Polarized Deuteron Target Research Articles

Time-reversal-invariance violation in the Nd system and large NC

A minimal set of five low energy constants (LECs) for time-reversal and parity violating $(\overline{)T}\overline{)P})$ nucleon-nucleon $(NN)$ interactions at low energies $(E<{m}_{\ensuremath{\pi}}^{2}/{M}_{N})$ is given. Using a large-${N}_{C}$ (number of colors in quantum chromodynamics) analysis we show that one linear combination of LECs is $\mathcal{O}({N}_{C})$, three LECs are $\mathcal{O}({N}_{C}^{0})$, and one linear combination of LECs is $\mathcal{O}({N}_{C}^{\ensuremath{-}1})$. We also calculate the $\overline{)T}\overline{)P}$ observables of neutron spin rotation through a polarized deuteron target and a spin correlation coefficient in nucleon-deuteron scattering using pionless effective field theory. Using the large-${N}_{C}$ analysis we show that the spin correlation coefficient and the neutron spin rotation are predominantly determined by the same two LECs in the large-${N}_{C}$ basis.

Measurement of the helicity dependence for single $$\pi ^{0}$$ photoproduction from the deuteron

The helicity-dependent single $\pi^{0}$ photoproduction cross section on the deuteron and the angular dependence of the double polarisation observable $E$ for the quasi-free single $\pi^0$ production off the proton and the neutron have been measured for the first time from the threshold region up to the photon energy 1.4 GeV. The experiment was performed at the tagged photon facility of the MAMI accelerator and used a circularly polarised photon beam and longitudinally polarised deuteron target. The reaction products were detected using the large acceptance Crystal Ball/TAPS calorimeter, which covered 97% of the full solid angle. Comparing the cross section from the deuteron with the sum of free nucleon cross sections provides a quantitative estimate of the effects of the nuclear medium on pion production. In contrast, comparison of $E$ helicity asymmetry data from quasi-free protons off deuterium with data from a free proton target indicates that nuclear effects do not significantly affect this observable. As a consequence, it is deduced that the helicity asymmetry $E$ on a free neutron can be reliably extracted from measurements on a deuteron in quasi-free kinematics.

Flow in collisions of light nuclei

In this talk we discuss several interesting aspects of collective flow in small systems in reference to planned future experiments. First, we bring in the novel possibility of exploring elliptic flow with heavy nuclei collisions on polarized deuteron targets, accessible in AFTER@LHC program after Long Shutdown 3. Then we discuss the Glauber model predictions for the presently considered 16O −16O program at RHIC and the LHC. Finally, we turn to our previous proposal concerning specific flow signatures of intrinsic correlations (such as the predicted α clusterization) in the structure of light nuclei in collisions with heavy nuclei. In particular, 12C–heavy nucleus ultrarelativistic reactions would provide insight into the ground-state 12C structure, complementary to traditional nuclear structure measures.

General analysis of polarization effects in coherent pseudoscalar photo- and electroproduction of mesons on the deuteron

General expressions for the unpolarized differential cross section and for various polarization observables in the coherent pseudoscalar meson photo- and electroproduction on the deuteron target have been obtained in one-photon-exchange approximation. The spin structure of the matrix element is explicitly derived in terms of structure functions. The correspondence with the helicity amplitudes is given. The polarization effects have been investigated for the case of a longitudinally polarized electron beam and vector or tensor polarized deuteron target. The polarization (vector or tensor) of the scattered deuteron for the case of unpolarized or a longitudinally polarized electron beam is also considered. In the case of the photoproduction reaction, we consider linearly, circularly or elliptically polarized photon beam. Numerical estimations have been done for the unpolarized differential cross section and for some polarization observables.

Influence of Nucleon Structure on Tensor and Vector Analyzing Powers in Elastic Electron–Deuteron Scattering

Influence of nucleon structure on single tensor-deuteron and double beam-vector-deuteron analyzing powers in the elastic electron-deuteron scattering process is investigated. We report numerical results for the tensor-deuteron (T20, T21, and T22), and beam-vector-deuteron (T10 and T11) analyzing powers as functions of the four-momentum transfer square Q2 and the electron scattering angle in the laboratory frame θe. This is made possible with the advent of recent polarization measurements with polarized electron beams and/or polarized deuteron targets at MIT-Bates, JLab, NIKHEF, VEPP-2, and VEPP-3. We found that the predicted results for T21, T22, T10, and T11 are sensitive to the nucleon electromagnetic form factors. On the contrary, the T20 analyzing power is found to be almost independent on the actual nucleon form factors. The predicted analyzing powers are compared with the available experimental data and a satisfactory agreement is obtained.

