双重子研究的一些新进展课件.ppt

1、Multi-Strangeness Dibaryon T.Goldman, TD, LANLY.X.Liu, Peking Univ.X.F.Lu, Sichuan Univ.J.L.Ping, Nanjing Normal Univ.Fan Wang, Nanjing Univ. Contents “Discovery” of multi-quark states. Candidates of multi-strangeness dibaryons. RHIC is a factory of multi-quark. Nonperturbative QCD basis of quark mo

2、dels. Proposal“Discovery” of Multiquark The “discovery” of multiquark states sets challenges as well asopportunities to quark models. Eleven groups claimed that they observed a penta quark state, called +: +: I=0, J=1/2, Parity=?, M=1540MeV, 25MeV, NA49 -: I=3/2, M=1862MeV, 18MeV, H1 c : I=0, M=3099

3、 MeV, Four groups clamed that they observed tetra quark states . Up to now no dibaryon or hexa quark state has been observed . If the Pendora box of multi quark really has been opened, all of these multiquark states should appear sooner or later. The discovery of multi-quark states sets challenges a

4、s well asopportunities to quark models, even lattice QCD and others. Four lattice QCD calculations gave totally different results. There have been more than 200 papers about pentaquark but noconsensus yet.Candidates of Dibaryons Candidates of Multi-Strangeness Dibaryons. Chiral soliton quark model p

5、rediction of the+played a vital role in the “discovery” of +. Quark model predictions of dibaryon:1. H(uuddss) I=0,Jp=0+,S=-2 Wang Zhang others Threshold M(MeV) 2228 2223 deeply bound 2231 2230 2233 to unbound (2230-32) Quite impossible to be deeply bound. More than 25 years search with null result.

6、 2. I=0,Jp=0+,S=-6 Wang Zhang Others Threshold M(MeV) 3298 3229 deeply bound 3345 3300 3292 to unbound (3300-4) Similar to H particle, weakly bound orunbound. 3.N I=1/2,Jp=2+,S=-2 Wang Zhang Others ThresholdM(MeV) 2549 2561 deeply bound 2611 2557 2607 to unbound (2590)(keV) 12-22Decay mode N- 1D2,3D

7、2.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.)RHIC, a multiquak factory RHIC is a factory of multiquark statesespecially multi strangeness dibaryons. High strangeness p

8、roduction. Hadronization and clustering at theboundary of fire ball. Shandong group estimation: no problem to produce N in one event, but hard to have in one event.Nonperturbative QCD basis of quark models Nonperturbative QCD basis of quark models. How reliable are these quark model predictions? Wan

9、g(QDCSM or Nanjing-Los Alamos model) Zhang(chiral quark model or Tokyo-Tuebingen-Beijing -Salamanka model) both fit the existed NB scattering data(Zhangs better)and deuteron properties(Wangs better). The effective attraction developed in and N channels is quite model independent. There are many othe

10、r quark models but I will not talkabout them here. Quark-Goldstone boson coupling From current-quark gluon QCD toconstituent quark Goldstone boson effective theory t Hooft-Shuryak-Diakonov dilute instantonliquid vacuum(DILM). (NPB 203,245,461) Negeles lattice QCD supports DILM(fig.1).(PRD49(94)6039)

11、 Our group reproduced part of Negeles result. It has not been proved but might be a goodapproximation of QCD vacuum. Current quark propagating within the DILM(fig.2) (NPB 272(86)457; hep-ph/0406043) Current quark m is dressed to be constituentquark M(q2) (fig.3) The QCD Lagrangian is transformed to

12、bethe effective Lagrangian caacFiqMi/exp52 Our group derive an effective Lagrangianbased on chiral symmetry spontaneouslybroken and its nonlinear realization, The constituent quark field operator c isrelated to the current quark operator byccfff3252512/4/2/cdcbcdeabeacbabcaaacffffff352512/4/2/5ice T

13、he form of dynamically derived effective Lagrangian, such as the former Diakonovs Lagragian, is model dependent, but the nonlinear coupling is dictated by the chiral symmetryspontaneously broken as we did. The linear approximation of Zhang(NPA 683(01)487)and others, such as Glozman & Riska, Phys. Re

14、ports, 268(96)263,missed the higher order terms, which should be important for shortrange physics, such as multi quark study. The SU(3) extension of linear approximation is evenquestionable, the universal u,d,s-quark meson couplingwill over estimate the induced attraction with strangenessparticles.Q

