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V. E. Markushin

Publications and source records attributed to V. E. Markushin.

27 records · Page 2Linked to original sources
arXiv1998

Loop Calculations and OZI Rule

The role of two step mechanisms in the OZI rule violation in NNbar annihilation at low energies is reviewed. The full calculation of two-meson doorway mechanisms shows that the off-mass-shell contributions are important. Moreover, for the (phi pi0) and (phi rho) annihilation channels three-meson doorway contributions are non-negligible and improve agreement with the data. A significant enhancement of phi production is found in the resonant rescattering mechanisms p pbar -> pi+ pi- K Kbar -> pi+ pi- phi and p pbar -> eta K Kbar -> eta phi.

hep-ph↗
arXiv1998

Cascade in Muonic and Pionic Atoms with Z=1

Recent theoretical and experimental studies of the exotic atoms with Z=1 are reviewed. An interplay between the atomic internal and external degrees of freedom is essential for a good description of the atomic cascade. The perspective of ab initio cascade calculations is outlined.

nucl-th↗
arXiv1998

Structure of f0(980) from a Coupled Channel Analysis of S-wave pi pi Scattering

A coupled channel model is used to study the nature of the f0(980) resonance. It is shown that the existence of two poles close to KKbar threshold, as found in many data fits and confirmed here, can be reconciled with the KKbar molecular origin of the f0(980). Due to a strong coupling between channels the number of the S-matrix poles close to the physical region in the physical case exceeds the number of bare states introduced in the model.

hep-ph↗
arXiv1997

A Precision Measurement of Nuclear Muon Capture on 3He

The muon capture rate in the reaction mu- 3He -> nu + 3H has been measured at PSI using a modular high pressure ionization chamber. The rate corresponding to statistical hyperfine population of the mu-3He atom is (1496.0 +- 4.0) s^-1. This result confirms the PCAC prediction for the pseudoscalar form factors of the 3He-3H system and the nucleon.

hep-ph↗
arXiv1996

Pion Absorption Cross Section for ^2H and ^3He in the Delta-Isobar Region: A Phenomenological Connection

The absorption of π^+ on ^3He in the $Δ$-region is evaluated with exact inclusion of the final state interaction among the three emerging protons. The absorption is described by a $πN \to Δ$ vertex and a $NΔ- NN$ transition t-matrix which are calculated from a phenomenological model for NN and πd reactions. In a calculation where the initial pion scattering effects are neglected, the predicted peaks of the pion absorption cross sections for ^2H and ^3He lie too high in energy in relation to the data. The effect of the final state three-nucleon interaction turns out to be too small for changing the magnitude and shifting the peak position of the total absorption cross section for ^3He. We demonstrate that the adjustment of the peak position for the deuteron cross section by small modifications of the $Δ$-parameters, automatically leads to the correct peak position in ^3He.

nucl-th↗
arXiv1996

Annihilation into Channels with Strangeness and the OZI Rule Violation

Two-step mechanisms in the $N\bar{N}$ annihilation and their role in the OZI rule violating reactions are discussed. In particular the two meson rescattering mechanism for $πϕ$ channel including all off-shell effects is typically two orders of magnitude bigger than the OZI tree level expectation and explains the observed ratio $ϕπ/ωπ$ in the annihilation at rest. The rates for the final states including photons, $γω$ and $γϕ$, can be explained in the vector dominance model. The observed rate for $p\bar{p}\toγω$ is suppressed due to destructive interference between the intermediate $ρ$ and $ω$ states while the interference in $p\bar{p}\toγϕ$ is required to be constructive leading to a large ratio $γϕ/γω$.

hep-th↗
arXiv1996

The $ππ$ Final State Interaction in $K\toππ$, $pp\to ppππ$ and Related Processes

Final state interactions in the $S$--wave $ππ$ system (I=0,2) are re-examined on the basis of the Omnès-Mus\-khe\-li\-shvili equation and the coupled channel formalism. The contributions to the pion scalar form factor from $ρ$ and $f_2(1270)$ exchange in the $t$--channel and from the $f_0(980)$ $s$--channel resonance are separately evaluated and the role of the nontrivial polynomial in the Omnès function in a coupled channel situation is elucidated. Applications are made to $K\to ππ$ and $pp\to ppππ$. It is found that the contribution from the $f_0$ resonance to the form-factor is strongly reduced by a nearby zero.

hep-ph↗
arXiv1995

On the relationship of the scaled phase space and Skyrme-coherent state treatments of proton antiproton annihilation at rest

We discuss pion multiplicities and single pion momentum spectra from proton antiproton annihilation at rest. Both the scaled phase space model and the Skyrme-coherent state approach describe these observables well. In the coherent state approach the puzzling size of the scale parameter relating the phase space integrals for different multiplicities is replaced by a well defined weight function. The strength of this function is determined by the intensity of the classical pion field and its spatial extent is of order 1 fm.

nucl-th↗