Search

The Low Energy Neutron Detector Array (LENDA) is a neutron time-of-flight (TOF) spectrometer developed at the National Superconducting Cyclotron Lab- oratory (NSCL) for use in inverse kinematics experiments with rare isotope beams. Its design has been motivated by the need to study the spin-isospin response of unstable nuclei using (p, n) charge-exchange reactions at intermediate energies (> 100 MeV/u). It can be used, however, for any reaction study that involves emission of low energy neutrons (150 keV - 10 MeV). The array consists of 24 plastic scintillator bars and is capable of registering the recoiling neutron energy and angle with high detection efficiency. The neutron energy is determined by the time-of-flight technique, while the position of interaction is deduced using the timing and energy information from the two photomultipliers of each bar. A simple test setup utilizing radioactive sources has been used to characterize the array. Results of test measurements are compared with simulations. A neutron energy threshold of < 150 keV, an intrinsic time (position) resolution of \sim 400 ps (\sim 6 cm) and an efficiency > 20 % for neutrons below 4 MeV have been obtained., Version accepted for publication in Nucl. Instr. Methods A. Revised text, 2 new figures added (one in section 4 and one in section 7)

Interaction cross sections (sigma(1)) for Me isotopes from the stability line to the vicinity of the neutron drip line have been measured at around 240 MeV/nucleon using BigRIPS at RIBF, RIKEN, The sigma(1) for Ne27-32 in every case exceed the systematic mass-number dependence of sigma(1) for stable nuclei, which can be explained by considering the nuclear deformation. In particular the sigma(1) for Ne-29 and Ne-31 are significantly greater than those of their neighboring nuclides. These enhancements of sigma(1) for Ne-29 and Ne-31 cannot be explained by a single-particle model calculation under the assumption that the valence neutron of Ne-29 (Ne-31) occupies the 0d(3/2) (0f(7/2)) orbital, as expected from the standard spherical shell ordering. The present data suggest an s dominant halo structure of Ne-29 and s- or p-orbital halo in Ne-31. (C) 2011 Elsevier B.V. All rights reserved.

Interaction cross sections ( σ I ) for neutron-rich Ne isotopes, 28–32Ne on C target have been measured at 240A MeV using the RIBF at RIKEN. A large enhancement of σ I beyond the systematics of stable nuclei have been observed for neutron-rich Ne isotopes, particularly for 31Ne. The possible halo structure for 29,31Ne which would be caused by the lowering of the pf-shell and nuclear deformation of Ne isotopes are discussed by the preliminary analysis.

The cluster structures of the excited states in 11B are studied by analyzing the isoscalar monopole and quadrupole strengths in the 11B(d,d′) reaction at E d = 200 MeV . The excitation strengths are compared with the predictions by the shell-model and antisymmetrized molecular-dynamics (AMD) calculations. It is found that the large monopole strength for the 3 / 2 3 − state at E x = 8.56 MeV is well described by the AMD calculation and is an evidence for a developed three-body 2 α + t cluster structure.

8 pages, 5 figures.-- PACS nrs.: 25.40.Ep, 25.70.De.-- ISI Article Identifier: 000247257800008., Published in the Proceedings of the 2nd International Conference on Collective Motion in Nuclei under Extreme Conditions (COMEX 2). Sankt Goar, Germany, June 20-23, 2006., Experimental technique for measuring proton inelastic scattering with high-resolution at 295 MeV and at forward angles including zero degrees have been successfully developed. An excitation energy resolution of less than 20 keV, good scattering angle resolution, low background condition, and reasonable background subtraction have been achieved. The experimental technique have been applied for several sd and pf shell nuclei for systematic study M1 and E1 excitations in nuclei. The experimental method and preliminary spectra are reported.

The cluster structures of the excited states in 11 B are studied by analyzing the isoscalar monopole and quadrupole strengths in the 11 B( d , d ′) reaction at E d = 200 MeV . The excitation strengths are compared with the predictions by the shell-model and antisymmetrized molecular-dynamics (AMD) calculations. It is found that the large monopole strength for the 3 / 2 3 − state at E x = 8.56 MeV is well described by the AMD calculation and is an evidence for a developed 2 α + t cluster structure.

The cluster structures of the excited states in 11B are studied by analyzing the isoscalar monopole and quadrupole strengths in the B 11 ( d , d ′ ) reaction at E d = 200 MeV . The excitation strengths are compared with the predictions by the shell-model and antisymmetrized molecular-dynamics (AMD) calculations. The large monopole strength for the 3 / 2 3 − state at E x = 8.56 MeV is well described by the AMD calculation and is suggested to be an evidence for a well developed 2 α + t cluster structure.

