Final state interaction effects in electrodisintegration of the deuteron in the Bethe-Salpeter approach

The electrodisintegration of the deuteron is considered in a relativistic model of nucleon-nucleon interaction based on the Bethe-Salpeter approach with a separable interaction kernel. The exclusive cross section is calculated in the impulse approximation under various kinematic conditions. Final state interactions between the outgoing nucleons are taken into account. The comparison of nonrelativistic and relativistic calculations is presented. Partial-wave states of the neutron-proton pair with total angular momentum J = 0, 1 are considered.     

Relativistic optical model on the basis of the Moscow potential and lower phase shifts for nucleon-nucleon scattering at laboratory energies of up to 3 GeV

Data of a partial-wave analysis of nucleon-nucleon scattering at energies of up to E _lab = 3 GeV (lower partial waves) and the properties of the deuteron are described within the relativistic optical model based on deep attractive quasipotentials involving forbidden states (as exemplified by the Moscow potential). Partial-wave potentials are derived by the inverse-scattering-problem method based on the Marchenko equation by using present-day data from the partial-wave analysis of nucleon-nucleon scattering at energies of up to 3 GeV. Channel coupling is taken into account. The imaginary parts of the potentials are deduced from the phase equation of the variable-phase approach. The general situation around the manifestation of quark effects in nucleon-nucleon interaction is discussed.     

Exclusive electrodisintegration of the deuteron within the point form of relativistic quantum mechanics

The process of exclusive deuteron electrodisintegration is considered within the point form of relativistic quantum mechanics. Relevant calculations are performed on the basis of the Nijmegen and Moscow nucleon-nucleon potentials, the latter involving forbidden states. Final-state interaction is taken into account. For either type of the potentials used, the results of the calculations describe well experimental data at final-neutron momenta p _n of up to 500 MeV/c.     

Exclusive charge exchange reaction pD↦n(pp) within the Bethe-Salpeter formalism

The exclusive charge exchange reaction pD↦n(pp) at intermediate and high energies is studied within the Bethe-Salpeter formalism. The final-state interaction in the detected pp pair at nearly zero excitation energy is described by the ¹ S ₀ component of the Bethe-Salpeter amplitude. Results of numerical calculations of polarization observables and differential cross-section persuade that, as in the non-relativistic case, this reaction i) can be utilized as a “relativistic deuteron polarimeter” and ii) delivers further information about the elementary nucleon-nucleon charge exchange amplitude. Received: 26 November 2002 / Accepted: 30 January 2003 / Published online: 29 April 2003     

The asymptoticS-state amplitude of the deuteron wave function

Bounds on the asymptoticS-state amplitudeA _S of the deuteron wave function are calculated as a function of assumed impulse approximation values for the quadrupole moment. Alternatively, for a given value ofA _S, a bound is obtained on the minimum contribution to the experimental value ofQ _D from meson-exchange currents, relativistic effects and isobar contributions. The extraction ofA _S from low energy elastic nucleon-nucleon scattering data is discussed in detail.     

Sensitivity of T20 indA →PX to the reaction mechanism and relativistic effects

A method for the analysis of interactions between fast deuterons and nucleons is developed, taking into account both the relativistic effects in the deuteron and the mechanism of their interaction. The inclusive proton spectra and the polarisation characteristics are investigated, taking for instance the fragmentation type processes of deuterons on nucleons. A strong sensitivity of the deuteron polarisation tensor component T₂₀ both to the reaction mechanism and to the relativistic structure of the deuteron is shown. It is shown that there can't be a direct indication of the 6q-state existence in the deuteron from the T₂₀ experimental data.     

Inelastic electron-deuteron scattering with final-state interactions

Measurements of the cross sectiond ² σ/dΩ dE′ for the inelastic electron-deuteron scattering processe+d→e+n+p have been used to determine the electromagnetic structure of the neutron. The effects on the theoretical cross section of the structure of the deuteron and of interactions between the outgoing nucleons are examined in detail. We start with the relativistic invariant expressions of the one-nucleon exchange diagram including deuteron structure to obtain the interaction Hamiltonian. For the disintegration near the quasi-elastic peak thed-n-p vertex function can be represented by nonrelativistic deuteron wave functions. The final state interaction is calculated from phenomenological nucleon-nucleon potentials. The rescattering corrections are found to lead to a decrease in the peak value of the cross section between ?6% and ?2% depending on the electron momentum transfer q² which has been varied between 2.5f ^?2 and 40f ^?2. These corrections are largest for smallq ²<5f ^?2. Furthermore the results show that the influence of our insufficient knowledge of the deuteron structure on the cross section is small.     

Charge-exchange reaction pd → n(pp) within the Bethe-Salpeter approach

The charge-exchange reaction pd → n(pp) at low momentum transfers and low excitation energies of the pp pair is considered within the Bethe-Salpeter approach. The method is proposed for calculating observables in the case where the pp pair is in the ¹ S ₀ state. The results of methodological numerical calculations for the differential cross sections and the tensor analyzing power T ₂₀ are presented. The possibility of using the reaction in question as a basic reaction for creating a deuteron tensor polarimeter at high energies and for obtaining additional information about the elementary amplitude for nucleon-nucleon charge-exchange is predicted.     

