arXiv subjects

Yu. T. Kiselev

Publications and source records attributed to Yu. T. Kiselev.

15 recordsLinked to original sources

arXiv2019

Pion-induced production of $Λ(1520)$ hyperons on nuclei near threshold

We study the pion-induced inclusive $Λ(1520)$ hyperon production from nuclei near threshold within a nuclear spectral function approach accounting for incoherent primary $π^-$ meson--proton ${π^-}p \to K^0Λ(1520)$ production processes. We calculate the absolute differential and total cross sections for the production of $Λ(1520)$ hyperons off carbon and tungsten nuclei at laboratory angles of 0$^{\circ}$--10$^{\circ}$, 10$^{\circ}$--45$^{\circ}$ and 45$^{\circ}$--85$^{\circ}$ by $π^-$ mesons with momentum of 1.7 GeV/c as well as their relative (transparency ratio) differential and integral yields from these nuclei within four scenarios for their total in-medium width. We demonstrate that these absolute observables, contrary to the relative ones, reveal some sensitivity to the $Λ(1520)$ in-medium width. Therefore, their measurement in a dedicated experiment at the GSI pion beam facility will allow to shed light on this width.

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arXiv2018

The role of hidden-charm pentaquark resonance $P^+_c(4450)$ in $J/ψ$ photoproduction on nuclei near threshold

We study the $J/ψ$ photoproduction from nuclei at near-threshold incident photon energies of 5--11 GeV within the nuclear spectral function approach by considering incoherent direct ($γN \to {J/ψ}N$) and two-step ($γp \to P^+_c(4450)$, $P^+_c(4450) \to {J/ψ}p$) photon--nucleon charmonium creation processes. We calculate the absolute and relative excitation functions within the different scenarios for in-medium modification of the directly photoproduced $J/ψ$ mesons. We show that the overall subthreshold $J/ψ$ production in $γA$ reactions reveals some sensitivity to adopted in-medium modification scenarios for $J/ψ$ mesons only if branching ratio $Br[P^+_c(4450) \to {J/ψ}p]$ $\sim$ 1% and less. Our studies also demonstrate that the presence of the $P^+_c(4450)$ resonance in $J/ψ$ photoproduction produces above threshold additional enhancements in the behavior of the total $J/ψ$ creation cross section on nuclei, which could be also studied in the future JLab experiments at the upgraded up to 12 GeV CEBAF facility to provide further evidence for its existence.

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arXiv2017

Medium effects in $ΛK^+$ pair production by 2.83 GeV protons on nuclei

We study $ΛK^+$ pair production in the interaction of protons of 2.83 GeV kinetic energy with C, Cu, Ag, and Au target nuclei in the framework of the nuclear spectral function approach for incoherent primary proton--nucleon and secondary pion--nucleon production processes, and processes associated with the creation of intermediate ${Σ^0}K^+$ pairs. The approach accounts for the initial proton and final $Λ$ hyperon absorption, final $K^+$ meson distortion in nuclei, target nucleon binding, and Fermi motion, as well as nuclear mean-field potential effects on these processes. We calculate the $Λ$ momentum dependence of the absolute $ΛK^+$ yield from the target nuclei considered, in the kinematical conditions of the ANKE experiment, performed at COSY, within the different scenarios for the $Λ$-nucleus effective scalar potential. We show that the above observable is appreciably sensitive to this potential in the low-momentum region. Therefore, direct comparison of the results of our calculations with the data from the ANKE-at-COSY experiment can help to determine the above potential at finite momenta. We also demonstrate that the two-step pion--nucleon production channels dominate in the low-momentum $ΛK^+$ production in the chosen kinematics and, therefore, they have to be taken into account in the analysis of these data.