The electric dipole strength distribution in 120Sn between 5 and 22 MeV has been determined at RCNP Osaka from a polarization transfer analysis of proton inelastic scattering at E_0 = 295 MeV and forward angles including 0{\deg}. Combined with photoabsorption data an electric dipole polarizability \alpha_D(120Sn) = 8.93(36) fm^3 is extracted. The dipole polarizability as isovector observable par excellence carries direct information on the nuclear symmetry energy and its density dependence. The correlation of the new value with the well established \alpha_D(208Pb) serves as a test of its prediction by nuclear energy density functionals (EDFs). Models based on modern Skyrme interactions describe the data fairly well while most calculations based on relativistic Hamiltonians cannot., Comment: 6 pages, 4 figures

Differential cross sections of isoscalar and isovector spin-M1 (0(+)→1(+)) transitions are measured using high-energy-resolution proton inelastic scattering at E(p)=295 MeV on (24)Mg, (28)Si, (32)S, and (36)Ar at 0°-14°. The squared spin-M1 nuclear transition matrix elements are deduced from the measured differential cross sections by applying empirically determined unit cross sections based on the assumption of isospin symmetry. The ratios of the squared nuclear matrix elements accumulated up to E(x)=16 MeV compared to a shell-model prediction are 1.01(9) for isoscalar and 0.61(6) for isovector spin-M1 transitions, respectively. Thus, no quenching is observed for isoscalar spin-M1 transitions, while the matrix elements for isovector spin-M1 transitions are quenched by an amount comparable with the analogous Gamow-Teller transitions on those target nuclei.

In order to study the Gamow–Teller (GT) transitions in the fp-shell nucleus 64Cu, the 64Ni(3He, t)64Cu charge-exchange reaction was investigated at MeV/nucleon [1]. The outgoing tritons were momentum analysed by the Grand Raiden spectrometer at 0°. The very high energy resolution of 35 keV (FWHM) allowed the separation of individual levels in the excitation energy region from 0 to 3.5 MeV. An angular distribution analysis was performed for the observed transitions to these states. In addition to the ground state (g.s.), known to be a Jπ = 1+ GT state, several excited states showed L = 0 nature, making them candidates of GT states. At higher excitation energies, the level density becomes very high and a bump-like structure, the so-called GT Giant Resonance, dominates the spectrum.

The analyzing power of the reaction p p→ppπ 0 has been measured at a beam energy of 390 MeV. The dependences of the analyzing power on the pion emission-angle and the relative momentum of two outgoing protons have been obtained. The angular dependence could be decomposed by Legendre polynomial and the relative contribution of the P 21 to the P 11 function is less than 4%. The momentum dependence of the analyzing power has been studied to obtain information about the pion-production mechanism. It has been deduced that pion production due to the long-range interaction plays an important role in the momentum dependence of the P -state amplitude.

The electric dipole strength in 120Sn has been extracted from proton inelastic scattering experiments at E_p = 295 MeV and at forward angles including 0 degree. Below neutron threshoild it differs from the results of a 120Sn(gamma,gamma') experiment and peaks at an excitation energy of 8.3 MeV. The total strength corresponds to 2.3(2)% of the energy-weighted sum rule and is more than three times larger than what is observed with the (gamma,gamma') reaction. This implies a strong fragmentation of the E1 strength and/or small ground state branching ratios of the excited 1- states., 7 pages, 6 figures

Under the assumption that isospin is a good quantum number, symmetry is expected for the transitions from the ground states of T = 1, T z = ±1 nuclei to the common excited states of the T z = 0 nucleus situated between the two nuclei. The symmetry can be studied by comparing the strengths of Gamow-Teller (GT) transitions obtained from a (p, n)-type charge-exchange reaction on a target nucleus with T z = 1 with those from the β-decay of the T z = - 1 nucleus. The A = 58 system is the heaviest for which such a comparison is possible. As a part of the symmetry study, we measured the GT transitions from 58Ni (T z = 1) to 58Cu (T z = 0) by using the zero-degree (3 He, t) reaction at 150 MeV/nucleon. With the achieved resolution of 50 keV, many hitherto unresolved GT states have been identified. The GT transition strengths were obtained for states up to 8 MeV excitation, i.e., near to the Q window limitation ( Q EC = 9.37 MeV) of the β-decay from 58Zn (T z = - 1) to 58Cu. The strength distribution is compared with that from shell-model calculations.

