Accurate evaluation of the 1s wave functions of kaonic hydrogen

Kaonic hydrogen is studied with realistic potentials in an accurate numerical approach based on Sturmian functions. It is found that the ground-state wave function of the exotic atom with realistic strong interactions is considerably different from the hydrogen-like ones at small distances. The K ^???p scattering length extracted from the 1s energy shift of the kaonic hydrogen by applying the Deser-Trueman formula is severely inconsistent with the one derived directly by solving the Schödinger equation. We pay special attention to the recent measurement of the energy shift and decay width of the 1s kaonic hydrogen state by the DEAR Collaboration. Our work strongly supports the argument that the DEAR data of the K ^???p scattering length extracted with the Deser-Trueman formula from the measured 1s energy shift and decay width are not accurate, if not to say, unreliable.     

Precision measurements of kaonic atoms at DA ΦNE and future perspectives

The DAΦNE electron-positron collider at the Frascati National Laboratories has made available a unique “beam" of negative kaons providing unprecedented conditions for the study of the low-energy kaon-nucleon interaction, a field still largely unexplored. The DEAR (DAΦNE Exotic Atom Research) experiment at DAΦNE and its successor SIDDHARTA (SIlicon Drift Detector for Hadronic Atom Research by Timing Application) aim at a precision measurement of the strong-interaction shift and width of the fundamental 1s level, via the measurement of the X-ray transitions to this level, for kaonic hydrogen and kaonic deuterium. The aim is to extract the isospin-dependent antikaon-nucleon scattering lengths and to contribute to the understanding of aspects of chiral symmetry breaking in the strangeness sector.     

Results from the kaonic hydrogen X-ray measurement at DAFNE and outlook to future experiments

The $\overline{K}N$ system at rest plays a key role for the understanding of strong interaction of hadrons with strangeness involved. The experiment SIDDHARTA used X-ray spectroscopy of kaonic atoms to measure the strong interaction induced shift and width of the ground state. It was the first experiment on kaonic He3 and deuterium ever, kaonic hydrogen was measured with improved precision resulting in $\epsilon_{1s} = -283 \pm 36 \mbox{(stat)} \pm 6 \mbox{(syst)}$ eV and $\Gamma_{1s} = 541 \pm 89 \mbox{(stat)} \pm 22 \mbox{(syst)}$ eV. Additionally a scheme for an improved future experiment on kaonic deuterium is introduced in this contribution.     

Measurement of the kaonic hydrogen x-ray spectrum

The DEAR (DAPhiNE exotic atom research) experiment measured the energy of x rays emitted in the transitions to the ground state of kaonic hydrogen. The measured values for the shift epsilon and the width Gamma of the 1s state due to the K(-)p strong interaction are epsilon(1s)=-193 +/- 37 (stat) +/- 6 (syst) eV and Gamma(1s)=249 +/- 111 (stat) +/- 30 (syst) eV, the most precise values yet obtained. The pattern of the kaonic hydrogen K-series lines, K(alpha), K(beta), and K(gamma), was disentangled for the first time.     

Phenomenological \boldsymbol{\bar{K}N} interaction with isospin-breaking effects

New strong coupled-channel $\bar{K}N - \pi \Sigma$ potential, reproducing all existing experimental data and suitable for using in accurate few-body calculations, is constructed. Isospin breaking effects of direct inclusion of the Coulomb interaction and the use of physical masses in calculations are taken into account. The 1s level shift and width of kaonic hydrogen, consistent with the scattering data, was obtained and the corresponding strong K ^??? p scattering length was calculated. One- and two-pole forms of Λ(1405) resonance were considered.     

Disentangling the K-complex of kaonic hydrogen with DEAR

The DEAR (DAΦNE Exotic Atom Research) experiment at the new φ-factory DAΦNE of Laboratori Nazionali di Frascati aims for a 1% measurement of the line shift of the K-complex due to strong interaction in kaonic hydrogen. This presentation is meant to prove that the high statistics and good resolution obtainable with DEAR will be able to disentangle the kaonic hydrogen K-complex lines (a cascade unconstrained fit), obtaining in this way constraints for what concerns the cascade parameters and, consequently, information regarding the physical processes involved in the kaonic hydrogen atomic cascade. This revised version was published online in August 2006 with corrections to the Cover Date.     

Observation of kaonic hydrogen atom X-ray

We successfully observed clear K-series kaonic hydrogen X-rays for the first time taking advantage of two charged pions tagging technique and a gaseous hydrogen target. The strong-interaction energy shift and width of 1s state of K ⁻p atom were determined to be ΔE _1s = -323 ± 63 (statistical) ± 11 (systematic) eV and Г_1s = 407 ± 208 ± 100 eV. Our result means that the K ⁻p strong interaction near threshold is repulsive and the long-standing kaonic hydrogen puzzle is solved. This revised version was published online in August 2006 with corrections to the Cover Date.     

