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Yongseok Oh

Publications and source records attributed to Yongseok Oh.

At least 109 records · Page 6Linked to original sources
arXiv2002

Form-factor dependence of the J/psi dissociation cross sections in meson exchange model

The $J/ψ$ dissociation by $π$ and $ρ$ mesons is examined in meson exchange model and compared to the quark interchange model. We found that the main difference between the predictions of the two models could be resolved by the form factors and the contact interactions in meson exchange model calculations. By adopting covariant form factors and adjusting the four-point couplings, we found that the meson exchange model could give similar predictions with the quark interchange models not only for the magnitudes but also for the energy dependence of the low-energy dissociation cross sections of the $J/ψ$ by $π$ and $ρ$ mesons. Our finding suggests a way to understand one of the discrepancies among the existing model predictions on the $J/ψ$ dissociation cross sections by light hadrons.

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arXiv2002

Quarkonium-hadron interactions in QCD

The leading order non-relativistic QCD result for the quarkonium-hadron interaction cross section is derived by using the QCD factorization formula combined with the Bethe-Salpeter amplitude for the heavy quark bound state. Our result shows the equivalence of this approach with the operator product expansion even for the bound state scattering to leading order in QCD. We also apply the formula to the charmonium system and investigate the relativistic correction coming from the phase space of the reaction. We find that although $J/ψ$-gluon cross-section gets a large relativistic correction at higher energies, the correction becomes small in the $J/ψ$-hadron cross section due to the increase of the gluon distribution at smaller $x$ inside the hadron.

hep-ph↗
arXiv2002

Charmonium-hadron interactions from QCD

The heavy quark system is an excellent probe to learn about the QCD dynamics at finite density. First, we discuss the properties of the $J/ψ$ and $D$ meson at finite nucleon density. We discuss why their properties should change at finite density and then introduce an exact QCD relation among these hadron properties and the energy momentum tensor of the medium. Second, we discuss attempts to calculate charmonium-hadron total cross section using effective hadronic models and perturbative QCD. We emphasize a recent calculation, where the cross section is derived using QCD factorization theorem. We conclude by discussing some challenges for SIS 200.

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arXiv2002

Final state interactions in omega photoproduction near threshold

Vector meson photoproduction and electroproduction have been suggested as a tool to find or confirm the nucleon resonances. In order to extract more reliable informations on the nucleon resonances, understanding the non-resonant background is indispensable. We consider final state interactions in omega photoproduction as a background production mechanism. For the intermediate states, we consider nucleon--vector-meson and nucleon-pion channels. The role of the final state interactions is discussed in omega meson photoproduction near threshold.

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arXiv2001

Asymmetries in phi photoproduction and the OZI violation

We study the vector meson density matrix and the associated polarization asymmetries in $ϕ$ photoproduction near threshold. In order to study the OZI violating processes, we consider the direct $ϕNN$ coupling as well as the knockout processes arising from the non-vanishing $s\bar{s}$ sea quarks in the nucleon. The polarization asymmetries in $ϕ$ meson decays are found to be very useful to constrain the $ϕNN$ coupling constant. The hidden strangeness of the nucleon can also be studied by these asymmetries, but mostly at large $|t|$ region.

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arXiv2001

Higher and missing resonances in omega photoproduction

We study the role of the nucleon resonances ($N^*$) in $ω$ photoproduction by using the quark model resonance parameters predicted by Capstick and Roberts. The employed $γN \to N^*$ and $N^* \to ωN$ amplitudes include the configuration mixing effects due to the residual quark-quark interactions. The contributions from the nucleon resonances are found to be important in the differential cross sections at large scattering angles and various spin observables. In particular, the parity asymmetry and beam-target double asymmetry at forward scattering angles are suggested for a crucial test of our predictions. The dominant contributions are found to be from $N\frac32^+ (1910)$, a missing resonance, and $N\frac32^- (1960)$ which is identified as the $D_{13}(2080)$ of the Particle Data Group.

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arXiv2000

J/psi absorption by pi and rho mesons in a meson exchange model with anomalous parity interactions

We reanalyze the dissociation process of the $J/ψ$ by $π$ and $ρ$ mesons into $D + \bar{D}$, $D^* + \bar{D}$, $D + \bar{D}^*$, and $D^* + \bar{D}^*$ within a meson exchange model. In addition to the dissociation mechanisms considered in the literature, we consider anomalous parity interactions, whose couplings are constrained by heavy quark spin symmetry and phenomenology. This opens new dissociation channels and adds new diagrams in the previously considered processes. Compared to the previous results, we find that these new additions have only a minor effect on the $ρ+ J/ψ$ total inelastic cross section, but reduce the one for $π+ J/ψ$ by about 50 % near the threshold.

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arXiv2000

Nucleon resonances in polarized omega photoproduction

The role of the nucleon resonances ($N^*$) in $ω$ photoproduction is investigated by using the resonance parameters predicted by Capstick and Roberts. The contributions from the nucleon resonances are found to be significant in various spin asymmetries. In particular, we found that a crucial test of our predictions can be made by measuring the parity asymmetry and beam-target double asymmetry at forward scattering angles.

