Paradigm change Mikhail Bashkanov University of Edinburgh UK Nuclear Physics Summer School II Naïve quark model N puzzle Molecular states Exotics Tetraquarks Pentaquarks Hexaquarks Hybrids ID: 476838
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Slide1
Hadron spectroscopy
Paradigm change
Mikhail BashkanovUniversity of EdinburghUK Nuclear Physics Summer School
IISlide2
Naïve quark modelN* puzzle
Molecular statesExoticsTetraquarksPentaquarks
HexaquarksHybridsGlueballsOutline2Slide3
Types of particles/resonances
color
anticolor
white
Meson
Baryon
3Slide4
Quarks
fermions
3 colorsParity +1Constituent quarks: 4Slide5
The early days
Baryons are 3 quark systems
Mesons are quark-antiquark systemsMurray Gell Mann 1964“A schematic model of baryons and mesons”5Slide6
Excited states?
Shell model
6Slide7
Nucleon excited states?
P – parityL – angular momentum7Slide8
Excited states - expectation
u
d
u
8Slide9
Excited states - expectation
u
d
u
u
d
u
9Slide10
Excited states - expectation
u
d
u
u
d
u
u
d
u
10Slide11
Excited states - expectation
u
d
u
11Slide12
Excited states - expectation
u
d
u
12Slide13
Excited states - reality
u
d
u
13Slide14
Hyperons
u
d
s
14Slide15
Excited hyperons?
u
d
s
15Slide16
Excited hyperons - reality
16Slide17
Lattice QCD
17Slide18
Lattice QCD
Models
Nature
Models
Nature
18Slide19
Missing states- extra states
19Slide20
Di-quark degrees of freedom
Ideas?
udu
u
d
u
20Slide21
Di-quark degrees of freedom
is a breathing mode
Ideas?ud
u
u
d
u
u
d
u
u
d
u
21Slide22
The Roper resonance:
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) 34022Slide23
The Roper resonance
Old days:
Mass=1440 MeV (1430-1470)Width=350 MeV (250-450)
Mass [MeV]
First radial excitation
23Slide24
The Roper resonance
Now:
Mass=1370 MeV Width=190 MeV
Mass [MeV]
molecule
24Slide25
Structure of the resonance. Transition form factor
25Slide26
Structure of the resonance. Transition form factor
JLab
26Slide27
The Roper resonance =
molecule
27Slide28
Excited hyperons - reality
28Slide29
molecule
29Slide30
from Lattice QCD
30Slide31
Molecular states. Mesons
molecule
molecule
molecule
31Slide32
Molecular states. Baryons
molecule:
molecule:
molecule:
32Slide33
T. Inoue,* E.
Oset, and M. J. Vicente Vacas, Phys. Rev. C 65, 035204 (2002) molecule:
33Slide34
Dynamically generated resonances
34Slide35
Types of particles/resonances
color
anticolor
white
Meson
Baryon
35Slide36
Possible particles
Pentaquark
Meson-Baryon moleculeHexaquarkBaryon-Baryon molecule
36
Tetraquark
Meson-Meson moleculeSlide37
Multiquark vs Molecule
37
TetraquarkMeson-Meson molecule
XY
Z
states in
charm sector
Slide38
Exotics: Hybrids
- forbidden for
38Slide39
Exotics: Hybrid baryons
Transition form factor measurements39Slide40
Exotics: Hybrid baryons
Hadron
Spectrum Collaboration40Slide41
Dibaryons, B=2 systems
41Slide42
Deuteron
n
p
n
p
L=2
0.9
fm
4
fm
L=0
6q
c
onfiguration
42Slide43
Deuteron to Deltaron
T
hresholdpn2.2 MeV
deuteron
Δ
Δ
80 MeV
d*
I(
J
p
) =
0(1
+
)
I(
J
p
) = 0(3
+
)
u
u
u
d
d
d
u
u
u
d
d
d
43Slide44
Dibaryon hadronic
decays
44
pn
d*(2380)
PRL 112 (2014)
202301
PRC
90
,
(2014) 035204
PLB 721 (2013) 229
PRL 106 (2011) 242302
PRC 88 (2013) 055208
PLB
743 (2015)
325
WASA
data
d*
d*
d* Slide45
Dibaryon in elastic scattering
p
n
n
p
background
+ dibaryon
45Slide46
Polarization is a key
46
SAID
New SAID
solutions
Effect of the resonanceSlide47
Hexaquark
vs molecule
47
e
-
d
*
d
*(2380)
Transition form factor
Charge distribution
Internal structure
e
-Slide48
48
Dibaryon in
Skyrm modelDavid Foster, Nicholas S. Manton arXiv:1505.06843 Slide49
d*(2380) SU(3) multiplet
*
*
J
p
=
3
+
49Slide50
Baryon Summary Table (PDG 2014)
50Slide51
51Slide52
Precise experiments change our knowledge about well known resonances
Transition form factors -> internal structureNew exotic statesMeson MoleculesT
etraquarksHybridsMeson-Baryon MoleculesPentaquarksHybrid baryonsBaryon-baryon moleculesHexaquarks… A lot of states still to be found and identifiedConclusion52Slide53
NN SU(3)
multiplet
pn
53
Deuteron +2.2 MeV
J
p
=
1
+
-166
keV
-400
keV