Review of quasi-elastic charge-exchange data in the nucleon-deuteron breakup reaction

The available data on the forward charge exchange of nucleons on the deuteron up to 2 GeV/nucleon are reviewed. The value of the inclusive nd → pnn/np → pn cross section ratio is sensitive to the fraction of spin-independent neutron-proton backward scattering. The measurements of the polarisation transfer in d(n, p){nn} or the deuteron analysing power in p{d, {pp})n in high-resolution experiments, where the final nn or pp pair emerge at low excitation energy, depend upon the longitudinal and transverse spin-spin up amplitudes. The relation between these types of experiments is discussed and the results compared with predictions of the impulse approximation model in order to see what new constraints they can bring to the neutron-proton database.     

Search for the NN → 6q phase transition in the np-polarized measurements at T kin = 1–6 GeV

The measurements of np-spin observables at 0° have been performed for the first time on the Delta-Sigma experimental facility of LHE JINR up to P _n = 4.5 GeV/c using the monochromatic neutron beam. They include detailed measurements of the Δσ _L(np) spin differences and the study of the np → pn elastic charge-exchange process. In the Δσ _L(np) and −Δσ _L(I = 0) energy dependencies over the energy region T_kin = 1.2–3.7 GeV the peculiarity at 1.8 GeV was observed. Such energy behavior was predicted by the QCD approach as a signal of the NN → 6q phase transition. For the exhaustive investigation of this effect it is necessary to measure the energy dependence of the complete set of np observables with both longitudinal (L) and transverse (T) polarizations of the neutron beam and proton target. This will allow Direct Reconstruction of all three NN forward Scattering Amplitudes (DRSA) to be performed, and the observed peculiarity to be checked around T_kin = 1.8 GeV and at the higher energies using the Argand diagrams method.     

Separation of differential np → pn charge-exchange cross section into flip and nonflip parts at Tn = 0.5–2.0 GeV

New results of the Delta-Sigma experiment on measuring the R _dp ratio made it possible to separate flip and nonflip parts of the differential cross section of the np → pn reaction at zero angle using the Dean formula. Phase-shift-analysis (PSA) solutions for elastic np → np scattering are transformed into a np → pn charge-exchange representation using unitary transformations, which testifies to the good agreement of the theoretical and experimental results.     

Spin structure of the “Forward” nucleon charge-exchange reaction <Emphasis Type="Italic">n</Emphasis> + <Emphasis Type="Italic">p</Emphasis> → <Emphasis Type="Italic">p</Emphasis> + <Emphasis Type="Italic">n</Emphasis> and the deuteron charge-exchange breakup

The structure of the nucleon charge-exchange process n + p → p + n is investigated basing on the isotopic invariance of the nucleon-nucleon scattering. Using the operator of permutation of the spin projections of the neutron and proton, the connection between the spin matrices, describing the amplitude of the nucleon charge-exchange process at zero angle and the amplitude of the elastic scattering of the neutron on the proton in the “backward” direction, has been considered. Due to the optical theorem, the spin-independent part of the differential cross section of the process n + p → p + n at zero angle for unpolarized particles is expressed through the difference of total cross sections of unpolarized proton-proton and neutron-proton scattering. Meantime, the spin-dependent part of this cross section is proportional to the differential cross section of the deuteron charge-exchange breakup d + p → (pp) + n at zero angle at the deuteron momentum k _d = 2 k _n (k _n is the initial neutron momentum). Analysis shows that, assuming the real part of the spin-independent term of the “forward” amplitude of the process n + p → p + n to be smaller or of the same order as compared with the imaginary part, in the wide range of neutron laboratory momenta k _n > 700 MeV/c the main contribution into the differential cross section of the process n + p → p + n at zero angle is provided namely by the spin-dependent term.     

The Ratio Rdp of the quasielastic nd → p(nn) to the elastic np → pn charge-exchange-process yields at the proton emitting angle θp,lab = 0° over 0.55–2.0 GeV neutron-beam energy region. Comparison of the results with the model-dependent calculations

Our new experimental results (see, e.g., Preprint JINR no. E1-2008-61 (Dubna, 2008)) on ratio R _dp of the quasielastic charge-exchange yield at the proton emitting angle θ _p,lab = 0° for the nd → p(nn) reaction to the elastic np → pn charge-exchange yield were presented. The measurements were carried out at the Nuclotron of the Veksler and Baldin Laboratory of High Energies of the JINR (Dubna) at the neutron-beam kinetic energies of 0.55, 0.8, 1.0, 1.2, 1.4, 1.8, and 2.0 GeV. In this paper the comparison of the experimental R _dp data with the obtained R _dp calculations within the impulse approximation by using the invariant-amplitude sets from the GW/VPI phase-shift analysis is made. The R _dp values calculated using the set of invariant amplitude data for the elastic np → pn charge exchange at θ _p,CM = 0°, agree with the experimental data. This confirmed the nd → p(nn) process yield at θ _p,CM = 0° is caused by the contribution of the spin-dependent part of the elastic np → pn charge-exchange reaction. Thus, it has been shown that the obtained experimental R _dp results can be used for the Delta-Sigma experimental program to reduce the total ambiguity in the extraction of the amplitude real parts. The text was submitted by the authors in English.     

