Precision calculation of the pi^- deuteron scattering length and its impact on threshold pi-N scattering

We present a calculation of the pi^- d scattering length with an accuracy of a few percent using chiral perturbation theory. For the first time isospin-violating corrections are included consistently. Using data on pionic deuterium and pionic hydrogen atoms, we extract the isoscalar and isovector pion-nucleon scattering lengths and obtain a^+=(7.6 +/- 3.1) x 10^{-3} mpi^{-1} and a^-=(86.1 +/- 0.9) x 10^{-3} mpi^{-1}. Via the Goldberger-Miyazawa-Oehme sum rule, this leads to a charged-pion-nucleon coupling constant g_c^2/4 pi = 13.69 +/- 0.20.Comment: 6 pages, 2 figures. Discussion of several points expanded, references added in this version, which will appear in Physics Letters

Hyperon production in near threshold nucleon-nucleon collisions

We study the mechanism of the associated Lambda-kaon and Sigma-kaon production in nucleon-nucleon collisions over an extended range of near threshold beam energies within an effective Lagrangian model, to understand of the new data on pp --> p Lambda K+ and pp --> p Sigma0 K+ reactions published recently by the COSY-11 collaboration. In this theory, the hyperon production proceeds via the excitation of N*(1650), N*(1710), and N*(1720) baryonic resonances. Interplay of the relative contributions of various resonances to the cross sections, is discussed as a function of the beam energy over a larger near threshold energy domain. Predictions of our model are given for the total cross sections of pp --> p Sigma+K0, pp --> n Sigma+K+, and pn --> n Lambda K+ reactions.Comment: 16 pages, 4 figures, one new table added and dicussions are updated, version accepted for publication by Physical Review

Interplay of quark and meson degrees of freedom in a near-threshold resonance

We investigate the interplay of quark and meson degrees of freedom in a physical state representing a near-threshold resonance for the case of a single continuum channel. We demonstrate that such a near-threshold resonance may possess quite peculiar properties if both quark and meson dynamics generate weakly coupled near-threshold poles in the S-matrix. In particular, the scattering t-matrix may possess zeros in this case. We also discuss possible implications for production reactions as well as studies within lattice QCD.Comment: LaTeX2e, 11 pages, minor typo corrections, to appear in Eur.Phys.J.

Arus Jenuh Dan Panjang Antrian Pada Simpang Bersinyal Angkatan 66 Kota Palembang

The high saturation flow, long queues, and long delays at the signalized intersection are the factors causing traffic congestion at the intersection. This study discussed saturation flow analysis and long queues at the Angkatan 66 signalized intersection in Palembang City. The intersection legs at this intersection, namely Jln. Sukamto toward Jln. Basuki Rakhmat, Jln. Amphibi toward Jln. Angkatan 66, have high saturation flows and long queues, so that the intersection needs to be improved. There are 3 improvement alternatives, including the change in cycle time period, the change in intersection geometric, and the construction of flyover. Of the three alternatives, only the construction of fly over construction can reduce significantly the queue lengths

Towards a high precision calculation for the pion-nucleus scattering lengths

We calculate the leading isospin conserving few-nucleon contributions to pion scattering on $^2$H, $^3$He, and $^4$He. We demonstrate that the strong contributions to the pion-nucleus scattering lengths can be controlled theoretically to an accuracy of a few percent for isoscalar nuclei and of 10% for isovector nuclei. In particular, we find the $\pi$-$^3$He scattering length to be $(62 \pm 4\pm 7)\times 10^{-3} m_{\pi}^{-1}$ where the uncertainties are due to ambiguities in the $\pi$-N scattering lengths and few-nucleon effects, respectively. To establish this accuracy we need to identify a suitable power counting for pion-nucleus scattering. For this purpose we study the dependence of the two-nucleon contributions to the scattering length on the binding energy of $^2$H. Furthermore, we investigate the relative size of the leading two-, three-, and four-nucleon contributions. For the numerical evaluation of the pertinent integrals, aMonte Carlo method suitable for momentum space is devised. Our results show that in general the power counting suggested by Weinberg is capable to properly predict the relative importance of $N$-nucleon operators, however, it fails to capture the relative strength of $N$- and $(N+1)$-nucleon operators, where we find a suppression by a factor of 5 compared to the predicted factor of 50. The relevance for the extraction of the isoscalar $\pi$-N scattering length from pionic $^2$H and $^4$He is discussed. As a side result, we show that beyond the calculation of the $\pi$-$^2$H scattering length is already beyond the range of applicability of heavy pion effective field theory.Comment: 24 pages, 14 figures, 10 table

