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Yu. N. Uzikov

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

At least 37 records · Page 2Linked to original sources
arXiv2011

Antiproton scattering off $^3 He$ and $^4 He$ nuclei at low and intermediate energies

Antiproton scattering off $^3\He$ and $^4\He$ targets is considered at beam energies below 300 MeV within the Glauber-Sitenko approach, utilizing the $\bar N N$ amplitudes of the Jülich model as input. A good agreement with available data on differential $\bar p ^4\He$ cross sections and on $\bar p ^3\He$ and $\pbar ^4\He$ reaction cross sections is obtained. Predictions for polarized total $\bar p ^3$He cross sections are presented, calculated within the single-scattering approximation and including Coulomb-nuclear interference effects. The kinetics of the polarization buildup is discussed.

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arXiv2011

Spin-dependent pbar-d cross sections at low and intermediate energies

Antiproton-deuteron (${\bar p}d$) scattering is calculated at beam energies below 300 MeV within the Glauber approach, utilizing the amplitudes of the Jülich $\bar N N$ models. A good agreement is obtained with available experimental data on upolarized differential and integrated $\bar p d$ cross sections. Predictions for polarized total ${\bar p}d$ cross sections are presented, obtained within the single scattering approximation including Coulomb-nuclear interference effects. It is found that the total longitudinal and transversal ${\bar p}d$ cross sections are comparable in absolute value to those for ${\bar p}p$ scattering. The kinetics of polarization buildup is considered.

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arXiv2009

Forward antiproton-deuteron elastic scattering and total spin-dependent antiproton-deuteron cross sections at intermediate energies

Spin-dependent total pbar-d cross sections are considered using the optical theorem. For this aim the full spin dependence of the forward pbar-d elastic scattering amplitude is considered in a model independent way. The single-scattering approximation is used to relate this amplitude to the elementary amplitudes of pbar-p and pbar-n scattering and the deuteron form factor. A formalism allowing to take into account Coulomb-nuclear interference effects in polarized pbar-d cross sections is developed. Numerical calculations for the polarized total pbar-d cross sections are performed at beam energies 20-300 MeV using the Nbar-N interaction models developed by the Julich group. Double-scattering effects are estimated within the Glauber approach and found to be in the order of 10-20%. Existing experimental data on differential pbar-d cross sections are in good agreement with the performed Glauber calculations. It is found that for the used Nbar-N models the total longitudinal and transversal pbar-d cross sections are comparable in absolute value to those for pbar-p scattering.

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arXiv2008

Dynamics of 1S0 diproton formation in the reactions pp-> (pp)_s+pi0$ and pp-> (pp)_s+gamma in the GeV region

COSY-ANKE data on the cross section of the reactions $pp\to \{pp\}_sπ^0$ and $pp\to \{pp\}_sγ$, where $\{pp\}_s$ is the proton pair in the $^1S_0$ state at small excitation energy $E_{pp}<3$ MeV, are analyzed at beam energies $0.5 - 2.0$ GeV within the one-pion exchange model. The model includes the subprocesses $π^0 p\to π^0 p$ and $π^0 p\to γp$ for the pion- and photo-production, respectively, and accounts for the final state pp-interaction. A broad maximum in the energy dependence of the $π^0$ production at $\sim 0.5 -0.6$ GeV and fast increase of the $γ$-production cross section at $0.3 - 0.55$ GeV observed in the data are explained by the $Δ$-isobar contribution. An analogy with the dynamics of the deuteron breakup reaction $pd\to \{pp\}_sn$ in the $Δ$-region is outlined.

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arXiv2008

Reaction pp-> {pp}_s pi^0 in the GeV region and pi^0 p rescattering

COSY data on the cross section of the reaction pp -> {pp}_s pi^0, where {pp}_s is the proton pair in the 1S0 state at small excitation energy E_{pp}=0-3 MeV, recently obtained for beam energies 0.5 - 2.0 GeV are analyzed within the one-pion exchange model. The model is based on the subprocess pi^0 p -> pi^0 p and final state pp-interaction. A broad maximum observed in the energy dependence of the cross section at 0.5 - 1.4 GeV in the forward direction is explained by this model as a dominant contribution of the isospin 3/2 in the pi^0 p-rescattering. The second maximum observed at 2 GeV is underpredicted within the model by one order of magnitude.

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arXiv2007

Spin observables of the reaction pd-3He eta and quasi-bound 3He-eta pole

A formalism for spin observables of the reaction $pd\to ~^3Heη$ is derived in a model independent way. The general case with a full set of six independent spin amplitudes is studied. Furthermore, approximations by five and four spin amplitudes are investigated in the near threshold region. This region is of great interest to search for a quasi-bound $^3He-η$ state, in particular, by measurement of energy dependence of relative phases of s- and p-wave amplitudes. Complete polarization experiments, allowing determination of spin amplitudes, are analyzed. It is shown that measurement of only analyzing powers and spin correlation coefficients hardly allows one to separate the s- and p-wave amplitudes, but additional measurement of polarization transfer coefficients simplifies this problem. Specific observables, given by products of one s- and one p-wave amplitudes, are found. Measurement of these observables will provide new independent information on the $^3He-η$ pole position.