Precise reaction cross sections (${\ensuremath{\sigma}}_{R}$) for $^{24\ensuremath{-}38}\mathrm{Mg}$ on C targets at energies around 240 MeV/nucleon have been measured at the Radioactive Isotope Beam Factory at RIKEN. The ${\ensuremath{\sigma}}_{R}$ for $^{36\ensuremath{-}38}\mathrm{Mg}$ have been measured for the first time. An enhancement of ${\ensuremath{\sigma}}_{R}$ compared to the systematics for spherical stable nuclei has been observed, especially in the neutron-rich region, which reflects the deformation of those isotopes. In the vicinity of the drip line the ${\ensuremath{\sigma}}_{R}$ for $^{37}\mathrm{Mg}$ is especially large. It is shown by analysis using a recently developed theoretical method that this prominent enhancement of ${\ensuremath{\sigma}}_{R}$ for $^{37}\mathrm{Mg}$ should come from the $p$-orbital halo formation breaking the $N=28$ shell gap.

The total charge-changing, charge pick-up, and partial charge-changing cross sections of very neutron-rich nuclei (Ne-30, Na-32,Na-33) with a proton target have been measured at similar to 240A MeV for the first time. We introduced the phenomenological correction factor in Glauber-model calculations for the total charge-changing cross sections with the proton target, and applied it to deduce the proton radii of these nuclei. For 30Ne and Na-32, the neutron skin thicknesses of the nuclei were deduced by comparing the proton radii with the matter radii deduced from the interaction cross-section measurements. A significant thick neutron-skin has been observed for the nuclei. We also found that the charge pick-up cross sections are much larger than those in the systematics of stable nuclei.

Y. Fujita et al. ; 5 pags. ; 3 figs. PACS numbers: 24.30.Cz, 25.55.Kr, 27.40.+z, Gamow-Teller (GT) transitions in atomic nuclei are sensitive to both nuclear shell structure and effective residual interactions. The nuclear GT excitations were studied for the mass number A=42, 46, 50, and 54 >f-shell> nuclei in (He3, t) charge-exchange reactions. In the Ca42→Sc42 reaction, most of the GT strength is concentrated in the lowest excited state at 0.6 MeV, suggesting the existence of a low-energy GT phonon excitation. As A increases, a high-energy GT phonon excitation develops in the 6-11 MeV region. In the Fe54→Co54 reaction, the high-energy GT phonon excitation mainly carries the GT strength. The existence of these two GT phonon excitations are attributed to the 2 fermionic degrees of freedom in nuclei. © 2014 American Physical Society., This work was in part supported by MEXT, Japan (Grants No. 13002001, No. 15540274, and No. 18540270); MICINN, Spain (Grant No. FPA200806419-C02-01). Y. F. and B. R. acknowledge the support of the Japan-Spain collaboration program by JSPS and CSIC.

Studying the Gamow-Teller (GT) transitions of stable as well as unstable pf-shell nuclei is one of the key issues in nuclear and astro-nuclear physics. Under the assumption that isospin T is a good quantum number, symmetry is expected for mirror nuclei and the GT transitions starting from the mirror nuclei. We study the GT transitions starting from Tz = ±1 mirror nuclei, respectively, by means of hadronic (3 He , t) charge-exchange reactions and complementary β decays.

Interaction cross sections have been measured for spin-aligned nuclear beams of deformed nucleus. The spin-aligned nuclear beams were created by selecting the momentum of fragments produced in the projectile fragmentation of intermediate energy heavy-ion beams. The directional correlation of nuclear reaction probability for heavy-ion beams of deformed nucleus has been directly observed for the first time.

Reaction cross sections ( σ R ) for 11Be and 8B on proton targets at 50 A ∼ 120 A MeV have been measured to distinguish between the proton- and neutron- density distributions at the nuclear surface. The σ R is connected with the nucleon density distributions by the Glauber theory. Since the nucleon-nucleon total cross sections in that energy region have a large isospin dependence, the σ R on proton targets should have a large difference between the proton and neutron in the halo structure. The experimental σ R on proton targets are in good agreement with the calculated ones assuming that the tail dominantly consists of a neutron for 11Be and a proton for 8B.

