Color Van Der Waals Force Research Articles

Quarkonium-nucleus bound states from lattice QCD

Quarkonium-nucleus systems are composed of two interacting hadronic states without common valence quarks, which interact primarily through multi-gluon exchanges, realizing a color van der Waals force. We present lattice QCD calculations of the interactions of strange and charm quarkonia with light nuclei. Both the strangeonium-nucleus and charmonium-nucleus systems are found to be relatively deeply bound when the masses of the three light quarks are set equal to that of the physical strange quark. Extrapolation of these results to the physical light-quark masses suggests that the binding energy of charmonium to nuclear matter is B < 40 MeV.

Stochastic Variational Method Applied to Pentaquarks

state of Λ(1405) is lower than the energy for the (q 3 ) state, even after eliminating the contribution from the color van der Waals force due to the phenomenological linear confinement potential. The present result suggests that the Λ(1405) is a pentaquark-dominated state if the color-magnetic potential plays a leading role of the quark-quark and quark-antiquark interactions.

Detailed analysis of the tetraquark potential and flip-flop in SU(3) lattice QCD

We perform the detailed study of the tetraquark (4Q) potential ${V}_{4\mathrm{Q}}$ for various $QQ\mathrm{\text{\ensuremath{-}}}\overline{Q}\overline{Q}$ systems in SU(3) lattice QCD with $\ensuremath{\beta}=6.0$ and ${16}^{3}\ifmmode\times\else\texttimes\fi{}32$ at the quenched level. For about 200 different patterns of 4Q systems, ${V}_{4\mathrm{Q}}$ is extracted from the 4Q Wilson loop in 300 gauge configurations, with the smearing method to enhance the ground-state component. We calculate ${V}_{4\mathrm{Q}}$ for planar, twisted, asymmetric, and large-size 4Q configurations, respectively. Here, the calculation for large-size 4Q configurations is done by identifying ${16}^{2}\ifmmode\times\else\texttimes\fi{}32$ as the spatial size and 16 as the temporal one, and the long-distance confinement force is particularly analyzed in terms of the flux-tube picture. When $QQ$ and $\overline{Q}\overline{Q}$ are well separated, ${V}_{4\mathrm{Q}}$ is found to be expressed as the sum of the one-gluon-exchange Coulomb term and multi-Y-type linear term based on the flux-tube picture. When the nearest quark and antiquark pair is spatially close, the system is described as a ``two-meson'' state. We observe a flux-tube recombination called a ``flip-flop'' between the connected 4Q state and the two-meson state around the level-crossing point. This leads to infrared screening of the long-range color forces between (anti)quarks belonging to different mesons, and results in the absence of the color van der Waals force between two mesons.

COLOR VAN DER WAALS FORCES BETWEEN HEAVY QUARKONIA IN EFFECTIVE QCD

The perturbative renormalization group for light-front QCD Hamiltonians produces a logarithmically rising inter-quark potential already in second order, when Fock sectors with effective (constituent) gluons are truncated. In this approach the quark self-interaction renders [Formula: see text] states unphysical if they are not color singlets. There is a question if this mechanism solves the problem of too strong color van der Waals forces between heavy quarkonia, which emerge in potential models not directly derivable from QCD. This article shows that such forces do exist in this approach, and estimates their strength with the result that they are on the border of exclusion, while more advanced calculation is possible.

Semiclassical quark model of the nuclear matter response

The longitudinal response function R(q,w) of nuclear matter is calculated in a semiclassical quark model. The model has a many‐body string‐flip potential that confines quarks into hadrons and avoids color van der Waals forces. Molecular dynamics simulations are used to calculate R(q,w) in one space dimension for a variety of momentum transfers q and excitation energies w. The response function decreases with density (compared to a free hadron response) because of quark exchange between hadrons. © 1995 American Institute of Physics.

Mott scattering as a probe of long range QCD effects.

We investigate the possibility of using the Mott scattering between identical nuclei to assess the existence of long range QCD effects, e.g., a color van der Waals interaction, as suggested recently. We show that the inclusion of atomic effects is very important and should be considered in order to extract limits on the strength of the color van der Waals force. We compare our calculations with the analysis of a recent heavy ion experiment.

Search for color van der Waals force in 208Pb+208Pb Mott scattering.

In a high precision experiment, Mott scattering of the [sup 208]Pb+[sup 108]Pb system was measured at [ital E][sub lab]=873.40 MeV and 1129.74 MeV with kinematic coincidences for angle pairs around [theta][sub lab]=30[degree], 60[degree] and [theta][sub lab]=45[degree], 45[degree]. The observed Mott oscillations exhibit an angular shift with respect to pure Mott scattering. A comparison with the angular shift produced by a color van der Waals force including nuclear polarizability, vacuum polarization, relativistic effects, and electronic screening provides a new upper limit for the strength of this force. Influence of atomic effects other than screening were identified for the first time.

Absolute measurement of the GANIL beam energy

The energy of the GANIL cyclotron beam was measured on-line during the 208Pb + 208Pb elastic scattering experiment “Search for Color van der Waals Force in the 208Pb + 208Pb Mott scattering” with an absolute precision of 7 × 10−5 at ∼ 1.0 GeV, which represents an improvement of one order of magnitude over previous absolute energy measurements. The energy was deduced from the time of flight between two beam-scanners, which only partially intercept the beam, situated on a straight line and separated by ∼ 48.0 m. It was found that the nominal beam energy was in good agreement with the present results.

