We study the short distance part of the intrinsic three-nucleon interaction in a constituent quark model with color-spin interaction. For that purpose we first calculate the transformation coefficient between the tribaryon configuration and their corresponding three baryon basis. Using a formula for the intrinsic three-body interaction in terms of a tribaryon configuration, we find that after subtracting the corresponding two-baryon contributions, the intrinsic three-body interaction vanishes in flavor SU(3) symmetric limit for all quantum numbers for the three nucleon states. We further find that the intrinsic three-body interaction also vanishes for flavor-spin type of quark interaction.
We have used the notion of the constituent quark model of nucleon, where a constituent quark carries its own internal structure, and applied it to determine nuclear structure functions ratios. It is found that the description of experimental data require the inclusion of strong shadowing effect for $x<0.01$. Using the idea of vector meson dominance model and other ingredients this effect is calculated in the context of the constituent quark model. It is rather striking that the constituent quark model, used here, gives a good account of the data for a wide range of atomic mass number from A=4 …
We consider the model of composite dark matter assuming stable particles of charge $-2$ bound with primordial helium nuclei by Coulomb force in $O$He atoms. We study capture of such dark atoms in matter and propose a possibility of existence of stable $O$-enriched superheavy nuclei and $O$-nuclearites, in which heavy $O$-dark matter fermions are bound by electromagnetic forces with ordinary nuclear matter. $O$He atoms accumulation in stars and its possible effect in stellar evolution is also considered, extending the set of indirect probes for composite dark matter.
The pretzelosity distribution function $h_{1T}^\perp$ is studied in a covariant the quark-parton model which describes the structure of the nucleon in terms of 3D quark intrinsic motion. This relativistic model framework supports the relation between helicity, transversity and pretzelosity observed in other relativistic models {\sl without} assuming SU(6) spin-flavor symmetry. Numerical results and predictions for SIDIS experiments are presented.
The probabilistic model of parton distributions, previously developed by one of the authors, is generalized to include the transversity distribution. When interference effects are attributed to quark level only, the intrinsic quark motion produces the transversity, which is about twice as large as the usual polarized distribution. The applicability of such a picture is considered and possible corrections, accounting for interference effects at the parton-hadron transition stage are discussed.
The electromagnetic form factors are the most fundamental quantities to describe the internal structure of the nucleon and the shape of a spatially extended particle is determined by its {\it intrinsic} quadrupole moment which is first order moment of the charge density operator. With some experimental indications of a deformed nucleon, we have calculated the {\it intrinsic} quadrupole moment of the octet and decuplet baryons in the framework of chiral constituent quark model \chiCQM which is quite successful in explaining some of the important baryon properties in the nonperturbative regime.
The spin structure of the system of quasifree fermions having total angular momentum $J=1/2$ is studied in a consistently covariant approach. Within this model the relations between the spin functions are obtained. Their particular cases are the sum rules Wanzura - Wilczek, Efremov - Leader - Teryaev, Burkhardt - Cottingham and also the expression for the Wanzura - Wilczek twist 2 term $g_{2}^{WW}$. With the use of the proton valence quark distributions as an input, the corresponding spin functions are obtained. The resulting structure functions $g_{1}$ and $g_{2}$ are well compatible with the…
The spin structure functions of the system of quasifree fermions on mass shell are studied in a consistently covariant approach. Comparison with the basic formulas following from the quark-parton model reveals the importance of the fermion motion inside the target for the correct evaluation of the spin structure functions. In particular it is shown, that regarding the moment $Γ_{1}$, both the approaches are equivalent for the static fermions, but differ by the factor 1/3 in the limit of massles fermions ($% m \ll p_0$, in target rest frame). Some other sum rules are discussed as well.
A Lorentz covariant kinetic equation for bound states and their constituents is presented and solved exactly in closed form. It describes in a unified way dynamical formation and dissociation of states such as quarkonia and (anti)-deuterons in the excited medium formed with a high-energy heavy-ion collision.
The binding energy of nuclear matter including exchange and pionic effects is calculated in a quark-meson coupling model with massive constituent quarks. As in the case with elementary nucleons in QHD, exchange effects are repulsive. However, the coupling of the mesons directly to the quarks in the nucleons introduces a new effect on the exchange energies that provides an extra repulsive contribution to the binding energy. Pionic effects are not small. Implications of such effects on observables are discussed.
