Search

We report measurements of cross sections and analyzing powers for nucleon-knockout $(\stackrel{P\vec}{p},np)$ reactions of $^{2}\mathrm{H}, ^{6}\mathrm{Li}$, and $^{12}\mathrm{C}$ at 296 MeV using the RCNP NPOL3 neutron detector and large acceptance spectrometer. The $1s$ and $1p$ knockout reactions were successfully separated with a separation-energy resolution of approximately 6 MeV. The resulting data were compared with plane-wave and distorted-wave impulse approximation calculations employing the nucleon-nucleon $t$ matrix in free space. No significant differences were identified in the case of the present analyzing power data, in contrast to the significant reductions observed in $(\stackrel{P\vec}{p},2p)$ values. The conventional Pauli blocking and nuclear binding effects with the $g$ matrix and the relativistic effect of nucleon mass reduction in the nuclei are also discussed.

We demonstrated a frequency offset locking between two laser sources using a waveguide-type electro-optic modulator (EOM) with 10th-order sidebands for magneto-optical trapping of Fr atoms. The frequency locking error signal was successfully obtained by performing delayed self-homodyne detection of the beat signal between the repumping frequency and the 10th-order sideband component of the trapping light. Sweeping the trapping-light and repumping-light frequencies with keeping its frequency difference of 46 GHz was confirmed over 1 GHz by monitoring the Doppler absorption profile of I2. This technique enables us to search for a resonance frequency of magneto-optical trapping of Fr., 6 pages, 6 figures

The search for the electric-dipole moment (EDM) of laser-cooled francium (Fr) atoms could lead to a measurement for the electron EDM. It is predicted that the electron EDM would be enhanced by approximately three orders of magnitude in heavy atoms such as Fr. Laser-cooling and trapping techniques are expected to suppress statistical and systematic errors in precision measurements. The magneto-optical trap was achieved using stable rubidium in a developing factory of laser-cooled radioactive atoms. In light of the results from the rubidium experiments, we found that an upgrade of each apparatus is preferred for Fr trapping.

For the measurement of the electron electric dipole moment using Fr atoms, a Fr ion-atom conversion is one of the most critical process. An ion-atom converter based on the "orthotropic" type of Fr source has been developed. This converter is able to convert a few keV Fr ion beam to a thermal atomic beam using a cycle of the surface ionization and neutralization. In this article, the development of the converter is reported.

A measurement of the proton spin structure function g1p(x,Q^2) in deep-inelastic scattering is presented. The data were taken with the 27.6 GeV longitudinally polarised positron beam at HERA incident on a longitudinally polarised pure hydrogen gas target internal to the storage ring. The kinematic range is 0.021, Comment: 7 pages, 3 figures, 1 table, RevTeX latex

Results are reported from the HERMES experiment at HERA on a measurement of the neutron spin structure function g1n(x, Q2) in deep inelastic scattering using 27.5 GeV longitudinally polarized positrons incident on a polarized 3He internal gas target. The data cover the kinematic range 0.023

We have measured the zero-degree cross sections for proton inelastic scattering to the 1{sup +}, {ital T}=0 (12.7 MeV) and 1{sup +}, {ital T}=1 (15.1 MeV) states in {sup 12}C at 65, 100, 200, 300, and 400 MeV. The ratios of cross sections [{ital d}{sigma}/{ital d}{Omega}(1{sup +},{ital T}=0)]/[{ital d}{sigma}/{ital d}{Omega}(1{sup +},{ital T}=1)] at 0 {degree} are compared with the calculations in the distorted wave approximation using various effective nucleon-nucleon interactions. The experimental ratios are found to be smaller than the theoretical predictions. It was found that the experimental results were better described by modifying the isovector tensor terms of the effective interactions.

The finite value of an electron electric dipole moment (eEDM) provides the direct evidence for the violation of time reversal symmetry. Fr atoms, whose enhancement factor is 895, trapped by laser cooling and trapping techniques are one of the strongest candidates for measuring the eEDM. We are constructing a beamline for measuring the eEDM using laser- cooled Fr atoms at the Cyclotron and Radioisotope Center. We have developed laser light sources including the frequency stabilization system and a magneto-optical trap system for Fr atoms. As the Fr production requires the cyclotron operation, we also use Rb atoms whose chemical properties are similar to those of the Fr atoms. Thus, the Rb beam is utilized for optimizing the operation parameters of the entire apparatus. We have also developed the laser light sources for Rb atoms and observed the beat signal for frequency stabilization of the source using the frequency offset locking method.

