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L. A. Kondratyuk

Publications and source records attributed to L. A. Kondratyuk.

At least 19 recordsLinked to original sources
arXiv2009

Measurement of the isospin-filtering dd -> 4He K+ K- reaction at Q=39 MeV

The total cross section for the dd -> 4He K+ K- reaction has been measured at a beam momentum of 3.7 GeV/c, corresponding to an excess energy of 39 MeV, which is the maximum possible at the Cooler Synchrotron COSY-Jülich. A deuterium cluster-jet target and the ANKE forward magnetic spectrometer, placed inside the storage ring, have been employed in this investigation. We find a total cross section of sigma(tot) < 14 pb, which brings into question the viability of investigating the dd -> 4He a0(980) reaction as a means of studying isospin violation.

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arXiv2007

K^- ^3He and K^+K^- interactions in the pd -> ^3He K^+K^- reaction

We investigate the K^- ^3He and K^+ K^- interactions in the reaction pd -> ^3He K^+ K^- near threshold and compare our model calculations with data from the MOMO experiment at COSY-Juelich. A large attractive effective K^- p amplitude would give a significant K^- ^3He final-state interaction effect which is not supported by the experimental data. We also estimate upper limits for the a_0(980) and f_0(980) contributions to the produced K^+ K^- pairs.

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arXiv2005

Interaction of K^- mesons with light nuclei

We calculate the scattering lenths A(K-,3He) and A(K-,4He) using the multiple scattering approach and different parameters sets for the elementary a(Kbar,N). Within the zero-range approximation, we find for both systems loosely bound states with binding energies in the range 2-7 MeV and widths 11-18 MeV. It is demonstrated that the existence of deeply bound K-,4He states, which have been predicted in literature, can be tested by measuring the reaction dd -> 4He K-K+ at COSY.

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arXiv2005

Comparative Regge analysis of $Λ, Σ^0, Λ(1520)$ and $Θ^+$ production in $γp$, $πp$ and $pp$ reactions

Using the Quark-Gluon Strings Model -- combined with Regge phenomenology -- we perform a comparative analysis of $Λ$, $Σ^0$, $Λ(1520)$ and $Θ^+$ production in binary reactions induced by photon, pion and proton beams on the nucleon. We find that the existing experimental data on the $γp \to K^+ Λ$ differential and total cross sections can be described very well by the model for photon energies $1 - 16$ GeV and $-t < 2$ GeV$^2$ assuming a dominant contribution of the $K^*$ Regge trajectory. Moreover, using the same parameters we also reproduce the total $γp \to K^+ Σ^0$ and $γp \to K^+ Λ(1520)$ cross sections suggesting a 'universality' of the Regge model. In order to check the consistency of the approach we evaluate the differential and total cross sections for the reaction $π^- p \to K^0 Λ$ which is also found to be dominated by the $K^*$ Regge trajectory. Using the apparent 'universality' of the Regge model we extend our scheme to the analysis of the binary reactions $γp \to \bar{K}^0 Θ^+$, $π^- p \to K^- Θ^+$ and $pp \to Σ^+ Θ^+$ as well as the exclusive and inclusive $Θ^+$ production in the reactions $pp \to p \bar{K}^0 Θ^+$ and $pp \to Θ^+ X$. Our detailed studies demonstrate that $Θ^+$ production does not follow the 'universality' principle thus suggesting an essentially different internal structure of the exotic baryon relative to conventional hyperons or hyperon resonances.

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arXiv2005

The K^- αscattering length and the reaction dd \to αK^+ K^-

We present predictions for the the K^- αscattering length obtained within the framework of the multiple scattering approach. Evaluating the pole position of the K^- αscattering amplitude within the zero range approximation, we find a loosely bound K^- αstate with a binding energy of E_R = -2 ... -7 MeV and a width Γ_R = 11 ... 18 MeV. We propose to measure the K^- αscattering length through the final state interaction between the αand K^- meson produced in the reaction dd \to αK^+ K^-. It is found that the K^-αinvariant mass distribution from this reaction at energies near the threshold provides a new tool to determine the s-wave K^- αscattering length.

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arXiv2005

a0+(980)-resonance production in the reaction pp -> dpi+eta close to the K(bar(K)) threshold

The reaction pp -> dpi+eta has been measured at a beam energy of T=2.65 GeV (p=3.46 GeV/c) using the ANKE spectrometer at COSY-Juelich. The missing mass distribution of the detected dpi+ pairs exhibits a peak around the eta mass on top of a strong background of multi-pion pp -> dpi+(n(pi)) events. The differential cross section d^4(sigma)/d(Omega_d)d(Omega_pi+)d(p_d)d(p_pi+) for the reaction pp -> dpi+eta has been determined model independently for two regions of phase space. Employing a dynamical model for the a0+ production allows one then to deduce a total cross section of sigma(pp -> da0+ -> dpi+eta)=(1.1 +/- 0.3_(stat) +/- 0.7_(syst)) microbarn for the production of pi+eta via the scalar a0+(980) resonance and sigma(pp -> dpi+eta) = (3.5 +/- 0.3_(stat) +/- 1.0_(syst)) microbarn for the non-resonant production. Using the same model as for the interpretation of recent results from ANKE for the reaction pp -> dK+(bar(K0)), the ratio of the total cross sections is sigma(pp -> d(K+(bar(K0)))_(L=0))/sigma(pp -> da0+ -> dpi+eta) = 0.029 +/- 0.008_(stat) +/- 0.009_(syst), which is in agreement with branching ratios in the literature.

