Measurement for p–3He elastic scattering with a 65 MeV polarized proton beam

We measured the cross section and the proton analyzing power Ay for p– 3He elastic scattering at the angles θ = 26.9◦–170.1◦ in the center of mass system with a 65 MeV polarized proton beam. We compared the data with the rigorous numerical calculations based on the various nucleon–nucleon potentials. For the cross section, clear discrepancy is seen at the angles where the cross section takes minimum. For the proton analyzing power Ay , the calculations have moderate agreements with the data. In this proceedings, we show only the experimental results.


Introduction
One of the most important topics of nuclear physics is to describe the properties of nucleus based on the nucleon-nucleon (N N ) interactions combined with the three-nucleon forces (3NFs). 3NFs are key elements to understand various nuclear phenomena, e.g. binding energies of light mass nuclei [1] and equation of state of nuclear matter [2].
To study the dynamical aspects of 3NFs, such as momentum, spin, and iso-spin dependencies, few-nucleon scattering is a good probe. The first indication of the 3NF effects in the few-nucleon scattering was found in the cross section minimum for deuteron-proton (d p) elastic scattering at intermediate energies (E/A ≳ 65 MeV) [3].
3NF effects could also be seen in four-nucleon scattering. In order to explain 3NF effects in four-nucleon scattering as well as to approach to the 3NFs with the channels of the total isospin T = 3/2 we have performed the measurement for the p-3 He scattering at intermediate energies.
Here we report the cross section and the proton analyzing power A y for the p-3 He elastic scattering at 65 MeV.

Experimental setup
The measurement of p-3 He elastic scattering was performed in the west experimental hall of the Research Center for Nuclear Physics (RCNP), Osaka University. The atomic beam type High Intensity Polarized Ion Source HIPIS [4] provided polarized protons. The polarized proton beam was accelerated by the AVF cyclotron up to 65 MeV and transported to the experimental hall. The extracted beam was focused onto a carbon foil target at the beam line polarimeter. It was refocused onto the 3 He gaseous target in the scattering chamber. After bombarding the 3 He gaseous target, the beam was stopped in a Faraday cup. The beam intensity was 20 -100 nA.
The 3 He gaseous target was operated at room temperature under atmospheric pressure. The pressure and temperature of the gaseous target were monitored by using the gas target system [5]. Figure 1 shows the schematic view of the experimental setup. The scattered particles from 3 He nuclei were detected by the d E-E detectors which consisted of plastic and NaI(Tl) scintillators. A double-slit collimator system was used to determine the effective target thickness. The measured angles were θ = 20 • -165 • in the laboratory system (θ = 26.9 • -170.1 • in the center of mass system).

Experimental procedure
The polarizations of the beam were measured by using the beam line polarimeter. The polarimetry was made by p-12 C elastic scattering. The analyzing power of p-12 C elastic scattering in the region of interest are reported in Ref [6]. The typical beam polarizations during the experiment were 45-55 %.
In order to calibrate the absolute value of the cross section for p-3 He elastic scattering, we measured p-p elastic scattering using the same experimental setup.  Double slit collimator (Ta, 5 mm-thick) 3 He gaseous target

Results and discussions
Particle identification was made by using the correlation between the d E and E detectors.  events from the p-3 He elastic scattering are clearly seen around the highest ADC channels of the E detector. Time of flight information was also used for the event selection.
The proton analyzing power A y was extracted by using the yields for the two beam polarization modes ("spin-up" and "spin-down"). It was calculated as, where p u(d) y denotes the beam polarization of the spin-up (spin-down) mode, N u(d) denotes the yields for the p-3 He elastic scattering obtained with the spin-up (spin-down) mode. Figure 3 shows the experimental results of the cross section and the proton analyzing power A y as a function of the scattering angle in the center of mass system (C.M.). Open circles are the experimental data. Only the statistical errors are shown. The obtained data are compared with the rigorous numerical four-nucleon calculations based on the several realistic N N potentials, namely AV18 [7], INOY [8], SMS51 [9], SMS53 [9], CD-Bonn [10] and the conbination of CD-Bonn and the degree of freedom of the ∆-isober [11]. We show only the experimental results in this conference proceedings. All the calculations based on the various N N potentials provide similar results. For the cross section, clear discrepancy is found at the angles θ C.M. = 80 • -140 • . For the proton analyzing power A y , the angular distribution of the experimental data has a moderate agreement with the theoretical calculations.

Summary
We performed the measurement of the cross section and the proton analyzing power A y for p- 3