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arXiv2007

Scaling behaviour of exclusive reactions with the deuteron and 3He at high p_T in the Gev region

The scaling behaviour s^{-11} of the cross section of the reaction γd-> pn observed at SLAC and Jlab at energies E_γ=1-4 GeV and large p_T most likely displays quark degrees of freedom in the deuteron. We show that the cross sections of the dd->3Hp and pd-> 3Hen reactions measured at SATURNE follow the scaling regime s{-22} at T_d= 0.5 -1.2 GeV and $θ_{cm}=50^\circ-60^\circ$. A necessity to get new data on this and other exclusive reactions is argued.

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arXiv2006

Dynamics of $^{1}S_0$ diproton formation in the $pd\to \{pp\}_sn$ and $pN\to \{pp\}_sπ$ reactions in the GeV region

Mechanisms for the production of $^1S_0$ diproton pairs, ${pp}_s$, in the $pd\to {pp}_s n$ reaction are studied at proton beam energies 0.5 -- 2 GeV in kinematics similar to those of backward elastic $pd$ scattering. This reaction provides valuable information on the short-range $NN$ and $pd$ interactions that is complementary to that investigated in the well known $pd\to dp$ and $dp\to p(0^\circ)X$ processes. The $pd\to {pp}_sn$ reaction is related to the subprocesses $π^0 d\to pn$ and $pN\to {pp}_s π$ using two different one--pion--exchange (OPE) diagrams. Within both these models a reasonable agreement could be obtained with the data below 1GeV. The similar energy dependence of the $pd\to\{pp\}_s n$ and $pd\to dp$ cross sections and the small ratio of about 1.5% in the production of $\{pp\}_s$ to deuteron final states follow naturally within the OPE models.

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arXiv2005

Spin observables of the reactions NN -> DeltaN and pd -> Delta (pp)(1S0) in collinear kinematics

A general formalism for double and triple spin-correlations of the reaction NN -> DeltaN is developed for the case of collinear kinematics. A complete polarization experiment allowing to reconstruct all of the four amplitudes describing this process is suggested. Furthermore, the spin observables of the inelastic charge-exchange reaction pd -> Delta^0(pp)(1S0) are analyzed in collinear kinematics within the single pN scattering mechanism involving the subprocess pn -> Delta^0p. The full set of spin observables related to the polarization of one or two initial particles and one final particle is obtained in terms of three invariant amplitudes of the reaction pd -> Delta (pp)(1S0) and the transition form factor d->(pp)(1S0). A complete polarization experiment for the reaction pd -> Delta^0(pp)(1S0) is suggested which allows one to determine three independent combinations of the four amplitudes of the elementary subprocess NN -> DeltaN.

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arXiv2005

Indication of asymptotic scaling in the reactions $dd\to p^3$H, $dd\to n^3$He and $dp\to dp$

It is shown that the differential cross sections of the reactions $dd\to ^3He n$ and $dd\to ^3H p$ measured at c.m.s.scattering angle$θ_{cm}=60^\circ$ in the interval of the deuteron beam energy 0.5 - 1.2 GeV demonstrate the scaling behaviour,$dσ/d t\sim s^{-22}$, which follows from constituent quark counting rules. It is found also that the differential cross section of the elastic $dp\to dp$ scattering at $θ_{cm}=125^\circ-135^\circ$ follows the scaling regime $\sim s^{-16}$ at beam energies 0.5 - 5 GeV. These data are parameterized here using the Reggeon exchange.

hep-ph↗
arXiv2004

Parity and spin of the $Θ^+$ pentaquark in the $NN\to YΘ^+$ reaction at the threshold

Spin observables of a binary reaction $1+2\to 3+4$ are discussed at the threshold in general form using P-parity and angular momentum conservation. General formulae for polarization transfer, spin-spin correlation parameters in the initial and final states and induced tensor polarization are derived for arbitrary spins of participating particles. This formalism is worked out in detail for the $NN\to YΘ^+$ reaction. Assuming that the spin of the pentaquark $Θ^+$ takes the values 1/2, 3/2 and 5/2, whereas the spin of the hyperon $Y$ equals 1/2, explicite formulae are obtained for the observables in terms of few non-vanishing at the threshold spin amplitudes separately for the spin-singlet and spin-triplet initial NN states. In case of all particles in the $NN\to YΘ^+$ reaction have the spin-1/2 a full spin-structure for totally polarized cross sections is derived. Some of the obtained spin observables strongly depend on the intrinsic P-parity of the $Θ^+$ and the total isospin of the reaction. Therefore, a measurement of these observables allows one to determine the P-parity of the pentaquark $Θ^+$ in a model independent way for any spin of the $Θ^+$.