25th International Nuclear Physics Conference, Florence, Italy, 2 Jun 2013 - 7 Jun 2013; The European physical journal / Web of Conferences Web of Conferences : proceedings proceedings 66, 02101 (2014). doi:10.1051/epjconf/20146602101, Published by EDP Sciences, Les Ulis

25th International Nuclear Physics Conference, Florence, Italy, 2 Jun 2013 - 7 Jun 2013; The European physical journal / Web of Conferences Web of Conferences : proceedings proceedings 66, 03084 (2014). doi:10.1051/epjconf/20146603084, Published by EDP Sciences, Les Ulis

Scattering of protons of several hundred MeV is a promising new spectroscopic tool for the study of electric dipole strength in nuclei. A case study of 208Pb shows that at very forward angles J^pi = 1- states are strongly populated via Coulomb excitation. A separation from nuclear excitation of other modes is achieved by a multipole decomposition analysis of the experimental cross sections based on theoretical angular distributions calculated within the quasiparticle-phonon model. The B(E1) transition strength distribution is extracted for excitation energies up to 9 MeV, i.e., in the region of the so-called pygmy dipole resonance (PDR). The Coulomb-nuclear interference shows sensitivity to the underlying structure of the E1 transitions, which allows for the first time an experimental extraction of the electromagnetic transition strength and the energy centroid of the PDR., Comment: submitted to Phys. Rev. C

We report on the first successful extraction of a ${\ensuremath{\beta}}^{+}$ Gamow-Teller strength distribution from a radioactive isotope in an intermediate-energy charge-exchange experiment in inverse kinematics. The ($^{7}\mathrm{Li},^{7}\mathrm{Be}+\ensuremath{\gamma}(429\text{ }\text{ }\mathrm{keV})$) reaction at $100A\text{ }\text{ }\mathrm{MeV}$ was used to measure Gamow-Teller transition strengths from $^{34}\mathrm{P}$ to states in $^{34}\mathrm{Si}$. The results show that little mixing occurs between $sd$ and $pf$ shell configurations for the low-lying ${0}^{+}$ and ${2}^{+}$ states even though $^{34}\mathrm{Si}$ neighbors the island of inversion and low-lying $2\ensuremath{\hbar}\ensuremath{\omega}$ intruder states exist. Shell-model calculations in the $sdpf$ model space are consistent with these findings.

Reaction cross sections for stable nuclei at intermediate energies have been measured precisely and systematically. The data have been found to be reproduced nicely by the optical‐limit approximation of Glauber theory modified to include the nucleon multiple scattering effect and the Fermi‐motion effect. Applying this prescription, the nucleon density distribution of 17Ne has been studied. The surface structure of 8B and 11Be has been also studied using this prescription and hydrogen targets. Using the RIBF that has just started application to studies of exotic nuclei, neutron‐rich Ne isotopes around the Island of Inversion have been investigated through measurements of their interaction cross sections.

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.

In violent neutrino‐induced reactions at the core‐collapse stage of type II supernovae, Gamow‐Teller (GT) transitions starting from stable as well as unstable pf‐shell nuclei play important roles. In the β‐decay study of these unstable pf‐shell nuclei, half‐lives can be measured rather accurately. On the other hand, in high‐resolution (3He,t) charge‐exchange reactions at 0°, individual GT transitions up to high excitations can be studied. Assuming the isospin symmetry for the strengths of Tz = ±2→±1 analogous GT transitions, we present a “merged analysis” for the determination of GT transition strengths starting from proton‐rich Tz = −2 nuclei. We applied this analysis to the A = 52, T = 2 system, and it was found that the GT transitions and the properties of the 52Ni β decay can be understood better by combining the mirror GT strength distribution obtained from the 52Cr(3He,t) reaction.

Gamow-Teller and dipole transitions to final states in $^{13}\mathrm{B}$ were studied via the $^{13}\mathrm{C}(t,^{3}\mathrm{He})$ reaction at ${E}_{t}=115A$ MeV. In addition to the strong Gamow-Teller transition to the $^{13}\mathrm{B}$ ground state, a weaker Gamow-Teller transition to a state at 3.6 MeV was found. This state was assigned a spin-parity of $3/{2}^{\ensuremath{-}}$ by comparison with shell-model calculations using the WBP and WBT interactions which were modified to allow for mixing between $n\ensuremath{\hbar}\ensuremath{\omega}$ and $(n+2)\ensuremath{\hbar}\ensuremath{\omega}$ configurations. This assignment agrees with a recent result from a lifetime measurement of excited states in $^{13}\mathrm{B}$. The shell-model calculations also explained the relatively large spectroscopic strength measured for a low-lying $1/{2}^{+}$ state at 4.83 MeV in $^{13}\mathrm{B}$. The cross sections for dipole transitions up to ${E}_{x}$$(^{13}\mathrm{B})=20$ MeV excited via the $^{13}\mathrm{C}(t,^{3}\mathrm{He})$ reaction were also compared with the shell-model calculations. The theoretical cross sections exceeded the data by a factor of about 1.8, which might indicate that the dipole excitations are ``quenched''. Uncertainties in the reaction calculations complicate that interpretation.

