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1.
We show the lattice QCD results on the axial charge gAN*-N* of negative parity nucleon resonances, N*(1535) and N*(1650), which are key clues to the chiral structure in baryon sector. The measurements are performed with up and down dynamical quarks employing the renormalization-group improved gauge action at β=1.95 and the O(a) improved clover quark action with the hopping parameters, κ=0.1375, 0.1390 and 0.1400. In order to properly separate signals of N* (1535) and N* (1650), we construct 2 × 2 correlation matrices and diagonalize them. Wraparound contributions in the correlator, which can be another source of signal contaminations, are eliminated by imposing the Dirichlet boundary condition in the temporal direction. We find that the axial charge of N* (1535) takes small values as gAN*N*-O(0.1), whereas that of N* (1650) is about 0.5, which is found independent of quark masses and consistent with the predictions by the naive nonrelativistic quark model.  相似文献   

2.
曹须 《中国物理 C》2009,33(12):1381-1384
In an effective Lagrangian model we find that the N*(1535) resonance contribution might be important to the interpretation of the present data of the pp →ppη' and pn →dφ reactions. The strong coupling strength of N* (1535) to η' and φ are indicated, and the possible implication to the intrinsic component of N*(1535) is explored. These results may provide hints to the real origin of the OZI rule violation. It is stressed that further measurements could be performed at China. the Cooling Storage Ring (CSR) at Lanzhou of  相似文献   

3.
4.
The strong decays of the N*(1535) resonance are investigated in an extended chiral quark model by including the low-lying qqqqq components in addition to the qqq component.The results show that these five-quark components in N*(1535) contribute significantly to the N*(1535)→ Nπ and N*(1535) → Nη decays.The contributions to the Nη decay come from both the lowest energy and the next-to-lowest energy five-quarks components,while the contributions to the Nπ decay come from only the latter one.Taking these contr...  相似文献   

5.
B. Julia-Diaz 《中国物理 C》2009,33(12):1296-1301
Within the Excited Baryon Analysis Center we have performed a dynamical coupled-channels analysis of the available p(e,e'π)N data in the region of W ≤ 1.6 GeV and Q2 ≤1.45 (GeV/c)2. The channels included are γ*N, π*N, ηN, and ηN which has π△, pN, and σN components. With the hadronic parameters of the model determined in our previous investigations of πN→ πN reaction, we have found that the available data in the considered W ≤ 1.6 GeV region can be fitted well by only adjusting the bare γ*N → N* helicity amplitudes for the lowest N* states in P33, P11, S11 and D13 partial waves. The meson cloud effect, as required by the unitarity conditions, on the γ*N → N* form factors are examined.  相似文献   

6.
Using relativistic spin-flavor wave functions of a Lorentz-covariant light cone quark model, we calculate the electromagnetic form factors of two S11 resonances, N(1535) and N(1650), and the helicity amplitudes A1/2 and S1/2 for electroexcitation of the S11 resonances from the nucleon. The electromagnetic form factors of these S11 resonances are found to be similar to those of the nucleon in shape, while the charge form factor of neutral N(1650) is nearly zero. The relative peak height of the S11 charge form factors is controlled by the mixing angle common to both resonance wave functions. As in most quark models, there is a systematic overestimate of A1/2 in both N(1535) and N(1650) cases at the photon point. A sizeable S1/2 for all cases is produced as suggested by experiments.  相似文献   

7.
We systematically investigate the mass spectra of {Qs}{Q(')s} molecular states in the framework of QCD sum rules. The interpolating currents representing the molecular states are proposed. Technically, contributions of the operators up to dimension six are included in operator product expansion (OPE). The masses for molecular states with various {Qs}{Q(')s} configurations are presented. The result 4.36 ± 0.08 Ge V for theDs* Ds0- * molecular state is consistent with the mass 4350+4.6 -5.1± 0.7 MeV of the newly observed X(4350), which could support X(4350) interpreted as a D*D*so molecular state.  相似文献   