Sensitivity of tensor and vector analyzing powers in elastic e-d scattering to modern local and nonlocal NN potentials

In this study, the sensitivity of tensor-deuteron and beam-vector-deuteron analyzing powers in elastic e-d scattering to modern local and nonlocal NN potentials is investigated. We report numerical results for the tensor-deuteron (T20, T21, T22) and beam-vector-deuteron (T10, T11) analyzing powers as functions of the four-momentum transfer square $$Q^2$$ and the electron scattering angle in the laboratory frame $$\theta _e$$ . This could be made possible with the advent of recent polarization measurements with polarized electron beams and polarized deuteron targets at MIT-Bates, JLab, NIKHEF, VEPP-2, and VEPP-3. We found that the estimated results for T20, T21, and T22 are slightly dependent on the local and nonlocal NN potential models adopted for the deuteron wave functions up to $$Q^2\simeq $$ 0.5 (GeV/c) $$^2$$ . At $$Q^2>$$ 0.5 (GeV/c) $$^2$$ , the theoretical discrepancies among various local and nonlocal NN potential models were found. As for the beam-vector-deuteron analyzing powers T10 and T11, we also found that they started to become model dependent when $$Q^2 > $$ 0.5 (GeV/c) $$^2$$ . The considerable dependence of T10 and T11 on the local and nonlocal NN potential models was observed at extremely forward electron angles. The T10 analyzing power was found to be smaller than T11. Therefore, in addition to the single analyzing power T20, the double beam-vector-deuteron analyzing power T11 can be used as another tool for extracting the three deuteron form factors, which provide an intuitive picture of the internal structure of the deuteron. The predicted results for analyzing powers are also compared with the available experimental data and a satisfactory agreement was obtained.

Research and Development of the Polarized Deuteron Source for the Van de Graaff Accelerator

An attempt is made to develop a polarized deuteron source suited for the Van de Graaff accelerator of Czech Technical University in Prague. We based on Kaminsky’s experiment on channeling deuterons through a Ni single crystal. The setup is described, which contains permanent magnets with a transversal magnetic field to increase the deuteron polarization using Sona-method (zero transition). The measurements of tensor polarization were carried out with TiT target. The result is $${{P}_{{zz}}} = - 0.12 \pm 0.04$$ for a weak field at the target without channeling. The ultimate aim is to produce 14-MeV polarized neutrons which will be used jointly with the frozen-spin polarized deuteron target for measurement $$\Delta {{\sigma }_{T}}$$ and $$\Delta {{\sigma }_{L}}$$ asymmetries in the $$nd$$ ‑transmission experiment.

Measurement of helicity dependence of single π0 photoproduction on deuteron

The study of the properties of the baryon resonances gives essential constraints on models for nucleon structure. Pion-photoproduction is a powerful tool to excite the nucleon to an intermediate resonant state and, in combination with polarised beams/targets, plays an important role in the investigation of the nucleon resonances. Data for polarisation observables accessible using a polarised photon beam and/or polarised nucleon targets are scarce in many channels, especially in those involving a neutron target. A systematic measurement is performed at the Mainz facility by the A2@MAMI collaboration. This talk will focus on the experiment performed at the Mainz Microtron, using a circularly polarised photon beam and a longitudinally polarised deuteron target, in conjunction with the large acceptance Crystal Ball/TAPS detection setup. An overview of the status of the experiment will be given, together with the preliminary results of polarised cross section from deuteron and of the double polarization observable E for the single π0 photoproduction reaction from the quasi-free proton and quasi-free neutron.

