Gluon Exchange Model Research Articles

Production of strangeonium phi (1680) state in electromagnetic probe-driven scatterings and hadron–hadron ultraperipheral collisions

In this work, the gamma prightarrow phi (1680) p reaction is systematically studied based on the two gluon exchange model and the pomeron model. The calculation results show that the total cross section of phi (1680) photoproduction can reach more than 80 nb near the center-of-mass energy W=4 GeV, so it is suggested that JLab and other experiments carry out relevant measurements. Moreover, under the framework of the vector meson dominance assumption, the scattering length of phi (1680) and proton interaction is estimated as 0.07pm 0.01 fm from the cross sections predicted by the theoretical models, which is on the same order of magnitude as the phi (1020)-p scattering length. In addition, the total cross section, number of events and rapidity distribution of phi (1680) production are predicted at Electron-Ion colliders (EICs) and ultra-peripheral collisions (UPCs) by using eSTARlight and STARlight code. The study of phi (1680) and relevant properties is of enlightening significance in better understanding the strangeonium family spectrum, and provides necessary data support for the future experiment of EICs and UPCs.

Analysis of the contribution of the quantum anomaly energy to the proton mass

Inspired by the recent Hall C and GlueX measurements of $J/\psi$ photoproduction, a systematic analysis of the contribution of quantum anomalous energy (QAE) to the proton mass is carried out under the framework of the vector meson dominance model. The results show that the effective Pomeron model and the parametrized two gluon exchange model can explain the cross section of $J/\psi$ photoproduction well. Based on the predicted cross section values given by the two models, the distribution of the QAE contribution with the energy is extracted for the first time. Finally, the average value of the QAE contribution is estimated to be (3.50$\pm$0.70)$\%$, which suggests that the QAE contribution to the proton mass is small. Accordingly, we compared this result with those of other groups and explored the causes for the differences.

Mass radius and mechanical properties of the proton via strange ϕ meson photoproduction

In this work, the cross sections of $\phi$ photoproduction are systematically investigated with the two gluon exchange model and the pomeron model. The results obtained show that the theoretical values of the two models agree well with the experimental data. Since the mass radius and mechanical properties of the proton are encoded in the scalar gravitational form factor of the momentum energy tensor, based on the differential cross sections of $\phi$ photoproduction at near-threshold predicted by the two gluon exchange model, the average mass radius of the proton is derived as $\sqrt{\left\langle r^{2}\right\rangle_\mathrm{m} }=0.78 \pm 0.06$ fm. As a comparison, we directly extract the proton mass radius from the experimental data of $\phi$ photoproduction to obtain an average value of $0.80\pm0.05$ fm, which is very close to the result given by the two gluon exchange model. Taking a similar approach, we extracted the average value of $m_{D}$ to obtain the distribution of the pressure and shear force contributed within the proton, and compared the results with other groups. The results of this paper may provide necessary theoretical information for the subsequent in-depth study of the internal structure and properties of proton.

ψ(*)p scattering length based on near-threshold charmonium photoproduction

Under the framework of Vector Meson Dominance model, the value of scattering length can be expressed as a function of the ratio between total cross section $\sigma (W)$ and $R (W)$, where $R(W)$ is the ratio between final momentum $|{\bf p}_3 |$ and initial momentum $|{\bf p}_1|$ and positively correlated with the center-of-mass energy. Based on the theoretical study of charmoniums photoproduction within two gluon exchange model and effective pomeron model, we research the scattering lengths of vector mesons and proton interaction in this work. Results show that the scattering length $\left|\alpha_{J/\psi p}\right|$ obtained from the two models are close and basically in agreement with the theoretical prediction of Strakovsky and co-workers. Additionally, we first calculate the scattering length of $\psi(2S) $-proton interaction in two gluon exchange model and effective pomeron model as $ 1.31\pm 0.92$ am (1 am = $10^{-3}$ fm) and $ 3.24 \pm 0.63$ am, respectively. This is a little bit different from the two models and requires precise measurements from subsequent experiments. In short, our results will provide a theoretical reference for future studies on characterizing the vector meson-proton scattering length.