The $^{64}\mathrm{Zn}$($t$,$^{3}\mathrm{He}$) reaction has been studied by using a secondary triton beam of 115 MeV/nucleon to extract the Gamow-Teller transition-strength distribution to $^{64}\mathrm{Cu}$. The results were compared with shell-model calculations with the $\mathit{pf}$-shell effective interactions KB3G and GXPF1A and with existing data from the $^{64}\mathrm{Zn}$($d$,$^{2}\mathrm{He}$) reaction. Whereas the experimental results exhibited good consistency, neither of the theoretical predictions managed to reproduce the data. The implications for electron-capture rates during late stellar evolution were investigated. The rates based on the theoretical strength distributions are lower by factors of 3.5--5 compared to the rates based on experimental strength distributions.

To study the Gamow-Teller (GT) transitions to the pf-shell nucleus Cu-64, the Ni-64(He-3,t)Cu-64 experiment was performed at the Research Center for Nuclear Physics (RCNP) Ring Cyclotron, Osaka, using a He-3 beam of 140 MeV/nucleon. The outgoing tritons were momentum analyzed by the Grand Raiden spectrometer at 0(degrees). A high energy resolution of 32 keV (full width at half-maximum) allowed the separation of individual levels in the excitation-energy region from 0 to 3.5 MeV. In addition to the ground state (gs), known to be a J(pi)=1(+) GT state, many low-lying states showed L=0 nature, suggesting that they are candidates for GT states. Because the GT strength B(GT) for the gs transition is known from the beta-decay measurement, the strengths for the excited states could be determined using the proportionality between the B(GT) and the reaction cross section extrapolated to q=0 momentum transfer. At higher excitation energies, the level density becomes high and the so-called GT giant resonance dominates the spectrum. The lower and the upper limits of the strength contained in this energy region were estimated. Our results show that less than 55% of the strength predicted by the Ikeda sum rule is located in the excitation-energy region from 0 to 17 MeV..

Experience NSCL; International audience; We report in this study the nuclear properties of proton-rich isotopes located along the rp-process path. The experiments have recently been performed at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. The level properties above the proton separation energy of the nuclei 30S, 36K and 37Ca were measured with precision of < 10 keV. This will allow a reduction in the determination of the astrophysical (p, ) reaction rate under rp-process conditions.

Gamow-Teller transitions from $^{24}\mathrm{Mg}$ to $^{24}\mathrm{Na}$ were studied via the ($t,{}^{3}\mathrm{He}$) reaction at $115A$ MeV using a secondary triton beam produced via fast fragmentation of $150A$ MeV $^{16}\mathrm{O}$ ions. Compared to previous ($t,{}^{3}\mathrm{He}$) experiments at this energy that employed a primary $\ensuremath{\alpha}$ beam, the secondary beam intensity is improved by about a factor of five. Despite the large emittance of the secondary beam, an excitation-energy resolution of $~200$ keV is achieved. A good correspondence is found between the extracted Gamow-Teller strength distribution and those available from other charge-exchange probes. Theoretical calculations using the newly developed USDA and USDB $\mathit{sd}$-shell model interactions reproduce the data well.

The $^{24}\mathrm{Mg}(^{3}\mathrm{He},t){}^{24}$Al reaction was studied at $E({}^{3}\mathrm{He})=420$ MeV. An energy resolution of 35 keV was achieved. Gamow-Teller strengths to discrete levels in $^{24}\mathrm{Al}$ were extracted by using a recently developed empirical relationship for the proportionality between Gamow-Teller strengths and differential cross sections at zero momentum transfer. Except for small discrepancies for a few weak excitations, good agreement with previous $^{24}\mathrm{Mg}$($p,n$) data and nuclear-structure calculations using the USDA/B interactions in the $\mathit{sd}$ shell-model space was found. The excitation energy of several levels in $^{24}\mathrm{Al}$ of significance for determination of the $^{23}\mathrm{Mg}$${(p,\ensuremath{\gamma})}^{24}$Al thermonuclear reaction rate were measured. Results are consistent with two of the three previous ($^{3}\mathrm{He}$,$t$) measurements, performed at much lower beam energies. However, a new state at ${E}_{x}({}^{24}\mathrm{Al})=2.605(10)$ MeV was found and is the third state above the proton separation energy.