We revisit the photo-absorption sum rule for real Compton scattering from the proton and from nuclear targets. In analogy with the Thomas-Reiche-Kuhn sum rule appropriate at low energies, we propose a new "constituent quark model" sum rule that relates the integrated strength of hadronic resonances to the scattering amplitude on constituent quarks. We study the constituent quark model sum rule for several nuclear targets. In addition we extract the $α=0$ pole contribution for both proton and nuclei. Using the modern high energy proton data we find that the $α=0$ pole contribution differs signi…
A formalism to evaluate the Sivers function, developed for calculations in constituent quark models, is applied to the Isgur-Karl model. A non-vanishing Sivers asymmetry, with opposite signs for the u and d flavor, is found; the Burkardt sum rule is fulfilled up to 2 %. Nuclear effects in the extraction of neutron single spin asymmetries in semi-inclusive deep inelastic scattering off 3He are also evaluated. In the kinematics of JLab, it is found that the nuclear effects described by an Impulse Approximation approach are under control.
The up-dated three-phase concept of nuclear matter evolution in course of cooling down - from the phase of quark-qluon plasma (QGP) through the intermediate phase allowing for massive constituent quarks (valons), pions and kaons (QPK) to the phase of hadronic matter (H) - is exploited for the treatment of relative hadronic yields in the central region of heavy ion collisions. The most attention is paid to the description of the QPK-phase which is argued to be a gaseous one and lasts until the valonic spacing approaches the confinement radius (at the temperature about 110 MeV), when the valons …
Major aspects of the subhadronic state of nuclear matter populated with deconfined color particles are reviewed. At high and even at rather low nuclear collision energies, this is expected to be a short-term quark-gluon plasma (QGP), but, seemingly, not only this. Emphasis is put on the self-consistency requirement that must be imposed on any phenomenological description of the evolution of a hot and dense nuclear medium as it expands (cools down) to the point where the final scattering of secondary particles starts. The view is argued and analyzed that massive constituent quarks should then p…
The electromagnetic form factors are the most fundamental quantities to describe the internal structure of the nucleon and the shape of a spatially extended particle is determined by its intrinsic quadrupole moment which can be related to the charge radii. We have calculated the electromagnetic form factors, nucleon charge radii and the intrinsic quadrupole moment of the nucleon in the framework of chiral constituent quark model. The results obtained are comparable to the latest experimental studies and also show improvement over some theoretical interpretations.
Information on the intrinsic deformation of the proton can be obtained by studying the electromagnetic p-->Delta+ quadrupole transition. Recent experiments have shown that the electric quadrupole (E2) strength in gamma p --> Delta+ is about 10 times larger than predicted by the simple quark model using only one-body currents. Our analysis provides evidence for the dominance of exchange currents in the N-->Delta quadrupole transition and identifies the physical mechanism leading to the observed E2 strength.
The off-shell behaviors of bound nucleons in deep inelastic lepton nucleus scattering are discussed in two scenarios with the basic constituents chosen to be baryon-mesons and quark-gluons respectively in light-cone formalism. It is found that when taking into account the effect due to internal quark structure of nucleons, the derived scaling variable for bound nucleons and the calculated nuclear structure functions are different from those in considering the baryon-mesons as the effective elementary constituents. This implies that the pure baryon-meson descriptions of nuclei give the inaccura…
Recoiling nuclei from Cold Dark Matter (CDM) elastic scattering interactions with the constituent elements of some minerals may produce etchable damage tracks in the crystal structure. Present calculations show that in muscovite mica, CDM tracks from recoiling potassium atoms could be readily distinguished from others due to alpha-decays in the uranium and thorium chains. Under favorable conditions, this technique could greatly improve the existing limits on Weakly Interacting Massive Particles as the constituents of the galactic halo.
Pion loop fluctuations of the constituent u and d quarks are shown to give only a minute contribution to the intrinsic charge radius of the neutron, under the assumption that the pion-quark coupling constant has its conventional value, with a cut-off scale of the order of 1.0 GeV. The contribution from the pion loops to the anomalous magnetic moment of the neutron represents a small ($\sim$ 12-14%) increase over of the static quark model value.
