Measurement of the tensor analyzing power for relativistic-deuteron fragmentation as a means for studying the deuteron structure within light-front dynamics

New data on the vector (A_y) and tensor (A_yy) analyzing powers for the reaction ⁹Be (d, p)X at a primary deuteron momentum of 5 GeV/c for a proton emission angle of 178 mrad are obtained by using the synchrophasotron of the Joint Institute for Nuclear Research (JINR, Dubna). The experimental data on A _yy are analyzed within the approach based on light-front dynamics, the relativistic wave function obtained by Karmanov and his colleagues being used for the deuteron. It is shown that, in contrast to what one has from calculations with standard nonrelativistic deuteron wave functions, all relevant data can be explained in this approximation without resort to additional degrees of freedom.     

Investigation of the deuteron spin structure at short nucleon-nucleon distances in the reaction of polarized-deuteron fragmentation to cumulative pions

Experimental results on the vector (A _y ) and tensor (A _yy ) analyzing powers in the fragmentation of 5- and 9-GeV/c polarized deuterons to high-momentum pions in the kinematical region corresponding to pion production on a strongly correlated nucleon pair (cumulative meson production) are presented. The angular and momentum dependences of A _yy are not described by calculations performed in the impulse approximation by using standard deuteron wave functions. An explanation for our data should be sought on the basis of models that treat the deuteron at short distances (deuteron-core region) as a multiquark state—for example, a 6q cluster, whose high orbital angular momentum (D wave) leads to the observed strong dependence of the reaction tensor analyzing power A( $\vec d$ , π)X on the pion transverse momentum.     

Measurement of the Tensor-Analyzing Power A yy in Deuteron Breakup at 4.5 GeV/c and 80 mr

 The tensor-analyzing power A _yy in inclusive breakup of 4.5 GeV/c deuterons on beryllium has been measured at ∼ 80 mr of the detected proton angle. The analyzing power remains positive up to the highest measured momentum of the proton, that is in definitive contradiction with the predictions of the existing models based on the standard deuteron wave functions. The results suggest that the deuteron structure at short distances may depend on more than one independent variable. E-mail address: ladygin@sunhe.jinr.ru Received October 2, 2001; accepted July 19, 2002     

Elastic scattering of polarized deuterons by protons at intermediate energies

The tensor analyzing power T₂₀(θ) in dp backward scattering has been measured at or near center-of-mass angle θ = 180° in the energy range 0.3–2.3 GeV. A pronounced structure is observed around T_d = 0.5 GeV which is explained by a predominant one-neutron-exchange mechanism. Other structures appear around 1 GeV and higher. They are not explained by calculations which include Δ-excitations in intermediate states. In addition, full angular distributions of vector A_y and tensor A_yy analyzing powers and differential cross sections have been obtained at 1.2 GeV and limited angular ranges explored at 0.5 GeV (back angles) and 1.6 GeV (forward angles).     

Elastic scattering of 56 MeV polarized deuterons on 4He

The differential cross section and the vector and tensor analyzing powers A_y, A_xx, A_yy and A_xz were measured for the d-⁴He elastic scattering at 56 MeV. The measurement of A_xz was performed using a deuteron beam polarized in the horizontal plane. An optical-model analysis of the experimental data was carried out. The magnitude of the tensor analyzing powers could not be reproduced without the tensor potential. By including the T_R type tensor potential, the optical-model calculations give a reasonable reproduction of the experimental data at θ_c.m. < 120°. The obtained T_R tensor potential was much stronger than that predicted by the folding model. The strength of the real T_R potential was roughly in accordance with that obtained from the optical-model analysis of d-⁴He elastic scattering at 20.2 MeV.     

Measurement of the tensor analyzing power Ayy in the inelastic scattering of deuterons in the vicinity of excitation of baryonic resonances

The tensor A_yy and vector A_y analyzing powers in the inelastic scattering of deuterons with a momentum of 4.5 GeV/c on beryllium at an angle of 80 mr in the vicinity of baryonic resonances excitation have been measured. The A_yy data being in good agreement with the previous results obtained at a zero angle demonstrate an approximate t scaling up to - 0.9 (GeV/c)². The results of the experiment are compared with the predictions of the multiple-scattering and -meson exchange models. Received: 20 April 2000 / Accepted: 29 May 2000     

Measurement of the tensor A yy and vector A y analyzing powers of the deuteron inelastic scattering of beryllium at 5.0 GeV/c and 178 mrad

Tensor A _yy and vector A _y analyzing powers in the inelastic scattering of deuterons with a momentum of 5.0 GeV/c on beryllium at an angle of 178 mrad in the vicinity of the excitation of baryonic resonances with masses up to ～ 1.8 GeV/c ² have been measured. The A _yy data are in good agreement with the previous data obtained at 4.5 and 5.5 GeV/c. The results of the experiment are compared with the predictions of the plane-wave impulse approximation and ω meson-exchange models.     

