Dibaryon Signals in NN Scattering data and high strangeness dibaryon
sesarch at RHIC Fan Wang
Dept. of Physics, Nanjing Univ.Joint Center for Particle-Nuclear Physics and Cosmology (CPNPC)
of NJU and PMOJ.L.Ping, H.X.HuangC.L.Chen, H.R.Pang
C.W.Wong, UCLAArxiv:0806.0458[nucl-th]
Outline
• I. Introduction
• II. Dibaryons in NN scattering data
• III. QCD models calculation
• IV. High strangeness dibaryon search at RHIC
I.Introduction
• NN scattetering and reaction data show evidences of dibaryon resonances:
NN scattering has been measured for more
than 70 years and vast data existed;
Phase shift analysis showed evidences of
dibaryon resonances, which had been there
about 15 years!
R.A.Arndt et al, Phys.Rev.D45,3995(1992);
C50,2731(1994)
No reliable theory to calculate multi-quark resonance:
The present lattice QCD is impossible to calculatethe broad resonance; Chiral perturbation is hard to extend to resonance energy region; The phenomenological meson exchange modelneeds new parameters ofπNΔ,πΔΔ couplingto deal with NΔ,ΔΔ channels coupling and soalmost no predictive power in calculating NΔandΔΔ dibaryon resonances. The strangenesschannels are even harder.
The advantage of quark model (chiral quarkmodel, quark delocalization and color screening model, etc.) is the model parameters can be fixed by hadron spectroscopy, at most the NN scattering andthen the dibaryon resonances can be“predicted” in detail;The disadvantage is it is just a model and the predictive power is limited.
II.Dibaryons in NN Scattering Data
Partial wave analysis (PWA) pp↔d
Dibaryon resonances parameters from PWA
CELSIUS-WASA
This results were observed recently by
SELSIUS-WASA collaboration through
pn->d and d doubleπproduction
reaction. The total and differential cross
sections can be fitted by assuming a ΔΔ
resonance with
0 0
2.41rE GeV 100r MeV
III.QCD models calculation
Two quark models have been employed to
do NN, NΔ,ΔΔ channels coupling
calculation to study the NΔ,ΔΔ dibaryon
resonances appearing in NN scattering data:
1.Chiral quark model, Salamanca version;
2.Quark delocalization color screening model
(QDCSM).
Salamanca chiral quark model
QDCSM
• Quark models fitted the NN scattering data
well (even though not as well as meson
exchange models) with much less adjustable
parameters might mean there is right physics
there.
• QDCSM with the fewest adjustable
parameters; it is the unique one which
explained the long standing fact that the
molecular and nuclear force are similar.
• Quark models are less repulsive for
partial waves in the higher scattering energy
region, some kind short range repulsion might
be missing.
• The P-wave phase shifts have not been
fitted well, both the central and spin-orbit
P-wave interactions have not enough
attraction.
1 30 1,S S
NΔ,ΔΔdibaryon resonancesin quark models
• Channel coupling calculations including NN, NΔ,ΔΔ and even hidden color channels with two quark models have been done to study the standard Feshbach resonances due to the coupling between closed channels NΔ,ΔΔ and the open channel NN.
• NΔ↔ and
dibaryon resonances obtained.5
2S 12D NN 7 3
3 3S D NN
• Quark models explained the
resonance discovered in PWA is an NΔ
resonance.
• The ΔΔ isoscalar resonance discovered
(if confirmed) by CELSIUS-WASA group is
a ΔΔ resonance.
• Quark model could not obtain the
and isoscalar resonances discovered in
PWA.
12NN D
52S
73S
3 32 2P F
33F
• These calculations show that the low
energy NN scattering data can not fix the BB
Interaction in the resonance energy region.• They also show that the bare quark model
prediction on the dibaryon resonances might
be far from reality, the open channel coupling
might shift the resonance energy few hundred
MeV.• The bare quark model calculated hadron
spectroscopy has the same uncertainty.
There should be dibaryon resonances
contributing to these broad structure of
the NN scattering in the resonance
energy region.
IV.High Strangeness dibaryon search at RHIC
Quark model predicted there should be
strong attraction for some decuplet-decuplet
BB channels and mild attraction for some
decuplet-octet BB channels; The octet-octet
channels will have repulsive core and weak
attraction.
The N-Delta and di-Delta resonance (if
confirmed) support this prediction.
• The relativistic heavy ion reaction should b
e an oven to produce the multiquark systems, to search NΔandΔΔresonance there might be hard but our model predict another interesting dibaryon resonance,
SI = -3 .
It is almost a NΩ dibaryon, which mainly decay to ΛΞ with an estimated width ~12-22 keV, so it can be searched through the reconstuction of theΛΞ invariant mass with the data stored in STAR and other detectors.
pJ 12 2
N I=1/2,Jp=2+,S=-3
Wang Zhang Others ThresholdM(MeV) 2549 2561 deeply bound 2611 2557 2607 to unbound (2590)(keV) 12-22
Decay mode N--> 1D2,3D2. D-wave decay, no strongπtensor interaction in N channel, one quark must be exch
angedto form from N. These factors all suppress the decay r
ate andmake N quite possible a narrow resonance.
(Wang:PRL 59(87)627, 69(92)2901, PRC 51(95)3411, 62(00)054007, 65(02)044003, 69(04)065207;
Zhang:PRC 52(95)3393, 61(00)065204, NPA 683(01)487.)
IV.Further measurements at CSR
• The NN scattering, pp and pd, in the resonance region
should be measured further.