Surprises in threshold antikaon-nucleon physics

Low energy KN interactions are studied within unitary chiral perturbation theory at next-to-leading order with ten coupled channels. We pay special attention to the recent precise determination of the strong shift and width of the kaonic hydrogen 1s state by the DEAR Collaboration that has challenged our theoretical understanding of this sector of strong interactions. We typically find two classes of solutions, both of them reproducing previous data, that either can or cannot accommodate the DEAR measurements. The former class has not been previously discussed.     

Kaonic hydrogen and K(-)p scattering

Chiral SU(3) effective field theory in combination with a relativistic coupled-channels approach is used to perform a novel analysis of the strong-interaction shift and width in kaonic hydrogen in view of the new accurate DEAR measurements. Questions of consistency with previous K(-)p data are examined. Coulomb and isospin breaking effects turn out to be important and are both taken into account in this work.     

Faddeev Treatment of the Quasi-Bound and Scattering States in the {\bar{K}NN - \pi\Sigma N} System

The three-body Faddeev-type AGS equations were used for investigation of scattering states in the ${\bar{K} NN - \pi \Sigma N}$ system. Newly constructed “chirally motivated” potentials describing ${\bar{K} N - \pi \Sigma}$ interaction were used as an input. The results of the three-body calculations were then used for calculations of the corresponding 1s level shift and width of kaonic deuterium.     

Optical-model analysis of exotic atom data: (I). Kaonic atoms

Data for kaonic atoms are fitted using a simple optical model with a potential proportional to the nuclear density. Very satisfactory fits to strong interaction shift and width values are obtained but difficulties in fitting yield values indicate that the model is not completely satisfactory. The potential strength can be related to the free kaon-nucleon scattering lengths using a model due to Deloft. A good overall representation of the data is obtained with a black-sphere model.     

Measurement of kaonic X-rays from Li,LiH AND Be

We have observed X-rays from kaons stopping in targets of Li, LiH and Be. The strong interaction widths, shifts and relative yield of the last observed X-ray have been measured. There is evidence for a difference in the yield of the n = 3 → 2 Li X-rays in Li metal and LiH. There is no evidence in the spectra for X-rays from kaonic hydrogen formed in LiH.     

First measurement of kaonic helium-3 X-rays

The first observation of the kaonic (3)He 3d→2p transition was made, using slow K- mesons stopped in a gaseous (3)He target. The kaonic atom X-rays were detected with large-area silicon drift detectors using the timing information of the K+K- pairs of ?-meson decays produced by the DAΦNE e+e- collider. The strong interaction shift of the kaonic (3)He 2p state was determined to be -2±2(stat)±4(syst) eV.     

The pion–nucleon scattering lengths from pionic hydrogen and deuterium

This is the final publication of the ETH Zurich–Neuchatel–PSI collaboration on the pionic hydrogen and deuterium precision X-ray experiments. We describe the recent hydrogen 3p–1s measurement, report on the determination of the Doppler effect correction to the transition line width, analyze the deuterium shift measurement and discuss implications of the combined hydrogen and deuterium results. From the pionic hydrogen 3p–1s transition experiments we obtain the strong-interaction energy level shift eV and the total decay width eV of the state. Taking into account the electromagnetic corrections we find the hadronic s-wave scattering amplitude for elastic scattering and for single charge exchange, respectively. We then combine the pionic hydrogen results with the 1s level shift measurement on pionic deuterium and test isospin symmetry of the strong interaction: our data are still compatible with isospin symmetry. The isoscalar and isovector scattering lengths (within the framework of isospin symmetry) are found to be and , respectively. Using the GMO sum rule, we obtain from a new value of the coupling constant () from which follows the Goldberger–Treiman discrepancy . The new values of and imply an increase of the nucleon sigma term by at least 9 MeV. Received: 20 April 2001 / Revised version: 6 July 2001 / Published online: 24 August 2001     

Isospin mixing \bar{K}N\hbox{-}{\pi}{\Sigma} interaction and \bar{K}NN\hbox{-}{\pi} {\Sigma}N quasi-bound state

A phenomenological isospin-dependent $\bar{K}N\hbox{-}\pi\Sigma$ potential reproducing a medium KEK value of 1s kaonic hydrogen level shift instead of a K ^? p scattering length is constructed. The corresponding three-body $\bar{K}NN\hbox{-}\pi\Sigma N$ calculation using the obtained potential is performed.     

Kaonic Hydrogen atom X-rays

The X-ray spectrum obtained with kaons stopping in liquid hydrogen has been measured. Possible candidates for X-ray lines from kaonic hydrogen atoms have been identified and the results compared with previous experiments and with theoretical predictions. X-ray lines from σ^?p atoms may also have been observed.     

Low-Energy Kaon�CNucleon/Nuclei Interaction Studies at DA��NE (SIDDHARTA and AMADEUS Experiments)

The DA??NE electron?Cpositron collider at the Laboratori Nazionali di Frascati of INFN has made available a unique quality low-energy negative kaons ??beam??. The SIDDHARTA experiment used this beam to perform unprecedented precision measurements on kaonic atoms, while the AMADEUS experiment plans to perform in the coming years precision measurements on kaon?Cnuclei interactions at low-energies, in particular to study the kaonic nuclei. The two experiments are briefly presented in this paper.