Tvorba eta mezona u nn sudarima

A model calculation for near-threshold η meson production in nucleon-nucleon collisions is presented. The η meson production is described by elementary rescattering processes via MN→ ηN, with M = π, ρ, η and σ. Corresponding amplitudes are taken from a multi-channel meson-exchange model of the πN system developed by the Jülich group. Effects of the NN interaction in the final as well as in the initial state are taken into account microscopically.Predstavljamo model za računanje tvorbe η mezona blizu praga u sudarima nukleon-nukleon. Tvorba η mezona opisuje se elementarnim procesima ponovnog raspršenja putem MN→ ηN, sa M = π, ρ, η i σ. Odnosne amplitude uzimaju se od višekanalnog modela izmjene mezona u sustavu πN koji je razvila grupa u Jülichu. Učinci međudjelovanja u konačnom stanju kao i u početnom stanju uzeti su u obzir mikroskopski

Three-body DDˉπD\bar{D}\pi dynamics for the X(3872)

We investigate the role played by the three-body $D\bar{D}\pi$ dynamics on the near-threshold resonance X(3872) charmonium state, which is assumed to be formed by nonperturbative $D\bar D^*$ dynamics. It is demonstrated that, as compared to the naive static-pions approximation, the imaginary parts that originate from the inclusion of dynamical pions reduce substantially the width from the $D\bar{D}\pi$ intermediate state. In particular, for a resonance peaked at 0.5 MeV below the $D^0\bar D^{*0}$ threshold, this contribution to the width is reduced by about a factor of 2, and the effect of the pion dynamics on the width grows as long as the resonance is shifted towards the $D^0\bar{D^0}\pi^0$ threshold. Although the physical width of the $X$ is dominated by inelastic channels, our finding should still be of importance for the $X$ line shapes in the $D\bar{D}\pi$ channel below $D{\bar D}^*$ threshold. For example, in the scattering length approximation, the imaginary part of the scattering length includes effects of all the pion dynamics and does not only stem from the $D^*$ width. Meanwhile, we find that another important quantity for the $X$ phenomenology, the residue at the $X$ pole, is weakly sensitive to dynamical pions. In particular, we find that the binding energy dependence of this quantity from the full calculation is close to that found from a model with pointlike $D\bar D^*$ interactions only, consistent with earlier claims. Coupled-channel effects (inclusion of the charged $D\bar{D}^*$ channel) turn out to have a moderate impact on the results.Comment: 34 pages, 6 figures, version to appear in Phys.Rev.

Tvorba eta mezona u nn sudarima

A model calculation for near-threshold η meson production in nucleon-nucleon collisions is presented. The η meson production is described by elementary rescattering processes via MN→ ηN, with M = π, ρ, η and σ. Corresponding amplitudes are taken from a multi-channel meson-exchange model of the πN system developed by the Jülich group. Effects of the NN interaction in the final as well as in the initial state are taken into account microscopically.Predstavljamo model za računanje tvorbe η mezona blizu praga u sudarima nukleon-nukleon. Tvorba η mezona opisuje se elementarnim procesima ponovnog raspršenja putem MN→ ηN, sa M = π, ρ, η i σ. Odnosne amplitude uzimaju se od višekanalnog modela izmjene mezona u sustavu πN koji je razvila grupa u Jülichu. Učinci međudjelovanja u konačnom stanju kao i u početnom stanju uzeti su u obzir mikroskopski