1 / 26

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

elma
Download Presentation

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

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  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

More Related