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arXiv2000

Nucleon resonances in omega photoproduction

The role of the nucleon resonances ($N^*$) in $ω$ photoproduction is investigated by using the resonance parameters predicted by Capstick and Roberts [Phys. Rev. D {\bf 46}, 2864 (1992); {\bf 49}, 4570 (1994)]. In contrast with the previous investigations based on the ${SU}(6) \times {O}(3)$ limit of the constituent quark model, the employed $N^* \to γN$ and $N^* \to ωN$ amplitudes include the configuration mixing effects due to the residual quark-quark interactions. The contributions from the nucleon resonances are found to be significant relative to the non-resonant amplitudes in changing the differential cross sections at large scattering angles and various spin observables. In particular, we suggest that a crucial test of our predictions can be made by measuring the parity asymmetry and beam-target double asymmetry at forward scattering angles.

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arXiv2000

Probing nucleon strangeness in phi electroproduction

We investigate $ϕ$ meson electroproduction to probe the hidden strangeness content of the nucleon. We found that even a small amount of the $s\bar{s}$ admixture in the nucleon wavefunction can lead to a significant change in several double polarization asymmetries in $ϕ$ electroproduction, which can be tested experimentally at current electron facilities.

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arXiv2000

Electromagnetic production of vector mesons at low energies

We have investigated exclusive photoproduction of light vector mesons ($ω$, $ρ$ and $ϕ$) on the nucleon at low energies. In order to explore the questions concerning the so-called missing nucleon resonances, we first establish the predictions from a model based on the Pomeron and meson exchange mechanisms. We have also explored the contributions due to the mechanisms involving $s$- and $u$-channel intermediate nucleon state. Some discrepancies found at the energies near threshold and large scattering angles suggest a possibility of using this reaction to identify the nucleon resonances.

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arXiv2000

Anomalous f_1 exchange in vector meson photoproduction asymmetries

We perform an analysis of the elastic production of vector mesons with polarized photon beams at high energy in order to investigate the validity of a recently proposed dynamical mechanism based on the dominance of the f_1 trajectory at large momentum transfer. The density matrix characterizing the angular distributions of the vector meson decays is calculated within an exchange model which includes the Pomeron and the f_1. The asymmetries of these decays turn out to be very useful to disentangle the role of these exchanges since their effect depends crucially on their quantum numbers which are different. The observables analyzed are accessible with present experimental facilities.

hep-ph↗
arXiv2000

New anomalous trajectory in Regge theory

We show that a new Regge trajectory with α_{f_1} (0) \approx 1 and slope α_{f_1}'(0) \approx 0 explains the features of hadron-hadron scattering and photoproduction of the rho and phi mesons at large energy and momentum transfer. This trajectory with quantum numbers P = C = +1 and odd signature can be considered as a natural partner of the Pomeron which has even signature. The odd signature of the new exchange leads to contributions to the spin-dependent cross sections, which do not vanish at large energy. The links between the anomalous properties of this trajectory, the axial anomaly and the flavor singlet axial vector f_1 (1285) meson are discussed.

hep-ph↗
arXiv1999

Probing nucleon strangeness structure with phi electroproduction

We study the possibility to constrain the hidden strangeness content of the nucleon by means of the polarization observables in phi meson electroproduction. We consider the OZI evading direct knockout mechanism that arises from the non-vanishing s\bar{s} sea quark admixture of the nucleon as well as the background of the dominant diffractive and the one-boson-exchange processes. Large sensitivity on the nucleon strangeness are found in several beam-target and beam-recoil double polarization observables. The small \sqrt{s} and W region, which is accesible at some of the current high-energy electron facilities, is found to be the optimal energy region for extracting out the OZI evasion process.

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arXiv1999

Baryon masses in large Nc chiral perturbation theory

We analyse the baryon mass spectrum in a framework which combines the 1/Nc expansion with chiral perturbation theory. Meson loop contributions involving the full SU(3) octet of pseudoscalar Goldstone bosons are evaluated, and the influence of explicit chiral and flavor symmetry breaking by non-zero and unequal quark masses is investigated. We also discuss sigma terms and the strangeness contribution to the nucleon mass.

hep-ph↗
arXiv1999

Phi-meson photoproduction and strangeness of the nucleon

The polarization observables in phi photoproduction are suggested for probing the nucleon strangeness. Based on models for phi photoproduction, some double polarization observables are shown to be very sensitive to the strangeness content of the proton because of the different spin structures of the amplitudes associated with different mechanisms.

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arXiv1998

Photoproduction of phi mesons from the proton: Polarization observables and strangeness in the nucleon

The polarization observables in phi meson photoproduction is studied to probe the strangeness content of the nucleon. In addition to the dominant diffractive production and the one-pion-exchange process, we take into account the direct knockout mechanism that arises from the possible hidden strangeness content of the nucleon. We find that some double polarization observables are very sensitive to the strangeness content of the proton because of the different spin structures of the amplitudes associated with different mechanisms. This suggests that such measurements could be very useful in probing the strangeness content in the proton. The orbitally excited quark-cluster configurations in the proton are included in the calculation and found to have little effect.

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