The dibaryon production cross section is in the order of μb
and the total pp cross section in the resonance energy
region is about 50 mb , a big challenge to the scattering
cross section measurement .• The pp->d should be measured again. It is a good
channel to study the isovector dibaryon resonances.• The pd->pd should be checked. WASA group
proposed to do further measurement at COSY, CSR is
almost a unique machine to do an independent check.
0 0,
Few words about γd
γd->dπ, dππ, NNπ, NNππ not only
provide N resonances information but also
dibaryon resonance information, especially
di-Δ or the d* resonance information. The
production cross section is about 10 nb.
It should be a good check of CELSIUS
-WASA di-Δ resonance signal, the γ
Energy should be around 500 MeV.
*N
Advertisement about nucleon spin structure
PRL100,232002(2008);
Arxiv:0806.3166[hep-ph];
0709.1284
0709.3649
0710.1247
'''''' LSLSJ eeQED
New decomposition''''''
ggqqQCD LSLSJ
2
3xdS q
i
DrxdL
phyq
3''
a
phy
a
g AExdS 3''
phyai
aig ArxEdL 3
''
Esential task:to define properly the pure gauge field and physical one
purephy AigD a
purea
pure ATA
pureA phyA
phypure AAA
0 purepurepurepurephy AAigAAD
0 phyphy AEEA
II.Color confinement Color structure of nucleon obtained from lattice QCD
Simplified version of the color structure, color string
nucleon meson
Color structure of multi-quark systems
Hadron phase
Multi-quark phase
Five quark Six quark
QCD quark benzene
• QCD interaction should be able to form a quark benzene consisted of six quarks
Lattice QCD results of the quark interaction PRL 86(2001)18,90(2003)182001,hep-lat/0407001
min
3 3 3 min 3
5 5 min 5
min
1
| |
4 | |
qqqq qq qq
q q q qi j i j
i jsq q q
i j i j
ii
AV L C
r
V A L C
V L C
L L
r r
r r
Suppose these lattice QCD results are qualitatively correct, then multi-quark system is a many body interaction multi-channel coupling problem.
• Two hadrons collide each other, if they are closeenough there should be a possibility that twohadrons rearrange there internal color structure totransform from hadron phase to multi-quark phase.• Once the multi-quark is formed, especially if thescattering energy is around the hidden color states itshould be a mixture of various color structure andcolorless hadronic molecular is only one of them.• All hidden color component cannot decay directly. Itmust transform to color singlet hadronic phase firstthen decay, so there must be resonance related tothese genuine multi-quark system similar to compoundnucleus.
• The product cross section and the decay
width of multi-quark system are determined by
the transition interaction between color singlet
hadrons and genuine color multi-quark systems.• Up to now we don’t have any reliable
information about this transition interaction.• One possibility is that such a transition from
color singlet hadrons to genuine color multi-quark
system only takes place at short distances, i.e.
through violent high energy processes only. The
color singlet hadrons like the inertial elements.
Quark delocalization, color screening model (QDCSM)
Based on the above understanding, we take Isgur model as our starting point, but modify it for multi quark systems by two new ingredients:
1. The confinement interaction is re-parameterized aimed to take into account the effect of multi channel coupling,
especially the genuine color channels coupling;2. The quark delocalization, similar to the electron d
elocalization in molecule, is introduced to describe the effect of mutual distortion.
• Color screening: qq interaction: intra baryon
inter baryon different
the color configuration mixing and channel coupling have been taken into account to some extent.
three gluons exchange 0 (intra baryon)
= 0 (inter baryons), etc.
2
2
6
2 2
2
( )2
41 1 1{ ( )[ ] ...}
4 2 3
,
1(1 )ij
ii ij
i i ji
Conf OGEij ij ij
i jOGE sij i j ij
ij i j i j
ijConf
rij i j
pH m V
m
V V V
Vr m m m m
r i j same orbitV a
e otherwise
r
Quark delocalization:
the parameter εis determined variationally by the dynamics of the quark systems.
of quark distribution and gluon distribution has been taken into account to some extent.
• the self-consistency
2
2
2
2
2
)2/(4/3
22
)2/(4/3
2 2
1,
2
1
/)(,/)(
br
bl
lrrrll
eb
eb
NNsrsr
Parameters of QDCSM mu=md=313 MeV
ms=560 MeV
α=1.54
b=0.603 fm
a=25.13 MeV/fm2
μ=1.0 fm-2
Almost the same as Isgur model except
the color screening
• This model, without invoking meson exchange
except pion, with only one additional adjustable
parameter-the color screening constant μ
reproduce the deuteron properties, the NN, NΛ,
NΣ scattering data. • Moreover it explains the long standing facts:
1. The molecular force is similar to nuclear force
except the energy and length scale;
2. The nucleus can be approximated as a nucleon system.
Thanks
QDCSM predicted another six quark stateM(MeV) 2549-2557 threshold 2611 (keV) 12-22Decay mode N--> 1D2,3D2. D-wave decay, no strongπtensor interaction in N channel, one quark must beexchanged to form from N. These factors all suppressthe decay rate and make N quite a narrow resonance.
This state might be created in RHIC and detected by STAR through the reconstruction of decay product.
(Wang:PRL 59(87)627, 69(92)2901, PRC 51(95)3411, 62(00)054007, 65(02)044003, 69(04)065207;
Zhang:PRC 52(95)3393, 61(00)065204, NPA 683(01)487.)
N I=1/2,Jp=2+,S=-3