Latest results concerning short range correlations obtained in the dp elastic and dp breakup processes at Nuclotron, JINR

Deuteron spin structure program is aimed on extraction of two and three nucleon forces information, including their spin dependent parts, from dp elastic and dp breakup processes investigated at intermediate energies. The dp elastic data were obtained at Internal Target Station of Nuclotron (JINR) in the energy range 400-1800 MeV using polarized deuteron beam. Strong sensitivity to the short range spin structure of the isoscalar nucleon-nucleon correlations is observed in deuteron analyzing powers. Preliminary results of the the cross section for the dp breakup reaction have been obtained at 400 MeV of deuteron energy.


Introduction
There are many evidences that realistic nucleon-nucleon (NN) potentials such as CD-Bonn [1], AV18 [2] and Nijm I, II and 93 [3] does not describe the NN data above ∼ 350 MeV. Binding energies of three [4] and four nucleon systems can not be described using only NN potentials, however theoretical models in which three nucleon forces (3NFs) are included as two pion 011.1 exchange, e.g. Urbana IX [5] and Tucson-Melbourne [6] give us reasonable agreement. The cross section of reactions with few nucleons involving is in general better described in unpolarized case than in the polarized one. In the vicinity of the Sagara discrepancy the currently known 3NFs contribute by up to 30% to the d p elastic scattering cross section at intermediate energies [7].
The d p breakup reaction at deuteron energy of 270 MeV was investigated at RIKEN [8] and IUCF [9]. It was found that vector analyzing power A y can be described using NN forces only, but other polarization observables need 3NFs to describe the data. Inclusion of 3NFs improve the description of a part of the data but breaks other. Relativistic effects for the nd elastic scattering cross section at 70 MeV and 250 MeV were investigated in [24]. It was found that relativistic effects contribution is located mainly at backward angles, but their contribution is not large enough to fill discrepancy between experimental data and theory, even in the case when standard three nucleon forces are used.
The main goal of Deuteron Spin Structure program (DSS) is to obtain information about two and three nucleon forces, including their spin dependent parts. For this purpose, d p elastic scattering and d p breakup reaction are investigated in the energy ranges from 300 MeV -2000 MeV and 300 MeV -500 MeV of deuteron energy.

Dp elastic scattering at 400 MeV -2000 MeV
Polarimetry at Internal Target Station (ITS) [11] is using d p elastic scattering at large scattering angles (θ cm ≥ 60 • ) at 270MeV [12], where precise data on analyzing powers [13] exist. Method gives us determination of deuteron polarization better than 2%. Polarimeter consists of a spherical hull in which up to six targets can be placed. There are 39 scintillation counters placed at the top, bottom, left and right with respect to the deuteron beam, downstream to the ITS of Nuclotron. Scattered deuterons and recoil protons are detected in the coincidence in angular range from 65 • − 135 • .Developed multichannel high voltage system power supply system can supply power to 70 Hamamatsu photomultipliers. Polarization measurements were performed with new control and data acquisition system [14]. Developed new polarized ion source (SPI) [15] provided polarization of deuteron beam whose ideal values are: P Z , P Z Z = (0, 0), (−1/3, −1) and (−1/3, +1). The measured values of beam polarization were from ∼ 65% to ∼ 75% of ideal values. Observed beam polarizations were reasonably stable and demonstrate good reproducibility after interruptions. The selection of d p elastic events are based on correlations of energy losses in scintillators for the proton and deuteron and by difference in theirs time of flight information. Additionally, in order to suppress background cut on interaction point between beam and target was applied, also.
The angular dependence of the cross section at deuteron energy of 1400 MeV is shown in Figure. 1. Curves are predictions based on relativistic-multiple scattering model, e.g. [16] when one nucleon exchange and single scattering term (dashed curve), additional double scattering term (dotted curve) and ∆ isobar (solid curve) are included. Nuclotron data are represented by closed symbols, world data at slightly different energies are shown by open symbols. One can see large contribution which comes from double scattering term. It describes the data up to 70 • . ∆ isobar contribution comes at larger angles above 80 • and rises with angle. However the data are described in this angular range only qualitatively.
The angular dependence of the vector A y , tensor A y y and A x x at deuteron energy of 400 MeV is shown in Figure.2. Curves are predictions based on relativistic-multiple scattering model when one nucleon exchange and single scattering term (dashed curve) and additional double scattering term (solid curve) are taken into account. Nuclotron data are represented by closed symbols, open ones are world data [17], [18] and [19]. The contribution which comes 011.2 from double scattering term is rather small at this energy and generally does not improve the description of the data. Vector A y and tensor A y y analyzing powers are described up to the 70 • . Tensor A x x analyzing powers is not described by the model. The reason of the deviation can be neglecting of three nucleon short range correlations.
Angular dependence of the vector A y , tensor A y y and A x x at deuteron energy of 700 MeV is shown in Figure.3. Curves are predictions based on relativistic-multiple scattering model when one nucleon exchange and single scattering term (dashed curve), additional double scattering term (dotted curve) and ∆ isobar (solid curve) are taken into account. One can see large contribution which comes from double scattering term and small contribution from ∆ isobar located in very backward angles. Very good description is obtained in case of tensor analyzing power A y y .
The Angular dependence of the vector A y , tensor A y y and A x x at deuteron energy of 1000 MeV is shown in Figure.4. Curves are the same as for the case of 700 MeV. One can see large contribution which comes from double scattering term and moderate to large contribution which comes from ∆ isobar, specially at angles larger than 140 • . Only part of the A y data up to 70 • is described. Possible reason is that spin structure of the NN interactions and deuteron is missing in relativistic multiple scattering model [16].

