O. O. Voskresenskaya

Electromagnetic corrections to final state interactions in K→3π decays

The final state interactions of pions in decays

Electromagnetic effects and scattering lengths extraction from experimental data on K → 3π decays

K^\pm\to\pi^\pm\pi^0\pi^0

Quantum-mechanical description of in-medium fragmentation

are considered using the methods of quantum mechanics. We show how to incorporate the electromagnetic effects in the amplitudes of these decays and to work out the relevant expressions valid above and below the two charged pions production threshold

The Influence of strong interaction on the pionium wave functions at small distances

M_c=2m

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

. The electromagnetic corrections are given as evaluated in a potential model.

The isospin-symmetry-breaking effects in Ke4 decays

The final state interactions in K± → π±π0π0 decays are considered using the methods of nonrelativistic quantum mechanics. It is shown how to take into account the largest electromagnetic effect in the analysis of experimental data using the amplitudes calculated earlier. The relevant expressions for amplitude corrections valid both above and below the two charged pions production threshold \( M_{\pi ^0 \pi ^0 } = 2m_{\pi ^ \pm } \), including the average effect for the threshold bin, are proposed. These formulae can be used in the procedure of pion scattering lengths measurement from \( M_{\pi ^0 \pi ^0 } \) spectrum.

Contribution of alpha**2 terms to the total interaction cross sections of relativistic elementary atoms with atoms of matter

We present a quantum-mechanical description of quark-hadron fragmentation in a nuclear environment. It employs the path-integral formulation of quantum mechanics, which takes care of all phases and interferences and contains all relevant time scales, such as production, coherence, and formation. The cross section includes the probability of prehadron (colorless dipole) production both inside and outside the medium. Moreover, it also includes inside-outside production, which is a typical quantum-mechanical interference effect (like twin-slit electron propagation). We observe a substantial suppression caused by the medium, even if the prehadron is produced outside the medium and no energy loss is involved. This important source of suppression is missed in the usual energy-loss scenario interpreting the effect of jet quenching observed in heavy ion collisions. This may be one reason for the too large gluon density reported by such analyses.

The electromagnetic effects in Ke4 decay

Abstract The influence of the strong π + π − -interaction of the behaviour of pionium n S-state wave functions at small distances is studied both analytically (perturbatively) and numerically. It is shown that on the whole the accounting of strong interaction results in multiplying pure Coulomb pionium wave functions by some function which is practically independent of the value of the principal quantum number n . Due to this reason, the n -dependence of π + π − -atom production probability in n S-state remains the same as in the case of the pure Coulomb π + π − -interaction.

Final-state interaction in kaon decays

The total interaction cross sections of the relativistic +--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 +--atom.

Coulomb corrections to the parameters of the Molière multiple scattering theory

The Fermi-Watson theorem is generalized to the case of two coupled channels with different masses and applied to final-state interaction inKe4 decays. The impact of the considered effect on the phase of ππ scattering is estimated and it is shown that it can be crucial for the scattering length extraction from experimental data on Ke4 decays.