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Nucleon resonances via H,D( g,h ) reactions

Nucleon resonances via H,D( g,h ) reactions. GeV g Experiments at GeV g Hall at LNS 2001-02: GeV g Hall, 2003: STB tagger II, SCISSORS II, STB special e-beam 2004-05: Experiments with 0.6 < E g < 1.15 GeV 2006: FOREST construction

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Nucleon resonances via H,D( g,h ) reactions

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  1. Nucleon resonances via H,D(g,h) reactions GeV g Experiments at GeV g Hall at LNS 2001-02: GeV g Hall, 2003: STB tagger II, SCISSORS II, STB special e-beam 2004-05: Experiments with 0.6 < Eg < 1.15 GeV 2006: FOREST construction 1. C,Cu(g,h) S11(1535) in nuclei; Phys. Lett. B639 (2006) 429 2. H(g,h) proton cross section; gp→hpp; Phys. Rev. C (2006) in press 3. D(g,h) neutron cross section; S11, D15, pentaquark; submitted soon 4. H,D(g,p0) Nucleon resonances 5. C,Si,Cu(g,h) Eg < 0.8 GeV, threshold region

  2. Why light baryon? Heavy baryon (with c/b/t quarks) 3 quarks in short distance one gluon exchange field Perturbed region Baryon internal energy r < 0.3 fm Non-perturbed region Light baryon (with u/d/s quarks) 3 dynamical (dressed) quarks effective chiral field (Goldstone boson exchange) Existence of pentaquark state constituent quark model chiral quark soliton model r ~ 1 fm diquark-quark clusterization? Baryon density

  3. Spontaneous Chiral symmetry breaking current-quarks (~5 MeV)  Constituent-quarks (~350 MeV) Particles  Quasiparticles

  4. Quark- Model • Three massive quarks • 2-particle-interactions: • confinement potential • gluon-exchange • meson-exchage • (non) relativistisc • chiral symmetry is not respected • Succesfull spectroscopy (?) Nucleon

  5. Chiral Soliton Mean Goldstone-fields (Pion, Kaon) Large Nc-Expansion of QCD ???? Nucleon

  6. Quantum numbers Quantum # Coupling of spins, isospins etc. of 3 quarks mean field  non-linear system  soliton  rotation of soliton Quantum # Natural way for light baryon exotics. Also usual „3-quark“ baryons should contain a lot of antiquarks Coherent :1p-1h,2p-2h,.... Quantum # Quark-anti-quark pairs „stored“ in chiral mean-field

  7. Nucleon Energy Spectrum P11 , P13 P11 , P13 S11 S11 S11 S11 h r p D15? D15? p H,D(g,h) reactions so far reported

  8. Electron Beam from 300MeVLINAC 1.2 GeVSTB Ring electron Synchrotron GeV-g Experimental Hall Tagged Photon Beam 17 m GeV g experiments at LNS

  9. SCISSORS II :206 pure CsI Crystals (1.57 str = 12.5% of 4 p) 16.2 X0 for Forward 148 crystals 13.5 X0 for Backward 58 crystals g + N→ h + X Identification of h meson Gh-gg= (39.43±0.26)% → gg Decay Channel Plastic Counters Pseudosphere 55 cm Forward Block(74) g2 Forward Block(74) Backward Block(29) g1 h ggInvariant Mass Analysis Mgg2 = 2Eg1Eg2(1 - cosFgg) Incident γ Hydrogen/Deuterium Solid Target t = 8 cm (NT～4×1023/cm2 ) Energy :E =S Ei Position :R =S Ri Ei /SEi Backward Block(29) Solid Target Chamber Experimental setup

  10. Mgg Gate : 440—620 MeV gg Invariant Mass Empirical Fitting Function: F(Mgg)= L(Mgg) + B(Mgg) L(x)=l0 exp[ l1(l2 - x) + exp( -l1(l2 - x))] B(x)=exp(b0 +b1x + b2x2) Double Differential Yieldd 2N/dp dcosQ(at g+N CMS)

  11. g p→h p ds/dW ds/dph g p→hpN channel open Momentum CutPh*(3b max)  g p→h p抽出

  12. H(g,h)H reaction For Eg < 1.15 GeV s(LNS)～s(CLAS, ELSA) no third S11 (Saghai and Li) s(Eg)～s(hMAID) S11(1535) largest S11(1650) destructive P11(1720) very small + direct (Born, r,w ex.) Eg > 1 GeV gp→hpN not negligible s(hpN)～s(hp) at 1.1 GeV hMAID s(gp→hp) s(gp→hpN)