The ratio R dp of the quasielastic nd → p(nn) to the elastic np → pn charge-exchange-process yields at the proton emitting angle θ p,lab = 0° over 0.55–2.0 GeV neutron beam energy region. Experimental results

New experimental results on ratio R _dp of the quasielastic charge-exchange yield at the outgoing proton angle θ _p,lab = 0° for the nd → p(nn) reaction to the elastic np → pn charge-exchange yield, are presented. The measurements were carried out at the Nuclotron of the Veksler and Baldin Laboratory of High Energies of the JINR (Dubna) at the neutron-beam kinetic energies of 0.55, 0.8, 1.0, 1.2, 1.4, 1.8, and 2.0 GeV. The intense neutron beam with small momentum spread was produced by breakup of deuterons which were accelerated and extracted to the experimental hall. In both reactions mentioned above the outgoing protons with the momenta p _p approximately equal to the neutron-beam momentum p _n,beam were detected in the directions close to the direction of incident neutrons, i.e., in the vicinity of the scattering angle θ _p,lab = 0°. Measured in the same data-taking runs, the angular distributions of the charge-exchange-reaction products were corrected for the well-known instrumental effects and averaged in the vicinity of the incident-neutron-beam direction. These corrected angular distributions for every of nd → p(nn) and np → pn charge-exchange processes were proportional to the differential cross sections of the corresponding reactions. The data were accumulated by Delta-Sigma setup magnetic spectrometer with two sets of multiwire proportional chambers located upstream and downstream of the momentum analyzing magnet. Inelastic processes were considerably reduced by the additional detectors surrounding the hydrogen and deuterium targets. The time-of-flight system was applied to identify the detected particles. The accumulated data treatment and analysis, as well as possible sources of the systematic errors are discussed. The text was submitted by the authors in English.     

Proposal on the measurements of d–p elastic scattering analyzing powers at 0.3–2.0 GeV at the Internal Target Station of the Nuclotron

A new high-energy beam polarimeter is proposed for Nuclotron, which uses the Internal Target Station (ITS). This polarimeter based on a measurement of asymmetry for the d–p elastic scattering will allow one to measure simultaneously both vector and tensor components of deuteron beam polarization. For this purpose an analyzing powers measurement for the d–p elastic scattering at energies T _d = 0.88–2 GeV is proposed. The precise measurements of the deuteron analyzing powers over the energy range T _d = 300–2000 MeV can give an irreplaceable clue to the study of the spin dependence of three nucleon forces. The text was submitted by the authors in English.     

Spin-rotating magnet for the ΔσL(np) experiment at LHEP JINR

The spin rotating magnet (SRM) is purposed for the orientation rotation of the nucleon spins in the polarized beam from the transverse (T) direction with respect to the nucleon beam momentum to the longitudinal (L) one. The longitudinally polarized neutron beam was used in the experiment for measuring the total cross section difference Δσ_L(np) with parallel and antiparallel orientation of the participant L polarization. To perform the nucleon spin rotation in the polarized nucleon beam through the angle of 90° over the beam momentum region of ～1.8–5.5 GeV/c, a proper spin rotation device had to be prepared. For this purpose, the necessary calculations of corresponding values of the magnetic induction integral were carried out. Using the calculations the dipole magnet SP 57 type was chosen for the Δσ_L(np) experiment and the required reconstruction of its pole tips was also accomplished. After the SRM installation at the neutron beam line the appropriate apparatus set for the magnetic measurements was prepared and the precise measurements of the whole set of the SRM characteristics were performed. The obtained results for the SRM magnetic field parameters were successfully used during the Δσ_L(np) experimental runs to specify the current at this magnet coil corresponding to the calculated magnetic induction integral for the given neutron beam momentum.     