Measurement of the differential cross section and of the tensor and vector analyzing powers for the fragmentation of 4.5-GeV/c deuterons on beryllium in the reaction involving proton emission at an angle of 80 mrad

The invariant differential cross section, the tensor analyzing power A _yy , and the vector analyzing power A _y for the reaction ⁹Be(d, p)X are measured at an initial deuteron momentum of 4.5 GeV/c and a proton detection angle of about 80 mrad. The data obtained for the differential cross section are consistent with the results of measurements at 3.5 and 5.78 GeV/c and a proton emission angle of 2.5°. The values found for the tensor analyzing power A _yy are compared with similar data obtained previously for the deuteron-fragmentation process occurring on a carbon target at various values of the initial deuteron momentum and leading to proton emission at zero angle. The data on the differential cross section for the reaction ⁹Be(d, p)X can be satisfactorily described within the relativistic impulse approximation by using standard deuteron wave functions; however, the approach based on this conceptual framework proves to be inadequate in dealing with data on the tensor analyzing power. These results indicate that it is necessary either to change the method for describing the relativistic deuteron or to take into account additional mechanisms.     

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.     

Deuteron form factors for the Nijmegen potentials

The deuteron form factors and tensor polarizations in elastic ed scattering are considered for four versions of the Nijmegen nucleon-nucleon potentials. The numerical deuteron wave functions in these potentials are approximated by a series of Gaussian functions with the result that it can be used in any computations of integrated characteristics. The quality of this approximation of the wave function is exemplified by comparing the results that it produces for the momentum distributions, the quadrupole moment, the D-state probability, and the deuteron radius with the results of the corresponding precise calculations.     

A three-body calculation of the πd → πnp reaction in the Δ-resonance region

The reaction d(π^±, pπ^±)n at incident pion momentum 340 MeV/c is analyzed based on a relativistic three-body formalism. The contributions of the various reaction mechanisms such as impulse processes, pion multiple scattering and nucleon-nucleon final-state interactions are investigated for several cases of typical kinematics. The impulse term is dominant when the recoil neutron momentum is small. On the other hand, the NN final-state interaction is found to be relatively important when the recoil neutron momentum is large. The effects of dibaryon resonances which have been suggested in πd elastic scattering are estimated using a phenomenological model. Comparisons with other work are also made.     

Analysis of the reaction np → dπ+π− below 3.5 GeV/c

The reaction np → dπ⁺π^? was studied from threshold up to 3.5 GeV/c neutron beam momentum. Cross-section values for this reaction are evaluated as a function of the beam momentum. The deuteron production features and the enhancement observed in the dπ mass spectrum at 2.17 GeV are adequately described in terms of an OPE model and nucleon-nucleon final-state interactions.     

Consistent treatment of relativistic corrections in deuteron photodisintegration in a one-pion-exchange model

Using a one-pion-exchange model for the nucleon-nucleon interaction the relativistic corrections to potential and to the electromagnetic operators are derived in a power expansion of (p/M). All corrections up to the order (p/M)³ are consistently included. Numerical results are shown for differential cross section and polarization observables for deuteron photodisintegration. A sizeable influence of relativistic effects on some observables is found even at low energies. A comparison of our operators with the expressions of other authors is given.Supported by Deutsche Forschungsgemeinschaft (SFB 201)     

Nucleon form factors for elastic electron-deuteron scattering at high momentum transfer

Elastic electron-deuteron scattering at high momentum transfer is investigated within the Bethe-Salpeter approach. The relativistic covariant Graz II separable kernel of nucleon-nucleon interactions is used to analyze the deuteron structure functions, form factors, and tensor of polarization components. The modern data for the electromagnetic structure of nucleons from the double polarization experiments, as well as some other models of the nucleon form factors, are considered.     

The structure of the high-momentum parts of the deuteron spectra from d-d collisions at 4.3, 6.3 and 8.9 GeV/c

The experimental data on d-d collisions at 4.3, 6.3 and 8.9 GeV/c, exhibiting the two-peak structure in the high-momentum parts of the secondary deuteron spectra at momentum transfers |t| ≈ 0.4–0.8 (GeV/c)², are presented. An analysis of the results in terms of the multiple nucleon-nucleon scattering model is given. Some conclusions about the mechanism of the elastic and quasielastic d-d scattering at the above-mentioned momentum transfers are made.     

Forward a production and nuclear stopping power in d+Au collisions at RHIC

Using the forward time projection chambers of STAR we measure the centrality dependent A and ā yields in d+Au collisions at √s _NN =200 GeV at forward and backward rapidities. The contributions of different processes to particle production and baryon transport are probed exploiting the inherent asymmetry of the d+Au system. While the d side appears to be dominated by multiple independent nucleon-nucleon collisions, nuclear effects contribute significantly on the Au side. Using the constraint of baryon number conservation, the rapidity loss of baryons in the incoming deuteron can be estimated as a function of centrality. This is compared to a model and to similar measurements in Au+Au, which gives insights into the nuclear stopping power at relativistic energies.     

Nucleon-nucleon potentials including πNΔ coupling effects

We show that in the nonrelativistic limit the two-pion exchange contribution to the nucleon-nucleon (NN) interaction can be well approximated by the twice iterated static pion-exchange potentials that couple the NN channel with the NΔ (1236 resonance) and ΔΔ channels. A phenomenological short (ω-meson) range potential is added to the pion-exchange potentials to study the NN phase shifts and the deuteron properties. The S- and P- state phase shifts can be well explained in this model with a very reasonable short-range interaction. The Δ-percentage in the deuteron is found to be ≈ 0.6%. Probably because of the nonrelativistic approximations, the D-state phase shifts at E_lab > 100 MeV are not too well reproduced.