Total interaction cross sections of relativistic pi⁺pi^--atoms with ordinary atoms in the eikonal approach

Abstract

The total interaction cross sections of the relativistic π + π − -atoms with ordinary atoms are obtained in the eikonal approach which takes into consideration all multiphoton exchange processes. The contribution of these processes strongly depends on the atom nucleus charge Z and varies from 1.5% for titanium (Z = 22) to 14% for tantalum (Z = 73). The formulae derived are applicable for an arbitrary initial state of the π + π − -atom.

A density-matrix kinetic equation describing the passage of fast atomic systems through matter

“…which coinside with the system equations of [9]. Taking into account the "selection rules" (48), we clearly see that this statement is also valid when there is only degeneracy with respect to the value of the magnetic quantum number that is, if the hadron-hadron interaction has only the central symmetry.…”

“…It is commonly supposed [9] that the dimesoatomic dynamics can be described with the help of a set of kinetic equations for the probabilities P i (z) to find the dimesotom in the definite quantum state |i at the distance z from the production point.…”

“…Since these effects cannot be treated in the classical approach of the paper [9], one have to use a more sophisticated approach for consideration of internal dimesoatom dynamics based on the density-matrix description of quantum systems.…”

“…In Section 3, a set of equations for density matrix elements is derived. In Section 4, the correspondence between density-matrix approach and probabilistic approach of the paper [9] is discussed. In Section 5, a brief summary of the main results is given.…”

Observation and investigation ofπKatoms

“…These pairs have small relative momentum (Q < 3 MeV/c) and a number of such pairs n A could be measured experimentally. Ratio of "atomic pair" number to a number of atom produced is a breakup probability: [15,16]. In Fig 1 dependence of A πK breakup probability is shown for two Ni target are used in experiment DIRAC for pair laboratory momentum range 5.1 ÷ 8.5 GeV/c.…”