Nucleon recoil for low-energy antikaon-deuteron scattering

The effect of the nucleon recoil for antikaon-deuteron scattering is studied in the framework of effective field theory. In particular, we performed a calculation of the nucleon recoil effect for the double scattering process. It is shown that the leading correction to the static term that emerges at order ξ ^1/2, where ξ?=?m _K /M _N , vanishes due to a complete cancellation of individually large terms. The resulting recoil effect for the double scattering process is found to be of order of 10–15% compared to the static term. We also developed a method to include the nucleon recoil effect in the calculation of the multiple scattering diagrams.     

Non-standard physics and nucleon strangeness in low-energy PV electron scattering

Contributions from physics beyond the Standard Model, strange quarks in the nucleon, and nuclear structure effects to the left-right asymmetry measured in parity-violating (PV) electron scattering from¹²C and the proton are discussed. It is shown how lack of knowledge of the distribution of strange quarks in the nucleon, as well as theoretical uncertainties associated with higher-order dispersion amplitudes and nuclear isospin-mixing, enter the extraction of new limits on the electroweak parametersS andT from these PV observables. It is found that a series of elastic PV electron scattering measurements using⁴He could significantly constrain thes-quark electric form factor if other theoretical issues are resolved. Such constraints would reduce the associated form factor uncertainty in the carbon and proton asymmetries below a level needed to permit extraction of interesting low-energy constraints onS andT from these observables. For comparison, the much smaller scale ofs-quark contributions to the weak charge measured in atomic PV is quantified. It is likely that only in the case of heavy muonic atoms could nucleon strangeness enter the weak charge at an observable level.     

Spin polarizabilities of the nucleon from polarized low-energy Compton scattering

As a guideline for forthcoming experiments, we present predictions from Chiral Effective Field Theory for polarized cross-sections in low-energy Compton scattering for photon energies below 170 MeV, both on the proton and on the neutron. Special interest is put on the role of the nucleon spin polarizabilities which can be examined especially well in polarized Compton scattering. We present a model-independent way to extract their energy dependence and static values from experiment, interpreting our findings also in terms of the low-energy effective degrees of freedom inside the nucleon: The polarizabilities are dominated by chiral dynamics from the pion cloud, except for resonant multipoles, where contributions of the -resonance turn out to be crucial. We therefore include it as an explicit degree of freedom. We also identify some experimental settings which are particularly sensitive to the spin polarizabilities.Received: 19 August 2003, Revised: 30 October 2003, Published online: 27 April 2004PACS: 13.40.-f Electromagnetic processes and properties - 13.60.Fz Elastic and Compton scattering - 14.20.Dh Protons and neutronsH.W. Grießhammer: Permanent address: Technische Universität MünchenT.R. Hemmert: Permanent address: Technische Universität München     

Veneziano model for nucleon nucleon and nucleon antinucleon scattering. I

The thermal conductivity has been measured on two niobium samples of different purity (ratio of mean free path to coherence length 220 and 10, respectively), in the mixed state, with heat current parallel (k _∥) and normal (k _⊥) to the magnetic field. The experimental results are compared with theories; the range of validity is discussed. Maki's relation (k-k _n) ～ (H _c2 -H)^1/2 could be verified only for the purer sample in the field range (H _c2 -H)?140 Oe. The relationsk _∥/k ₁>1 forT?T _c andk _∥/k ₁<1 forT?T _c were found to be valid for the whole range of fields in the mixed state.     

The nucleon-nucleon triple scattering parameters for recoil particles

Relativistic formulae are obtained, expressing the polarization of the initially unpolarized particle in the scattering of an unpolarized nucleon on a polarized one, in terms of the polarization transfer tensor and in terms of the scattering matrix elements.On leave of absence from theFaculty of Technical and Nuclear Physics, Czech Technical University, Prague, Czechoslovakia.On leave of absence from theNuclear Research Institute of the Czechoslovak Academy of Sciences, e, Czechoslovakia.In conclusion the authors express their profound gratitude to S. M. Bilenky, L. I. Lapidus, R. M. Ryndin and Ya. A. Smorodinsky for useful discussions and to E. Dudova and J. Fingerova for help in the work.     

Aspects of nucleon Compton scattering

We consider the spin-averaged nucleon forward Compton scattering amplitude in heavy baryon chiral perturbation theory including all terms to order . The chiral prediction for the spin-averaged forward Compton scattering amplitude is in good agreement with the data for photon energies110 MeV. We also evaluate the nucleon electric and magnetic Compton polarizabilities to this order and discuss the uncertainties of the various counter terms entering the chiral expansion of these quantities.     