The differential cross section and analyzing power ${A}_{y}$ of the $\stackrel{\ensuremath{\rightarrow}}{p}p\ensuremath{\rightarrow}\mathit{pp}{\ensuremath{\pi}}^{0}$ reaction have been measured at RCNP in coplanar geometry at a beam energy of 390 MeV and the dependence on both the pion emission angle and the relative momentum of the final protons has been extracted. The angular variation of ${A}_{y}$ for the large values of the relative momentum studied here shows that this is primarily an effect of the interference of pion $s$ and $p$ waves and this interference can also explain the momentum dependence. Within the framework of a very simple model, these results would suggest that the pion-production operator has a significant long-range component.

Experimental technique for measuring proton inelastic scattering with high‐resolution at 295 MeV and at forward angles including zero degrees is described. The method is useful for extracting spin part of the M1 strength via nuclear excitation as well as E1 strength via Coulomb excitation. An excitation energy resolution of 20 keV, good scattering angle resolution, and low background condition have been achieved. The experimental technique was applied for several sd and pf shell nuclei.

The Gamow-Teller (GT) transition strengths in fp-shell nuclei are important parameters in presupernova models. A high-energy-resolution (He-3,t) experiment was performed on the T-z=1 nucleus Ti-46 at 0(degrees) and at an intermediate incident energy of 140 MeV/nucleon for the study of precise GT transition strengths to the final T-z=0 nucleus V-46. With an energy resolution of 33 keV, individual GT transitions were observed and GT strengths were derived for them up to the excitation energy of 4.5 MeV. The GT strengths were compared with shell-model calculations using various effective interactions. In this low-lying region, most GT states have isospin T=0. A few GT states with isospin T=1 were identified from the existence of the corresponding (analog) M1 states in Ti-46. By comparing the GT strength with the corresponding (analogous) M1 transition strength studied in Ti-46(e,e(')) or (gamma,gamma(')) measurements, a large constructive interference of orbital and spin terms was suggested for one of these M1 transitions.

The fine structure of the Gamow-Teller resonance in a medium-heavy nucleus is observed for the first time in a high-resolution $^{90}\mathrm{Zr}(^{3}\mathrm{He},t)^{90}\mathrm{Nb}$ experiment at the Research Center for Nuclear Physics, Osaka. Using a novel wavelet analysis technique, it is possible to extract characteristic energy scales and to quantify their relative importance for the generation of the fine structure. This method combined with the selectivity of the reaction permits an extraction of the level density of ${1}^{+}$ states in $^{90}\mathrm{Nb}$.

Some aspects of the importance of neutrino‐induced reactions on nuclei within supernova physics are discussed. It is argued that important constraints on the experimentally unknown cross sections can be obtained from experimental studies of the nuclear response in selected cases. Examples are neutral‐current induced reactions on fp‐shell nuclei extracted from high‐resolution inelastic electron scattering data providing the M1 strength distributions and the production of the exotic heavy, odd‐odd nuclei 138La and 180Ta through charged‐current reactions dominated by Gamow‐Teller transitions. The Gamow‐Teller strength can deduced from the (3He,t) charge‐exchange reaction at zero degree.

Isospin symmetry is expected for the T-z=+/- 1 -> 0 isobaric analogous transitions in isobars with mass number A, where T-z is the z component of isospin T. Assuming this symmetry, strengths of analogous Gamow-Teller (GT) transitions within A=50 isobars were determined from a high energy-resolution T-z=+1 -> 0, Cr-50(He-3,t)Mn-50 study at 0 degrees in combination with the decay Q value and lifetime from the T-z=-1 -> 0, Fe-50 ->Mn-50 beta decay. This method can be applied to other pf-shell nuclei and can be used to study GT strengths of astrophysical interest.

