arXiv subjects

E. Ya. Paryev

Publications and source records attributed to E. Ya. Paryev.

47 records · Page 3Linked to original sources

arXiv2011

Photoproduction of $Λ(1520)$ hyperons from nuclei near the threshold

We present a theoretical investigation of $Λ(1520)$ attenuation in $γA$ reactions near the threshold. It is performed in the framework of a collision model based on the nuclear spectral function. The model accounts for both primary photon-nucleon $γN \to KΛ(1520)$ and secondary pion-nucleon $πN \to KΛ(1520)$ production processes. We calculate the target mass and momentum dependences of the forward $Λ(1520)$ hyperon production from nuclei at photon energy of 2 GeV as well as for two options for its in-medium width. We find that the considered dependences are markedly sensitive to this width. Our studies also demonstrate that the secondary channel $πN \to KΛ(1520)$ plays a substantial role in the intermediate momentum $Λ(1520)$ photoproduction on nuclei in the chosen kinematics and, hence, is to be taken into account in the analysis of $Λ(1520)$ hyperon photoproduction from nuclei with the aim to get information on its width in the matter.

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arXiv2010

Testing the Lambda(1520) hyperon in-medium width in near-threshold proton-nucleus reactions

In the framework of the nuclear spectral function approach for incoherent primary proton-nucleon and secondary pion-nucleon production processes we study the inclusive Lambda(1520) hyperon production in the interaction of 2.83 GeV protons with nuclei. In particular, the A and momentum dependences of the absolute and relative Lambda(1520) hyperon yields are investigated in two scenarios for its in-medium width. Our model calculations show that the pion-nucleon production channel contributes distinctly to the "low-momentum" Lambda(1520) creation both in light and heavy nuclei in the chosen kinematics and, hence, has to be taken into consideration on close examination of the dependences of the Lambda(1520) hyperon yields on the target mass number with the aim of getting information on its width in the medium. They also demonstrate that both the A dependence of the relative Lambda(1520) hyperon production cross section and momentum dependence of the absolute Lambda(1520) hyperon yield at incident energy of interest are appreciably sensitive to the Lambda(1520) in-medium width, which means that these observables may be an important tool to determine the above width.

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arXiv2010

Measurement of the in-medium phi-meson width in proton-nucleus collisions

The production of phi mesons in the collisions of 2.83 GeV protons with C, Cu, Ag, and Au at forward angles has been measured via the phi -> K+K- decay using the COSY-ANKE magnetic spectrometer. The phi meson production cross section follows a target mass dependence of A^0.56+/-0.02 in the momentum region of 0.6-1.6 GeV/c. The comparison of the data with model calculations suggests that the in-medium phi width is about an order of magnitude larger than its free value.

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arXiv2009

Subthreshold and near-threshold kaon and antikaon production in proton-nucleus reactions

The differential production cross sections of K^+ and K^- mesons have been measured at the ITEP proton synchrotron in p+Be, p+Cu collisions under lab angle of 10.5^0, respectively, at 1.7 and 2.25, 2.4 GeV beam energies. A detailed comparison of these data with the results of calculations within an appropriate folding model for incoherent primary proton-nucleon, secondary pion-nucleon kaon and antikaon production processes and processes associated with the creation of antikaons via the decay of intermediate phi mesons is given. We show that the strangeness exchange process YN->NNK^- gives a small contribution to the antikaon yield in the kinematics of the performed experiment. We argue that in the case when antikaon production processes are dominated by the channels with KK^- in the final state, the cross sections of the corresponding reactions are weakly influenced by the in-medium kaon and antikaon mean fields.

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arXiv2008

Near-threshold $ϕ$ meson production in proton-nucleus reactions and $ϕ$ width in finite nuclei

In the framework of the nuclear spectral function approach for incoherent primary proton-nucleon and secondary pion-nucleon production processes we study the inclusive $ϕ$ meson production in the interaction of 2.83 GeV protons with nuclei. In particular, the A- and momentum-dependences of the absolute and relative phi meson yields are investigated within the different scenarios for its in-medium width. Our model calculations take into account the acceptance window of the ANKE facility used in a recent experiment performed at COSY. They show that the pion-nucleon production channel contributes distinctly to the "low-momentum" $ϕ$ creation in heavy nuclei in the chosen kinematics and, hence, has to be taken into consideration on close examination of the dependences of the phi meson yields on the target mass number with the aim to get information on its width in the medium.