We have performed a study of the isovector, octet and singlet axial charges of the proton in an extended chiral constituent quark model, where all the possible $uudq\bar{q}$~($q=u,d,s$) five-quark Fock components in the proton wave function are taken into account. The $^3P_0$ quark-antiquark creation mechanism is assumed to account for the transition coupling between three- and five-quark components in proton, and the corresponding transition coupling strength is fixed by fitting the intrinsic sea flavor asymmetry $\bar{d}-\bar{u}$ data for proton. Accordingly, with all the parameters fixed by…
A set of exactly computable orthonormal basis functions that are useful in computations involving constituent quarks is presented. These basis functions are distinguished by the property that they fall off algebraically in momentum space and can be exactly Fourier-Bessel transformed. The configuration space functions are associated Laguerre polynomials multiplied by an exponential weight, and their Fourier-Bessel transforms can be expressed in terms of Jacobi polynomials in $Λ^2/(k^2 + Λ^2)$. A simple model of a meson containing a confined quark-antiquark pair shows that this basis is much bet…
We discuss the relation between the polarization of inclusively produced (anti)-hyperons and the incident baryon states in the framework of the constituent quark-diquark cascade model. We assume that there is an intrinsic diquark-antidiquark state in the incident baryon, in which the intrinsic diquark immediately fragments into a non-leading baryon and the antidiquark behaves as a valence constituent. It is also assumed that the valence (anti)diquark in the incident nucleon tends to combine selectively with a spin-down sea quark and, on the othe hand, the spin-up valence quark in the projectil…
Cold nuclear matter effects on J/psi production in proton-nucleus and nucleus-nucleus collisions are evaluated taking into account the specific J/psi production kinematics at the partonic level, the shadowing of the initial parton distributions and the absorption in the nuclear matter. We consider two different parton processes for the c-cbar pair production: one with collinear gluons and a recoiling gluon in the final state and the other with initial gluons carrying intrinsic transverse momentum. Our results are compared to RHIC observables. The smaller values of the nuclear modification fact…
Kaon electroweak properties in symmetric nuclear matter are studied in the Nambu--Jona-Lasinio model using the proper-time regularization. The valence quark properties in symmetric nuclear matter are calculated in the quark-meson coupling model, and they are used as inputs for studying the in-medium kaon properties in the NJL model. We evaluate the kaon decay constant, kaon-quark coupling constant, and $K^+$ electromagnetic form factor by two different approaches. Namely, by two different ways of calculating the in-medium constituent quark masses of the light quarks. We predict that, in both a…
Ab initio calculations in Nuclear physics for atomic nuclei require a specific knowledge of the interactions among their constituents, protons and neutrons. In particular, NN interactions can be constrained down to scale resolutions of $Δr \sim 0.6 {\rm fm}$ from the study of phase shifts below the pion production threshold. However, this allows for ambiguities and uncertainties which have an impact on finite nuclei, nuclear- and neutron-matter properties. On the other hand the nuclear many body problem is intrinsically difficult and the computational cost increases with numerical precision an…
Using the quark-meson coupling (QMC) model we study nuclear matter from the point of view of quark degrees of freedom. As the nucleon model we adopt the MIT bag model and the relativistic constituent quark model, where a square well and harmonic oscillator potentials are used to confine the quarks. We introduce the Lorentz-vector type confining potential as well as the Lorentz-scalar type one in order to examine how the vector confining potential contributes to the properties of the nucleon and nuclear matter. Next, we perform a re-definition of the scalar field in matter and transform the QMC…
Properties of cold nuclear matter are studied within a generalized Nambu-Jona-Lasinio model formulated on the level of constituent nucleons. The model parameters are chosen to reproduce simultaneously the observed nucleon and pion masses in vacuum as well as saturation properties of nuclear matter. The strongest constraints on these parameters are given by the empirical values of the nucleon effective mass and compression modulus at nuclear saturation density. A preferable value of the cut-off momentum, determining density of active quasinucleon states in the Dirac sea, is estimated to about 4…
Sea quark contents of the octet baryons are investigated by employing an extended chiral constituent quark approach, which embodies higher Fock five-quark components in the baryons wave-functions. The well-known flavor asymmetry of the nucleon sea $\bar{d}-\bar{u}$, is used as input to predict the probabilities of $\bar{u}$, $\bar{d}$ and $\bar{s}$ in the nucleon, $Λ$, $Σ$ and $Ξ$ baryons, due to the intrinsic five-quark components in the baryons wave functions.