Systematic analysis of the proton mass radius based on photoproduction of vector charmoniums

In this work, the cross-section of the reaction $\gamma p \rightarrow V(J/\psi,\psi(2S)) p$ from the production threshold to medium energy is studied and systematically analyzed within two gluon exchange model. The obtained numerical results are in agreement with experimental data and other theoretical predictions. Under the assumption of the scalar form factor of dipole form, the value of proton mass radius is calculated as $0.55\pm 0.09$ fm and $ 0.77\pm 0.12$ fm from the fit to the predicted $J/\psi $ and $\psi(2S)$ differential cross-section, respectively. Finally the average value of proton mass radius is estimated to be $\sqrt{\left<R^2_m \right>}=0.67\pm 0.11$ fm. Moreover, one find that extracting mass radius from the near-threshold differential cross-section of heavy quarkoniums is always affected by large $|t|_{min}$. These obtained results may provide important theoretical reference for understanding of nucleon structure and future relevant experiments.

The Gluon Exchange Model in Proton–Nucleus Collisions

We apply our recently formulated Gluon Exchange Model (GEM) to baryon production in proton-nucleus reactions involving N>1 proton-nucleon collisions. We propose a description scheme for the process of soft color octet (gluon) exchange, based on the assumption that probabilities to form an effective diquark are equal for all allowed pairs of quarks. The latter effective diquark can form either from two valence, one valence and one sea, or from two sea quarks. Consequently we calculate the probabilities for different color configurations involving diquarks of valence-valence, valence-sea and sea-sea type. These probabilities appear to depend on the number of exchanged gluons, which results in increasing baryon stopping as a function of the number of proton-nucleon collisions in the nucleus. As such, the nuclear stopping power appears to be governed by the emergence of new color configurations as a function of N rather than by the energy loss of the original valence diquark. The advantage of our approach lies in its high predictive power which makes it verifiable by the new, precise data on proton and neutron production from the CERN SPS. The latter verification, and a set of predictions for the N-dependence of the baryon stopping process, are included in the letter.

Baryon number in proton-proton and proton-nucleus high energy collisions

New analyses of baryon spectra in proton-proton and proton-carbon collisions at sqrt{s}_mathrm {_{NN}}=17.3 GeV, made in the framework of two phenomenological models are presented. The first model in question is the classic Dual Parton Model by Capella and Tran Thanh Van, the second is the Gluon Exchange Model very recently proposed by the authors. For both studies, the usage of modern experimental data from the CERN SPS eliminates several of the most important limitations inherent to earlier studies of this type. In both studies, the standard mechanism of baryon stopping with preservation of the diquark, proposed by Capella and Tran Thanh Van fails to describe the distribution of non-strange baryons in collisions of the projectile proton with more than one nucleon from the carbon target obtained from experimental data, and the upper limit for the contribution of this mechanism can be established. In both cases, the conclusion is that the projectile diquark must be very often disintegrated. This opens new diagrams not available in proton-proton collisions which lead to the transport of baryon number over long distances in rapidity. The present limitations, and possibility of improvement in both approaches are discussed. The implications of our findings for new measurements are addressed, in particular using antiproton beams.

The Gluon Exchange Model for diffractive and inelastic collisions

We propose a new model for a homogeneous description of hadron-hadron and hadron-nucleus collisions, the Gluon Exchange Model, fundamentally based on color octet (gluon) exchange. In proton-proton collisions we provide an exact description of the final state proton and neutron spectrum including the proton diffractive peak. In proton-nucleus reactions we find that the projectile proton diquark cannot survive in more than about half of multiple proton-nucleon processes and consequently must be very frequently disintegrated, leading to long transfers of baryon number over rapidity space.