Color screening effect in the quark potential model

By using the color confinement potential which includes the color screening effect, we studied the baryon spectra and the nucleon-nucleon interaction. The results show that the color screening effect not only improves the baryon spectrum calculation, but also can solve the long-tail problem of the color Van der Waals force. A part of the medium attraction of the nuclear force can be obtained from the color Van der Waals force.

Color van der Waals force acting in heavy-ion scattering at low energies.

The influence of the color van der Waals force in the elastic scattering of $^{208}\mathrm{Pb}$ on $^{208}\mathrm{Pb}$ at sub-barrier energies is studied. The conspicuous changes in the Mott oscillation found here are suggested as a possible experimental test.

Color Van der Waals forces in the nucleon-nucleon interaction

Color Van der Waals forces arise from two-quark confinement potentials. Here the limitations of these models are studied for the first time in a dynamical treatment of the nucleon-nucleon (NN) scattering. The Van der Waals forces are only present if one includes intermediate orbital-excited color-octet states. Phase shifts calculated by a coupled channel resonating group method including intermediate color-octet states show strong attraction. Although this attraction is less than found in an adiabatic treatment, the results of this calculation are in contradiction with the experimental data on NN scattering and show explicitly the failure of an additive two-body confinement potential.

Nucleon-nucleon interaction with a flip-flop model for quark confinement

The nucleon-nucleon interaction with a flip-flop confining interaction which is free from the pathology of the color van der Waals force is studied in the framework of the quark cluster model supplemented by an effective meson-exchange potential (EMEP). The experimental phase shifts for spin-singlet states ( 1S 0, 1P 1, 1D 2) are well reproduced. The spin-orbit interaction from the confinement potential is also studied and compared with the one from the one-gluon exchange potential (OGEP). The strength of the former is determined so that it cancels the latter in the excited states of a nucleon. The cancellation does not occur in the NN interaction and the resulting spin-orbit force including both contributions has roughly the required strength for the 3P and 3D channels. This fact suggests the possibility that the substantial part of the NN spin-orbit force can be attributed to the quark contribution.

Baryon-baryon interaction with a flip-flop model for quark confinement: The case of color SU(2)

The baryon-baryon interaction with a new type of confinement potential (a flip-flop model) free from the pathology of the color van der Waals force is studied in the framework of the quark-cluster model in the case of color SU(2). For moderate values of the parameter describing the confinement of the “hidden-color” part, the confinement potential turns out not to contribute to the scattering so much. The Galilei-invariant part of the spin-orbit interaction arising as a relativistic effect from the confinement potential is also studied in comparison with the one from the OGEP. The former does not contribute significantly between baryons even if its strength is determined so as to cancel the latter in the excited state of a single baryon, which suggests the possibility that the latter is an important source of the baryon-baryon spin-orbit interaction. Similar results are expected for the more realistic case of color SU(3).

Hadron-hadron interaction in a string-flip model of quark confinement. II. Nucleon-nucleon interaction.

The string-flip model of quark confinement is extended and applied to two-baryon systems with color, spin, and flavor degrees of freedom. The model avoids a pathological color van der Waals force, unlike a conventional two-body quark-confining potential model. Resonating-group-method calculations of the N-N phase shifts are presented for several different color-dependent potentials. A realistic model with a short-range interquark potential and an effective meson-exchange interaction is proposed and found to reproduce $^{1}\mathrm{S}_{0}$ N-N scattering data very well.

The Discussion on Solving the Coupling Equations with Color Van Der Waals Force in the Quark Potential Model

The second order homogeneous ordinary differential equations were derived by introducing the Gaussian type quark confinement potential in order to study color-analog Van der Waals force in N-N interaction. In this paper, it is proved theoretically that the existence and uniqueness of non-zero solution of problem of boundary value in this kind of equations and the non-zero solution are calculated by numerical method (Gill method).

The Quark Cluster Model of Nuclear Force: (II) Quark Confinement Potential and Color Van der Waals Force

The color-analog Van der Waals force between two hadrons is studied by the coupling channel resonating group method in the framework of the Gaussian-type quark confinement potential. The problem of the boundary values for the two channel coupling differential equations is changed to the problem of the initial values. The equations are solved numerically by the Gill method. The calculated results show that there is no color Van der Waals force between hadrons in the confinement potential model. This indicates that the confinement potential model not only can describe the internal structure of hadrons but also can be used to calculate the hadron-hadron interactions.

Color van der Waals force in the coupled channel approach

A modified inverse-power law of the color van der Waals potential is derived in the coupled channel formalism. It approaches the inverse-power law potential from below asymptotocally. Possible screening mechanisms are briefly discussed.

Quartic confinement, QCD and the nucleon-nucleon interaction

We show that even the quartic qq-potential, the only one that does not imply color Van der Waals forces, fails to produce the attractive intermediate range NN S-state central potential if the parameters are fixed from baryon mass differences.

Can we see color van der Waals forces between leptons made of colored constituents?

We estimate the color van der Waals-type forces between leptons in a model in which leptons are made from color-carrying subquark constituents for momenta for which quantum-chromodynamic interactions are weak but weak interactions are still negligible. We find that there are no experimentally measurable effects for lepton-lepton scattering.

Link-operator formulation of quark confinement without van der Waals forces

We give a second-quantized model in which, using link operators, quarks and antiquarks are permanently confined without color van der Waals forces between hadrons. We also sketch how to include short-range interactions between hadrons, quark-antiquark creation and annihilation, and, string breaking.