arXiv subjects

Yu. N. Uzikov

Publications and source records attributed to Yu. N. Uzikov.

48 records · Page 3Linked to original sources

arXiv2001

A Possibility to Observe Short-Range NN Properties in the Deuteron Breakup $pd\to ppn$

Quasi-binary reaction of the deuteron breakup $p+d\to (pp)+n$ with the final proton-proton pair $(pp)$ in the $^1S_0$ state is analyzed at initial energies $0.5 - 2$ GeV in the kinematics of backward elastic pd-scattering $pd\to dp$. On the basis of the main mechanisms of the $pd\to dp$ process, including initial and final state interaction, we show that unpolarized cross section and spin observables of this reaction exhibit important properties of the half-off-shell $pp(^1S_0)$-scattering amplitude, which are relevant to the nucleon-nucleon interaction at short distances.

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arXiv2001

On contribution of three-body forces to $Nd$ interaction at intermediate energies

Available data on large-angle nucleon-deuteron elastic scattering $Nd\to dN$ below the pion threshold give a signal for three-body forces. There is a problem of separation of possible subtle aspects of these forces from off-shell effects in two-nucleon potentials. By considering the main mechanisms of the process, we show qualitatively that in the quasi-binary reaction $N+d\to (NN)+N$ with the final spin singlet NN-pair in the S-state the relative contribution of the 3N forces differs substantially from the elastic channel. It gives a new testing ground for the problem in question.

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arXiv2001

Singlet-to-triplet ratio in the deuteron breakup reaction $pd\to pnp$ at 585 MeV

Available experimental data on the exclusive $pd\to pnp$ reaction at 585 MeV show a narrow peak in the proton-neutron final-state interaction region. It was supposed previously, on the basis of a phenomenological analysis of the shape of this peak, that the final spin-singlet $pn$ state provided about one third of the observed cross section. By comparing the absolute value of the measured cross section with that of $pd$ elastic scattering using the Fäldt-Wilkin extrapolation theorem, it is shown here that the $pd\to pnp$ data can be explained mainly by the spin-triplet final state with a singlet admixture of a few percent. The smallness of the singlet contribution is compatible with existing $pN\to pNπ$ data and the one-pion exchange mechanism of the $pd\to pnp$ reaction.

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arXiv2001

Spin-triplet final-state dominance in the pp -> pn pi+ reaction at 492 MeV

The near-forward cross section for the pp -> pn pi^+ reaction has been measured at 492 MeV by using the large acceptance ANKE magnetic spectrometer placed at an internal target position of the storage ring COSY-Juelich. Protons and pions emitted near zero degrees were detected in coincidence, and those with theta_pi <= 2 degrees and theta_p <= 2.5degrees were subjected to detailed analysis. Under these conditions, the excitation energy in the np system was below 3 MeV over the measured momentum range. This is the region of the np final-state-interaction peak, which was measured with a resolution of a fraction of an MeV. The shape of the peak allows one to conclude that the fraction of final spin-singlet np pairs is below about 10%. By using the results of scattering theory, this limit is confirmed through a comparison with the cross section for pp -> d pi^+. The smallness of the singlet contribution is consistent with trends seen in lower energy data.

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arXiv2000

Deuteron Breakup pd\to pnp in Specific Kinematics and Short-Range NN-Interaction

Deuteron breakup processes $p+d\to (NN)_{s,t}+N$ are studied in the kinematics of backward elastic pd-scattering at law relative momenta of the NN-pair $k\sim 0-50 MeV/c$ for initial energies $T_0=0.5-2.5 GeV$ in the framework of the known mechanisms of the $pd\to dp$ process including rescatterings in the initial and final states. A considerable suppression of the $Δ-$ and $N^*-$ isobar excitation mechanisms is found for the production of the singlet $(NN)_s$-pair. As a result, one nucleon exchange mechanism can be identified in the cross section and polarization observables by the node of the half-off-shell NN$(~^1S_0)$-scattering amplitude, $t(q,k)$, at $q\sim 0.4 $ GeV/c.

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arXiv1998

Structure of the ^3He in Backward Elastic p ^3He-Scattering

Backward elastic $p ^3He$-scattering at incident proton kinetic energies $T_p>1$ GeV is investigated in the framework of the np-pair transfer mechanism and triangular diagram of one-pion exchange with a subprocess $pd\to ^3Heπ^0$ using a realistic three-body wave function of the $^3He$ nucleus. It is found that the $np-$pair transfer mechanism dominates owing to a rich high momentum component of the $^3He$ wave function. We show that the experimental cross section of this process is defined mainly by the values of the Faddeev component of the $^3He$ wave function, $ϕ^{23}({\bf q}_{23}, {\bf p}_1)$, at high relative momenta $q_{23}> 0.6 GeV/c$ of the NN-pair in the $^1S_0$-state and at low spectator momenta $p_1\leq 0.1$ GeV/c. The spin-spin correlation parameter is calculated in the framework of the dominating mechanism for the case of polarized target and beam. Rescatterings in the initial and final states are taken into account. Comparison with the $pd\to dp$ process is performed.