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arXiv2004

Determination of the \bar K^0 d scattering length from the reaction pp \to d \bar K^0 K^+

The real and imaginary parts of the \bar K^0 d scattering length are extracted from the \bar K^0 d mass spectrum obtained from the reaction pp \to d \bar K^0 K^+ measured recently at the Cooler Synchrotron COSY at Jülich. We extract a new limit on the K^- d scattering length, namely Im a \le 1.3 fm and |Re a| \le 1.3 fm. The limit for the imaginary part of the K^- d scattering length is supported by data on the total K^- d cross sections.

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arXiv2004

Near-threshold production of a0(980) mesons in the reaction pp -> d K^+ \bar{K}^0

Using an effective Lagrangian approach as well as the Quark-Gluon Strings Model we analyze near-threshold production of a0(980)-mesons in the reaction NN -> d K \bar{K} as well as the background of non-resonant K\bar{K}-pair production. We argue that the reaction pp -> d K^+ \bar{K}^0 at an energy release Q<=100 MeV is dominated by the intermediate production of the a0(980)-resonance. At larger energies the non-resonant K^+\bar{K}^0-pair production - where the kaons are produced in a relative P-wave - becomes important. Then effects of final-state interactions are evaluated in a unitarized scattering-length approach and found to be in the order of a 20% suppression close to threshold. Thus in present experiments at the Cooler Synchrotron COSY-Jülich for Q<=107 MeV the a_0^+ signal can reliably be separated from the non-resonant K^+\bar{K^0} background.

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arXiv2003

Forward-backward angle asymmetry and polarization observables in high-energy deuteron photodisintegration

Deuteron two-body photodisintegration is analysed within the framework of the Quark-Gluon Strings Model. It is found that the forward-backward angle asymmetry predicted by the model is confirmed by the recent data at different photon energies from Jlab. New calculations for polarization observables, the cross section asymmetry $Σ$ and the polarization transfer $C_{z^{\prime}}$, for photon energies $(1.2\div6)$ GeV are presented and compared with the data available up to 2 GeV.

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arXiv2002

In-medium spectral functions of charmonia studied by $\bar p + A$ reactions

We study the perspectives of resonant charmonium production in $\bar{p} + A$ reactions within the Multiple Scattering Monte Carlo (MSMC) approach. We calculate the production of the resonances $Ψ(2S)$ and $Ψ(3770)$ on various nuclei, their propagation and decay to dileptons and $D+ \bar{D}$ in the medium and vacuum, respectively, employing parametrizations for the $D,\bar{D}$ self energies taken from QCD sum rule studies. The elastic and inelastic interactions of the charmonia and open charm mesons in the medium are taken into account, too. It is found that the $D, \bar{D}$ invariant mass spectra from light and heavy nuclei are not sufficiently sensitive to the in-medium properties of the $Ψ(2S)$ and $Ψ(3770)$. However, a 'suppression' of low mass dileptons from the $Ψ(3770)$ might be seen experimentally as well as a small broadening of the $Ψ(2S)$ dilepton spectra.

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arXiv2002

Exclusive and semi-inclusive strangeness and charm production in $πN$ and $NN$ reactions

Using the Quark-Gluon Strings Model (QGSM) combined with Regge phenomenology we consider the reactions $π^- p \to K^0 Λ$ and $π^- p \to D^- Λ_c^+$ which are dominated by the contributions of the $K^*$ and $D^*$ Regge trajectories, respectively. The spin structure of the amplitudes is described by introducing Reggeized Born terms. It is found that the existing data for the reaction $π^- p \to K^0 Λ$ are in reasonable agreement with the model predictions. To describe the absolute values of the cross sections it is necessary to introduce also suppression factors which can be related to absorption corrections. Furthermore, assuming the SU(4) symmetry to hold for Regge residues and the universality of absorption corrections we calculate the cross section of the reaction $π^- p \to D^- Λ_c^+$. Employing the latter results from $π^- p$ reactions we then estimate the contributions of the pion exchange mechanism to the cross sections of the reactions $NN \to NKΛ$ and $NN \to N\bar D Λ_c$ and compare them with the contributions of the $K$ and $D$ exchanges. We find that the $NN$ reactions are dominated not by pion exchange but by $K$ and $D$ exchanges, respectively. Moreover, assuming the SU(4) symmetry to hold approximately for the coupling constants $g_{ND Λ_c}$ = $g_{NK Λ}$ we analyze also the production of leading $Λ_c$ hyperons in the reaction $NN \to Λ_c X$. It is shown that the non-perturbative mechanism should give an essential contribution to the $Λ_c$ yield for $x \geq 0.5$.