The thermodynamic properties of weakly interacting quark-gluon plasma via the one-gluon exchange interaction

The thermodynamic properties of the quark gluon plasma($QGP$) as well as its phase diagram are calculated as a function of baryon density (chemical potential) and temperature. The $QGP$ is assumed to be composed of the light quarks only, i.e. the up and the down quarks, which interact weakly and the gluons which are treated as they are free. The interaction between quarks is considered in the framework of the one gluon exchange model which is obtained from the Fermi liquid picture. The bag model is used, with fixed bag pressure (${\cal B}$) for the nonperturbative part and the quantum chromodynamics ($QCD$) coupling is assumed to be constant i.e. no dependence on the temperature or the baryon density. The effect of weakly interacting quarks on the $QGP$ phase diagram are shown and discussed. It is demonstrated that the one gluon exchange interaction for the massless quarks has considerable effect on the $QGP$ phase diagram and it causes the system to reach to the confined phase at the smaller baryon densities and temperatures. The pressure of excluded volume hadron gas model is also used to find the transition phase-diagram. Our results depend on the values of bag pressure and the $QCD$ coupling constant which the latter does not have a dramatic effect on our calculations . Finally, we compare our results with the thermodynamic properties of strange quark matter and the lattice $QCD$ prediction for the $QGP$ transition critical temperature.

Spectrum of low-lyings3QQ¯configurations with negative parity

Spectrum of low-lying five-quark configurations with strangeness quantum number $S=-3$ and negative parity is studied in three kinds of constituent quark models, namely the one gluon exchange, Goldstone Boson exchange, and instanton-induced hyperfine interaction models, respectively. Our numerical results show that the lowest energy states in all the three employed models are lying at $\sim$1800 MeV, about 200 MeV lower than predictions of various quenched three-quark models. In addition, it is very interesting that the state with the lowest energy in one gluon exchange model is with spin 3/2, but 1/2 in the other two models.

Quark Forces from Hadronic Spectroscopy

We consider the implications of the most general two-body quark-quark interaction Hamiltonian for the spin-flavor structure of the negative parity L = 1 excited baryons. Assuming the most general two-body quark interaction Hamiltonian, we derive two correlations among the masses and mixing angles of these states, which constrain the mixing angles, and can be used to test for the presence of three-body quark interactions. We find that the pure gluon-exchange model is disfavored by data, independently of any assumptions about hadronic wave functions.

Publisher's Note: Mesonic content of the nucleon and the Roper resonance [Phys. Rev. C 75, 067001 (2007)

We investigate colorless (mesonic) 3q-q qbar components in the nucleon and the Roper resonance N*(1440). Starting from constituent quarks and gluons we estimate the excitation of quark-antiquark pairs in a gluon exchange model with the strong coupling constant extracted from a comparison with a non-perturbative resonating group calculation of the pi, eta, rho and omega content of the nucleon. Applying the same model to the Roper resonance, we find as the most striking result a very strong scalar-isoscalar sigma content of the N*(1440) with a strength of the 3q-q qbar configurations comparable to the 3q component itself.

Mesonic content of the nucleon and the Roper resonance

We investigate colorless (mesonic) 3q-qq components in the nucleon and the Roper resonance N*(1440). Starting from constituent quarks and gluons we estimate the excitation of qq pairs in a gluon exchange model with the strong coupling constant extracted from a comparison with a nonperturbative resonating group calculation of the {pi},{eta},{rho}, and {omega} content of the nucleon. Applying the same model to the Roper resonance, we find as the most striking result a very strong scalar-isoscalar {sigma}-content of the N*(1440) with a strength of the 3q-qq configurations comparable to the 3q component itself.

WHICH CONSTITUENT QUARK MODEL IS BETTER?

A comparative study has heen done by calculating the effective baryon-baryon interactions of the 64 lowest channels consisting of octet and decuplet baryons with three constituent quark models: the extended quark gluon exchange model, the Goldstone boson exchange model and the quark gluon meson exchange hybrid model. We find that these three models give similar results for 44 channels. Further tests of these models are discussed.

Spin effects in two-body hadronic decays of the B c mesons

We consider spin effects in two-particle hadronic decays of B_c and B_c^* mesons into J/psi plus \rho(\pi) in the frame work of hard gluon exchange model. It is shown that polarization of the J/psi meson is very different in decays of B_c and B_c^* mesons as well as their decay widths into J/psi plus \rho(\pi).

