34
O. Yu. Khetselius et al.
1 Introduction
The theoretical and experimental study of the spectra, energy and spectroscopic
characteristics of exotic quantum systems, in particular, hadronic (kaonic, pionic
and other) atoms is of great interest both for the development of quantum physics
and chemistry of finite Fermi systems with electromagnetic and strong interactions,
as well as for further understanding and development of advanced concepts of atomic
and nuclear structures (e.g., Refs. [1–90]). It is well known that the concept of exotic
atom was first introduced in 1947 by Fermi, Teller, Wheeler to explain experiments
on the absorption of negative muons in matter. In recent years, the study of kaonic
atoms has become especially relevant in the light of the well-known progress of
experimental studies (at meson factories in the laboratories of LAMPF (USA), PSI
(Switzerland), TRIUMF (Canada), IFF (Russia), RIKEN (KEK, Japan), RAL (United
Kingdom), DEAR at the DAPNE (Italy) and further substantial development of
modern nuclear theory, quantum mechanics of atoms etc.
The study of spectra and spectroscopic, radiation and other properties of the kaonic
atoms is a unique tool for studying fundamental interactions, including validation
of the Standard Model, giving extremely important data on properties of a nucleus
and hadrons themselves, the nature of their interaction with nucleons. In principle,
it allows to determine the masses and magnetic moments of the particles (kaon,
pion, antiproton etc.), which are the most accurate so far. The light kaonic atoms are
candidates for the creation of new, efficient low-energy X-ray standards. Moreover,
the experiments with different hadronic atoms allow to determine the spins and
pairs of the hadrons. Since the products of the reactions of hadrons (kaons) with
neutrons and protons are different, this allows to obtain the quantitative data on the
distribution of protons and neutrons in nuclei from measurements of the widths of
X-ray transitions and the relative probabilities of different reactions.
One of the fundamental questions in the modern hadron’s physics is connected
with the hadron masses being much higher than the mass of their quark content. The
current mass of the up (u) and down (d) quarks is two orders of magnitude smaller
than a typical hadron’s mass of about 1 GeV. This extraordinary phenomenon is
proposed to originate from spontaneous breaking of chiral symmetry of massless
quarks in strong interaction physics [1–5]. One of the most sensitive tests for the
chiral symmetry breaking scenario in the modern hadron’s physics is provided by
studying the exotic (in particular, kaonic) atomic systems. It should be reminded that
the most comprehensive theory of the hadronic multielectron atoms must be based on
the principles of a quantum chromodynamics (QCD) and quantum electrodynamics
(QED).
From the modern viewpoint, QCD is the most fundamental gauge theory of strong
interactions with the coloured quarks and gluons. Nowadays the energy and spectral
properties of the hadronic atoms are determined with an unprecedented precision
and it is possible to study the strong interaction at low energies measuring the energy
O. Yu. Khetselius et al.
1 Introduction
The theoretical and experimental study of the spectra, energy and spectroscopic
characteristics of exotic quantum systems, in particular, hadronic (kaonic, pionic
and other) atoms is of great interest both for the development of quantum physics
and chemistry of finite Fermi systems with electromagnetic and strong interactions,
as well as for further understanding and development of advanced concepts of atomic
and nuclear structures (e.g., Refs. [1–90]). It is well known that the concept of exotic
atom was first introduced in 1947 by Fermi, Teller, Wheeler to explain experiments
on the absorption of negative muons in matter. In recent years, the study of kaonic
atoms has become especially relevant in the light of the well-known progress of
experimental studies (at meson factories in the laboratories of LAMPF (USA), PSI
(Switzerland), TRIUMF (Canada), IFF (Russia), RIKEN (KEK, Japan), RAL (United
Kingdom), DEAR at the DAPNE (Italy) and further substantial development of
modern nuclear theory, quantum mechanics of atoms etc.
The study of spectra and spectroscopic, radiation and other properties of the kaonic
atoms is a unique tool for studying fundamental interactions, including validation
of the Standard Model, giving extremely important data on properties of a nucleus
and hadrons themselves, the nature of their interaction with nucleons. In principle,
it allows to determine the masses and magnetic moments of the particles (kaon,
pion, antiproton etc.), which are the most accurate so far. The light kaonic atoms are
candidates for the creation of new, efficient low-energy X-ray standards. Moreover,
the experiments with different hadronic atoms allow to determine the spins and
pairs of the hadrons. Since the products of the reactions of hadrons (kaons) with
neutrons and protons are different, this allows to obtain the quantitative data on the
distribution of protons and neutrons in nuclei from measurements of the widths of
X-ray transitions and the relative probabilities of different reactions.
One of the fundamental questions in the modern hadron’s physics is connected
with the hadron masses being much higher than the mass of their quark content. The
current mass of the up (u) and down (d) quarks is two orders of magnitude smaller
than a typical hadron’s mass of about 1 GeV. This extraordinary phenomenon is
proposed to originate from spontaneous breaking of chiral symmetry of massless
quarks in strong interaction physics [1–5]. One of the most sensitive tests for the
chiral symmetry breaking scenario in the modern hadron’s physics is provided by
studying the exotic (in particular, kaonic) atomic systems. It should be reminded that
the most comprehensive theory of the hadronic multielectron atoms must be based on
the principles of a quantum chromodynamics (QCD) and quantum electrodynamics
(QED).
From the modern viewpoint, QCD is the most fundamental gauge theory of strong
interactions with the coloured quarks and gluons. Nowadays the energy and spectral
properties of the hadronic atoms are determined with an unprecedented precision
and it is possible to study the strong interaction at low energies measuring the energy