The $^{11}$B($^3$He$, t$), $^{11}$B($d, d'$), and $^{11}$B($p, p'$) reactions were measured at forward scattering angles including $0^\circ$ to study the isovector and isoscalar spin-flip M1 strengths in $^{11}$B. The measured $^{11}$B($^3$He$, t$) cross sections were compared with the results of the distorted-wave impulse-approximation (DWIA) calculation, and the Gamow-Teller (GT) strengths for low-lying states in $^{11}$C were determined. The GT strengths were converted to the isovector spin-flip M1 strengths using the isobaric analog relations under the assumption of the isospin symmetry. The isoscalar spin-flip M1 strengths were obtained from the ($d, d'$) analysis by assuming that the shape of the collective transition form factor with the same ${\Delta}J^\pi$ is similar in the $^{11}$B($d, d'$) and $^{12}$C($d, d'$) reactions. The obtained isovector and isoscalar strengths were used in the DWIA calculations for the $^{11}$B($p, p'$) reaction. The DWIA calculation reasonably well explains the present $^{11}$B($p, p'$) result. However, the calculated cross section for the 8.92-MeV 3/2$^-_2$ state was significantly smaller than the experimental values. The transition strengths obtained in the shell-model calculations were found to be 20-50% larger than the experimental strengths. The transition strengths for the neutrino induced reactions were estimated by using the isovector and isoscalar spin-flip M1 strengths. The present results are quantitatively in agreement with the theoretical estimation discussing the axial isoscalar coupling in the neutrino scattering process, and are useful in the measurement of the stellar neutrinos using the neutral- and charged-current reactions on $^{11}$B.

A high energy-resolution $^{11}\mathrm{B}(^{3}\mathrm{He},t)^{11}\mathrm{C}$ experiment was performed at $0\ifmmode^\circ\else\textdegree\fi{}$ and an intermediate incident energy of $140\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}∕\mathrm{nucleon}$ for the study of precise Gamow-Teller (GT) transition strengths. Two doublet states at $\ensuremath{\approx}4.5$ and $\ensuremath{\approx}8.4\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$ were clearly resolved with a resolution of $45\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$. The strengths are compared with a calculation using an ab initio no-core shell model, which became available for the $A=11$ system recently. It was found that a calculation including a three-nucleon interaction better reproduces the observed GT transition strengths.

The Gamow-Teller (GT) states in Cu-58 have been studied via the Ni-58(He-3, t+p) and Ni-58(He-3, t+gamma) coincidence experiments. The GT states in Cu-58 at E-x=6-12 MeV, where both T=1 and T=2, 1(+) states exist, are excited strongly in the Ni-58(He-3, t) reaction at E(He-3)=450 MeV and theta=0degrees. Proton emissions from the GT states in Cu-58 to the hole states in Ni-57 have been observed with solid-state detectors in coincidence with high energy tritons measured with a magnetic spectrometer. For the first time, the gamma-ray emissions from the excited states in Cu-58 and in Ni-57, following the Ni-58(He-3, t+p) reaction at intermediate energies, have also been observed in coincidence with tritons. Strengths of proton decay into several neutron-hole states in Ni-57 and gamma-decay strengths are used to discuss the wave functions of the GT states in Cu-58. The T=1 and T=2 GT states do only weakly decay into a T=3/2,f(7/2)(-1) neutron-hole state at 5.230 MeV in Ni-57, which is strongly excited via the Ni-58(p, d)Ni-57 reaction. The wave functions of the T=1 and T=2 GT states with the f(7/2)(-1) neutron-hole configuration are inferred to be strongly coupled to 2p-2h configurations, making fragmented GT strengths in Cu-58.

Under the assumption that isospin T is a good quantum number, isobaric analog states and various analogous transitions among these states are expected in isobars with mass number A. Strengths of analogous Gamow-Teller (GT) and $M1$ transitions have been compared for an $A=26$ isobar triplet with ${T}_{z}=+1, 0,$ and $\ensuremath{-}1,$ where ${T}_{z}$ is defined by ${T}_{z}=(N\ensuremath{-}Z)/2.$ The ${T}_{z}=+\stackrel{\ensuremath{\rightarrow}}{1}0$ GT transitions from the ${J}^{\ensuremath{\pi}}{=0}^{+}$ ground state of ${}^{26}\mathrm{Mg}$ to excited ${J}^{\ensuremath{\pi}}{=1}^{+}$ states in ${}^{26}\mathrm{Al}$ were studied up to the excitation energy ${(E}_{x})$ of 9 MeV by using a high energy-resolution ${(}^{3}\mathrm{He},t)$ reaction. The distribution of observed GT strengths was well reproduced in a shell-model calculation. The isospin symmetric ${T}_{z}=\ensuremath{-}\stackrel{\ensuremath{\rightarrow}}{1}0$ GT transitions can be studied in the ${}^{26}\mathrm{Si}$ $\ensuremath{\beta}$ decay. The GT strengths from the ${(}^{3}\mathrm{He},t)$ reaction were in good agreement with the $\ensuremath{\beta}$-decay values evaluated up to ${E}_{x}=2.7\ensuremath{-}\mathrm{MeV}$ states in ${}^{26}\mathrm{Al}.$ The GT strengths were further compared with the strengths of analogous $M1$ $\ensuremath{\gamma}$ transitions in ${}^{26}\mathrm{Al},$ i.e., the $M1$ transitions from the excited ${1}^{+}$ states to the isobaric analog state of the ${}^{26}\mathrm{Mg}$ ground state in ${}^{26}\mathrm{Al}.$ Through this comparison, contributions of spin and orbital terms in these $M1$ transitions were studied. The GT and $M1$ strengths as well as spin and orbital contributions in $M1$ strengths are interpreted by both the shell model and the particle-rotor model assuming a correlated proton and neutron pair around a ${}^{24}\mathrm{Mg}$ core. The isospin T of each excited ${1}^{+}$ state in ${}^{26}\mathrm{Al}$ was also studied by examining the existence or the nonexistence of the analog ${1}^{+}$ state in the ${T}_{z}{=1}^{26}\mathrm{Mg}$ nucleus.