Nuclear final-state interactions in deep inelastic scattering off the lightest nuclei

We review recent progress in studies of nuclear final-state interactions in deep inelastic scattering (DIS) off the lightest nuclei tagged by a recoil nucleon. These processes hold a lot of potential for resolving the outstanding issues related to the dynamics of hadronization in QCD. Within the minimal Fock component framework, valid at large Bjorken [Formula: see text], the main features of the theoretical approach based on the virtual nucleon approximation are elaborated. In this approach, the strong final-state interaction of the DIS products with the nuclear fragments is described by an effective eikonal amplitude, whose parameters can be extracted from the analysis of semi-inclusive DIS off the deuteron target. The extraction of the [Formula: see text] and [Formula: see text] mass dependences of these parameters gives a new observable in studying the QCD structure of DIS final states. Another important feature of tagged DIS off the lightest nuclei is the possibility of performing pole extrapolation with a high degree of accuracy. Such extrapolation allows an extraction of the neutron structure function in a model independent way due to suppression of the final-state interaction in the on-shell limit of the struck nucleon propagator. We review the first application of the pole extrapolation to recent experimental data. Finally, we outline the extension of the framework to inclusive DIS, including a polarized deuteron target as well as its application to the tagged DIS reactions for future experiments at fixed target and collider energies.

Factorization breaking of AdT for polarized deuteron targets in a relativistic framework

We discuss the possible factorization of the tensor asymmetry $A^T_d$ measured for polarized deuteron targets within a relativistic framework. We define a reduced asymmetry and find that factorization holds only in plane wave impulse approximation and if p-waves are neglected. Our numerical results show a strong factorization breaking once final state interactions are included. We also compare the d-wave content of the wave functions with the size of the factored, reduced asymmetry and find that there is no systematic relationship of this quantity to the d-wave probability of the various wave functions.

Test of Time-Reversal Invariance at COSY (TRIC)

At the Cooler Synchrotron COSY a novel (P-even, T-odd) null test of time-reversal invariance to an accuracy of 10[Formula: see text] is planned as an internal target transmission experiment. The parity conserving time-reversal violating observable is the total cross-section asymmetry A[Formula: see text]. This quantity is measured using a polarized proton beam with an energy of 135 MeV and an internal tensor polarized deuteron target from the PAX atomic beam source. The reaction rate will be determined by the lifetime of the beam. Consequently, the accuracy of the current measurement of the circulating proton beam is crucial for this experiment. Thus, the cooler synchroton ring serves as an ideal forward spectrometer, as a detector, and an accelerator.

Gluon contribution to the Sivers effect. COMPASS results on deuteron target

Sivers effect for gluons is connected to gluon orbital angular momentum which may be the missing part of the nucleon spin puzzle. We present a method of extraction of Sivers effect for gluons from COMPASS SIDIS data on transversely polarised target. In order to access the Sivers effect for gluons photon-gluon fusion (PGF) process is used. To enhance the fraction of PGF in the sample high-pT hadron pair events are selected. The method is based on a assumption that there are 3 processes contributing to the muon-nucleon scattering: PGF, leading process and QCD Compton process. Then one performs a weighting procedure which enables to extract the asymmetries for the 3 contributing processes simultaneously. In order to do that a neural network trained by a Monte Carlo to assign to each event 3 probabilities corresponding to the 3 processes is needed. Finaly we show results of Sivers effect for gluons extraction on COMPASS data with transversely polarised deuteron target. A PGF sinΦ 2h –Φ S = −0.14 ± 0.15 (stat.) at ‹XG › = 0.126.

Polarization observables in lepton-deuteron elastic scattering including the lepton mass

Expressions for the unpolarized differential cross section and for various polarization observables in the lepton-deuteron elastic scattering, $\ell+D\to \ell+D$, $\ell=e$, $\mu$, $\tau$, have been obtained in one-photon-exchange approximation, taking into account the lepton mass. Polarization effects have been investigated for the case of a polarized lepton beam and polarized deuteron target which can have vector or tensor polarization. Numerical estimations of the lepton mass effects have been done for the unpolarized differential cross section and for some polarization observables and applied to the case of low energy muon deuteron elastic scattering.

Final-state interactions in deep-inelastic scattering from a tensor polarized deuteron target

Deep-inelastic scattering (DIS) from a tensor polarized deuteron is sensitive to possible non-nucleonic components of the deuteron wave function. To accurately estimate the size of the nucleonic contribution, final-state interactions (FSIs) need to be accounted for in calculations. We outline a model that, based on the diffractive nature of the effective hadron-nucleon interaction, uses the generalized eikonal approximation to model the FSIs in the resonance region, taking into account the proton-neutron component of the deuteron. The calculation uses a factorized model with a basis of three resonances with mass W < 2 GeV as the relevant set of effective hadron states entering the final-state interaction amplitude for inclusive DIS. We present results for the tensor asymmetry observable Azz for kinematics accessible in experiments at Jefferson Lab and Hermes. For inclusive DIS, sizeable effects are found when including FSIs for Bjorken x > 0.2, but the overall size of Azz remains small. For tagged spectator DIS, FSIs effects are largest at spectator momenta around 300 MeV and for forward spectator angles.