In principle, quantum chromodynamics provides a fundamental description of hadronic and nuclear structure and dynamics in terms of their elementary quark and gluon degrees of freedom. In practice, the direct application of QCD to reactions involving the structure of hadrons is complex because of the interplay of nonperturbative effects such as color confinement and multi-quark coherence. A crucial tool in analyzing such phenomena is the use of relativistic light-cone quantum mechanics and Fock state methods to provide tractable and consistent treatments of relativistic many-body systems. We be…
Nuclei are transparent for a heavy intrinsic charm (IC) component of the beam hadrons, what leads to an enhanced nuclear dependence of open charm production at large Feynman x_F. Indeed, such an effect was observed recently in the SELEX experiment. Our calculations reproduce well the data, providing strong support for the presence of IC in hadrons in amount less than 1%. Moreover, we performed an analysis of nuclear effects in J/Psi production and found a similar, although weaker effect
The magnetic moments of baryon decuplet are studied in vacuum as well as in the symmetric nuclear matter at finite temperature using a chiral SU(3) quark mean field model approach. The contributions coming from the valence quarks, quark sea and the orbital angular momentum of the quark sea have been considered to calculate magnetic moment of decuplet baryons. The decuplet baryon masses decrease, whereas, the magnetic moments increase significantly with the rise of baryonic density of the symmetric nuclear medium. This is because of the reason that constituent quark magnetic moment and the quar…
Effective chiral Lagrangians involving constituent quarks, Goldstone bosons and long-distance gluons are believed to describe the strong interactions in an intermediate energy region between the confinement scale and the chiral symmetry breaking scale. Baryons and mesons in such a description are bound states of constituent quarks. We discuss the combined use of the techniques of effective chiral field theory and of the field theoretic method known as Fock-Tani representation to derive effective hadron interactions. The Fock-Tani method is based on a change of representation by means of a unit…
The radiative baryonic decay $\mathcal{B}^{*}\left(\frac{3}{2}\right)\to\mathcal{B}\left(\frac{1}{2}\right)+γ$ is a magnetic dipole $(M1)$ transition. It requires the transition magnetic moment $μ_{\mathcal{B}\left(3/2\right)\to\mathcal{B}\left(1/2\right)}$. The transition magnetic moments for the helicities $1/2$ and $3/2$ are evaluated in the frame work of constituent quark model in which the intrinsic spin and the magnetic moments of quarks $u,d$ and $s$ play a key role. Within this framework, the radiative decays $Δ^{+}\to p +γ$, $Σ^{*0}\to Λ+γ$, $Σ^{*+}\to Σ^{+}+γ$ and $Ξ^{*0}\to Ξ^{0}+γ$…
The possibility of unified description of hadron multiple production in heavy ion collisions over the wide energy interval, from few hundreds MeV/n at GSI/SIS through 11 GeV/n at BNL/AGS up to 160 GeV/n at CERN/SPS, has been emphasized recently by J. Cleymans and K. Redlich. They, and somewhat later B. Muller and J. Rafelski, treated this fact as an indication that quark-gluon plasma (QGP) can be produced even at very low energies of impinging nuclei. In our opinion, it rather witnesses that a massive constituent quark (valon) - not massless current quark and gluon! - is just what becomes "qui…
Using the light-front pion wave function based on a Bethe-Salpeter amplitude model, we study the properties of the pion in symmetric nuclear matter. The pion model we adopt is well constrained by previous studies to explain the pion properties in vacuum. In order to consistently incorporate the constituent up and down quarks of the pion immersed in symmetric nuclear matter, we use the quark-meson coupling model, which has been widely applied to various hadronic and nuclear phenomena in a nuclear medium with success. We predict the in-medium modifications of the pion lectromagnetic form factor,…
An extended chiral constituent quark approach, which embodies higher Fock five-quark components in the baryons wave-functions, is employed to study the sea quark content of the octet baryons. We report on the probabilities of $\bar{u}$, $\bar{d}$ and $\bar{s}$ in the nucleon, $Λ$, $Σ$ and $Ξ$ baryons, arising from the intrinsic five-quark states in the baryons wave functions. Based on those probabilities, results for meson-nucleon $σ$-terms; namely $σ_{πN}, σ_{K N}$ and $σ_{ηN}$, are presented.