15、DCSM Nanjing-Los Alamos model QCD basis of Nanjing-Los Alamos model The constituent quark-Goldstone bosoncoupling effective Lagrangian is still anonperturbative strong interaction field theory. We did a self consistent mean field approximationcalculation and found that the self-consistent meson mean

16、 field increases as the increasing of quarkexcitation, i.e., the mean field try to keep thequark confined, within a limited excitation. -0.08-0.07-0.06-0.05-0.04-0.03-0.02-0.010.0020s13s20s12s20s11s30sGeVfm420 Quenched lattice QCD calculation(hep-lat/0407001 andthe ref.s there in) shows that the gro

17、und state gluon fieldenergy for systems can all be expressedas where the Lmin is the minimum length of the gluonflux tube or string.(fig.4)(hep-lat/0407 Unquench will modify the long range behavior bycolor screening(fig.5).5 , 3 , 2,14minnCLkrrAVnnjijijinqqqqqqqqqq, For individual color configuratio

18、n, the quenched latticeQCD result can be approximately expressed by a twobody confinement potential,(Nuovo Cmento, 86A(85)283) Vij=-kijrijp p=1,2, the unquenched one can be approximated as Vij=-kij rijp (1-exp(-rijp)/, p=1,2, is color screening constant. These color configurations will be mixed due

19、to gluon fluctuation and excitation.qq In the nave quark model, meson and baryon have unique color structure: baryon mesonSo De Rujula, Georgi, Glashow and Isgur can havesimple Hamiltonian for hadron spectroscopy. For pentaquark there are more color structures: In principle one should have a multi b

20、ody interaction,multi channel coupling model. Numerically it is quiteInvolved. We developed a quark delocalization, color screeningmodel (QDCSM), where the multi color couplings aremodeled by an extended effective matrix elementswithin a two cluster Hilbert space where the color screeningconstant is

21、 left as a variational parameter; the multi quarkorbital configurations are modeled by means of delocalizedquark orbits within a two cluster space where thedelocalization parameteris left as another variationalparameter. The variational calculation will allow the multi quark system to adjust themsel

22、ves to arrive at a self consistency. We can not derive this model from QCD. The fitof hadron interaction data shows that this modelcomprises right physics at least partly. Proposal H particle : At most weakly bound or unbound, keep it as acandidate at RHIC search , but not very promised. Di- Possibl

23、y a weakly bound state, keep it as anothercandidate, but the production rate is very low. N The most promised one, it is a very narrow resonancearound 2.55 GeV, even narrower than the +. Thanks 谢谢(xie xie) QDCSM Hamiltonian:RGM Wavefunctions:Model Parameters M=313 MeV, b=0.602 fm, s=1.555, a=25.03 M

24、eV/fm2, Ms=634 MeV. r0=0.8 fm are fixed by ground state masses of baryons =0.9 fm-2Is fixed by deuteron properties, should be adjusted forevery multi quark system. Delocalization parameteris determined for everyseparation and every channel by the dynamics of themulti quark systemDibaryons Deuteron(S

25、trangeness=0,I=0,J=1) : Md=1875.8 MeV, =1.92 fm, PD=4.92%, two-baryon state The components of deuteron is consistent with the Salamanca result. H(Strangeness=-2,I=0,J=0): First predicted by Jaffe in 1977 with MIT bag model. MH=2228-2230 MeV. A weakly bound or unbound one. d* (Strangeness=0,I=0,J=3):

26、 Md*=2165 MeV, =1.3 fm. (6-quark state) (d*NN D-wave)=7 MeV. Quite different from Zhangs ,because of the differentMechanisms of intermediate range attraction. di-(Strangeness=-6,I=0,J=0): M =3300 MeV, =1.2 fm. (6-quark state) Quite different from Zhangs, because of the differentmechanisms of interme

27、diate range attraction. d (Strangeness=0,I=0,J=0,Parity=-): 2060 MeV Md=2454 MeV. Original resonance signal disappeared later. (I=0,J=1): M=2078 MeV, ( NN S-wave)=147 MeV (I=1,J=0): M=2131 MeV, ( NN S-wave)=228 MeV (I=1,J=2): M=2205 MeV, ( N S-wave)=10 MeV N(I=1/2,J=2): M=2549 MeV, (N S=0, D-wave ) =0.012 MeV (N S=1, D-wave ) =0.022 MeVPysical reasons for narrow width:D-wave dicay, tensor interaction, no in N channel,One quark must be exchanged between N and .Quite possible a narrow resonance.