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1.
陈妍  马伯强 《中国物理 C》2009,33(12):1362-1365
We report our investigation on the octet baryon spectrum in the nonrelativistic quark model by taking into account the two-gluon exchange effect. The calculated octet baryon masses agree better with the experimental data. It is also shown that the two-gluon exchange interactions bring a significant correction to the Gell-Mann-Okubo mass formula.  相似文献   

2.
We study radiative decays of T to light quark jets in nonrelativistic QCD by taking both the color singlet and color octet b^-b operators into consideration. The cut for quark jet energy and cut for the angle between two quark jets are introduced. The sensitivity to the soft and collinear singularities in the loop integrals are greatly reduced by these cuts. With the jet energy cut of about 1 GeV, and the jet angle cut of about 36°, the branching ratio for γ→ rq^- is found to be 8.2 × 10^-4 from color singlet contributions. The color octet contributions could be much larger than that of color singlet, depending on the estimate of the color octet matrix elements. This process may provide a new test for the color octet mechanism in nonrelativistic QCD.  相似文献   

3.
We study the quark loop effects on the dressed gluon propagator and also on the quark propagator itself. We find that the gluon propagators are different in two phases. The quark mass effects on the gluon propagator are small but not negligible. We also study the current quark mass dependence on the bag constant.  相似文献   

4.
In light of the developments of the chiral constituent quark model(χ~(CQM)) in studying low energy hadronic matrix elements of the ground-state baryons, we extend this model to investigate their transition properties.The magnetic moments of transitions from the J~P=3/2~+ decuplet to J~P=1/2~+ octet baryons are calculated with explicit valence quark spin, sea quark spin and sea quark orbital angular momentum contributions. Since the experimental data is available for only a few transitions, we compare our results with the results of other available models. The implications of other complicated effects such as chiral symmetry breaking and SU(3) symmetry breaking arising due to confinement of quarks are also discussed.  相似文献   

5.
We have calculated the nucleon effective mass in symmetric nuclear matter within the framework of the Brueckner-Bethe-Goldstone (BBG) theory, which has been extended to include both the contributions from the ground-state correlation effect and the three-body force (TBF) rearrangement effect. The effective mass is predicted by including the ground-state correlation effect and the TBF rearrangement effect, and we discuss the momentum dependence and the density dependence of the effective mass. It is shown that the effect of ground state correlations plays an important role at low densities, while the TBF-induced rearrangement effect becomes predominant at high densities.  相似文献   

6.
We present a study of associated ηc and γ double diffractive production in p-p collision based on Ingelman-Schlein model, and the framework of non-relativistic QCD factorization formalism for quarkonia production. The predic-tion of ηc and γ is more reliable than J/ψ production, because the associated ηc and γ production is a pure color-octetprocess, and the dominant contribution comes from color octet 1So(8) subprocess, which is related to the color octet matrixelement of 1So(8) of J/ψ by the heavy quark spin symmetry and the large PT J/ψ production data. We find that the ratioof diffractive to inclusive cross sections is independent of the values of color octet matrix elements, but is sensitive to thegluon factor of the Pomeron and renormalized Pomeron flux factors. So experimental measurement of this ratio can giveus more information of the nature of Pomeron and test the assumption of hard diffractive factorization in hadron-hadron collisions.  相似文献   

7.
Charmed meson charmonium spectra are studied with improved quark actions on anisotropic lattices. We measured the pseudo-scalar and vector meson dispersion relations for four lowest lattice momentum modes with quark mass values ranging from the strange quark to charm quark with three different values of gauge coupling β and four different values of bare speed of light v. With the bare speed of light parameter v tuned in a mass-dependent way, we study the mass spectra of D, Ds, ηc, D^*, D^*s and J/ψ mesons. The results extrapolated to the continuum limit are compared with the experiment, and a qualitative agreement is found.  相似文献   

8.
In this paper, the gluon propagator in Landau gauge has been studied on a lattice, including the quenched and the unquenched one. The small geometry size of lattice we use is 16^3 × 32, and the big one is 20^3 × 64. For the quenched approximation, we fit the numerical results and give a little different fitting values. We also obtain unquenched effects by comparing the gluon propagator resulting from the quenched and unquenched configurations, for both the two-flavor and three-flavor cases. For the unquenched configurations, an obvious quark mass dependence has not been found in the small quark mass case, but is found in the three-flavor case when the quark mass is big.  相似文献   

9.
We calculate diquark correlation functions in the Landau gauge on the lattice using overlap valence quarks and 2+1-flavor domain wall fermion configurations. Quark masses are extracted from the scalar part of quark propagators in the Landau gauge. The scalar diquark quark mass difference and axial vector scalar diquark mass difference are obtained for diquarks composed of two light quarks and of a strange and a light quark. The light sea quark mass dependence of the results is examined. Two lattice spacings are used to check the discretization effects.The coarse and fine lattices are of sizes 24~3×64 and 32~3×64 with inverse spacings 1/a = 1.75(4) Ge V and 2.33(5) Ge V,respectively.  相似文献   

10.
Bauer recently presented a formula for the ionization rate of a hydrogen atom in a strong linearly polarized laser field[J.Phys.B 49145601(2016)].He started from the Keldysh probability amplitude in the length gauge and utilized Reiss’s method in the velocity gauge.Instead,according to the Reiss probability amplitude in the velocity gauge and Keldysh’s derivation for the length gauge,we derive a formula for the ionization rate of a ground-state hydrogen atom or a hydrogenlike atom in a strong linearly polarized laser field.We compare the numerical results of the total ionization rate and the photoelectron energy distribution calculated from our formula with the results from Keldysh,Reiss,and Bauer.We find that the apparent discrepancies in the ionization rate are caused not only by different gauges,but also by different analytical methods used to derive the ionization rate.  相似文献   

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