Measurements of the total-cross-section difference ΔσL(np) at 1.39, 1.69, 1.89, and 1.99 GeV

New accurate data of the neutron-proton spin-dependent total-cross-section difference Δσ _L(np) at the neutron-beam kinetic energies 1.39, 1.69, 1.89, and 1.99 GeV are presented. In general, these data complete the measurements of energy dependence of Δσ _L(np) over the Dubna Synchrophasotron energy region. Measurements were carried out at the Synchrophasotron of the Veksler and Baldin Laboratory of High Energies of the Joint Institute for Nuclear Research. The quasi-monochromatic neutron beam was produced by breakup of extracted polarized deuterons. The deuteron (and hence neutron) polarization direction was flipped every accelerator burst. The initial transverse (with respect to beam momentum) neutron polarization was changed to a longitudinal one and longitudinally polarized neutrons were transmitted through the large proton longitudinally polarized target. The target polarization direction was inverted after one to two days of measurements. Four different combinations of the beam and target parallel and antiparallel polarization directions, both oriented along the neutron-beam momentum, were used at each energy. A fast decrease in −Δσ _L(np) with increasing energy above 1.1 GeV and a structure in the energy dependence around 1.8 GeV, first observed from our previous data, seem to be well revealed. The new results are also compared with model predictions and with phase-shift analysis fits. The Δσ _L quantities for isosinglet state I = 0, deduced from the measured Δσ _L(np) values and known Δσ _L(pp) data, are also given. The results of the measurements of unpolarized total cross sections σ _0tot(np) at 1.3, 1.4, and 1.5 GeV and σ _0tot(nC) at 1.4 and 1.5 GeV are presented as well. These data were obtained using the same apparatus and high-intensity unpolarized deuteron beams extracted either from the Synchrophasotron or from the Nuclotron. From Yadernaya Fizika, Vol. 68, No. 11, 2005, pp. 1858–1873. Original English Text Copyright ? 2005 by Sharov, Anischenko, Antonenko, Averichev, Azhgirey, Bartenev, Bazhanov, Belyaev, Blinov, Borisov, Borzakov, Borzunov, Bushuev, Chernenko, Chernykh, Chumakov, Dolgii, Fedorov, Fimushkin, Finger, Finger, Jr., Golovanov, Gurevich, Janata, Kirillov, Kolomiets, Komogorov, Kovalenko, Kovalev, Krasnov, Krstonoshich, Kuzmin, Ladygin, Lazarev, Lehar, de Lesquen, Liburg, Livanov, Lukhanin, Maniakov, Matafonov, Matyushevsky, Moroz, Morozov, Neganov, Nikolaevsky, Nomofilov, Panteleev, Pilipenko, Pisarev, Plis, Polunin, Prokofiev, Prytkov, Rukoyatkin, Schedrov, Schevelev, Shilov, Shindin, Slunečka, Slunečková, Starikov, Stoletov, Strunov, Svetov, Usov, Vasiliev, Volkov, Vorobiev, Yudin, Zaitsev, Zhdanov, Zhmyrov.     

Developing a generalized diffraction model for elastic pd scattering at intermediate energies

A generalization of the Glauber-Sitenko diffraction model that includes the spin dependence of NN amplitudes, the D-wave of the deuteron, and the charge exchange effects is constructed for elastic pd scattering at intermediate energies. The developed model was used to analyze differential cross sections and some spin observables (analyzing powers) at the incident proton energies T _p = 1 GeV, 440 and 250 MeV. It was shown that predictions of the generalized diffraction model agree both with the experimental data and with the exact Faddeev calculations at low transfer momenta.     

Spin structure of the “forward” charge-exchange reaction n + p → p + n and deuteron charge-exchange breakup d + p → (pp) + n

The spin structure of the nucleon charge-exchange process n + p → p + n is investigated. Analysis shows that the spin-dependent part of the differential cross section of the process n + p → p + n at zero angle, which is proportional to the differential cross section of the deuteron charge-exchange breakup d + p → (pp) + n in the “forward” direction, plays the predominant role in the wide range of neutron momenta.     

Quark-Model Nucleon–Nucleon Interaction Applied to Nucleon-Deuteron Scattering

We have examined the neutron-deuteron low-energy effective-range parameters, differential cross sections and spin polarization observables of the elastic nucleon-deuteron scattering up to the incident nucleon energy E _N  = 65 MeV, using the quark-model nucleon–nucleon interaction fss2. These observables are consistently described without introducing three nucleon forces except for the nucleon analyzing power A _y (θ) and the deuteron vector analyzing power iT ₁₁(θ) in the low-energy region E _N  ≤ 25 MeV. The long-standing A _y puzzle is slightly improved, but still remains. We have incorporated the screened Coulomb force to the proton-deuteron scattering, modifying the Vincent–Phatak approach for the sharp cutoff Coulomb force. The Coulomb effect on the elastic scattering observables is discussed.     

Asymmetry in the scattering of protons on polarized deuterons at 1.21 GeV/c

By using a polarized deuteron target we have measured the asymmetry in the differential cross section for elastic scattering of protons on deuterons and for quasi-elastic scattering of protons on protons bound in deuterons between the two states of opposite polarization, normal to the scattering plane of the initial deuteron. The beam momentum was 1.21 GeV/c. It is checked that the neutrons bound in the deuterons are polarized to approximately 20%.     

