Hadron-Hadron interactions from meson exchange

Several recent developments in the meson exchange theory of hadronic interactions are reviewed. After some introductory remarks about the relevance of the meson exchange concept in the era of QCD we will describe a dynamical model for correlated 2-exchange in the NN as well as the N interaction; for the NN system, it should replace the (sharp mass) and exchange used in the Bonn potential. Next we turn our attention to the interaction. A recently proposed meson exchange model can resolve in a natural way apparent discrepancies occurring in the analysis of different experiments in connection with the A₁ meson and leads to an appreciable softening of the NN form factor.Lecture presented at the Indian-Summer School on Interaction in Hadronic Systems, Praha (The Czech Republic), 25–31 August 1993.     

Recent progress on the chiral unitary approach to meson meson and meson baryon interactions

We report on recent progress on the chiral unitary approach, analogous to the effective range expansion in Quantum Mechanics, which is shown to have a much larger convergence radius than ordinary chiral perturbation theory, allowing one to reproduce data for meson meson interaction up to 1.2 GeV. Applications to physical processes so far unsuited for a standard chiral perturbative approach are presented. Results for the extension of these ideas to the meson baryon sector are discussed, together with applications to kaons in a nuclear medium and K⁻ atoms.     

Constraints on four-Fermi contact interactions from low-energy electroweak experiments

We investigate the constraints on four-Fermi contact interactions from low-energy lepton-quark and lepton-lepton scattering experiments – polarization asymmetries in electron (muon)-nucleon scattering experiments, cesium and thallium atom parity violation measurements, neutrino-nuclei and neutrino-electron scattering experiments. These constraints are then combined by assuming the lepton and quark universalities and gauge invariance of the contact interaction, which leave independent six lepton-quark and three pure-leptonic interactions. Impacts of these constraints on models with an additional -boson are briefly discussed. We also present updates of the low-energy constraints on the and parameters. Received: 28 November 1997 / Published online: 26 February 1998     

Consequences of partial vector meson dominance for the phenomenology of colored technihadrons

In this paper we address the question: do the limits on technirho production at the Tevatron mean what we think they do? These limits are based on calculations that rely on vector meson dominance (VMD). VMD was invented in order to describe the interaction of electrons with hadrons (the rho meson and pions). The method has been used also as a tool in the study of technicolor phenomenology. Nevertheless there is evidence in the sense that, even in its original context, VMD is not completely realized. In this work we investigate the consequences of a deviation from complete VMD for the phenomenology of colored technihadrons. We focus specially on the production of the color octet technirho and color triplet technipions. We found that a relatively small direct coupling of the proto-technirho to quarks is enough to suppress or even eliminate the interaction among quarks and the physical technirho. On the other hand, it is possible to suppress the coupling of the physical technirho to technipions, but in this case a large interaction among the technipions and the proto-gluon must be introduced. The consequences for the limits on the mass of the color octet technirho and colored triplets technipions are also investigated.     

Disorder-recrystallization effects in low-energy beam-solid interactions

It is widely believed that high-kinetic-energy (>1 keV) recoils in crystalline Si result in the formation of amorphous regions, whereas low-kinetic-energy recoils lead directly to isolated point defects. Here we study the response of a Si crystal using dynamical density-functional calculations and show that recoils of much less than 1 keV result in highly disordered regions that persist for hundreds of femtoseconds. Therefore, beam-induced defect formation is controlled by recrystallization processes during dynamic annealing even following low-energy ion implantation.     

Soliton strings and interactions in mode-locked lasers

Soliton strings in mode-locked lasers are obtained using a variant of the nonlinear Schrödinger equation, appropriately modified to model power (intensity) and energy saturation. This equation goes beyond the well-known master equation often used to model these systems. It admits mode-locking and soliton strings in both the constant dispersion and dispersion-managed systems in the (net) anomalous and normal regimes; the master equation is contained as a limiting case. Analysis of soliton interactions show that soliton strings can form when pulses are a certain distance apart relative to their width. Anti-symmetric bi-soliton states are also obtained. Initial states mode-lock to these states under evolution. In the anomalous regime individual soliton pulses are well approximated by the solutions of the unperturbed nonlinear Schrödinger equation, while in the normal regime the pulses are much wider and strongly chirped.     

Effective chiral meson lagrangian with Weinberg and KSFR relations from microscopic four-quark interactions

An effective chiral meson lagrangian is derived from a microscopic quark lagrangian. It contains a partial Higgs mechanism for ϱ-A₁ mass splitting reproducing Weinberg and KSFR relations, and includes quartic derivative “Skyrme” terms and the gauges Wess-Zumino term. The connection to previous approaches deriving the effective lagrangian exclusively from the chiral anomaly including “normal-parity” terms is established.     

Consistency of nuclear Dirac phenomenology with meson-nucleon interactions

The phenomenological relativistic theory of nuclear single-particle dynamics is reviewed and its salient characteristics discussed. The phenomenological (relativistic) potential strengths necessary to secure agreement with the usual low-energy properties of nuclei are determined. These phenomenological potentials are then related to the time-independent meson fields generated by nuclei, and it is shown by direct calculation that the potential strengths predicted on the basis of renormalized meson-nucleon couplings (as measured in, say, NN scattering) are consistent with those deduced empirically. Thus the phenomenological theory is shown to be consistent with a more microscopic approach, in agreement with the work of previous authors. The role of the ρ-meson is then examined, and it is shown that the time-independent ρ-field leads to isovector terms in both the central and spin-orbit terms of the equivalent Schrödinger potential. The signs and magnitudes of these terms agree with those determined from fits to the isobaric analogue (p, n) reactions, or to the systematics of single-particle energies.     