Inclusive and Exclusive Scatterings from Tensor Polarized Deuteron

The possibility of using a tensor polarized deuteron target in electroproduction reactions creates new opportunities for studying different phenomena related to the short-range hadronic and nuclear physics. The use of the tensor polarized deuteron allows us to isolate smaller than average inter-nucleon distances for the bound two-nucleon system. In this report we consider several high Q2 reactions which are particularly sensitive to the short-range two- nucleon configurations in the deuteron. One is the relativistic dynamics of electron-bound- nucleon scattering, which can be studied in both inclusive and exclusive reactions, and the other is the strong final state interaction in close proximity of two nucleons that can be used as a sensitive probe for color-transparency phenomena.

Test of time-reversal invariance at COSY (TRIC)

At the Cooler Synchrotron COSY a novel (P-even, T-odd) null test of time-reversal invariance to an accuracy of 10 − 6 is planned as an internal target transmission experiment. The parity conserving time-reversal violating observable is the total cross-section asymmetry Ay,xz. This quantity is measured using a polarized proton beam with an energy of 135 MeV and an internal tensor polarized deuteron target from the PAX atomic beam source. The reaction rate will be measured by means of an integrating beam current transformer. Thus, in this experiment the cooler synchroton ring serves as ideal forward spectrometer, as a detector, and an accelerator.

Hard quasi-real photo-production of charged hadrons at COMPASS energies

The Common Muon Proton Apparatus for Structure and Spectroscopy (COMPASS) at CERN with its use of beams of naturally polarized muons scattered of a polarized deuteron target, provides an environment of hard scattering between quasi-real photons and partons. Hard hadron quasi-real photo-production with polarized initial states is sensitive to the polarized gluon distribution ΔG through γ-gluon(g) direct channels as well as q-g resolved processes. Comparisons of unpolarized differential cross section measurements to next-to-leading order (NLO) pQCD calculations are essential to develop our understanding of proton-proton and lepton-nucleon scattering at varying center of mass energies. These measurements are important to asses the applicability of NLO pQCD in interpreting polarized processes. In this talk we will discuss unidentified charged separated hadron production at low Q2 (Q2 < 0.1 GeV2/c2) and high transverse momenta (pT > l.0GeV/c). < p2T > spectra of charged hadrons at Q2 > 1 GeV2/c2 will also be discussed.

Exclusive Scattering from Unpolarized and Polarized Deuteron

We present results for exclusive electron scattering from polarized and unpolarized deuteron. We employ the Gross equation to describe the deuteron ground state, and we use the SAID parametrization of the full NN scattering amplitude to describe the final state interactions. We discuss properties of various asymmetries accessible with a polarized deuteron target and/or a polarized beam.

New method of experimental determination of all three deuteron electromagnetic form factors

By elastic scattering of unpolarized electrons on a polarized deuteron target in the direction of the three momenta of the outgoing deuteron and by measuring the vector polarization of the final deuteron in the same direction and at the same values of squared transferred momenta $t$ as the unpolarized elastic electron-deuteron cross-section is measured, one can find out all three deuteron electromagnetic form factors in the space-like region.

Gluon polarisation in the nucleon and longitudinal double spin asymmetries from open charm muoproduction

The gluon polarisation in the nucleon has been determined by detecting charm production via D0 meson decay to charged K and π in polarised muon scattering off a longitudinally polarised deuteron target. The data were taken by the COMPASS Collaboration at CERN between 2002 and 2006 and correspond to an integrated luminosity of 2.8 fb−1. The dominant underlying process of charm production is the photon–gluon fusion to a cc¯ pair. A leading order QCD approach gives an average gluon polarisation of 〈Δg/g〉x=−0.49±0.27(stat)±0.11(syst) at a scale μ2≈13 (GeV/c)2 and at an average gluon momentum fraction 〈x〉≈0.11. The longitudinal cross-section asymmetry for D0 production is presented in bins of the transverse momentum and the energy of the D0 meson.