38. Exotics: Hybrids 𝒒 𝒒𝒈 𝐽=𝐿+𝑆 𝑃= −1 𝐿+1 𝐶= −1 𝐿+𝑆
𝑃= −1 𝐿+1
𝐶= −1 𝐿+𝑆
𝐽 𝑃𝐶 = 0 −− , 0 +− , 1 −+ , 2 +− - forbidden for 𝑞 𝑞
𝒒 𝒒𝒈

39. Exotics: Hybrid baryons
𝒒𝒒𝒒𝒈
Transition form factor measurements

40. Exotics: Hybrid baryons
Hadron Spectrum Collaboration

41. Dibaryons, B=2 systems

42. Deuteron
L=0 n p n p
L=2
4 fm
0.9 fm
≈5%
6q configuration ≈0.15%

43. Deuteron to Deltaron I(Jp) = 0(3+) I(Jp) = 0(1+) Threshold p n Δ Δ
2.2 MeV p n
80 MeV Δ Δ
deuteron d*

44. 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*

45. Dibaryon in elastic scatteringp n
+ dibaryon
background

46. Polarization is a key
Effect of the resonance
SAID
New SAID solutions

47. Hexaquark vs molecule Transition form factor Charge distribution*
d*(2380) d
Transition form factor
Charge distribution
Internal structure

48. Dibaryon in Skyrm model
David Foster, Nicholas S. Manton arXiv:  

49. d*(2380) SU(3) multiplet Jp = 3+  * *  𝑑 ∗ (2380)
𝑀 𝑑 ∗ − 𝑀 Δ + 𝑀 Σ ∗ < 𝑀 𝑑 𝑠 ∗ ≤ 𝑀 Δ + 𝑀 Σ ∗
*
𝑑 𝑠 ∗ (2.53−2.60)
*
𝑑 𝑠𝑠 ∗ (2.68−2.76) 
𝑑 𝑠𝑠𝑠 ∗ (2.82−2.90)

50. Baryon Summary Table (PDG 2014)

52. Conclusion
Precise experiments change our knowledge about well known resonances
Transition form factors -> internal structure
New exotic states
Meson Molecules
Tetraquarks
Hybrids
Meson-Baryon Molecules
Pentaquarks
Hybrid baryons
Baryon-baryon molecules
Hexaquarks …
A lot of states still to be found and identified

53. NN SU(3) multiplet Jp = 1+ pn Deuteron +2.2 MeV ΛN -166 keV ΞNΞΣ