Hadronic atoms

Production of 7r+7r- atoms (and of other hadronic atoms) in inclusive processes was considered and a method of their observation and lifetime measurement was proposed [30]. The atoms are produced in 5-states with the cross section ... 

Production of atoms (and of other hadronic atoms) in inclusive processes... 

Numerous models have been proposed for describing the formation of exotic atoms via Coulomb capture. The muons in atoms do reach the atomic ground state (as opposed to hadronic atoms), and the lack of strong interaction effects makes them good probes to study Coulomb capture. One of the most important experimental methods is measuring Coulomb capture ratios. In a mixture of two elemental gases (e.g., N2 + O2) or in binary compounds, one can determine the amount of muons captured in the different elements by summing up the amplitudes of the muonic Lyman series, the (n p —> Is) transitions. 

The decay of the exotic atom can be a simple decay of the exotic particle in the case of light muonic atoms however, due to the strong nuclear interaction in hadronic atoms, the negative hadron can be absorbed by the nucleus leading to nuclear reaction (O Fig. 28.5). 

As mentioned before, the neutral exotic hydrogen atom (having neither Coulomb nor Pauli repulsion) can penetrate other atoms and lose its exotic particle to a heavier nucleus. As the rate of this reaction is proportional to the number of collisions, it can be detected for hadronic atoms but it is really dramatic for muonic hydrogen as its lifetime is many orders of magnitude longer in the muon-catalyzed fusion measurements, for example, the concentration of heavy impurities has to be below 10 to avoid the distortion of the results by transfer. This feature was used to study muon capture in rare gas isotopes as it is sufficient to have less than 1% krypton in hydrogen to have all muons ended up in muonic krypton states. 

Physical information can be obtained, e.g., by measuring the shift and broadening of the energy levels of the hadron in the atom due to nuclear interactions as compared to a purely electromagnetic case. The shifts and widths can be measured for one or two levels only in each kind of hadronic atom as the strong nuclear absorption - which causes the level broadening -terminates the atomic cascade at a certain principal quantum number This lowest n sensitively depends on the mass of the particle and on the atomic number of the nucleus min = 1 for pionic oxygen and 8 for antiprotonic nickel. 

As pionic hydrogen atoms found important applications in chemistry most of this chapter is devoted to that particular topic and the rest of hadronic atoms is only briefly summarized. 

Methods for influencing the radioactive decay rate have been sought from early years of Nuclear physics. Nuclear transmutation (i.e. change in the nuclear charge) induced by nuclear reactions are often accompanied by a redistribution of the electrons, muons (mesons in the hadronic atoms) around the final transmuted nucleus. Muonic atoms have always been useful tools for nuclear spectroscopy employing atomic-physics techniques. Muonic atoms also play an important role... 

Jorgensen CK (1981) The Conditions for Total Symmetry Stabilizing Molecules, Atoms, Nuclei and Hadrons. 43 1-36... 

Remarkably, the Wigner distribution could be observed in a number of systems by physical experiments and computer simulations evading the whole quantum world from atomic nuclei to the hydrogen atom in a magnetic field to the metal-insulator transition (Guhr, Muller-Groeling and Weidenmuller, 1998). In this contribution we address the situation in QCD and in hadrons. 

It may be noted that several authors (56,57) have calculated many properties of a rich spectrum of hadrons with few parameters in a phenomenological model. In all of these cases, the quark inside a nucleon has a much smaller effective mass than the free quark outside a nucleon. It has also been discussed (58) whether there exist quasi-stable hadrons containing superheavy quarks with atomic weights around 30. 

The effects connected with the electron vacuum polarization contributions in muonic atoms were first quantitatively discussed in [4]. In electronic hydrogen polarization loops of other leptons and hadrons considered in Subsect. 3.2.5 played a relatively minor role, because they were additionally suppressed by the typical factors (mg/m). In the case of muonic hydrogen we have to deal with the polarization loops of the light electron, which are not suppressed at all. Moreover, characteristic exchange momenta mZa in muonic atoms are not small in comparison with the electron mass rUg, which determines the momentum scale of the polarization insertions m Za)jme 1.5). We see that even in the simplest case the polarization loops cannot be expanded in the exchange momenta, and the radiative corrections in muonic atoms induced by the electron loops should be calculated exactly in the parameter m Za)/me-... 

