SummaryA new fit to the world data on (ep) and (en) elastic scattering, and on (\n$$\\bar p$$\np) annihilation into lepton pairs, has been obtained by using a model for the isovector and isoscalar nucleon form factors, which is suggested by the use of unitary symmetry and of its breaking. The fit allows for a nonpointlike behaviour of one out of the two couplings which enter in the expression for nucleon electromagnetic form factors. The fit is a one-parameter fit and the corresponding values ofχ2 for the proton and neutron data are discussed. The contributions coming from the possible existence of « core-terms » and of «q2-dependent background » in the expression of the nucleon electromagnetic form factors are found to be lower than a few per cent. Theq2 dependence of the vector-meson-nucleon couplings is also discussed.RiassuntoSi è ottenuta una nuova approssimazione ai dati universali sullo scattering elastico (ep) e (en) e sulla annichilazione (\n$$\\bar p$$\np) in coppie di leptoni, facendo uso di un modello per i fattori di forma isovettoriali ed isoscalari del nucleone, suggerito dall’uso della simmetria unitaria e della sua infrazione. L’approssimazione tiene conto del comportamento non puntiforme di uno dei due accoppiamenti che entrano nell’espressione dei fattori di forma elettromagnetici del nucleone. L’approssimazione è ad un solo parametro e si discutono i corrispondenti valori di χ2 per i dati dei protoni e dei neutroni. Si trova che i contributi derivanti dalla possibile esistenza di « core terms » e di « un fondo dipendente da ϱ2 » nell’espressione dei fattori di forma elettromagnetici del nucleone sono inferiori ad alcuni percento. Si discute anche la dipendenza daq2 dell’accoppiamento mesone vettoriale-nucleone.

One-paramenter fit to the electromagnetic form factors of the nucleon

The QCD vacuum is populated by instantons that correspond to the tunneling processes in the vacuum. This mechanism creates the strong vacuum gluon fields. As result, the QCD vacuum instantons induce very strong interactions between light quarks, initially almost massless. Such a strong interactions bring a large dynamical mass M of the light quarks and bound them to produce almost massless pions in accordance with the spontaneous breaking of the chiral symmetry (SBCS). On the other hand, the QCD vacuum instantons also interact with heavy quarks and responsible for the generation of the heavy-heavy and heavy-light quarks interactions, with a traces of the SBCS. If we take the average instanton size fm, and the average inter-instanton distance fm we obtain the dynamical light quark mass to be M = 365 MeV and the instanton media contribution to the heavy quark mass ΔM =70 MeV. These factors define the coupling between heavy-light and heavy-heavy quarks induced by the QCD vacuum instantons. We consider first the instanton effects on the heavy-heavy quarks potential, including its spin-dependent part. We also discuss those effects on the masses of the charmonia and their hyperfine mass splittings. At the second part we discuss the interaction between a heavy and light quarks generated by instantons and it’s effects.

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Heavy-heavy and heavy-light quarks interactions generated by QCD vacuum

In the present work, we consider the influence on the heavy quark correlators due to the instanton background in the framework of instanton liquid model (ILM) of QCD vacuum by taking into account also the perturbative gluon effects. For a single heavy quark, this leads to the mass shift due to the direct-instanton nonperturbative and ILM modified perturbative contributions, respectively. In the heavy quark-antiquark ($Q\overline{Q}$) sector, we obtain the potential consisting the direct instanton induced part and the one-gluon exchange (OGE) perturbative part, which is screened at large distances due to the nonperturbative dynamics. At the region of interest corresponding to the heavy quark physics, the screening effect in OGE can be well approximated by a Yukawa-type potential in terms of the dynamically generated gluon mass. A possible implication of the present studies to the phenomenology of heavy quarkonium is also discussed.

Heavy quark correlators in an instanton liquid model with perturbative corrections

Quark potential model of baryon spin - orbit mass splittings

Quark models of 1S0 nucleon-nucleon scattering lengths

Nucleon core size and nuclear forces

Abstract The Mindanao Current (MC) bridges the North Pacific low-latitude western boundary current system region and the Indonesian Seas by supplying the North Pacific waters to the Indonesian Throughflow. Although the previous study speculated that the diapycnal mixing along the MC might be strong on the basis of the water mass analysis of the gridded climatologic dataset, the real spatial distribution of diapycnal mixing along the MC has remained to be clarified. We tackle this question here by applying a finescale parameterization to temperature and salinity profiles obtained using two rapid-sampling profiling Argo floats that drifted along the MC. The western boundary (WB) region close to the Mindanao Islands and the Sangihe Strait are the two mixing hotspots along the MC, with energy dissipation rate ε and diapycnal diffusivity K ρ enhanced up to ~ 10 –6 W kg −1 and ~ 10 –3 m 2 s −1 , respectively. Except for the above two mixing hotspots, the turbulent mixing along the MC is mostly weak, with ε and K ρ to be 10 –11 –10 –9 W kg −1 and 10 –6 –10 –5 m 2 s −1 , respectively. Strong mixing in the Sangihe Strait can be basically attributed to the existence of internal tides, whereas strong mixing in the WB region suggests the existence of internal lee waves. We also find that water mass transformation along the MC mainly occurs in the Sangihe Strait where the water masses are subjected to strong turbulent mixing during a long residence time. 

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Yin He

Papers

Nucleon core size and nuclear forces

Spatial distribution of turbulent diapycnal mixing along the Mindanao current inferred from rapid-sampling Argo floats