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arXiv2015

Kaon pair production in proton-nucleus collisions at 2.83 GeV kinetic energy

The production of non-phi K+K- pairs by protons of 2.83 GeV kinetic energy on C, Cu, Ag, and Au targets has been investigated using the COSY-ANKE magnetic spectrometer. The K- momentum dependence of the differential cross section has been measured at small angles over the 0.2--0.9 GeV/c range. The comparison of the data with detailed model calculations indicates an attractive K- -nucleus potential of about -60 MeV at normal nuclear matter density at a mean momentum of 0.5 GeV/c. However, this approach has difficulty in reproducing the smallness of the observed cross sections at low K- momenta.

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arXiv2015

Near-threshold $J/ψ$ photoproduction off nuclei

We study the $J/ψ$ photoproduction from nuclei near the kinematic threshold within the first collision model, based on the nuclear spectral function, for incoherent primary photon--nucleon charmonium creation processes. The model takes into account the final $J/ψ$ absorption, target nucleon binding and Fermi motion, the formation length of $J/ψ$ mesons as well as the effect of their nuclear mean-field potential on these processes. We calculate the A dependences of the absolute and relative (transparency ratio) charmonium yields as well as its absolute and relative excitation functions within the different scenarios for the $J/ψN$ absorption cross section, for the $J/ψ$ formation length and for $J/ψ$ in-medium modification. We demonstrate that the studied observables, on the one hand, are not practically affected by the charmonium formation length and mass shift effects and, on the other hand, they are appreciably sensitive to the genuine $J/ψN$ absorption cross section at above threshold beam energies, which means that these observables can be useful to help determine the $J/ψN$ absorption cross section from the comparison of the results of our calculations with the future data from the experiments in the Hall C at the upgraded up to 12 GeV CEBAF facility. We also show that the absolute and relative excitation functions for $J/ψ$ subthreshold production in $γA$ reactions reveal some sensitivity to adopted in-medium modification scenarios for $J/ψ$ mesons. Therefore, such observables, measured in the subthreshold energy domain, may be an important tool to get valuable information on the charmonium in-medium properties in cold nuclear matter.

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arXiv2015

Non-resonant kaon pair production and medium effects in proton-nucleus collisions

We study the non-resonant (non-$ϕ$) production of $K^+K^-$ pairs by protons of 2.83 GeV kinetic energy on C, Cu, Ag, and Au targets within the collision model, based on the nuclear spectral function, for incoherent primary proton--nucleon and secondary pion--nucleon creation processes. The model takes into account the initial proton and final kaon absorption, target nucleon binding and Fermi motion as well as nuclear mean-field potential effects on these processes. We calculate the antikaon momentum dependences of the exclusive absolute and relative $K^+K^-$ pair yields in the acceptance window of the ANKE magnetic spectrometer, used in a recent experiment performed at COSY, within the different scenarios for the antikaon-nucleus optical potential. We demonstrate that the above observables are strongly sensitive to this potential. Therefore, they can be useful to help determine the $K^-$ optical potential from the direct comparison of the results of our calculations with the data from the respective ANKE-at-COSY experiment. We also show that the pion--nucleon production channels dominate in the low-momentum $K^-$, $K^+$ production in the considered kinematics and, hence, they have to be accounted for in the analysis of these data.

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arXiv2014

Near-threshold J/Psi production in proton-nucleus collisions

We study the J/Psi production from nuclei near the kinematic threshold within the collision model, based on the nuclear spectral function, for incoherent primary proton-nucleon charmonium creation processes. The model takes into account the initial proton and final J/Psi absorption, target nucleon binding and Fermi motion, the formation length of J/Psi mesons as well as the effect of their nuclear mean-field potential on these processes. We calculate the A dependences of the absolute and relative (transparency ratio) charmonium yields as well as its excitation function within the different scenarios for the J/PsiN absorption cross section, for the J/Psi formation length and for J/Psi in-medium modification. We demonstrate that the former observables, on the one hand, are not practically affected by the charmonium formation length effects and, on the other hand, they are appreciably sensitive to the genuine J/PsiN absorption cross section at beam energies of interest, which means that these observables can be useful to help determine the above cross section from the comparison of the results of our calculations with the future data from the CBM experiment at FAIR-the upcoming accelerator facility at GSI-Darmstadt, Germany. We also show that the excitation function for J/Psi subthreshold production in pA reactions reveals some sensitivity to adopted its in-medium modification scenarios. Therefore, such observable may be an important tool to get valuable information on the charmonium in-medium properties.