The dynamical breaking of chiral symmetry in QCD is caused by nonperturbative interactions on a scale rho ~ 0.3 fm, much smaller than the hadronic size R ~ 1 fm. These short-distance interactions influence the intrinsic transverse momentum distributions of partons and their correlations at a low normalization point. We study this phenomenon in an effective description of low-energy dynamics based on chiral constituent quark degrees of freedom, which refers to the large-N_c limit of QCD. The nucleon is obtained as a system of constituent quarks and antiquarks moving in a self-consistent classic…
This dissertation investigated selected processes involving baryons and nuclei in hard scattering reactions. Through these processes, this work explored the constituent structure of baryons and the mechanisms through which the interactions between these constituents ultimately control the selected reactions. First, hard nucleon-nucleon elastic scattering was studied considering the quark exchange (QE) between the nucleons to be the dominant mechanism of interaction in the constituent picture. It was found that an angular asymmetry exhibited by proton-neutron (pn) elastic scattering data is exp…
We study the medium-induced gluon emission process experienced by a hard jet parton propagating through the dense nuclear matter in the framework of deep inelastic scattering off a large nucleus. We work beyond the collinear rescattering expansion and the soft gluon emission limit, and derive a closed formula for the medium-induced single gluon emission spectrum from a heavy or light quark jet interacting with the dense nuclear medium via transverse and longitudinal scatterings. Without performing the collinear rescattering expansion, the medium-induced gluon emission spectrum is controlled by…
Background: A nonperturbative charm production contribution, known as intrinsic charm, has long been speculated but has never been satisfactorily proven. The SeaQuest experiment at FNAL is in an ideal kinematic region to provide evidence of $J/ψ$ production by intrinsic charm. Purpose: $J/ψ$ production in the SeaQuest kinematics is calculated with a combination of perturbative QCD and intrinsic charm to see whether the SeaQuest data can put limits on an intrinsic charm contribution. Methods: $J/ψ$ production in perturbative QCD is calculated to next-to-leading order in the cross section. Cold …
An approach is suggested, invoking vitally the notion of constituent massive quarks (valons) which can survive and propagate rather than hadrons (except of pions) within the hot and dense matter formed below the chiral transition temperature in course of the heavy ion collisions at high energies. This approach is shown to be quite good for description of the experimentally observed excess in dilepton yield at masses 250 MeV < M < 700 MeV over the prompt resonance decay mechanism (CERES cocktail) predictions. In certain aspects, it looks to be even more successful, than the conventional approac…
The orbital angular momentum ($L_q$) of the proton is studied by employing the extended constituent quark model. Contributions from different flavors, namely, up, down, strange, and charm quarks in the proton are investigated. Probabilities of the intrinsic $q\bar{q}$ pairs are calculated using a $^{3}P_{0}$ transition operator to fit the sea flavor asymmetry $I_a=\bar{d}-\bar{u}=0.118\pm0.012$ of the proton. Our numerical results lead to $L_q=0.158 \pm 0.014$, in agreement with $4/3I_a=0.157 \pm 0.016$, and consistent with findings based on various other approaches.
We study the temperature and baryon density dependence of the masses of the lightest charmed baryons $Λ_c$, $Σ_c$ and $Σ^*_c$. We also look at the effects of the temperature and baryon density on the binding energies of the $Λ_c N$ and $Λ_c Λ_c$ systems. Baryon masses and baryon-baryon interactions are evaluated within a chiral constituent quark model. Medium effects are incorporated in those parameters of the model related to the dynamical breaking of chiral symmetry, which are the masses of the constituent quarks, the $σ$ and $π$ meson masses, and quark-meson couplings. We find that while th…
In the extended chiral constituent quark model, the intrinsic $c \bar{c}$ content of the nucleon is investigated. The probabilities of the quark-antiquark components in the nucleon wave functions are calculated by taking the nucleon to be admixtures of three- and five-quark components, with the relevant transitions handled {\it via} the $^{3}$P$_{0}$ mechanism. Predictions for the probability of the $c \bar{c}$ in the nucleon wave function and the charmness-nucleon sigma term are presented. Our numerical results turn out to be consistent with the predictions from various other approaches repor…
In the frame work of a nuclear overlap model, we estimate the number of nucleon and quark participants in proton-proton, proton-nucleus and nucleus-nucleus collisions. We observe the number of nucleon ($N_{N-part}$)-normalized enhancement of multi-strange particles which show a monotonic increase with centrality, turns out to be a centrality independent scaling behavior when normalized to number of constituent quarks participating in the collision ($N_{q-part}$). In addition, we observe that the $N_{q-part}$-normalized enhancement, when further normalized to the strangeness content, shows a st…
Background: A nonperturbative charm production contribution, known as intrinsic charm, was predicted in the early 1980s. Recent results have provided new evidence for its existence but further confirmation is needed. Purpose: $J/ψ$ and $\bar D$ meson production are calculated with a combination of perturbative QCD and intrinsic charm to determine the best energy range to study intrinsic charm production. Methods: $J/ψ$ and $\bar D$ meson production are calculated in perturbative QCD to next-to-leading order in the cross section. Cold nuclear matter effects, including nuclear modification of th…
The complete understanding of the basic constituents of hadrons and the hadronic dynamics at high energies are two of the main challenges for the theory of strong interactions. In particular, the existence of intrinsic heavy quark components in the hadron wave function must be confirmed (or disproved). In this paper we propose a new mechanism for the production of $D$-mesons at forward rapidities based on the Color Glass Condensate (CGC) formalism and demonstrate that the resulting transverse momentum spectra are strongly dependent on the behavior of the charm distribution at large Bjorken $x$…
Properties of \r{ho}-meson in symmetric nuclear matter are investigated within a light-front constituent quark model (LFCQM), using the in-medium input calculated by the quark-meson coupling (QMC) model. The LFCQM used here was previously applied in vacuum to calculate the \r{ho}-meson electromagnetic properties, namely, charge G 0 , magnetic G 1 , and quadrupole G 2 form factors, as well as the electromagnetic radius and decay constant. We predict the in-medium modifications of the \r{ho}-meson electromagnetic form factors in symmetric nuclear matter.