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arXiv1998

Backward Elastic p^3He-Scattering and High Momentum components of ^3He Wave Function

It is shown that owing to a dominance of $np-$pair transfer mechanism of backward elastic $p^3He$- scattering for incident proton kinetic energies $T_p>1$ GeV the cross section of this process is defined mainly by the values of the Faddeev component of the wave function of $^3He$ nucleus, $ϕ^{23}({\bf q}_{23}, {\bf p}_1)$, at high relative momenta $q_{23}> 0.6 GeV/c$ of the NN-pair in the $^1S_0-$ state and at low spectator momenta $p_1\sim 0-0.2$ GeV/c.

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arXiv1998

Role of Deuteron NN^* -components in proceses pd - dp and pd- dN^*

The contribution of nucleon isobar $N^*$ exchanges to backward elastic pd-scattering is calculated on the basis of deuteron 6q-model and found to be negligible in comparison with the neutron exchange. It is shown that the pole amplitude of neutron pickup from the deuteron $nN^*$-component is favoured in the reaction $pd\to dN^*$ for backward going $N^*(1440)$ and $N^*(1710)$ at kinetic energy of incident proton of 1.5--2 GeV whereas the triangular diagram with subprocess $pp\to dπ^+$ related to the usual $pn-$component of deuteron is considerable suppressed.

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arXiv1998

Backward Elastic p3He Scattering at Energies 1 - 2 GeV

The two-body transfer amplitude for the rearrangement process i+(jkl) - j+(ikl) is constructed on the basis of technique of 4-dimensional covariant nonrelativistic graphs. The developed formalism is applied to describing backward elastic $p^3He$ scattering in the energy range 0.5 - 1.7 GeV. Numerical calculations performed using the 5- channel wave function of the $^3He$ nucleus show that the transfer of a noninteracting np- pair dominates and explains satisfactorily the energy and angular dependence of the differential cross section at energies 0.9 - 1.7$ GeV. A weak sensitivity to high momentum components of the $~^3He$ wave function in spite of large momentum transfer as well as a very important role of rescatterings in the initial and final states are established.

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arXiv1998

The $pd\to ^3H_ΛK^+$ reaction cross section

The one- and two-step mechanisms of the $pd\to ^3H_ΛK^+$ reaction in the range of incident proton kinetic energy 1.13-3.0 GeV have been investigated. A remarkable peculiarity of the two-step mechanism which incorporates subprocesses $pp\to dπ^+$ and $π^+n\to K^+Λ$ is the so called velocity matching providing the presence of all intermediate particles nearly to the on-mass-shell. The differential cross section has been calculated using a realistic model for the hypertritium $^3H_Λ$ wave function. The maximum value of the cross section is estimated as $\sim $1nb/sr. The contribution of the one-step mechanism with the elementary process $pN\to NKΛ$ into the cross section has been found to be two - three orders of magnitude smaller in comparison with the two-step mechanism.

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arXiv1997

Deuteron Disintegration by Protons in Kinematics of Quasi-Elastic Backward pd-Scattering

The deuteron break-up exclusive reaction $p+d \to N(180^{\circ}) + (NN)(0^{\circ})$ is considered in the framework of the one-nucleon-exchange mechanism at the incident proton kinetic energy 0.2--2 GeV and the relative energy of nucleons in the forward going final NN-pair $E_{NN}=0$--20 MeV, that is close to the kinematical conditions of the planned experiment at COSY. The off-energy-shell effects resulting, in particular, in the node of the half-off-shell $^1S_0$-state partial NN-scattering amplitude and the role of higher partial waves in the subprocess $pN\to pN$ are analysed and found to be very important, especially for the reaction $p+d \to n(180^{\circ}) + (pp)(0^{\circ})$. The accuracy of some approximate relations between the cross sections of elastic $pd$-scattering and deuteron break-up is examined in the framework of the mechanism in question.

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arXiv1995

Two step mechanism of $η, η', ω, ϕ$ meson prodction in $pD \to ^3He $ reaction$

The differential cross sections of $pD\to ^3He X$ reactions, where $X=η, \ η'\ ,ω, \ ϕ$, are calculated on the basis of a two-step mechanism involving the subprocesses $pp\to dπ^+$ and $π^+n\to Xp $. It is shown that this model describes well the form of energy dependence of available experimental cross sections at the final c.m.s. momentum $p^*$=0.4-1$ GeV/c$ for the $η$ and at $p^*=0-0.5$ GeV/c for the $ω$ meson as well as the ratios $R(η'/η) $ and $R(ϕ/ω)$. The absolute value of the cross section is underestimated by an overall normalization factor of about 3 for $η, \ η'$ and by nearly one order of magnitude for $ω$ and $ϕ$. The spin-spin correlations are predicted for the reaction ${\vec D}{\vec p}\to ^3He X$ in the forward-backward approximations for the elementary amplitudes.

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