U.-G. Meissner

K- p scattering length from scattering experiments

The strong K{sup -}p scattering length is extracted within chiral SU(3) unitary approaches from a very large variety of fits to low-energy K{sup -}p scattering data. Very good overall agreement with available scattering data is obtained and the resulting scattering length is compared with the new accurate kaonic hydrogen data from DEAR. The pole structures of the obtained fits to experiment are critically examined.

Dispersion analysis of the nucleon form factors including meson continua

Dispersion relations provide a powerful tool to analyze the electromagnetic form factors of the nucleon for all momentum transfers. Constraints from meson-nucleon scattering data, unitarity, and perturbative quantum chromodynamics (QCD) can be included in a straightforward way. In particular, we include the 2{pi},{rho}{pi}, and KK continua as independent input in our analysis and provide an error band for our results. Moreover, we discuss two different methods to include the asymptotic constraints from perturbative QCD. We simultaneously analyze the world data for all four form factors in both the spacelike and timelike regions and generally find good agreement with the data. We also extract the nucleon radii and the {omega}NN coupling constants. For the radii, we generally find good agreement with other determinations with the exception of the electric charge radius of the proton, which comes out smaller. The {omega}NN vector coupling constant is determined relatively well by the fits, but for the tensor coupling constant even the sign cannot be determined.

Jülich hyperon-nucleon model revisited

A one-boson-exchange model for the hyperon-nucleon (\Lambda N, \Sigma N) interaction is presented. The model incorporates the standard one boson exchanges of the lowest pseudoscalar and vector meson multiplets with coupling constants fixed by SU(6) flavor symmetry relations. As the main new feature of the model, the contributions in the scalar--isoscalar (\sigma) and vector--isovector (\rho) exchange channels are now constrained by a microscopic model of correlated \pi\pi and K \bar K exchange. Additional short-ranged ingredients of the model in the scalar--isovector (a_0) and scalar--isospin-1/2 (\kappa) channels are likewise viewed as arising from meson-meson correlations but are treated phenomenologically. With this model a satisfactory reproduction of the available hyperon-nucleon data can be achieved.

Analytic properties of the scattering amplitude and resonances parameters in a meson exchange model

The analytic properties of scattering amplitudes provide i mportant information. Besides the cuts, the poles and zeros on the different Riemann sheets determine the global behavior of the amplitude on the physical axis. Pole positions and residues al low for a parameterization of resonances in a well-defined way, f ree of assumptions for the background and energy dependence of the resonance part. This is a necessary condition to relate r esonance contributions in different reactions. In the present study, we determine the pole structure of pion-nucleon scattering in an analytic model based on meson exchange. For this, the sheet structure of the amplitude is determined. To show the precision of the resonance extraction and discuss phenomena such as resonance interference, we discuss the S 11 amplitude in greater detail.

Subleading contributions to the chiral three-nucleon force II: short-range terms and relativistic corrections

We derive the short-range contributions and the leading relativistic corrections to the three-nucleon force at next-to-next-to-next-to-leading order in the chiral expansion.

Chiral extrapolations of baryon masses for unquenched three flavor lattice simulations

We have analyzed the chiral expansion of the baryon masses to second order in the quark masses, including strong isospin violation. The calculations are performed in Lorentz-invariant baryon chiral perturbation theory. Chiral extrapolation functions for three-flavor unquenched lattice simulations are derived. The matching to the two-flavor case and the sigma terms are also considered.

Baryon magnetic moments in chiral perturbation theory

Abstract We consider the chiral expansion of the octet baryon magnetic moments in heavy baryon chiral perturbation theory including all terms which are of order q 4 . These terms are formally of quadratic order in the quark masses. We show that despite the large non-analytic quark mass corrections to the Coleman-Glashow relations at order q 3 , including all analytic and non-analytic corrections at order q 4 , which in total are of moderate size, allows for a fit to the measured magnetic moments due to the appearance of counter terms with free coupling constants of natural size. In this scheme, the ΛΣ 0 transition moment is predicted to be μ ΛΣ 0 = (1.40 ± 0.01) μ N .

Rescattering and chiral dynamics in B ! decay

We examine the role of B 0 ( ¯ B 0 ) ! �� 0 ! � + � − � 0 decay in the Dalitz plot analysis of B 0 ( ¯ B 0 ) ! �� ! � + � − � 0 decays, employed to extract the CKM parameter �. The �� channel is significant because it can break the relationship between the penguin contributions in B ! � 0 � 0 , B ! � + � − , and B ! � − � + decays consequent to an assumption of isospin symmetry. Its presence thus mimics the effect of isospin violation. The �� 0 state is of definite CP, however; we demonstrate that the B ! �� analysis can be generalized to

Complete One-Loop Analysis of the Nucleon's Spin Polarizabilities

We present a complete one-loop analysis of the four nucleon spin polarizabilities in the framework of heavy baryon chiral-perturbation theory. The first nonvanishing contributions to the isovector and first corrections to the isoscalar spin polarizabilities are calculated. No unknown parameters enter these predictions. We compare our results to various dispersive analyses. We also discuss the convergence of the chiral expansion and the role of the delta isobar.

VIRTUAL PHOTONS IN BARYON CHIRAL PERTURBATION THEORY

Abstract We construct the general Lagrangian for relativistic and heavy baryon chiral perturbation theory with virtual photons to fourth order. We work out the electromagnetic and strong isospin violating contributions to the nucleon self-energy, the nucleon mass and the scalar form factor of the nucleon. Electromagnetic effects for the shift to the Cheng-Dashen point can be as large as 2 MeV We also discuss the corrections to Weinbergs prediction for the scattering length difference a(π0p) − a(π0n) and show that they are small.We construct the general Lagrangian for relativistic and heavy baryon chiral perturbation theory with virtual photons to fourth order. We work out the electromagnetic and strong isospin violating contributions to the nucleon self-energy, the nucleon mass and the scalar form factor of the nucleon. Electromagnetic effects for the shift to the Cheng-Dashen point can be as large as 2 MeV. We also discuss the corrections to Weinbergs prediction for the scattering length difference