Investigation of the Three-Nucleon System Dynamics in the Deuteron–Proton Breakup Reaction

Precise and large sets of cross section, vector A _x , A _y and tensor A _xx , A _xy , A _yy analyzing power data for the ¹ H(d, pp)n breakup reactions were measured at 100 and 130 MeV deuteron beam energies with the SALAD and BINA detectors at KVI and the Germanium Wall setup at FZ-Jülich. Results are compared with various theoretical approaches which model the three-nucleon system dynamics. The cross section data reveal a sizable three-nucleon force (3NF) and Coulomb force influence. In case of the analyzing powers very low sensitivity to these effects was found and the data are well describe by 2N models only. For A _xy at 130 MeV, serious disagreements were observed when 3NF models are included in the calculations.     

Angular dependences of the tensor analyzing powers in the dd → 3Hen reaction at intermediate energies

The tensor analyzing powers A _yy, A _xx, and A _xx in the dd → ³Hen reaction at intermediate energies are considered in the framework of the one-nucleon-exchange approximation. Their strong sensitivity to the ³He and deuteron spin structure at short distances is shown.     

Measurement of the tensor analyzing power A yy in the inelastic scattering of 4.5-GeV/c deuterons on beryllium at an angle of 80 mrad

The tensor analyzing power A _yy and the vector analyzing power A _y for the inelastic scattering of 4.5-GeV/c deuterons on beryllium nuclei at angle of about 80 mrad are measured in the vicinity of baryon-resonance excitation. These new data, presented as a function of t, comply well with the results of previous 4.5-, 5.5-, and 9-GeV/c measurements at zero angle in overlapping regions of t; all available data are described by a unified dependence on |t| upto about 0.9 (GeV/c)². The experimental results are compared with the results of calculations performed within the multiple-scattering model and the model involving omega-meson exchange in the t channel.     

Measurement of coherent elastic and inelastic deuteron-proton scattering at s = 2800 GeV2

Data on coherent elastic and inelastic deuteron-proton scattering are presented. The measurements were made at the CERN ISR with a single arm spectrometer, at s = 2800 GeV² and momentum transfer squared (?t) in the range 0.15 to 0.42 GeV².The data are compared with elastic and inelastic diffractive proton-proton scattering data taken with the same apparatus at the same s and t values. The t dependence of the elastic dp → dp differential cross section is compared to simple predictions based on Glauber theory. The differential cross sections for pp → pX and dp → dX are also compared for M_X² → 280 GeV², where M_X denotes the mass of system X recoiling against the measured proton and deuteron.     

Investigations of Few-Nucleon System Dynamics in Medium Energy Domain

Precise and large set of cross sections, vector A _x , A _y and tensor A _xx , A _xy , A _yy analyzing powers for the ¹ H(d, pp)n breakup reactions were measured at 100 and 130 MeV deuteron beam energies with the use of the SALAD and BINA detectors at KVI and Germanium Wall setup at FZ-Jülich. Results are compared with various theoretical approaches which model the three-nucleon (3N) system dynamics. The calculations are based on different two-nucleon (2N) potentials which can be combined with models of the three-nucleon force (3NF) and other pieces of the dynamics can also be included like the Coulomb interaction and relativistic effects. The cross sections data reveal seizable 3NF and Coulomb force influence. In case of analyzing powers very low sensitivity to the effects was found and the data are well describe by 2N models only. At 130 MeV for A _xy serious disagreements appear when 3NF models are included into calculations.     

