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Search Results: 1 - 10 of 335953 matches for " Ye. S. Golubeva "
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Omega- and Phi-meson production in pn -> dV reactions and OZI-rule violation
L. A. Kondratyuk,Ye. S. Golubeva,M. Buescher
Physics , 1998,
Abstract: We investigate the reactions p n -> d omega and p n -> d phi close to threshold and at higher energies. Near threshold we calculate the S-wave amplitudes within the framework of the two-step model which is described by a triangle graph with pi-mesons in the intermediate state and find a ratio of the S-wave amplitudes squared of R =|A(phi)|^2/|A(omega)|^2 = (4-8) x 10^{-3}. Any significant enhancement of the experimental value of R(phi/omega) over this prediction can be interpreted as a possible contribution of the intrinsic s - anti s component in the nucleon-wave function. We present arguments that there is a strong resonance effect in the omega N channel close to threshold. At higher energies we calculate the differential cross sections of the reactions p n -> d omega, p n -> d phi and the ratio of the phi/omega yields within the framework of the quark-gluon string model. An irregular behavior of the phi/omega-ratio is found at s <= 12 GeV^2 due to the interference of the t- and u-channel contributions.
Medium effects in the production and decay of vector mesons in pion-nucleus reactions
Ye. S. Golubeva,L. A. Kondratyuk,W. Cassing
Physics , 1997, DOI: 10.1016/S0375-9474(97)00471-5
Abstract: The $\omega$-, $\rho$- and $\phi$-resonance production and their dileptonic decay in $\pi^- A$ reactions at 1.1 - 1.7 GeV/c are calculated within the intranuclear cascade (INC) approach. The invariant mass distribution of the dilepton pair for each resonance can be decomposed in two components which correspond to their decay 'inside' the target nucleus and in the vacuum, respectively. The first components are strongly distorted by the nuclear medium due to resonance-nucleon scattering and a possible mass shift at finite baryon density. These medium modifications are compared to background sources in the dilepton spectrum from $\pi N$ bremsstrahlung as well as the Dalitz decays of $\omega$ and $\eta$ mesons produced in the reaction. Detailed predictions for $\pi^- Pb$ reactions at 1.3 and 1.7 GeV/c are made within several momentum bins for the lepton pair.
Interactions of charmed mesons with nucleons in the $\bar p d$ reaction
W. Cassing,Ye. S. Golubeva,L. A. Kondratyuk
Physics , 1999, DOI: 10.1007/PL00013607
Abstract: We study the possibility to measure the elastic $\Phi N$ ($\Phi \equiv J/\psi, \psi(2S), \psi(3770),\chi_{2c}$) scattering cross section in the reaction $\bar p{+}d{\to}\Phi{+}n_{sp}$ and the elastic $D(\bar D) N$ scattering cross section in the reaction $\bar p{+}d \to D^- D^0 p_{sp}$. Our studies indicate that the elastic scattering cross sections can be determined for $\Phi$ momenta about 4-6 GeV/c and $D/ \bar D$ momenta 2 -- 5 GeV/c by selecting events with $p_t \geq 0.4$ GeV/c for $\Phi$'s and $p_t(p_{sp})\geq$ 0.5 GeV/c for $D/\bar D$-meson production.
Probing the interactions of charmed mesons with nuclei in $\bar p$ induced reactions
Ye. S. Golubeva,W. Cassing,L. A. Kondratyuk
Physics , 2002,
Abstract: 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 $\Psi(3770), \Psi(4040)$ and $\Psi(4160)$ 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.
Medium effects in the production and decay of $ω$- and $ρ$-resonances in pion-nucleus interactions
W. Cassing,Ye. S. Golubeva,A. S. Iljinov,L. A. Kondratyuk
Physics , 1996, DOI: 10.1016/S0370-2693(97)00137-8
Abstract: The $\omega$- and $\rho$-resonance production and their dileptonic decay in $\pi^- A$ reactions at GSI energies are calculated within the intranuclear cascade (INC) approach. The invariant mass distribution of the dilepton pair for each resonance is found to have two components which correspond to the decay of the resonances outside and inside the target nucleus. The latter components are strongly distorted by the nuclear medium due to resonance-nucleon scattering and a possible mass shift at finite baryon density. These medium modifications are compared to background sources in the dilepton spectrum from $\pi N$ bremsstrahlung and the Dalitz decays of $\Delta$'s and $\eta$ mesons produced in the reaction.
Nuclear transparency in quasielastic A(e,e'p): intranuclear cascade versus eikonal approximation
Ye. S. Golubeva,L. A. Kondratyuk,A. Bianconi,S. Boffi,M. Radici
Physics , 1997, DOI: 10.1103/PhysRevC.57.2618
Abstract: The problem of nuclear propagation through the nuclear medium in quasielastic A(e,e'p) reactions is discussed in the kinematic range 1
Density dependence of resonance broadening and shadowing effects in nuclear photoabsorption
S. Boffi,Ye. Golubeva,L. A. Kondratyuk,M. I. Krivoruchenko,E. Perazzi
Physics , 1996,
Abstract: Medium effects as a function of the mass number $A$ are studied in the total photonuclear cross section from the $\Delta$-resonance region up to the region where shadowing effects are known to exist. A consistent picture is obtained by simply assuming a density dependence of the different mechanisms of resonance broadening and shadowing. The $\Delta$-mass shift is found to increase with $A$.
In-medium spectral functions of charmonia studied by $\bar p + A$ reactions
Ye. S. Golubeva,E. L. Bratkovskaya,W. Cassing,L. A. Kondratyuk
Physics , 2002,
Abstract: 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 $\Psi(2S)$ and $\Psi(3770)$ 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 $\Psi(2S)$ and $\Psi(3770)$. However, a 'suppression' of low mass dileptons from the $\Psi(3770)$ might be seen experimentally as well as a small broadening of the $\Psi(2S)$ dilepton spectra.
Medium effects in the production and pi0 gamma decay of omega-mesons in pA collisions in the GeV region
Ye. S. Golubeva,L. A. Kondratyuk,M. Buescher,W. Cassing,V. Hejny,H. Stroeher
Physics , 2001, DOI: 10.1007/s100500170088
Abstract: 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.
Studying the $ωN$ elastic and inelastic cross section with nucleons
Ye. S. Golubeva,W. Cassing,L. A. Kondratyuk,A. Sibirtsev,M. Büscher
Physics , 1999, DOI: 10.1007/PL00013602
Abstract: We explore the possibility to measure the elastic and inelastic $\omega N$ cross section in $p{+}d{\to}d{+}\omega{+}p_{sp}$ and $p{+}A$ reactions. Our studies indicate that the elastic scattering cross sections can be determined for $\omega$ momenta above 1 GeV/c in $p{+}d$ reactions by gating on high proton spectator momenta whereas the $\omega N$ absorption cross section down to low relative $\omega$ momenta is most effectively studied in $p{+}A$ reactions at beam energies 2.0--2.7 GeV
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