  13. N*D* p S11 h p h h P33 p N Direct 3 Body D(1720) S(1750) L(1670) N(1535) Dh-> Nhp L=0 h L=0 h L=0 h L=0 h gp→hpp process New observation: gp→D*→hD→hpN ～50% 1/2- 3/2- 1/2- 1/2- 1/2+ 3/2+ 1/2+ S(1192) D(1232) L(1116) 1/2+ N(938)

  14. h g p N* N* N N gpN*N*/gpNN =+ or -? gp→phN, gp→p0hp gp→p0hN process Jido, Oka, Hosaka Prog. Theor. Phys.106,873 (2001) N(938)-S11(1535): parity partner chiral transformation scheme phase space Doring et al. S11(1535) only is not enough Doring, Oset, Stottman Phys. Rev. C73,045209 (2006) Chiral unitary approach for meson-baryon scattering D33(1700), S11(1535), D13(1520) Jido et al. s(gp→phN) = (2～3)×s(gp→p0hN)

  15. D(g,h) reaction Original motivation: <u|e|u>=2/3, <d|e|d>=-1/3 →difference in magnetic transitions between proton and neutron proton target: only S11(1535), S11(1650) neutron target: D15(1675) should be enhanced ? Present interest: antidecuplet state N* (S=0) originally assigned to P11(1710) reanalisys pN scattering PR C69(04)035208 W=1680, G～10 MeV GRAAL preliminary hn coin. Data W=1675 MeV sharp state

  16. The anti-decuplet Modified analysis pN scattering Arndt et al. PRC69(04)035208 Reevaluation by Diakonov and Petrov, 04 1539 G < 25 MeV ～1646 hn measurement in D(g,hn)p Kunznetsov et al. preprint (05) ～1754 1862 Jp:1/2+ or 1/2- ? Width: very small < 10 MeV? Other members: S=0 sector? strongly observed in gn >> gp sharp resonance

  17. proceedings, preliminary Results GRAAL (hep-ex0601002) gn→hn exclusive measurement Differential Cross Section cosQ~-0.7 CB-ELSA (IX International Workshop On Meson Photoproduction, Crakow,Poland,9.-13,June 2006) gN→hN exclusive measurement Total Cross Section hn measurement: quasi-free kinematics (advantage) incomplete arrangement of neutron detectors →low statistics, not high Eg resolution, spectrum deformed inclusive h measurement gd→hpn: whole kinematics, complex analysis (disadvantage) high statistics, high Eg resolution, spectrum not deformed W, G, Jp, g transition strength,….. may be obtained precisely.

  18. h momentum distributions in gd→hpn Comparison with proton data ・broader momentum distribution ～20 MeV increased due to the deuteron target ・however, good separation between g d→h pn, g d→hp pn

  19. h angular distributions in c.m. frame of photon incident on nucleon at rest (‘c.m.’)

  20. Total cross section vs Eg Narrow resonance! rough estimate peak at Eg=1020 MeV apparent width DEg～80 MeV gd→hpn g’p’→hp s(gd)-s(g’p’)

  21. Hulthen Wave Function • F(pN) =pN2/((pN2+a 2)(pN2+b 2)) 2 • =45.7 MeV b=260 MeV G=10MeV (18MeV in Eg ) solid line : F(pN) open circles: CD-Bonn G=60 MeV(GEg~100MeV) FWHM =75 MeV 1s = 0.5 Angular Distribution E=1 GeV sn cosQ* cosQ* Effects of nucleon motion in the deuteron

  22. Analysis: isobar model +impulse approx. ; neglect p-n interference and f.s.i ; on shell cross section result of hMAID for gp→hp ; result of the isobar model similar to the hMAID calculation Direct term (Born and r and w exchange): from hMAID Resonances: Mass GbhN A1/2 A3/2 D13(1520) 1520 120 0.06 -59 -139 S11(1535) 1541 191 50 varied S11(1650) 1638 114 7.9 varied D15(1675) 1665 150 17 varied F15(1680) 1681 130 0.06 29 -33 D13(1700) 1700 100 26 0.0 -3.0 P11(1710) 1721 100 36 varied P13(1720) 1720 150 3.0 varied + narrow P11 or S11

  23. Angular distributions compared with calculations S11 at 1660 MeV, G= 8.5 MeV, P11 at 1670 MeV, G= 7.5 MeV

  24. Total cross section P11 at 1670 MeV, G= 7.5 MeV S11 at 1660 MeV, G= 8.5 MeV A1/2 = 12.5 for P11 = -12.5 for S11 Anti-decuplet N* is established! 1/2+ or 1/2-

  25. Narrow P11 Narrow S11 D15(1675) P11(1710) P13(1720) S11(1535) S11(1650) neutron cross section Further measurement with FOREST hn coincidence with good geometry Parity + or – need more statistics Branching ratio p0 channel: Miyahara pp channel Anti-decuplet in nuclei 7Li(g,h) S11(1535) resonance molecular nature? Magnetic moment

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