The CLAS Collaboration recently reported measured ratios of pion and kaon electroproduction cross sections from a proton target and extracted the ratios for light and strange quark--antiquark pairs, ${u\bar{u}}/ {d\bar{d}}$ and ${s\bar{s}}/ {d\bar{d}}$. Within an extended chiral constituent quark formalism, we investigate contributions to those ratios from the nonperturbative mechanism due to all possible intrinsic $|uudQ \bar{Q}\rangle$ Fock states in the proton; with $Q \bar{Q} \equiv u\bar{u},~ d\bar{d},~s\bar{s},~c\bar{c}$. Our results are compared with the CLAS data and findings from othe…
In $\XQM$, a quark can emit Goldstone bosons. The flavor symmetry breaking in the Goldstone boson emission process is used to intepret the nucleon flavor-spin structure. In this paper, we study the inner structure of constituent quarks implied in $\XQM$ caused by the Goldstone boson emission process in nucleon. From a simplified model Hamiltonian derived from $\XQM$, the intrinsic wave functions of constituent quarks are determined. Then the obtained transition probabilities of the emission of Goldstone boson from a quark can give a reasonable interpretation to the flavor symmetry breaking in …
Understanding hadron structure within the framework of QCD is an extremely challenging problem. In order to solve it, it is vital that our thinking should be guided by the best available insight. Our purpose here is to explain the model independent consequences of the approximate chiral symmetry of QCD for two famous results concerning the structure of the nucleon. We show that both the apparent success of the constituent quark model in reproducing the ratio of the proton to neutron magnetic moments and the apparent success of the Foldy term in reproducing the observed charge radius of the neu…
It is often assumed that few- and many-body systems can be accurately described by considering only pairwise two-body interactions of the constituents. We illustrate that three- and higher-body forces enter naturally in effective field theories and are especially prominent in strongly interacting quantum systems. We focus on three-body forces and discuss examples from atomic and nuclear physics. In particular, we highlight the importance and the challenges of three-nucleon forces for nuclear structure and reactions, including applications to astrophysics and fundamental symmetries.
Pion valence distributions in nuclear medium and vacuum are studied in a light-front constituent quark model. The in-medium input for studying the pion properties is calculated by the quark-meson coupling model. We find that the in-medium pion valence distribution, as well as the in-medium pion valence wave function, are substantially modified at normal nuclear matter density, due to the reduction in the pion decay constant.
The tetramixing of pseudoscalar mesons $π$-$η$-$η'$-$η_c$ and vector mesons $ω$-$ρ$-$ϕ$-$J/ψ$ are studied in the light-cone constituent quark model, and such mixing of four mesons provides a natural source for the intrinsic charm $c\bar{c}$ components of light mesons. By mixing with the light mesons, the charmonium states $J/ψ$ and $η_c$ could decay into light mesons more naturally, without introducing gluons or a virtual photon as intermediate states. Thus, the introduction of light quark components into $J/ψ$ is helpful to reproduce the new experimental data of $J/ψ$ decays. The mixing matri…
Quantum chromodynamics (QCD) is the theory of strong interactions of quarks and gluons collectively called partons, the basic constituents of all nuclear matter. Its non-abelian character manifests in nature in the form of two remarkable properties: color confinement and asymptotic freedom. At high energies, perturbation theory can result in the growth and dominance of very gluon densities at small-x. If left uncontrolled, this growth can result in gluons eternally growing violating a number of mathematical bounds. The resolution to this problem lies by balancing gluon emissions by recombinati…
