N*(2007) observed at LNS Sendai 　

H. ShimizuLaboratory of Nuclear Science

Tohoku UniversitySendai

NSTAR2007, Sep.5-8, 2007, Bonn

1670

search for

Exotic Hadronsin these decades

intensive work on• dibaryons• baryoniums• hybrid hadrons• glueballs• ……

gg

gqqqqqg

qqqq

qqqqqq

,

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 suudd

10

Search for other members of the anti-decuplet

Latest data from SPring-8/LEPS

prelim

i

nary

presented by T. Nakano @ INPC07

M (GeV/c2)nK+

nKKn '

)( Xdtot

n

p

np

in Fermi motion

• employment of-MAID parameters

• -MAID parameters reproduce the d data

Xd

npd

npd

the result of our experiment

pp '

nn '

npd

nn '

p

simple subtraction

neutron

proton

nn ' pp

MeVW 1670

(the same setup)

Antidecuplet )(10 21

1650-1690

1760-1810

mixing with 2nd

octet baryons

Reevaluation of N5 massesD.Diakonov and V.PetrovPRD69(2004)094011

Modified N PWAR.A. Arndt et al., PRC69 (2004) 035208

A possible narrow resonance at W=1680 MeV228

)(

)(*10

*10

pp

nn

10NNCalculation of

Hyun-Chul Kim et al., PRD71 (2005)094023

Gell-Mann Okubo

Our experimental result: consistent with these theoretical predictions

U-spin conservationEM interaction a given U-spin multiplet has the same Q.

I-spin

U-spin

pentaquark nucleons2315

05

spinU

NN

Members of with hidden-strangeness

10

23210

110

5

05

Np

Nn

This scenario accounts for the experiment?

counters

120t magnet160cm DC

Layout of beam lines

internal radiator

for production of a Brems. beam

Angular and momentum distributionsfor in the reactionXp

channel opensNp

Total cross sectionfor the reactionpp

Resonance parametersemployed in the MAID calculation

for the p→p reactionstate mass width N N N

S11(1535) 1541 191 0.40 0.10 0.50 118 0

S11(1650) 1638 114 0.77 0.15 0.079 68 0

D15(1675) 1665 150 0.40 0.43 0.17 18 24

P11(1710) 1721 100 0.14 0.60 0.26 23 0

P13(1720) 1720 150 0.15 0.82 0.03 -18 19

pA 21pA 23

MeV 21310 GeV

MAID calculation reproduces angular distributions very well for E > 800 MeV

pp

coef.s of cos exp. of d/dcmcos

Momentum distributions of for the reaction Xd

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

pnd n

the total cross section

V. Kuznetsov et al. hep-ex 0606065 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.

)~()~()( nnd

dpp

d

dpnd

d

d

; neglect p-n interference terms and FSI

)~( ppd

d

)~( nnd

d

; on shell amplitudesdefault parameters of MAID(Fermi motion)

; resonance parameters were searched

Born and and exchange; CGLN amplitudes for direct terms from MAID

d/d 　← F1,F2,F3,F4 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

npd

Resonance parameters for ’→ (MAID default values)

state mass width N N N

S11(1535) 1541 191 0.40 0.10 0.50 118 0 -96 0

S11(1650) 1638 114 0.77 0.15 0.079 68 0 -56 0

D15(1675) 1665 150 0.40 0.43 0.17 18 24 -43 -58

P11(1710) 1721 100 0.14 0.60 0.26 23 0 0 0

P13(1720) 1720 150 0.15 0.82 0.03 -18 19 -1 29

pA 21pA 23

nA 23nA 21

MeV 21310 GeV

not well determined

Defaults values cannot explain the data.

our calculationresonance parameters: MAID default values

coef.s of cos exp. of d/dW

npd

2 = 136/84=1.62: P < 0.1% Interpretation by the known D15 is rejected.Unknown resonance!!

Does the known resonance D15(1675) account for the bump?

M, , A1/2 and A3/2 of the known D15(1675) are fitted to the data.

M A1/2 2 P

S11 1659 47 -9.84 85/83=1.02 46% acceptableP11 1660 11 0.22 106/83=1.28 5 % acceptable?

New S11(red) and P11(blue) fit to +a1+a2

npd

M A1/2 A3/2 2 P

D13 1671 43 -9.45 -12.28 83/84=0.99 50% acceptableP13 1669 <1 -1.97 -19.99 123/84=1.46 < 1%

J=3/2 possibilityNew D13 (red) and P13 (blue)

npd

n → n

→ cross sections based on the present data tentative assignment to the new resonance

p → p

total

double S11

D15 new S11

total

double S11

(n)/(p) QM(Koniuk-Isugar)S11(1535) 0.60 0.65S11(1650) 0.16 0.16D15(1675) 6.10 10.4 enhanced in neutron excitationS11(1659) ( > 30 ) - only seen in neutron excitation

D15

(+new S11)+new S11

(S11)=47MeV

21PJ

New analysis is underway.

fitted result

nn '

2N

approximation:The spectator nucleon has the available minimum momentum.

simulation

Summary

• We have measured momentum and angular distributions for photoproduction (d→X) for 600E 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.