Dipole interactions and diffusion of μ meson in copper

The dipole relaxation rate and the diffusion coefficient of μ⁺-meson in copper are measured at different temperatures. The activation energy of μ⁺-meson in a crystal of copper is determined.     

The role of the rho meson in pion-nucleus interactions

It is shown that the static model gives a large overestimate of the effects of rho-meson propagation for pionic scattering and reactions at low and medium energies. In a relativistic treatment, the effect of intermediate stateρ-propagation is shown to be small and often negligible within present uncertainties. An improved value for theρNΔ coupling constant is extracted from Ragge pole fits.     

Scales, couplings revisited and low-energy phenomenology in M-theory on S^1/Z_2

We reconsider the dimension-11 Planck scale, the physical scale of the eleventh dimension, the physical scale of the Calabi–Yau manifold and the coupling in the hidden sector in M-theory on . Also we discuss reasonable bounds on them. Considering the F-term of the dilaton and moduli SUSY breaking and choosing two representative points which correspond to the scalar quasi-massless scenario and the dilaton dominant SUSY breaking scenario, respectively, we analyze experimental constraints on the parameter space. The sparticle spectrum and some phenomenological predictions are also given. Received: 9 June 1999 / Revised version: 12 July 2000 / Published online: 27 November 2000     

DN interaction from meson exchange

A model of the DN interaction is presented which is developed in close analogy to the meson-exchange [`(K)] \bar{{K}} N potential of the Jülich group utilizing SU(4) symmetry constraints. The main ingredients of the interaction are provided by vector meson (r \rho , w \omega exchange and higher-order box diagrams involving D <sup>*</sup> N , D D \Delta , and D <sup>*</sup> D \Delta intermediate states. The coupling of DN to the p \pi L<sub>c</sub> \Lambda_{c}^{} and p \pi S<sub>c</sub> \Sigma_{c}^{} channels is taken into account. The interaction model generates the L<sub>c</sub> \Lambda_{c}^{}(2595) -resonance dynamically as a DN quasi-bound state. Results for DN total and differential cross sections are presented and compared with predictions of two interaction models that are based on the leading-order Weinberg-Tomozawa term. Some features of the L<sub>c</sub> \Lambda_{c}^{}(2595) -resonance are discussed and the role of the near-by p \pi S<sub>c</sub> \Sigma_{c}^{} threshold is emphasized. Selected predictions of the orginal [`(K)] \bar{{K}} N model are reported too. Specifically, it is pointed out that the model generates two poles in the partial wave corresponding to the L \Lambda(1405) -resonance.     

Coupled channel dynamics close to a threshold. phenomenology of the f0(975) meson

A ππ and KK̄ coupled channels scheme, with separable s wave interaction, allows to discuss, from a hadronic point of view, some properties of the f₀(975) meson. An intriguing case where the weak binding and narrow width are crucially related to the coupling of the channels leads to some interesting consequences for the f₀(975) production in nuclear matter.     

Magnetic monopole interactions: Shell structure of meson and baryon states

It is suggested that a low-mass magnetic monopole of Dirac chargeg=(137/2)e may be interacting with ac-quark's magnetic dipole moment to produce Zeeman splitting of meson states. The massM ₀=2397 MeV of the monopole is in contrast to the 10¹⁶-GeV monopoles of grand unification theories (GUT). It is shown that shell structure of energyE _n =M ₀+1/4nM ₀+ exists for meson states. The presence of symmetric meson states leads to the identification of the shell structure. The possible existence of the 2397-MeV magnetic monopole is shown to quantize quark masses in agreement with calculations of quantum chromodynamics (QCD). From the shell structure of meson states, the existence of two new mesons is predicted:(1814±50 MeV) withI ^G(J ^PC =0⁺(0^–+) and _c (3907±100 MeV) withJ ^PC =0^–+. The presence of shell structure for baryon states is shown.     

D meson production in deep-inelastic diffractive interactions at HERA

A measurement is presented of the cross section for D^*± meson production in diffractive deep-inelastic scattering for the first time at HERA. The cross section is given for the process ep→eXY, where the system X contains at least one D^*± meson and is separated by a large rapidity gap from a low mass proton remnant system Y. The cross section is presented in the diffractive deep-inelastic region defined by 2<Q²<100 GeV², 0.05<y<0.7, , M_Y<1.6 GeV and |t|<1 GeV². The D^*± mesons are restricted to the range p_T,D^*>2 GeV and |η_D^*|<1.5. The cross section is found to be 246±54±56 pb and forms about 6% of the corresponding inclusive D^*± cross section. The cross section is presented as a function of various kinematic variables, including which is an estimate of the fraction of the momentum of the diffractive exchange carried by the parton entering the hard-subprocess. The data show a large component of the cross section at low where the contribution of the boson–gluon-fusion process is expected to dominate. The data are compared with several QCD-based calculations.