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arXiv2004

Spin observables in the $NN\to YΘ^+$ reaction at the threshold and quantum numbers of the $Θ^+$ pentaquark

General formulae for the spin-spin correlation parameters $C_{i,j}$ and spin-transfer coefficients $K_i^j$ are derived for the reaction $N N\to Y Θ^+$ at the threshold for an arbitrary spin of the pentaquark $Θ^+$. It is shown that a measurement of the sign of $C_{y,y}$ or an observation of the non-zero polarization transfer from the nucleon to the hyperon $Y$ allow one to determine the P-parity of the $Θ^+$ unambiguously and independently on the spin of the $Θ^+$. Measurement of these spin observables in the both $pp$- and $pn$- channels of this reaction determines also the isospin of the $Θ^+$.

hep-ph↗
arXiv2004

A possibility to determine the P-parity of the $Θ^+$ pentaquark in the ${p}{n}\to Λ^0Θ^+$ reaction

Spin structure of the reaction ${\vec p}{\vec n}\to {\vec Λ^0} {\vec Θ}$ is analysed at the threshold in a model independent way under assumption that the $Θ^+$ is an isosinglet. We found that the sign of the spin-spin correlation parameter $C_{x,x}$ being measured in a double-spin experiment, determines the P-parity of the $Θ^+$ unambiguously. Furthermore we show that the polarization coefficients $K_x^x,K_y^y$ and $K_z^z$ which describe the polarization transfer from polarized beam or target to the final $Λ^0$ and $Θ^+$ are nonzero for a positive parity of the $Θ^+$ and equal zero for a negative parity. It allows one to determine the P-parity of the $Θ^+$ in a single-spin measurement, since the polarization of the $Λ^0$ can be measured via its decay $Λ^0\to π^-+ p$.

hep-ph↗
arXiv2003

NN($^1S_0$) pairs in $^3$He and in p$^3$He backward elastic scattering

It is shown that the shoulder observed in the cross section of $p^3He$ backward elastic scattering at proton beam energies of 0.4 -- 0.7 GeV can be explained by the mechanism of virtual $π$-meson production with a dominant contribution from the subprocesses $pd^*\to ^3$He$ π^0$ and $p(pp)\to^3$He$ π^+$, where $d^*$ denotes the singlet deuteron and the $pp$ pair is in the $^1S_0$ state. At high energies, 1-3 GeV, the mechanism of $np$-pair transfer dominates and probes high-momentum $NN(^1S_0$) correlations in $^3$He.

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arXiv2003

$^3$He Structure and Mechanisms of $p^3$He Backward Elastic Scattering

The mechanism of $p^3$He backward elastic scattering is studied. It is found that the triangle diagrams with the subprocesses $pd\to ^3$He$ π^0$, $pd^*\to ^3$He$ π^0$ and $p(pp)\to^3$He$ π^+$, where $d^*$ and $pp$ denote the singlet deuteron and diproton pair in the $^1S_0$ state, respectively, dominate in the cross section at 0.3-0.8 GeV, and their contribution is comparable with that for a sequential transfer of a $np$ pair at 1-1.5 GeV. The contribution of the $d^*+pp$, estimated on the basis of the spectator mechanism of the $p(NN)\to ^3$He$ π$ reaction, increases the $p^3$He$\to ^3$He$ p$ cross section by one order of magnitude as compared to the contribution of the deuteron alone. Effects of the initial and final states interaction are taken into account.

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arXiv2003

The reaction $pd\to(pp)n$ at high momentum transfer and short-range NN properties

A recent cross section measurement of the deuteron breakup reaction $pd\to (pp)(0^\circ)+n(180^\circ)$, in the GeV region in a kinematics similar to backward $pd$ elastic scattering, strongly contradicts predictions of a $pd \to dp$ model based on the one-nucleon exchange, single pN scattering and $Δ$ excitation mechanisms, and on the wave functions of the Reid soft core and Paris $NN$ potentials. We show within the same model that for the CD Bonn $NN$ potential there is qualitative agreement with the data. It is attributed to a reduction of the one-nucleon exchange at energies above 1 GeV and an increase of the $Δ(1232)$-isobar contribution, both related to the short-range properties of the wave functions generated by this potential.

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arXiv2002

Short-range NN-properties in the processes $pd\to dp$ and $pd\to (pp)n$

The data from the first measurement, performed at ANKE/COSY, of the unpolarized cross section of the reaction $pd\to (pp)n$ in the kinematics of backward elastic $pd\to dp$ scattering at proton-beam energies between 0.6 and 1.9 GeV are analyzed in a phenomenological approach. The $pd\to (pp)n$ data and the triplet cross section of the reaction $pd\to (pn)p$, calculated from the $pd\to dp$ data on the basis of the Fäldt-Wilkin extrapolation, are used here to derive the ratio $ζ$ of the singlet production matrix element squared to the triplet one. This ratio, defined in our earlier analysis of $pd\to (pn)p$ data in a largely model-independent way, depends on the dynamics of the $pd$ interaction. We find here $ζ\approx 0.02$ and show that the smallness of this value may point toward softness of the deuteron at short NN distances.

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