We have performed the 0 degree measurements of proton inelastic scattering for the 1+, T=0 (12.7 MeV) and 1+, T=1 (15.1 MeV) states in 12C at Ep=100, 200, 300, 400 MeV. The ratio of the excitation cross sections for these two states significantly deviates from the estimation of the distorted wave analysis, suggesting that the effective interactions VτT or Vσ might be modified to reproduce the experimental data.

We performed a 37Cl(3He, t)37Ar experiment at E = 140 MeV/nucleon and 0° with a resolution of 30 keV. The Gamow‐Teller (GT) strength distribution was obtained up to the excitation energy (Ex) of 14.2 MeV in 37Ar. Under the assumption of isospin symmetry, the GT strengths in the 37Cl→37Ar and 37Ca→37K transitions are analogous. The obtained strength distribution was compared with the mirror 37Ca β decay up to Ex = 8.6 MeV. The overall shapes of the distributions were similar, but the details were not necessary the same. In order to understand those differences, the experimental distribution was compared with the shell model (SM) calculation using the USD interaction. The SM calculation suggests that differences at lower energies can be caused by a large tensor contribution in the charge‐exchange reaction. On the other hand, the differences seen at higher energies are due to the breaking of the mirror symmetry. The neutrino cross section for the 8B solar neutrino source was calculated using the obtained data.

It has been shown that the (3He,t) charge exchange reaction at intermediate energies, used at zero momentum transfer in combination with high‐resolution magnetic spectrometers is a very powerful probe for Gamow‐Teller strengths. Several N = Z nuclei such as 46V [1] or 50Mn [2] have been investigated. Recently ab‐initio nuclear structure calculations have become possible for light nuclei. Thus experimental studies on light nuclei have become of great current interest [3]. We review previous results obtained in 11C with respect to nuclear structure aspects and the Hoyle state, and present some early results of a 9Be(3He,t)9B experiment carried out recently, pointing out the significance of high‐resolution charge‐exchange reactions and the investigation of Gamow‐Teller strengths for the understanding of nuclear structure in light nuclei.

We present measurements of the cross section and a complete set of polarization observables for the Gamow‐Teller 12C(p,n)12N(g.s.;1+) reaction at an incident proton energy of 296 MeV. The complete set of polarization observables is used to separate the cross section into spin‐longitudinal and spin‐transverse components. From the comparison with the distorted wave impulse approximation calculations employing random phase approximation response functions, we found that our data showed the existence of the pionic and rho‐mesonic correlations in nuclei.

The double differential cross sections for the 116Cd(p,n) and 116Sn(n,p) reactions at 300 MeV have been measured over a wide excitation‐energy region including Gamow‐Teller (GT) giant resonance (GTGR) for studying GT transition strengths in the intermediate nucleus of the 116Cd double‐β decay, namely 116In. A large amount of the strengths in the β+ direction has been newly found in the energy region up to 30 MeV, which may imply that the GT strengths in the GTGR region contribute to the nuclear matrix element of the two‐neutrino double‐β decay.

The search for the violation of the fundamental symmetry in a radioactive atom is the promising candidate for precision tests of the standard model and its possible extensions. The subtle signal arising from the symmetry violation is enhanced in heavy atoms, such as a francium (Fr). To realize high precision measurements, a large amount of radioactive isotopes is required. The Fr is produced via a nuclear fusion reaction using a melted gold target with a (18)O primary beam at Cyclotron and Radioisotope Center, Tohoku University. The maximum extraction efficiency of the Fr ion was achieved at approximately 35%. The beam line consists of an electrostatic deflector, three electrostatic quadrupole triplets to the measurement area at 10 m away from the reaction point, and several beam diagnosis systems. We optimized parameters of the beam line.

We plan to measure the permanent electric dipole moment (EDM) of the elec- tron, which has the sensitivity to the CP violation in theories beyond the standard model by using the laser-cooled francium (Fr) atom. This paper reports the present status of the EDM measurement system. A high voltage application system was constructed in order to produce the strong electric field (100 kV /cm) needed for the experiment. After condi- tioning, the leakage current was 10 pA when a high voltage of 43 kV was applied. Also, a drift of an environmental field was measured at the planned location of the Fr-EDM experiment. The drift is suppressed at present down to the level of 10 pT by installing a 4-layer magnetic shield. Improvements are still needed to reach the required field stability of 1 fT.

A laser cooled heavy atom is one of the candidates to search for the permanent electric dipole moment (EDM) of the electron due to the enhancement mechanism and its long coherence time. The laser cooled francium (Fr) factory has been constructed to perform the electron EDM search at the Cyclotron and Radioisotope Center, Tohoku University. The present status of Fr production and the EDM measurement system is presented.