相关论文: Progress in NN --> NNpi

We show that the tail of the chiral two-pion exchange nucleon-nucleon potential is proportional to the $\pi N$ scalar form factor and discuss how it can be translated into effective scalar meson interactions. We then construct a kernel for…

The N-Delta axial form factors are determined from neutrino induced pion production ANL & BNL data by using a state of the art theoretical model, which accounts both for background mechanisms and deuteron effects. We find violations of the…

We present an extraction of the E2/M1 ratio of the $\Delta$(1232) from experimental data applying an effective Lagrangian model. We compare the result obtained with different nucleonic models and we reconcile the experimental results with…

A chiral quark-model approach is adopted to study the $\gamma p\rightarrow \pi^0p$ and $\gamma n\rightarrow \pi^0 n$ reactions. Good descriptions of the total and differential cross sections and single-polarization observables are obtained…

Recently developed chiral nucleon-nucleon (NN) forces at next-to-leading order (NLO) that describe NN phase shifts up to about 100 MeV fairly well have been applied to 3N and 4N systems. Faddeev-Yakubovsky equations have been solved…

We have measured cross sections for the $ (\pi^+,\pi^\pm p)$ reactions on ${\rm ^3H}$, ${\rm ^4He}$, ${\rm ^6Li}$ and ${\rm ^7Li}$ in quasi-free kinematics at incident pion beam energy 500 MeV. An enhancement of the $(\pi^+,\pi^- p)$ cross…

A procedure is proposed which accounts for final state interaction corrections for near threshold meson production in nucleon-nucleon scattering. In analogy with the Watson-Migdal approximation, it is shown that in the limit of extremely…

The near threshold $\phi$ meson production in proton-proton and $\pi^- p$ collisions is studied with the assumption that the production mechanism is due to the sub-$N\phi$-threshold $N^*(1535)$ resonance. The $\pi^0$, $\eta$ and…

We determine the $\pi NN$ and $\pi N\Delta$ formfactors from the $P_{11}$ resp. $P_{33}$ partial wave of $\pi N$ scattering by dressing corresponding bare vertices with the help of $\pi N$ non--pole contributions. The underlying model is…

Differential cross sections of the reactions $pp \to d\pi^+$ and $pp \to pn\pi^+$ have been measured at $T_p = 400$ MeV by detecting the charged ejectiles in the angular range $4^0 \leq \Theta_{Lab} \leq 21^\circ$. The deduced total cross…

At sufficiently high energies the production of a very large number of particles is kinematically allowed. However, it is well-known that already in the simplest case of a weakly-coupled massive $\lambda \varphi^4$ theory, $n$-particle…

We extend our recent phenomenological study of $pN \to NN\pi\pi$ reactions to the $\bar{p}N \to \bar{N}N\pi\pi$ reactions for anti-proton beam momenta up to 3.0 GeV within an effective Lagrangian approach. The contribution of $N^*(1440)$…

The 1/N expansion of the two-particle irreducible effective action offers a powerful approach to study quantum field dynamics far from equilibrium. We investigate the effective convergence of the 1/N expansion in the O(N) model by comparing…

We present a calculation of single pion electroproduction cross sections on heavy targets in the kinematic region of the Delta(1232) resonance. Final state interactions of the pions are taken into account using the pion multiple scattering…

The charged current one pion production induced by $\nu_\mu$ from nucleons and nuclei like $^{12}$C and $^{16}$O nuclei has been studied. The calculations have been done for the incoherent and the coherent processes from nuclear targets…

I review the use of the 2PI effective action in nonequilibrium quantum field theory. The approach enables one to find approximation schemes which circumvent long-standing problems of non-thermal or secular (unbounded) late-time evolutions…

Nucleon-nucleon (NN) forces from chiral perturbation theory at next-to-leading (NLO) and next-to-next-to-leading order (NNLO) are applied to systems with two, three and four nucleons. At NNLO, we consider two versions of the chiral…

The properties of low-energy neutron-proton systems are studied in an effective field theory where only nucleons figure as relevant degrees of freedom. With a finite momentum cut-off regularization scheme, we show that the large scattering…

In this paper, we firstly varify that the factorization hypothesis is valid for the exclusive process $\rho \gamma^{\star} \to \pi$ at the next-to-leading order (NLO) with the collinear factorization approach, and then extend this proof to…

Incoherent pion photoproduction on the deuteron in the $\Delta$(1232)-resonance region is investigated with special emphasis on polarization observables. For the elementary pion photoproduction operator an effective Lagrangian model which…