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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.