Workshop on “Extractions and interpretations of hadron resonances and multi-meson production reactions with 12 GeV upgrade”, May 27-28, 2010 Cascade Baryons: Spectrum and production in photon-nucleon reactions Yongseok Oh (Kyungpook National University, Korea)
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Cascade Baryons: Spectrum and production in photon-nucleon reactions
Cascade Baryons: Spectrum and production in photon-nucleon reactions. Yongseok Oh ( Kyungpook National University, Korea). Workshop on “Extractions and interpretations of hadron resonances and multi-meson production reactions with 12 GeV upgrade”, May 27-28, 2010. Overview. Introduction - PowerPoint PPT Presentation
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Workshop on “Extractions and interpretations of hadron resonances and multi-meson production reactions with 12 GeV upgrade”, May 27-28, 2010
Cascade Baryons: Spectrum and production in photon-nucleon re-
actionsYongseok Oh
(Kyungpook National University, Korea)
2010-05-27 EBAC Workshop, JLab 2
1. Introduction2. Strangeness and baryons
1) In experiments2) In theory
3. Photoproduction of X4. Outlook
Overview
2010-05-27 EBAC Workshop, JLab 3
1. Introduction What do we know about X baryons?
Strangeness baryons: (: light u/d quark) Baryon number = 1, isospin = ½
Strangeness baryons: (: light u/d quark) Baryon number = 1, isospin = ½ If flavor SU(3) symmetry is exact for the classification of all
particles, then we have N(X*) = N(N*) + N(D*) Currently, only a dozen of X baryons have been identified so
far.(cf. more than 20 N*s & more than 20 D*s)
2010-05-27 EBAC Workshop, JLab 6
X in PDG
• What do we know about X baryons?Particle Data Group (2008): 11 X’s
States whose is known
P is not directly measured
Cf. Spin of (
was confirmedonly recently
by BaBarPRL 97 (2006)
1/2+¿ ¿3 /2+¿¿
3 /2−
2010-05-27 EBAC Workshop, JLab 7
1. Introduction What do we know about X baryons?
Strangeness baryons: (: light u/d quark) Baryon number = 1, isospin = ½ If flavor SU(3) symmetry is exact for the classification of all
particles, then we have N(X*) = N(N*) + N(D*) Currently, only a dozen of X baryons have been identified so
far.(cf. more than 20 N*s & more than 20 D*s)
Only and are in the four star status Only three states with known spin-parity the quantum num-
bers of other states should be identified Advantages & difficulties
2010-05-27 EBAC Workshop, JLab 8
Advantages
Difficulties
• Small decay widths• Identifiable in missing mass plots• Isospin is .
( nonstrange sector: and )• No flavor singlet state (unlike hyper-
ons)
• In most cases, initial state has been used no hadron beams for X physics
• With initial state, 3-body final states at least cross section is very small ~ other technical difficulties PDG 2008
2010-05-27 EBAC Workshop, JLab 9
1. Introduction What do we know about X baryons?
Strangeness baryons: (: light u/d quark) Baryon number = 1, isospin = ½ If flavor SU(3) symmetry is exact for the classification of all
particles, then we have N(X*) = N(N*) + N(D*) Currently, only a dozen of X baryons have been identified so
far.(cf. more than 20 N*s & more than 20 D*s)
Only and are in the four star status Only three states with known spin-parity the quantum num-
bers of other states should be identified Advantages & difficulties No meaningful information for the X resonances it can open a new window for studying hadron structure
• Baryon structure from X spectroscopy• Properties of hyperons (in production mechanisms)• New particles
2010-05-27 EBAC Workshop, JLab 10
2.1 Strangeness and baryons (Expt.)Experiments
WA89 (CERN-SPS) EPJC, 11 (1999), hep-ex/0406077
-nucleus collisions
1690
2010-05-27 EBAC Workshop, JLab 11
CLAS@JLab
PRC 71 (2005) PRC 76 (2007)
2010-05-27 EBAC Workshop, JLab 12
Questions PDG 2008
The 3rd lowest state
1. Does really exist?2. or ?
Most recent report on : NPB 189 (1981)3. What are their spin-parity quantum num-
bers? comparison with theoretical predictions
CLAS: PRC 76 (2007)
1620?1690?
2010-05-27 EBAC Workshop, JLab 13
2.2 Strangeness and baryons (Theory)
• Classify the states as members of octet or decuplet• Use spin-parity (if known) and Gell-Mann—Okubo mass rela-
tion• Works before 1975: reviewed by
Samlos, Goldberg, Meadows RMP 46 (1974)• Recent work along this line
Guzey & Polyakov, hep-ph/0512355 (2005)• No dynamics
Direct extension of the classification in the quark model
• Most parameters of models are fixed by the and sector in principle, no free parameter for the
• Most models give (almost) correct masses for and Requirement to survive SU(3) group structure
• But they give very different spectrum for the excited states!
Hadron models for X baryons
2010-05-27 EBAC Workshop, JLab 14
Nonrelativistic quark modelChao, Isgur, Karl PRD 23 (1981)
from S. Capstick
• has ?• The first negative parity
state appears at MeV.• Decay widths are not fully
calculated by limiting the final state (but indicates narrow widths)The 3rd lowest state
• Includes parameters• They should be computed with a given Lagrangian (dynam-
ics).• Or fix them to known masses and then predict.
Mass formula
2010-05-27 EBAC Workshop, JLab 23
Hyperon spectrum (expt.)
289 MeV
290 MeV
285 MeV positive parity
negative parity
parity undetermined
2010-05-27 EBAC Workshop, JLab 24
Hyperon spectrum (Skyrme model)
YO, PRD 75 (2007)
spin-parity
Recently confirmed by COSY
PRL 96 (2006)
BaBar : of is PRD 78 (2008)NRQM predicts
Unique prediction of this model.
The should be there.still one-star resonance
High precision experiments are re-quired!
W’s would be discovered in future.
2010-05-27 EBAC Workshop, JLab 25
More comments
• Kaons: one in p-wave and one in s-wave ()
: soliton spin (), : spin of the p(s)-wave kaon (): both of them can lead to statesTherefore, two states and one state
In this model, it is natural to have two states and their masses are 1616 MeV & 1658 MeV!
• Clearly, different from quark models
Two states
Unitary extension of chiral perturbation theoryRamos, Oset, Bennhold PRL 89 (2002)
state at MeVGarcia-Recio, Lutz, Nieves, PLB 582 (2004)
Claim that the and are states
Other ap-proaches
2010-05-27 EBAC Workshop, JLab 26
• Earlier work– A few experiments on inclusive photoproduction– Tagged Photon Spectrometer Collab. NPB 282 (1987)
• photoproduction by CLAS@JLab PRC 76 (2007)– The reaction of – Total cross sections– Differential cross sections for X and production angles– Invariant mass distributions in the KK and K X channels