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arXiv2012

Probing of compact baryonic configurations in nuclei in $A(p,{\bar p})X$ reactions and antiproton formation length in nuclear matter

Inclusive cross sections $σ^A=Ed^3{σ(X,P_t^2)/d^3p}$ of antiproton and negative pion production on Be, Al, Cu and Ta targets hit by 10 GeV protons were measured at the laboratory angles of 10.5$^{\circ}$ and 59$^{\circ}$. Antiproton cross sections were obtained in both kinematically allowed and kinematically forbidden regions for antiproton production on a free nucleon. The antiproton cross section ratio as a function of the longitudinal variable $X$ exhibits three separate plateaus which gives evidence for the existence of compact baryon configurations in nuclei-small-distance scaled objects of nuclear structure. Comparability of the measured cross section ratios with those obtained in the inclusive electron scattering off nuclei suggests a weak antiproton absorption in nuclei. Observed behavior of the cross section ratios is interpreted in the framework of a model considering the hadron production as a fragmentation of quarks (antiquarks) into hadrons. It has been established that the antiproton formation length in nuclear matter can reach the magnitude of 4.5 fm.

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arXiv2012

The production of K+K- pairs in proton-proton collisions at 2.83 GeV

Differential and total cross sections for the pp -> ppK+K- reaction have been measured at a proton beam energy of 2.83 GeV using the COSY-ANKE magnetic spectrometer. Detailed model descriptions fitted to a variety of one-dimensional distributions permit the separation of the pp -> pp phi cross section from that of non-phi production. The differential spectra show that higher partial waves represent the majority of the pp -> pp phi total cross section at an excess energy of 76 MeV, whose energy dependence would then seem to require some s-wave phi-p enhancement near threshold. The non-phi data can be described in terms of the combined effects of two-body final state interactions using the same effective scattering parameters determined from lower energy data.

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arXiv2012

Momentum dependence of the phi-meson nuclear transparency

The production of phi mesons in proton collisions with C, Cu, Ag, and Au targets has been studied via the phi -> K+K- decay at an incident beam energy of 2.83 GeV using the ANKE detector system at COSY. For the first time, the momentum dependence of the nuclear transparency ratio, the in-medium phi width, and the differential cross section for phi meson production at forward angles have been determined for these targets over the momentum range of 0.6 - 1.6 GeV/c. There are indications of a significant momentum dependence in the value of the extracted phi width, which corresponds to an effective phi-N absorption cross section in the range of 14 - 21 mb.

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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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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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arXiv2003

New method of studying slow strange meson properties in nuclear matter

We suggest the new experimental method to explore the properties of slow strange mesons at normal nuclear matter density. We show that the $K^{+}$ and $K^{-}$ mesons with extremely small momenta relative to the surrounding medium rest frame can be produced in nucleus-nucleon collisions and their production cross sections are experimentally measurable. The experiments on study of the momentum dependence of meson-nuclear potentials are discussed.

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arXiv1999

The program of research at hadronic beams of ITEP accelerator. (Collection of experimental proposals)

This is a collection of proposals of experiments at hadronic beams of 10 GeV accelerator, situated at the Institute of Theoretical and Experimental Physics (Moscow, Russia). The proposals were presented by the leaders of several ITEP experimental groups and include selected problems of hadron-hadron (exotic states, scalar mesons, electomagnetic form factors, polarization phenomena etc.) and hadron-nucleon interactions (flucton and nuclear matter properties, hadron properties inside nuclei, interactions at small distances). Most of proposals are united by an idea of a common magnetic spectrometer with LiH(D) and polarized targets, wich could be built on the base of an existing 3m magnet. Some of them also refer to the intrinsic accelerator beam and to the new ion ring.

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