8.
9.
We focus on the investigation of the spatial distribution and temporal evolution of N2(A3Σ+u, ν=0) in a very early afterglow of a pulsed dc nitrogen discharge. The results indicate that a fast quenching process of N2(A3Σ+u, ν=0) exists in the very early afterglow. We study the dependence of this fast quenching process on the discharge pressure 20–40 torr. It seems that this fast quenching behavior of N2(A3Σ+u, ν=0) found in our experiment can be ascribed to the combined action of pooling reaction and collisions with N atoms through N2(A3Σ+u)+N2(A3Σ+u)→ N2*+N2(N2*=N2(B3Πg, C3Πu, C'3Πu, C"5Πu)) and N2(A3Σ+u)+N(4S)→N(2P)+N2, respectively. Meanwhile, the decay studies of N2(A3Σ+u, ν=0) near the anode and cathode infer that the production of N(4S) atoms does not distribute uniformly along the axis of the discharge gap at relatively low pressure, and this effect becomes gradually inconspicuous with the increasing discharge pressure.  相似文献   

10.
Klaus Gö  tzen 《中国物理 C》2010,34(6):638-643
The BES-Ⅲ Detector is a very versatile multipurpose device located at the Institute of High Energy Physics (IHEP) in Beijing, China. Concerning the physics program it ties stringently up to the past BES and BES-Ⅱ experiments. Since start of the data taking in the middle of 2008 the accumulated dataset of 200.10^6 J/ψ events and 100.10^6 ψ' events already exceeds the world data on these resonances. In addition to studies of the charmonium systems the data offers great opportunity for investigations in the light hadron sector. In detail it will be reported about the confirmation of the enhancement in pp invariant mass in radiative J/ψ decays, the search for decays Y(2175) → K*0K*0, observation of a charged K^± in K^±π^0 and observation of a new excited baryon N*(2065) decaying to pπ^0 and charged onjugate. The first result is based on data taken by BES-Ⅱ and BES-Ⅲ, the latter three on data collected by BES-Ⅱ only.  相似文献   

11.
By employing the QCD factorization approach for the exclusive B→Vу decays, we study the exclusive decay B→K^*у in the top-quark two-Higgs-doublet mode/(T2HDM). Within the considered parameter space, we find the following conclusions (a) A hght charged-Higgs boson with a mass about 200 GeV is clearly excluded by the date of B→K^*у decay, and this lower limit is comparable with that from the inclusive B→X8*у decay; (b) The theoretical predictions for CP asymmetry of B→K^*у in the T2HDM is always less than 1% in size; and (c) The isospin symmetry breaking for B→K^*у decay in the SM and T2HDM considered here is around 6% in size and well consistent with the data and the general expectations.  相似文献   

12.
We analyse the vertex D^*D^*ρ with the light-cone QCD sum rules. The strong coupling constant gD^*D^*ρ is an important parameter in evaluating the charmonium absorption cross sections in searching for the quark-gluon plasmas. Our numerical value for the gD^*D^*ρ is consistent with the prediction of the effective SU(4) symmetry and vector meson dominance theory.  相似文献   

13.
In this article, we calculate the branching ratios of B→K0^* (1430)K decays by employing the pertur-bative QCD (pQCD) approach at leading order. We perform the evaluations in the two scenarios for the scalar meson spectrum. We find that (i) The leading order pQCD predictions for the branching ratio Br(B^+→K^+K0^*(1430)^0)are in good agreement with the experimental upper limit in both scenarios, while the pQCD predictions for other considered B→K0^*(1430)K decay modes are also presented and will be tested by the LHC experiments; (ii) The annihilation contributions play an important role in these considered decays, for B^0→K0^*(1430)^±K^± decays,for example,which are found to be (1-4)×10^-6.  相似文献   

14.
何军  B. Saghai 《中国物理 C》2009,33(12):1389-1392
In this report we investigate Wmeson productions on the proton via electromagnetic and hadron probes in a chiral quark model approach. The observables, such as, differential cross section and beam asymmetry for the two productions are calculated and compared with the experiment. The five known resonances S11(1535),S11(1650), P13(1720), D13(1520), and F15(1680) are found to be dominant in the reaction mechanisms in both channels. Significant contribution "missing resonances, no evidence is found within πp→ηn are also presented. from a new S11 resonances are deduced. For the so-called the investigated reactions. The partial wave amplitudes for  相似文献   