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arXiv2002

Polarization observables in high-energy deuteron photodisintegration within the Quark-Gluon Strings Model

Deuteron two-body photodisintegration is analysed within the framework of the Quark-Gluon Strings Model. The model describes fairly well the recent experimental data from TJNAF in the few GeV region. Angular distributions at different $γ$-energies are presented and the effect of a forward-backward asymmetry is discussed. New results from the QGSM for polarization observables from 1.5 -- 6 GeV are presented and compared with the available data.

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arXiv2002

Production of $a_0$-mesons in pp and pn reactions

We investigate the cross section for the reaction $NN \to NNa_0$ near threshold and at medium energies. An effective Lagrangian approach with one-pion exchange is applied to analyze different contributions to the cross section for different isospin channels. The Reggeon exchange mechanism is also considered. The results are used to calculate the contribution of the $a_0$ meson to the cross sections and invariant $K \bar K$ mass distributions of the reactions $pp\to pn K^+\bar K^0$ and $pp\to pp K^+K^-$. It is found that the experimental observation of $a_0^+$ mesons in the reaction $pp\to pn K^+\bar K^0$ is much more promising than the observation of $a_0^0$ mesons in the reaction $pp\to pp K^+K^-$.

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arXiv2002

Near-threshold production of $a_0(980)$-mesons in $πN$ and NN collisions and $a_0/f_0$-mixing

We consider near-threshold $a_0(980)$-meson production in $πN$ and $NN$ collisions. An effective Lagrangian approach with one-pion exchange is applied to analyze different contributions to the cross section for different isospin channels. The Reggeon exchange mechanism is also evaluated for comparison. The results from $πN$ reactions are used to calculate the contribution of the $a_0$ meson to the cross sections and invariant $K \bar K$ mass distributions of the reactions $pp\to pn K^+\bar K^0$ and $pp\to pp K^+K^-$. It is found that the experimental observation of $a_0^+$ mesons in the reaction $pp\to pn K^+\bar K^0$ is much more promising than the observation of $a_0^0$ mesons in the reaction $pp\to pp K^+K^-$. Effects of isospin violation in the reactions $pN \to d a_0$, $pd \to \mathrm{^3He/^3H} a_0$, and $ dd \to \mathrm{^4He} a_0$, which are induced by $a_0(980)$--$f_0(980)$ mixing, are also analyzed.

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arXiv2002

Probing the interactions of charmed mesons with nuclei in $\bar p$ induced reactions

We study the perspectives of resonant and nonresonant charmed meson production in $\bar{p} + A$ reactions within the Multiple Scattering Monte Carlo (MSMC) approach. We calculate the production of the resonances $Ψ(3770), Ψ(4040)$ and $Ψ(4160)$ on various nuclei, their propagation and decay to $D, \bar{D}, D^*, \bar{D}^*, D_s, \bar{D}_s$ in the medium and vacuum, respectively. The modifications of the open charm vector mesons in the nuclear medium are found to be rather moderate or even small such that dilepton spectroscopy will require an invariant mass resolution of a few MeV. Furthermore, the elastic and inelastic interactions of the open charm mesons in the medium are taken into account, which can be related to $(u,d)$-, $s$- or $c$-quark exchange with nucleons. It is found that by studying the $D/\bar{D}$ ratio for low momenta in the laboratory ($\leq 2-2.2$ GeV/c) as a function of target mass $A$ stringent constraints on the $c$-quark exchange cross section can be obtained. On the other hand, the ratios $D^-_s/D^+_s$ as well as $D/D^-_s$ and $D/D^+_s$ at low momenta as a function of $A$ will permit to fix independently the strength of the $s$-quark exchange reaction in $D^-_s N$ scattering.

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arXiv2001

Medium effects in the production and pi0 gamma decay of omega-mesons in pA collisions in the GeV region

The omega-resonance production and its pi0 gamma decay in p-A reactions close to threshold is considered within the Intranuclear Cascade (INC) Model. The pi0 gamma invariant mass distribution shows two components which correspond to the omega decay 'inside' and 'outside' the nucleus, respectively. The 'inside' component is distorted by medium effects, which introduce a mass shift as well as collisional broadening for the omega-meson and its decaying pion. The relative contribution of the 'inside' component is analyzed in detail for different kinematical conditions and nuclear targets. It is demonstrated that a measurement of the correlation in azimuthal angle between the pi0 and gamma momenta allows to separate events related to the 'inside' omega decay from different sources of background when uncorrelated pi0's and gamma's are produced.

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