Under the assumption that nuclear interaction is charge symmetry, isospin T is a good quantum number. Exotic nuclei have large |T z | values, where T z is defined by (N — Z)/2. Assuming isospin is a good quantum number, the analog states of the low-lying states in the T z = ±(T 0+ 1) nuclei can be found as the highly excited T 0+ 1 states in T z = ±T 0 nuclei. Therefore, if T 0 + 1 states are identified in highly excited region of T z = ±T 0 nuclei, the structure of the exotic nuclei with T z = ±(T 0 + 1) can be deduced.

The cross sections and analyzing powers were measured for 3He+12C, 58Ni, and 90Zr elastic scattering at T3He=450 MeV. The incident energy dependence of the volume integral per nucleon for 3He shows the similar behavior to that of protons if the spin‐orbit potential is taken into account. This result supports the assumption that interactions between 3He and nucleus are dominated by the interactions between constituent nucleons of 3He and target nucleus in the intermediate energy region. The results of the single folding calculation suggest the interaction between point nucleon and target nucleus is modified in the 3He+nucleus elastic scattering.

The angular dependence of analyzing power for pp→ppπ0 reaction was measured at 392 MeV using a polarized proton beam and liquid hydrogen target. It is demonstrated that meson exchange model fails to reproduce observed behavior of the analyzing power.

Assuming isospin symmetry of structures in mirror nuclei, the four terms of the title in M1 transitions have been decomposed by comparing the strengths of analogous M1 transitions in Tz=±1/2 nuclei and Gamow-Teller transitions, which are caused only by the isovector-spin term. For details, see Y. Fujita et al., Phys. Rev. C 59 (1999) 90 and Y. Fujita et al., Phys. Rev. C 62 (2000) 044314.

High-resolution measurements of proton inelastic and charge-exchange (3He,t) reactions at 0° on 58Ni were performed. These reactions mainly cause isovector spin flip transitions of M1 states in 58Ni and GT states in 58Cu. The “level-by-level” comparison of analogous M1 and GT transition strengths allows the study of the isospin symmetry structure of highly-excited analog states in 58Ni and 58Cu and identification of isospin T (T=1 and 2) based on the different sensitivities of inelastic and charge exchange reactions.

The cluster structures of the excited states in 11B are studied by analyzing the isoscalar monopole and quadrupole strengths in the 11B(d, d') reaction at Ed = 200 MeV. The excitation strengths are compared with the theoretical predictions by the antisymmetrized molecular-dynamics (AMD) calculations. It is found that the large monopole strength for the 3/2?3 state at Ex = 8.56 MeV is well described by the AMD wave function with a dilute 2? + tcluster structure.

Gamow–Teller (GT) transitions starting from unstable pf-shell nuclei are of interest not only in nuclear physics, but also in astrophysics, e.g. in violent neutrino induced reactions at the core-collapse stage of type II supernovae. In the β-decay study of these pf-shell nuclei, half-lives can be measured rather accurately. On the other hand, in high-resolution (3He, t) charge-exchange reactions at 0°, individual GT transitions up to high excitations can be studied. Assuming the isospin symmetry for the strengths of Tz = ±1 → 0 analogous GT transitions, we present a unique 'merged analysis' for the determination of absolute B(GT) values.