15.
The initial single pion emission (ISPE) mechanism is applied to the processes r(5S)→πB(*)B-(*), whose details have been recently reported at ICHEP2012, and we obtain reasonable agreement with Bell's measurements; that is, we succeed in reproducing the enhancement structures of Zb(10610) and Zb(10650). Inspired by this success, we also predict the corresponding enhancement structures in open charm oue-pion decays of higher charmonia near the thresholds of D*D- and D*D-*.  相似文献   

16.
The reaction mechanisms of Al(CH3 )3 (TMA) adsorption on H-passivated GeSi(100)-2 × 1 surface are investigated with density functional theory. The Si-Ge and Ge-Ge one-dimer cluster models are employed to represent the GeSi(100)-2 × 1 surface with different Ge compositions. For a Si-Ge dimer of a H-passivated SiGe surface, TMA adsorption on both Si-H^* and Ge-H^* sites is considered. The activation barrier of TMA with the Si-H^* site (1.2eV) is higher than that of TMA with the Ge-H^* site (0.91 eV), which indicates that the reaction proceeds more slowly on the Si-H^* site than on the Ge-H^* site. In addition, adsorption of TMA is more energetically favorable on the Ge-Ge dimer than on the Si-Ge dimer of H-passivated SiGe.  相似文献   

17.
H. Machner 《中国物理 C》2010,34(9):1218-1223
The η meson can be bound to atomic nuclei.Experimental search is discussed in the form of final state interaction for the reactions dp → 3 Heη and dd → 4 Heη.For the latter case tensor polarized deuterons were used in order to extract the s-wave strength.For both reactions complex scattering lengths are deduced: a 3 Heη = ± 10.7±0.8 +0.1 -0.5 +i· 1.5±2.6 +1.0-0.9 fm and a 4 Heη = [±(3.1±0.5)+i·(0±0.5)] fm.In a two-nucleon transfer reaction under quasi-free conditions,p^ 27 Al → ^3 HeX,was investigated.The system X can be the bound 25 Mg  η at rest.When a possible decay of an intermediate N  (1535) is required,a highly significant bump shows up in the missing mass spectrum.The data give for a bound state a binding energy of 13.3±1.6 MeV and a width of σ=4.4±1.3 MeV.  相似文献   

18.
The hybrid density functional theory B3LYP with basis sets 6-31G* has been used to study on the equilibrium geometries and electronic structures of possible isomers of Si3N4 clusters. 24 possible isomers are obtained. The most stable isomer of Si3N4 is a 3D structure with 7 Si-N bonds and 2 N-N bonds that could beformed by 3 quadrangles. The bond properties of the most stable isomer was analyzed by using natural bond orbital method (NBO), the results suggest that the charges on Si and N atoms in Si-N bonds are quite large, so theinteraction of N-Si atoms in Si3N4 cluster is of strongly electric interaction. The primary IR and Raman vibrational frequency located at 1033.40 cm^-1, 473.63 cm^-1 respectively. The polarizabilities and hyperpolarizabilities of the most stable isomer are also analyzed.  相似文献   

19.
We study the semileptonic decays of the lowest-lying bc baryons to the lowest-lying cc baryons (Ξ (*) bc → Ξ (*) cc and Ω ( *) bc → Ω (*) cc ),in the limit m b,m c Λ QCD and close to the zero recoil point.The separate heavy quark spin symmetries make it possible to describe all these decays using a single form factor.We also show how these constraints can be used to test the validity of different quark model calculations.bb to bc baryon decays are also discussed.  相似文献   

20.
The reactions π-p →ηn and γ'p →ηP are investigated within a dynamical coupledJchannels model of meson production reactions in the nucleon resonance region. The meson-baryon channels included are πN, ηN, π△, σN, and pN. The direct wphotoproduction process is studied within a formalism based on a chiral constituent quark model approach, complemented with a one-gluon-exchange mechanism, to take into account the breakdown of the SU(6)0(3) symmetry. In the models search, the following known nucleon resonances are embodied: Sll (1535), $11(1650), Pll (1440), Pl1(1710), P13(1720), D13(1520), D13(1700), D15(1675), and F15(1680). Data for the π-p →ηnreaction from threshold up to a total center-of-mass energy of W ≈ 2 GeV are satisfactorily reproduced. For the photoproduction channel, two additional higher mass known resonances, P13 (1900) and F15 (2000), are also considered. However, reproducing the data for γ'p →ηP requires, within our approach, two new nucleon resonances, for which we extract mass and width.  相似文献   

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