The fixed scatterer approximation and nucleon deuteron scattering

A method of solving the Schroedinger Equation for the scattering from two fixed local potentials is presented. The solutions are used within the framework of the fixed scatterer approximation to perform model calculations of N-D scattering using both effective range theory potentials and a “semi-realistic” potential with a strong repulsive core. For smooth potentials approximate solutions to the fixed scatterer problem are proposed and found to be quite accurate.Other procedures for calculating elastic scattering were compared with the exact fixed scatterer approximation. The results show that the neglect of longitudinal momentum transfer in the Glauber multiple diffraction theory is a severe effect except in the forward direction. For small angle scattering the Glauber prediction for the double scattering amplitude is quite accurate, and does not depend strongly upon either the extent of potential overlap, or the ratio $\text{V}\text{E}$. Comparisons with the Agassi and Gal results for nonoverlapping potentials indicate that the effects of potential overlap are important, at least for the lowest partial waves. Conclusions about the overall importance of off-energy shell effects in nucleon-deuteron scattering, and about the interference of these effects with the determination of the correlation structure of nuclei are not free from ambiguities.     

Theory of low-energy ππ scattering

A four-parameter family of solutions to the ππ partial-wave dispersion relations is obtained using the inverse amplitude method. Choosing the parameters consistent with phenomenological values and so as to maximize agreement with rigorous sum rules and inequalities leads to a firm prediction of the phase shifts for S and P wave scattering and for the amplitudes below threshold. Neglecting inelasticity, the I = 0S-wave resonates near $\text{s}\text{= 540}\text{MeV}$, the I = 2 S-wave falls to about ?12° near 1 GeV, and the P-wave is ?-dominated. The S-waves have subthreshold zeroes consistent with the Adler condition. Inelastic effects are estimated and found to be small below the rho meson mass.     

Phenomenology of low-energy ππ scattering

Exact representations of the low-energy ππ amplitudes by (for the S-waves) generalized effective range formulas and by (for the P-wave) a resonance plus background expression are derived from inverse-amplitude partial-wave dispersion relations, and applied to the phenomenological analysis of a typical set of phase shifts deduced from peripheral pion production. With the aid of rigorous crossing conditions it is found that the simplest satisfactory account of the S-waves is provided by a current algebra type solution with (Adler) zeros and small scattering lengths. Solutions without zeros (S-wave dominant) are completely ruled out. Inelasticity is important in describing the rise of the isoscalar phase shift above the σ resonance, but can be neglected below 1 GeV in other channels. The P-wave is ?-dominated, but its width is sensitive to background terms. The phenomenological importance of rigorous results is stressed.     

The role of nine-quark-state in three nucleon systems

The nine-quark-state role in three nucleon systems is discussed. The hybrid model for the³He wave function which takes into account only the three-nucleon and the ninequark components is used to describe the³He magnetic form factor. The probability of the nine-quark-state in³He is estimated to be 20%.     

Retardation effects from quark confinement on low-energy nucleon dynamics

We investigate effects from quark confinement on low-energy nucleon dynamics. These effects are shown to give rise to a peculiar dynamical situation: Low-energy nucleon dynamics is not Hamiltonian and is governed by a nonlocal-in-time interaction operator. In the leading order of the two-nucleon EFT we show that after renormalization the nucleon dynamics is governed by the same interaction operator.     

The slowing-down of low-energy recoil atoms in solids and liquids investigated by nuclear resonance fluorescence

Using the nuclear resonance-fluorescence technique, the slowing down mechanisms of recoiling¹⁴⁰Ce nuclei in La, LaMg₃ and La₂O₃, are studied via the Dopler shift of the 1.596 MeV transition, following the decay of¹⁴⁰La. In LaMg₃ the slowing down time shows a pronounced temperature dependence with a sharp drop close to the melting point. In the oxide, as well as in the metal with only a small oxygen content, the slowing down time is considerably smaller than in the pure metal. These results are in support of a model, describing the slowing down process in solids in terms of a damped oscillation, with a time dependence related to the phonon frequency spectrum.Supported by Deutsche Forschungsgemeinschaft through contract Schu 222     

Real and virtual Compton scattering: The nucleon polarisabilities

We give an overview of low-energy Compton scattering γ^(∗) p → γp with a real or virtual incoming photon. These processes allow the investigation of one of the fundamental properties of the nucleon, i.e. how its internal structure deforms under an applied static electromagnetic field. Our knowledge of nucleon polarisabilities and their generalization to non-zero four-momentum transfer will be reviewed, including the presently ongoing experiments and future perspectives.