ππ scattering and the meson resonance spectrum

A ππ, ˉKK, and ρρ(ωω) fully coupled channel model is used to predict the lowest isospin S, P, D, F-wave phase shifts and inelasticities for elastic ππ scattering from threshold to 2.0 GeV. As input the S-matrix is required to exhibit poles corresponding to the meson resonance table of the Particle Data Group. As expected, the ππ inelasticity is very strongly related to the opening of the ˉK channel near 1 GeV, and the opening of ρρ(4π) and ωω(6π) channels in the 1.5 GeV region. The predictions of this model are compared to the various elastic ππ→ππ amplitudes, that were obtained from analyses of π⁻ p →π⁻π⁺n data. The role of the various resonances, in particular the glueball candidate f ₀(1500) and the f _J(1710) is investigated. Received: 19 November 1997     

Single and double πo-photoproduction from the deuteron

Photoproduction of neutral pions from the deuteron has been studied for incident photon energies from 200 MeV to 792 MeV with the TAPS detector at the Mainz MAMI accelerator. Total and differential cross sections covering the full angular range have been obtained for coherent and incoherent single π^o-photoproduction. Good agreement between model predictions and the data was found for the coherent process. The incoherent cross section in the energy region of the Δ(1232)-resonance is overestimated by existing models. A comparison to model predictions indicates that final state interaction effects are much more important than for the coherent reaction. However, the angular dependence of the data in the Δ-peak region follows the pattern expected from the dominant excitation of the M₁₊-multipole on the free nucleon. The energy and angular dependence of single π^o-photoproduction in the second resonance region is remarkably different from the reaction on the free proton, indicating a strong nuclear effect. Finally the total cross section for double π^o-photoproduction from the deuteron has been measured for the first time and was used to estimate the cross section for double π^o-photoproduction from the neutron. Received: 24 June 1999 / Revised version: 30 August 1999     

π−-meson and nucleon yields from light targets irradiated by deuterium and tritium nuclei beams at energies of 1 GeV/nucleon

In this paper, we present a model of calculation with respect to the interactions of high-energy nuclei with matter. Based on this model, we obtain results on energy and angular spectra of the n- and π⁻-particles produced in collisions of deuterium and tritium nuclei at energiesT _d=1 GeV/nucleon with light targets such as Li, Be. We have also estimated the production yields of neutrons and π⁻-mesons in targets of various radii, as well as mean energies of these these particles. Summarizing, we find that the lithium target of radiusR=10−12 cm for which the energy cost ε_π to produce one π⁻-meson is estimated as 6.7 GeV/π for a d-beam and 5.3 GeV/π for a t-beam is the most preferred pion-production target.     

What Can High-Energy Elastic Scattering Tell Us About Nucleon Structure?

Basic assumptions used in the analysis of elastic differential cross section data will be discussed and the arguments for the transparency of nucleons will be analyzed. It will be shown that the transparency of nucleon is a direct consequence when a weak t dependence of hadronic amplitude phase is used in analogy with optics. The phase t dependence may be hardly uniquely determined from elastic scattering data, being only partially limited by the Coulomb-hadronic interference existing in a very narrow region of small |t| values. The given situation will be demonstrated with the help of data for collisions at 541 GeV; nucleons being transparent or having hard cores may be admitted by the elastic data themselves. However, when further characteristic of inelastic and elastic processes are compared, the nucleon with hard core should be preferred. The most probable characteristics of nucleon structure derived from the data will be presented.     

The Nambu–Jona–Lasinio model of light nuclei

The Nambu–Jona–Lasinio model of the deuteron suggested by Nambu and Jona–Lasinio (Phys. Rev. 124 (1961) 246) is formulated from the first principles of QCD. The deuteron appears as a neutron–proton collective excitation, i.e. a Cooper np–pair, induced by a phenomenological local four–nucleon interaction in the nuclear phase of QCD. The model describes the deuteron coupled to itself, nucleons and other particles through one–nucleon loop exchanges providing a minimal transfer of nucleon flavours from initial to final nuclear states and accounting for contributions of nucleon–loop anomalies which are completely determined by one–nucleon loop diagrams. The dominance of contributions of nucleon–loop anomalies to effective Lagrangians of low–energy nuclear interactions is justified in the large N _C expansion, where N _C is the number of quark colours. Received: 10 March 2000     

The dp → ppn reaction as a method to study neutron-proton charge-exchange amplitudes

The differential cross section and deuteron analysing powers of the p → {pp}n charge-exchange reaction have been measured with the ANKE spectrometer at the COSY storage ring. Using a deuteron beam of energy 1170MeV, data were obtained for small momentum transfers to a {pp} system with low excitation energy. A good quantitative understanding of all the measured observables is provided by the impulse approximation using known neutron-proton amplitudes. The proof of principle achieved here for the method suggests that measurements at higher energies will provide useful information in regions where the existing np database is far less reliable.