DiffractiveJ/ψproduction through the color-octet mechanism in resolved photon processes at DESY HERA

We use the color-octet mechanism combined with the two gluon exchange model for the diffractive $J/\psi$ production in resolved photon processes. In the leading logarithmic approximation in QCD, we find that the diffractive $J/\psi$ production cross section is related to the off-diagonal gluon density of the proton, the gluon density of the photon and to the nonperturbative color-octet $^3 S_{1}^{(8)}$ matrix element of $J/\psi$. The cross section is found to be very sensitive to the gluon density of the photon. As a result, this process may provide a wide window for testing the two-gluon exchange model, studying the nature of hard diffractive factorization breaking and may be particularly useful in studying the gluon distribution of the photon. And it may also be a golden place to test the color-octet mechanism proposed by solving the $\psi'(J/\psi)$ surplus problem at the Tevatron.

Possible probe of the QCD odderon singularity through the quasidiffractiveηcproduction in γγ collisions

The reactions $\ensuremath{\gamma}\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}}{\ensuremath{\eta}}_{c}{\ensuremath{\eta}}_{c}$ and $\ensuremath{\gamma}\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}}{\ensuremath{\eta}}_{c}+X$ are discussed within the three-gluon-exchange model. We give predictions for the differential cross sections and discuss the feasibility of measuring these processes at CERN LEP2 and Cornell TESLA. The total cross sections were estimated to be approximately equal to 40 fb and 120 fb for $\ensuremath{\gamma}\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}}{\ensuremath{\eta}}_{c}{\ensuremath{\eta}}_{c}$ and $\ensuremath{\gamma}\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}}{\ensuremath{\eta}}_{c}+X,$ respectively, assuming exchange of elementary gluons that corresponds to the odderon with intercept equal to unity. These values can be enhanced by a factor equal to 2.4 and 2.9 for LEP2 and TESLA energies if the odderon intercept is equal to 1.07. The estimate of cross sections $\ensuremath{\sigma}{(e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}{\ensuremath{\eta}}_{c}{\ensuremath{\eta}}_{c})$ and $\ensuremath{\sigma}{(e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}{\ensuremath{\eta}}_{c}X)$ for antitagged ${e}^{+}$ and ${e}^{\ensuremath{-}}$ is also given.

DiffractiveJ/ψproduction through the color-octet mechanism at hadron colliders

We propose the color-octet mechanism combined with the two gluon exchange model for the diffractive $J/\psi$ production in hadron collisions. In the leading logarithmic approximation (LLA) in QCD, we find that the diffractive $J/\psi$ production rate is related to the off-diagonal gluon density in the proton and to the nonperturbative color-octet matrix element of $J/\psi$. The rate is found to be very sensitive to the gluon density at very small values of $x$ (down to $x=O(10^{-6})$). As a result, this process may provide a wide window for testing the two-gluon exchange model, and may be particularly useful in studying the small $x$ physics. And it may also be a golden place to test the color-octet mechanism proposed by solving the $\psi'(J/\psi)$ surplus problem at the Tevatron.

The interpretation of rapidity gaps at HERA

In leading twist deep inelastic ep scattering, the virtual photon interaction is fast compared to the time scale of soft color rearrangement. We compare the Pomeron exchange model, in which a neutral cluster is preformed, with a gluon exchange model, in which color is exchanged after the hard interaction. We find several features of the DIS data and of data on exclusive hard processes that favor a gluon exchange scenario. If correct, the postulate of soft color interactions between the produced (̄qq) system and the target has important implications for other processes. In particular, this may explain the puzzles of charmonium hadroproduction.

Inclusive jet production within the two gluon exchange model

The work presents the predictions for the inclusive jet production in the two gluon exchange model for the LEP energies. It is shown that there is a region of the produced jet transverse momentapT where the two gluon contribution is the only important one. The two gluon exchange model is not able to reproduce the exponential slope of the jet inclusive production cross section, which seems to be an essential feature of the hadronic component of a photon.