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

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

Latest data from SPring-8/LEPS preliminary presented by T. INPC07 M (GeV/c 2 ) nK + 

in Fermi motion employment of  -MAID parameters reproduce the d data the result of our experiment

simple subtraction

neutron proton (the same setup)

Antidecuplet mixing with 2 nd octet baryons Reevaluation of N 5 masses D.Diakonov and V.Petrov PRD69(2004) Modified  N PWA R.A. Arndt et al., PRC69 (2004) A possible narrow resonance at W=1680 MeV Calculation of Hyun-Chul Kim et al., PRD71 (2005) Gell-Mann Okubo Our experimental result: consistent with these theoretical predictions

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

 counters 120t magnet 160cm  DC Layout of beam lines

internal radiator for production of a Brems. beam

Angular and momentum distributions for  in the reaction channel opens

Total cross section for the reaction

Resonance parameters employed in the  MAID calculation for the  p→  p reaction statemasswidth NN   N NN S 11 (1535) S 11 (1650) D 15 (1675) P 11 (1710) P 13 (1720) MeV

 MAID calculation reproduces angular distributions very well for E  > 800 MeV coef.s of cos  exp. of d  /d 

Momentum distributions of  for the reaction assuming  N’→  N with nucleon at rest Comparison with proton data ・ broader momentum distribution ～ 20 MeV increased due to the deuteron target ・ however, good separation between  d→  pn,  d→  pn deuteron data proton data given in the  N c.m. system

Angular distributions of  for the quasi-free reaction in the c.m. frame assumed the initial nucleon at rest the total cross section

V. Kuznetsov et al. hep-ex  n coincidence measurement M ～ 1680 MeV  ≦ 30 MeV Breit-Wigner + smooth BG M ～ 1666 MeV  ≦ 40 MeV There is a resonance whose width is smaller than 50 MeV, however, resonance parameters strongly depend on BG shape!! Simple analysis: compared with GRAAL  p’→  p (  MAID) conclution

Analysis: isobar model +impulse approx. ; neglect p-n interference terms and FSI ; on shell amplitudes  default parameters of  MAID  (Fermi motion) ; resonance parameters were searched Born and  and  exchange; CGLN amplitudes for direct terms from  MAID

d  /d  ← F 1,F 2,F 3,F 4 CGLN Amplitudes (Photoproduction of a pseudo-scalar meson) BT + VME = Direct term Resonance Resonance Term Non-Resonance Term (BT) Non-Resonance Term (VME) Resonance Contribution = Breit Wigner Amplitude

Resonance parameters for  ’→  (  MAID default values) statemasswidth NN   N NN S 11 (1535) S 11 (1650) D 15 (1675) P 11 (1710) P 13 (1720) MeV not well determined

Defaults values cannot explain the data. our calculation resonance parameters:  MAID default values coef.s of cos  exp. of d  /dW

 2 = 136/84=1.62: P  < 0.1% Interpretation by the known D 15 is rejected. Unknown resonance!! Does the known resonance D 15 (1675) account for the bump? M, , A 1/2 and A 3/2 of the known D15(1675) are fitted to the data.

M  A 1/2  2 P  S /83= % acceptable P /83= % acceptable? New S 11 (red) and P 11 (blue) fit to  +a 1 +a 2

M  A 1/2 A 3/2  2 P  D /84= % acceptable P < /84=1.46 < 1% J=3/2 possibility New D13 (red) and P13 (blue)

 n →  n  →  cross sections based on the present data tentative assignment to the new resonance  p →  p total double S 11 D 15 new S 11 total double S 11  (n)/  (p) QM(Koniuk-Isugar) S 11 (1535) S 11 (1650) D 15 (1675) enhanced in neutron excitation S 11 (1659) ( > 30 ) - only seen in neutron excitation D 15 (+new S 11 ) +new S 11  (S 11 )=47MeV New analysis is underway. fitted result

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

simulation

Summary We have measured momentum and angular distributions for  photoproduction (  d→  X) for 600  E   1150 MeV. A new resonance is established at W ～ 1670 MeV in the  n→  n 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  n→  n 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.