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N*(2007) observed at LNS Sendai

1670. N*(2007) observed at LNS Sendai. H. Shimizu Laboratory of Nuclear Science Tohoku University Sendai. NSTAR2007, Sep.5-8, 2007, Bonn. search for Exotic Hadrons in these decades. intensive work on dibaryons baryoniums hybrid hadrons glueballs ……. Q + comes in. S=+1.

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N*(2007) observed at LNS Sendai

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  1. 1670 N*(2007) observed at LNS Sendai H. Shimizu Laboratory of Nuclear Science Tohoku University Sendai NSTAR2007, Sep.5-8, 2007, Bonn

  2. search for Exotic Hadrons in these decades • intensive work on • dibaryons • baryoniums • hybrid hadrons • glueballs • …… Q+ comes in. S=+1 • pentaquark narrowness of the width No clear exotics were established before! the key for identification of exotics not have to be narrow (fall-apart decay) extra degrees of freedom Search for other members of the anti-decuplet

  3. Latest data from SPring-8/LEPS Q+ preliminary M (GeV/c2) nK+ presented by T. Nakano @ INPC07

  4. the result of our experiment • employment of • h-MAID parameters • h-MAID parameters • reproduce the d data in Fermi motion

  5. simple subtraction

  6. neutron proton (the same setup)

  7. 1650-1690 1760-1810 Modified pN PWA R.A. Arndt et al., PRC69 (2004) 035208 A possible narrow resonance at W=1680 MeV Antidecuplet Gell-Mann Okubo Reevaluation of N5 masses D.Diakonov and V.Petrov PRD69(2004)094011 mixing with 2nd octet baryons Calculation of Hyun-Chul Kim et al., PRD71 (2005)094023 Our experimental result: consistent with these theoretical predictions

  8. I-spin U-spin Members of with hidden-strangeness U-spin conservation EM interaction a given U-spin multiplet has the same Q. pentaquark nucleons This scenario accounts for the experiment?

  9. Layout of beam lines 120t magnet 160cmf DC g counters

  10. for production of a Brems. beam internal radiator

  11. channel opens Angular and momentum distributionsfor h in the reaction

  12. Total cross sectionfor the reaction

  13. Resonance parametersemployed in the hMAID calculation for the gp→hp reaction MeV

  14. hMAID calculation reproduces angular distributions very well for Eg> 800 MeV coef.s ofcosQexp. ofds/dW

  15. Momentum distributions of hfor the reaction assuming g N’→h N with nucleon at rest 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 deuteron data proton data given in the hN c.m. system

  16. Angular distributions of hfor the quasi-free reactionin the c.m. frame assumed the initial nucleon at rest the total cross section

  17. Simple analysis: compared with GRAAL V. Kuznetsov et al. hep-ex 0606065 hn coincidence measurement gp’→hp (hMAID) Breit-Wigner + smooth BG M ～ 1666 MeV G ≦ 40 MeV M ～ 1680 MeV G ≦ 30 MeV There is a resonance whose width is smaller than 50 MeV, however, resonance parameters strongly depend on BG shape!! conclution

  18. Analysis: isobar model +impulse approx. ; neglect p-n interference terms and FSI • ; on shell amplitudes • default parameters ofhMAID • (Fermi motion) ; resonance parameters were searched Born and r and w exchange; CGLN amplitudes for direct terms fromhMAID

  19. Resonance ds/dW　← F1,F2,F3,F4CGLN Amplitudes (Photoproduction of a pseudo-scalar meson) Resonance Term Non-Resonance Term (BT) Non-ResonanceTerm(VME) Resonance Contribution = Breit Wigner Amplitude BT + VME = Direct term

  20. Resonance parameters for gN’→hN(hMAID default values) MeV not well determined

  21. our calculation resonance parameters:hMAIDdefault values Defaults values cannot explain the data. coef.s of cosQ exp. of ds/dW

  22. Does the known resonance D15(1675) account for the bump? M, G, A1/2 and A3/2 of the known D15(1675) are fitted to the data. c2 = 136/84=1.62: Pc < 0.1% Interpretation by the known D15 is rejected. Unknown resonance!!

  23. New S11(red) and P11(blue) fit tos+a1+a2 M G A1/2c2 Pc S11 1659 47 -9.84 85/83=1.02 46% acceptable P11 1660 11 0.22 106/83=1.28 5 % acceptable?

  24. J=3/2 possibility New D13 (red) and P13 (blue) M G A1/2 A3/2c2 Pc D13 1671 43 -9.45 -12.28 83/84=0.99 50% acceptable P13 1669 <1 -1.97 -19.99 123/84=1.46 < 1%

  25. gN → hN cross sections based on the present data tentative assignment to the new resonance fitted result gp → hp gn → hn G(S11)=47MeV total total (+new S11) double S11 +new S11 D15 double S11 new S11 D15 s(n)/s(p) QM(Koniuk-Isugar) S11(1535) 0.60 0.65 S11(1650) 0.16 0.16 D15(1675) 6.10 10.4 enhanced in neutron excitation S11(1659)(> 30 ) - only seen in neutron excitation New analysis is underway.

  26. 2N approximation: The spectator nucleon has the available minimum momentum.

  27. simulation

  28. Summary • We have measured momentum and angular distributions for h photoproduction (gd→hX) for 600 < Eg< 1150 MeV. • A new resonance is established at W ～ 1670 MeV in the gn→hn reaction. • The width of the resonance is smaller than 50 MeV: at least less than half of those known nucleon resonances. • The new resonance is strongly enhanced in the gn→hn reaction. No coupling is observed so far of the resonance with the proton channel. Thus, the new resonance is a candidate for the antidecuplet member with S=0.

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