Elastic <Emphasis Type="Italic">Nd</Emphasis> scattering at intermediate energies as a tool for probing the short-range deuteron structure

A calculation of the deuteron polarization observables A _y ^d , A _yy , A _xx , A _xz and the differential cross section for elastic nucleon-deuteron scattering at incident deuteron energies 270 and 880 MeV in lab is presented. A comparison of the calculations with two different deuteron wave functions derived from the Bonn-CD NN-potential model and the dressed-quark-bag model is carried out. A model-independent approach, based on an optical-potential framework, is used in which a nucleon-nucleon T matrix is assumed to be local and taken on the energy shell, but still depends on the internal nucleon momentum in a deuteron. The text was submitted by the author in English.     

Deuteron d-state effects for the reactions 117Sn(d, p)118Sn and 119Sn(d, p)120Sn

Angular distributions of the differential cross section and the three tensor analyzing powers were measured for the reactions ¹¹⁷Sn($\text{d}$, p)¹¹⁸Sn and ¹¹⁹Sn($\text{d}$, p)¹²⁰Sn at E_d = 12 MeV. In addition, excitation functions of the tensor analyzing power T₂₀ were measured at proton lab angles of 0° and 5° for energies ranging from 10 to 12 MeV. At forward angles, the tensor analyzing powers for the ground state (l_n = 0) transitions are more than an order of magnitude larger than the predictions of distorted-wave calculations which neglect the deuteron D-state. Qualitative agreement with the measurements is obtained when the D-state is included.     

Deuteron-proton elastic scattering at intermediate energies

The deuteron-proton elastic scattering has been studied in the multiple-scattering expansion formalism. Primary attention has been given to such relativistic problems as a deuteron wave function in a moving frame and transformation of spin states due to Wigner rotation. Parametrization of the nucleon—nucleon t matrix has been used to take the off-energy-shell effects into account. The vector, A _y , and tensor, A _yy , analyzing powers of the deuteron have been calculated at two deuteron kinetic energies: 395 and 1200 MeV. The obtained results are compared with the experimental data. The text was submitted by the authors in English.     

d + α Scattering from 12 to 17 MeV

A previous phase-shift analysis of the d + α system had indicated that the solution obtained might not describe the backward-angle tensor analyzing powers very well above about 10 MeV. We have measured differential cross sections and all four analyzing powers A_y, A_xx, A_yy and A_xz at deuteron bombarding energies of 12, 14, 15 and 17 MeV, with some emphasis on the backward-angle region. The discrepancy with the previous phase-shift analysis was confirmed, and we have studied the changes in the phase parameters necessary to improve the fit to our new measurements.     

Observation of deuteron D-state and compound nucleus effects in (d,p) reactions on 46Ti and 52Cr with a polarized deuteron beam

The cross section and the vector and tensor analyzing powers have been measured for ⁴⁶Ti(d, p)⁴⁷Ti at deuteron energies of 6 and 10 MeV and ⁵²Cr(d, p)⁵³Cr at 6 MeV. Transitions were observed to the states at E_x=0.159, 1.549 and 1.793 MeV in ⁴⁷Ti and the states at E_x=0.0, 0.564, 1.006 and 2.321 MeV in ⁵³Cr. In addition, the cross sections and vector analyzing powers for deuteron elastic scattering were measured for the same targets and deuteron energies and compared to optical model calculations. The choice of optical parameters for the DWBA analysis of the (d, p) reactions is discussed. Calculations made with the DWBA method show that the deuteron D-state must be included to reproduce even qualitatively the (d, p) tensor analyzing power measurements. The j-dependence of the tensor analyzing power T₂₂ is discussed. The validity of the local energy approximation (which was used to incorporate the deuteron D-state into the DWBA calculations) is evaluated by comparison to finite range calculations. The contribution of compound nucleus reactions to the measured cross sections and analyzing powers was investigated. In order to determine the compound cross section, the Ericson fluctuations in excitation functions of cross section and vector analyzing power were measured from 5 to 7 MeV on each target. The formulas used to calculate the polarization observables from the Hauser-Feshbach theory are presented.     

The 4He(d, αp)n reaction at 12 and 17 MeV

The cross section and the analyzing powers A_y, A_xx and A_yy for the reaction ⁴He($\text{d}$, αp)n are studied with kinematically complete measurements at incident energies of 12 and 17 MeV. Spectral structures due to the final-state interactions and quasifree scattering are measured. A three-body model of the Faddeev type gives a satisfactory fit to the cross-section and A_y data, but it fails to fit adequately the tensor analyzing-power data. The tensor analyzing powers in the breakup process should be sensitive to the input two-body force, and that sensitivity seems to be somewhat greater near the three-body 1⁺ resonance.