Dp breakup process at 300 MeV -500 MeV
Dp breakup data have been accumulated using polarized and unpolarized deuteron beam at 300 MeV, 400 MeV and 500 MeV. Analyzing powers i T 11 and T 20 are investigated at deuteron energy of 400 MeV. There are two important settings in which unpolarized data are collected. First settings could give us possibility to investigate two and three nucleon forces, second one could be suitable in searching for relativistic effects. In the first setting, the detectors are placed in configurations in which momentum vectors of outgoing particles have equal momenta in the center of mass system and are separated by 120 • . Detectors were placed in various configurations in so called intermediate star. In the second setting, one arm is fixed and second scans angular range.

011.3
Analyzing powers i T 11 and T 20 were obtained at deuteron energy of 400 MeV at ITS of Nuclotron. Values of polarization of deuteron beam were obtained using polarimetry method described in section 2. Polyethylene and Carbon targets are enclosed in a spherical hull of ITS. Up to six various targets can be placed inside of ITS. Details of the ∆E −E detector construction can be found in [20]. i T 11   analyzing powers at polar angles of 34.8 • and 36.8 • and difference between azimuthal angles of 135 • are 0.47 ± 0.10 and 0.02 ± 0.20 [21]. Beam luminosity needs to be increase at least of one order in order to substantially decrease errors of analyzing powers.
Dp breakup reaction using unpolarized deuteron beam has been investigated at 300 MeV, 400 MeV and 500 MeV of deuteron energy. ∆E-E correlation of energy losses of charged particles and prediction which comes from GEANT4 simulation is shown in Figure.  tude of all photomultiplier tubes (PMTs) were monitored during all data acquisition. Detailed description of LED system of PMTs can be found in [20]. Calibration procedure is described in [23].
Relativistic effects have been found to be important in nd breakup reaction at 200 MeV in special kinematics in which one arm is fixed and second scans angular interval [24]. It was found specific pattern in differential cross section as a function of scattering angle. Relativistic contribution varies from no contribution to very large one. We performed the measurement of

Conclusion
Cross section of d p elastic scattering and predictions of relativistic-multiple scattering model at 1400 MeV is presented. Good agreement is observed up to 70 • . Angular dependence of the vector A y , tensor A y y and A x x at deuteron energy of 400, 700 and 1000 MeV is presented along with the predictions based on relativistic multiple scattering model. Large contribution which comes from double scattering term is observed, but it does not improve the description of analyzing powers in all cases, rather at small angles. Moderate contribution which comes from ∆ isobar is found at higher energies. ∆ isobar contribution improves the qualitative description of the cross section at 1400 MeV. Preliminary results of the five fold differential cross section of d p breakup reaction investigated at 400 MeV for the case of detector arms placed at the angles of 31 • and 43 • , 35 • and 43 • , 39 • and 43 • are presented. One can see some structures in kinematic S− curve at the vicinity of ≈ 100 MeV and ≈ 260 MeV. The next step is to obtain results at other angles to investigate observed structure in recent data.