The prediction of a heavy boson has received preliminary empirical support [92,96] from an anomaly in Z decay widths that points toward the existence of Z bosons with a mass of 812 GeV 1 33j [92,96] within the SO(l) grand unified field model, and a Higgs mechanism of 145 GeV4gj3. This suggests that a new massive neutral boson has been detected. Analysis of the hadronic peak cross sections obtained at LEP [96] implies a small amount of missing invisible width in Z decays. The effective number of massless neutrinos is 2.985 0.008, which is below the prediction of 3 by the standard model of electroweak interactions. The weak charge Qw in atomic parity violation can be interpreted as a measurement of the S parameter. This indicates a new Qw = 72.06 0.44, which is found to be above the standard model pre-... 

HADRONS. These are subatomic particles, the strong interactions of which are manifested by the forces lhal hold neutrons and protons together in the atomic nucleus. Hadrons include Ihe proton, the neutron, and pion. among others. These particles show signs of an inner structure, i.e.. they are made up of other panicles, which has led over a period of the last several years to consider the hadrons as combinations of constituents known as quarks. See also Quarks and Particles (Subatomic). 

When the two conjugated atoms approach each other, the leptons might in principle annihilate before the hadrons do. We have found that this is not the case. Even though the annihilation reaction constant for para-positronium is larger than that for protonium, the probability of e+ — e annihilation at any given interhadronic distance R is weighted by the hadronic probability density at that distance. Because of that, the e+ — e annihilation occurs mainly at R 1 whereas the hadrons annihilate basically at R = 0. 

It is interesting to note that a similar radiative association process is not possible for the two hydrogen atoms. On the symmetry grounds the dipole moment of the H — H system (which is inversion symmetric) vanishes. In that case the nuclear dipole moment is identically 0 and the electronic dipole moments induced in the two approaching atoms have opposite orientations and cancel each other. For the H — H system (which lacks the inversion symmetry) the dipole moment (in the adiabatic and non-relativistic approximation) is finite. In that case the hadronic moment is e R and the induced leptonic moments of H and H have the same orientations and add together to a non vanishing dipole moment (which tends to 0 in the limit of infinite separation R between the atoms). 

C.K.Jorgensen The Conditions for Total Symmetry Stabilizing Molecules, Atoms, Nuclei and Hadrons. - J. C. Green Gas Phase Photoelectron Spectra of d- and f-Block Organometallic Compounds. - R. Englman Vibrations in Interaction with Inpurities. - W.L.Smith, K, N. Raymond Actinide-Specific Sequestering Agents and Decontamination Applications.- Y Y G. Mourn, I.Moura, A. V.Xavier Novel Structures in Iron-Sulfur Proteins. 

There is a kind of atom where the nuclear effects are very large - exotic atoms, containing hadrons, i.e. particles that can interact strongly pions, antiprotons, kaons etc. In such atoms any advanced high-accurate QED theory is not necessary and a goal to study such atoms is to measure these nuclear parameters. An important feature of any spectroscopic measurement is its high accuracy in respect to non-spectroscopic methods. That is very important for exotic atoms, because some, like e.g. pionium (7r+7r -system or bound 7rp-system), are available in very small quantities (a few hundreds) [35],... 

The dominant interaction within the muonium atom is electromagnetic. This can be treated most accurately within the framework of bound state Quantum Electrodynamics (QED). There are also contributions from weak interaction which arise from Z°-boson exchange and from strong interaction due to vacuum polarization loops with hadronic content. Standard theory, which encompasses all these forces, allows to calculate the level energies of muonium to the required level of accuracy for all modern precision experiments1. 

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