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arXiv2008

Absorption of phi mesons in near-threshold proton-nucleus reactions

In the framework of the nuclear spectral function approach for incoherent primary proton--nucleon and secondary pion--nucleon production processes we study the inclusive $ϕ$ meson production in the interaction of 2.83 GeV protons with nuclei. In particular, the A-dependences of the absolute and relative $ϕ$ meson yields are investigated within the different scenarios for its in-medium width as well as for the cross section ratio $σ_{pn \to pnϕ}/{σ_{pp \to ppϕ}}$. Our model calculations take into account the acceptance window of the ANKE facility used in a recent experiment performed at COSY. They show that the pion--nucleon production channel contributes distinctly to the $ϕ$ creation in heavy nuclei in the chosen kinematics and, hence, has to be taken into consideration on close examination of the dependences of the phi meson yields on the target mass number with the aim to get information on its width in the medium. They also demonstrate that the experimentally unknown ratio $σ_{pn \to pnϕ}/{σ_{pp \to ppϕ}}$ has a weak effect on the A-dependence of the relative $ϕ$ meson production cross section at incident energy of present interest, whereas it is found to be appreciably sensitive to the phi in-medium width, which means that this relative observable can indeed be useful to help determine the above width from the direct comparison the results of our calculations with the future data from the respective ANKE-at-COSY experiment.

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arXiv2006

Antikaon angular distributions in the reaction $γd \to K^-Θ^+p \to K^-K^+np$ near the threshold and the parity of the $Θ^+$ pentaquark

Within spectator model we study the reaction $γd \to K^-Θ^+p \to K^-K^+np$ in the threshold energy region. We present the predictions for the exclusive and inclusive antikaon angular distributions in the laboratory system for this reaction calculated for two possible parity states of the $Θ^+$ resonance at 1.5 and 1.75 GeV beam energies with and without imposing the relevant kinematical cuts on those parts of the sampled phase space where contribution from the main background sources associated with the $ϕ(1020)$, $Λ(1520)$ production as well as with the $K^-p$--rescattering in the final state, is expected to be dominant. We show that under chosen kinematics these distributions are sensitive to the $Θ^+$ parity and, therefore, can be used as a filter for the determination of its parity.

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arXiv2006

Antiproton Absorption in Nuclei

We present the analysis of experimental data on forward antiproton production on nuclei. The calculations are done in the framework of a folding model which takes properly into account both incoherent direct proton-nucleon and cascade pion-nucleon antiproton production processes as well as internal nucleon momentum distribution. The effective antiproton-nucleon cross section in nuclear matter and the imaginary part of the antiproton nuclear optical potential are estimated to be 25-45 mb and -(38-56) MeV at normal nuclear matter density, respectively. The results of the performed analysis evidence for the decreasing of antiproton absorption in the nuclear medium.

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arXiv1997

Subthreshold K+ Meson Production in Proton-Nucleus Reactions

The inclusive K+ mesons production in proton-nucleus collisions in the near threshold and subthreshold energy regimes is analyzed with respect to the one-step (pN->K+YN, Y=Lambda,Sigma) and the two-step (pN->NNpi, NN2pi; piN->K+Y) incoherent production processes on the basis of an appropriate new folding model, which takes properly into account the struck target nucleon removal energy and momentum distribution (nucleon spectral function), extracted from recent quasielastic electron scattering experiments and from many-body calculations with realistic models of the NN interaction. Comparison of the model calculations of the K+ double differential cross sections for the reaction p+C at 1.2, 1.5 and 2.5 GeV beam energies with the existing experimental data from the SATURNE experiment is given, illustrating both the relative role of the primary and secondary production channels at considered incident energies and those features of the cross sections which are sensitive to the high momentum and high removal energy part of the nucleon spectral function that is governed by nucleon-nucleon short-range and tensor correlations. In--medium modifications of the available for pion and hyperon production invariant energies squared due to the respective optical potentials are needed to account for the experimental data on K+ production in the energy region under consideration.

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arXiv1995

Production of $K^-$-mesons in proton-proton and proton-nucleus interactions at various energies

The experimental data on the production of $K^-$-mesons in pp-collisions are analyzed and a method of the unified description of these data in a broad energy range for primary protons is proposed. The $K^-$-mesons production in pA-collisions is considered. The simple formulas for inclusive cross sections of the $K^-$ production in these collisions are given. The results of the calculations by these formulas are compared with the available experimental data.

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arXiv1995

Subthreshold $K^+$ Production on Nuclei by $π^+$ Mesons

The inclusive $K^+$ mesons production in $π^+$--nucleus reactions in the subthreshold energy regime is analyzed with respect to the one--step ($π^+n\to K^+Λ$) and the two--step ($π^+n\to ηp_1,~ ηp_2\to K^+Λ$) incoherent production processes on the basis of an appropriate folding model, which allows one to take into account the various forms of an internal nucleon momentum distribution as well as on-- and off--shell propagation of the struck target nucleon. Contrary to proton--nucleus reactions primary reaction channel is found to be significant practically at all considered energies. Detailed predictions for the $K^+$ total and invariant differential cross sections from \piC-- and \piPb--collisions at subthreshold energies are provided.

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