Narrow Results

Formation spectra of model systems excited by reaction are investigated in order to get a theoretical basis for proper interpretation of experimental data concerning kaonic nuclear quasi-bound states. It is argued that experimentally observable kaonic nuclear peak should be regarded as the decaying state introduced by Kapur-Peierls.

The new experimental data of kaon photoproduction on the nucleon γp → K⁺Λ have been analyzed by means of a multipoles model. Different from the previous models, in this analysis the resonance decay widths are constrained to the values given by the Particle Data Group (PDG). The result indicates that constraining these parameters to the PDG values could dramatically change the conclusion of the important resonances in this reaction found in the previous studies.

Neutral kaon photoproduction on the deuteron has been investigated by including the final state effects and compared with the experimental data. Comparison shows that the models used in this calculation can reproduce the data in the Σ channel regions fairly well but still give over predictions in the Λ channel. It seems that the tensor target asymmetries are more suitable for studying the final state effects. The extractions of the elementary photoproduction amplitude are also demonstrated.

The K⁰ photoproduction process is investigated in the threshold region, E_γ = 0.8-1.1 GeV at LNS-Tohoku. K⁰ events are measured via π⁺π^- decay channel. Obtained momentum spectra for the deuteron target are compared with those calculated in the spectator model using a realistic deuteron wave function. Recent isobar models and a simple phenomenological model are used as elementary amplitudes to investigate the effect of the new data on the angular behavior of the elementary cross section. The data favor a backward-peaked angular distribution of the elementary n(γ, K⁰)Λ process in the center-of-mass (c.m.) system, which provides additional constraints on current models of kaon photoproduction. The present study shows that the n(γ, K⁰)Λ reaction can provide key information on the mechanism of the photoproduction of strangeness.

We have investigated the effects of different hadronic form factors on the performance of an isobaric model developed for kaon photo-production off the proton. We found that there is no ideal form factor in this case. The dipole and generalized dipole form factors can help to nicely reproduce the differential cross-section and hyperon polarization data. However, in the case of double polarization data C_x and C_z the Gaussian form factor is found to be superior.

Using KAON-MAID, an operator for kaon photo- and electro-production on the nucleon, we calculate contributions of kaon–hyperon final states to the Gerasimov–Drell–Hearn (GDH) integrals on the proton. We also calculate the corresponding contributions to the forward spin polarizability γ₀ of the proton. By extending the operator to the finite Q² region we then calculate kaon contributions to the generalized GDH integrals, as well as to the longitudinal-transverse polarizability δ₀. Our results show relatively small but still sizable contributions.

The FINUDA spectrometer is installed at one of the interaction points of the DAΦNE e⁺e^- collider in Frascati(I). By stopping the low energy K^- from the ɸ(1020) decays, FINUDA performed a rich program of studies of K^- induced interactions on a set of nuclear targets. A survey of the results will be given, with emphasis on the study of non-mesonic weak decays of Λ-hypernuclei and on the search for deeply bound kaonic nuclear clusters.

Search for heavy neutral lepton (HNL) production in charged kaon decays using the data collected by kaon experiments NA48/2 and NA62 at CERN are reported. Upper limits are established on the elements of the extended neutrino mixing matrix for heavy neutral lepton mass in the range 130–450 MeV, improving on the results from previous HNL production search.

The present status of kaon photo- and electroproduction on the nucleon is briefly reviewed. Some current important issues in this field are discussed.

Recent progress on the precision laser spectroscopy of antiprotonic helium atoms, as well as on the x-ray spectroscopy of kaonic helium atoms are presented. These two may appear to be unrelated topics (except for the fact that both being exotic helium atoms), but in fact a past study of kaonic helium system led to the serendipitous discovery of antiprotonic helium. Some historical background connecting these two exotic helium atoms, as well as future prospects are discussed.

We have phenomenologically investigated the kaon photoproduction process γp → K⁺Λ by combining different types of hadronic form factors (HFFs) inside a covariant isobar model. We obtained the best model with the smallest χ²/N by using the dipole form factor in the Born terms and a combination of the dipole, Gaussian, as well as generalized dipole form factors in the hadronic vertices of the nucleon, kaon and hyperon resonances. By utilizing this model we found that the experimental data used in the analysis are internally consistent, whereas the behavior of differential cross-section at forward angles is not significantly affected by the variation of hadronic coupling constants (CCs) and form factor cutoffs in the model.

The NA48/2 experiment presents preliminary measurements of the form factors of the charged kaon semileptonic decays. The Ke3 and Kμ3 results are in good agreement allowing for a combined result which matches the precision of the current world average on the vector and scalar form factors. Recent study of the rare decay K^± → π^±γγ from the NA48/2 and NA62 data samples is also reported.

Rare kaon decays provide unique opportunity to test the Standard Model and probe its possible extensions. The primary goal of the NA62 experiment is the measurement of the decay with a precision of 10% in two years of data taking. The detector setup together with the analysis technique is described.

This talk presents the results of recent experimental searches for antikaon-nuclear bound systems on different nuclei, performed with the FINUDA spectrometer at the DAφNE φ-factory (Frascati,Italy).

Data taking for the KLOE experiment at the DAΦNE ϕ factory was completed in 2005, with the acquisition of ~2.5 fb^-1 of luminosity integrated at the ϕ peak. From the analysis of a ~ 400-pb^-1 subsample, by far the most precise test of the validity of the time evolution of kaon pairs predicted by quantum mechanics has been obtained. Moreover, the sensitivity to possible violations of the CPT symmetry has been sizeably improved by exploiting the unitarity relation while including recent results from the KLOE experiment. Perspectives on results that will be obtained from the analysis of the final data set are briefly discussed.

The following sections are included:

• Introduction

• Neutron Star Model

• Relativistic Mean Field Model with Kaons (Pions)

• Conclusions

• Bibliography

The present status of kaon photo- and electroproduction on the nucleon is briefly reviewed. Some current important issues in this field are discussed.

Recent progress on the precision laser spectroscopy of antiprotonic helium atoms, as well as on the x-ray spectroscopy of kaonic helium atoms are presented. These two may appear to be unrelated topics (except for the fact that both being exotic helium atoms), but in fact a past study of kaonic helium system led to the serendipitous discovery of antiprotonic helium. Some historical background connecting these two exotic helium atoms, as well as future prospects are discussed.