T. Nakagawa

Excitation of giant resonances in the 40Ca(e,e'n)39Ca reaction.

Decay neutrons from the [sup 40]Ca([ital e],[ital e][prime][ital n])[sup 39]Ca reaction were studied in the giant resonance region. The cross sections and angular distributions, separated for [ital n][sub 0] and [ital n][sub 1] decays, were obtained for excitation energies between 19 and 27 MeV, at the effective momentum transfer of 0.35 fm[sup [minus]1]. Legendre polynomial coefficients obtained from fitting the data are compared with those from the ([ital e],[ital e][prime][ital p]) reaction. In the energy range 19--21 MeV, the interference coefficients [ital b][sub 1] and [ital b][sub 3] for the ground state transition are in agreement, but the noninterference coefficient [ital b][sub 2] is different. The different behavior of the angular distribution for protons and neutrons may suggest the interference of the decay from a [ital T]=0 quadrupole resonance and the [ital T]=1 giant dipole resonance. A similar tendency was also seen in comparing with the ([ital e],[ital e][prime][ital p][sub 1]) reaction. The Legendre polynomial coefficients for the [ital n][sub 0] decay in the ([ital e],[ital e][prime][ital n]) reaction, transformed to the photon point, agree well with those of the ([gamma],[ital n][sub 0]) reaction. The reduced total cross section is consistent between the ([ital e],[ital e][prime][ital n]) and ([gamma],[ital n])morexa0» reactions, but the cross section for ([ital e],[ital e][prime][ital n][sub 0]) is larger than that of ([gamma],[ital n][sub 0]) near the peak of the resonance. The values of the longitudinal-transverse interference term are close to zero in the present region, which is rather small compared with the value near the resonance of the ([ital e],[ital e][prime][ital p]) reaction.«xa0less

Energy-dependent measurements of the pp elastic analyzing power and narrow dibaryon resonances

Abstract The energy dependence of the pp elastic analyzing power has been measured using an internal target during polarized beam acceleration. The data were obtained in incident-energy steps varying from 4 to 17 MeV over an energy range from 0.5 to 2.0 GeV. The statistical uncertainty of the analyzing power is typically less than 0.01. A narrow structure is observed around 2.17 GeV in the two-proton invariant mass distribution. A possible explanation for the structure with narrow resonances is discussed.

Excitation of giant resonances in the [sup 40]Ca([ital e],[ital e][prime][ital n])[sup 39]Ca reaction

Decay neutrons from the [sup 40]Ca([ital e],[ital e][prime][ital n])[sup 39]Ca reaction were studied in the giant resonance region. The cross sections and angular distributions, separated for [ital n][sub 0] and [ital n][sub 1] decays, were obtained for excitation energies between 19 and 27 MeV, at the effective momentum transfer of 0.35 fm[sup [minus]1]. Legendre polynomial coefficients obtained from fitting the data are compared with those from the ([ital e],[ital e][prime][ital p]) reaction. In the energy range 19--21 MeV, the interference coefficients [ital b][sub 1] and [ital b][sub 3] for the ground state transition are in agreement, but the noninterference coefficient [ital b][sub 2] is different. The different behavior of the angular distribution for protons and neutrons may suggest the interference of the decay from a [ital T]=0 quadrupole resonance and the [ital T]=1 giant dipole resonance. A similar tendency was also seen in comparing with the ([ital e],[ital e][prime][ital p][sub 1]) reaction. The Legendre polynomial coefficients for the [ital n][sub 0] decay in the ([ital e],[ital e][prime][ital n]) reaction, transformed to the photon point, agree well with those of the ([gamma],[ital n][sub 0]) reaction. The reduced total cross section is consistent between the ([ital e],[ital e][prime][ital n]) and ([gamma],[ital n])morexa0» reactions, but the cross section for ([ital e],[ital e][prime][ital n][sub 0]) is larger than that of ([gamma],[ital n][sub 0]) near the peak of the resonance. The values of the longitudinal-transverse interference term are close to zero in the present region, which is rather small compared with the value near the resonance of the ([ital e],[ital e][prime][ital p]) reaction.«xa0less

The 9Be(d, n)10B reaction at 25 MeV

Abstract Differential cross sections for the 9Be(d, n)10B reaction have been measured at Ed=25 MeV using the time-of-flight technique. Experimental angular distributions for the states below Ex=6.57 MeV were analysed with the distorted-wave theory including the S-wave deuteron-breakup effects in the adiabatic approximation. The extracted spectroscopic factors were compared with previous data. Coupled-reaction-channel (CRC) calculations were also performed, and significant improvements were seen for weakly excited states.

The 17,18O(p, n)17,18F reaction at Ep = 35 MeV

Abstract The 17,18 O(p, n) 17,18 F reactions were studied at E p = 35 MeV. Neutron spectra were measured at laboratory angles between 0° and 140°. Results were compared with distorted-wave calculations using the shell-model wave functions. For the 17 O(p, n) reaction, cross-section magnitudes as well as the angular-distribution shapes were well described by the calculation. On the other hand, normalization factors of 0.60 were required for the spin-flip excitations observed in the 18 O(p, n) reaction leading to the ground (1 + ), 1.700 MeV (1 + ) and 2.100 MeV (2 − ) states. Possible origins of such differences were discussed.

Gamow-Teller strengths near the ground states in A=110 – 120 nuclei studied by (p,n) reaction

Abstract An experimental study of the (p,n) reactions on 110, 112, 114, 116Cd and 116, 118, 120Sn has been carried out. The GT type ΔJπ=1+ transitions leading to the ground states or to those close to g. s.. have been systematically observed in addition to the ΔJπ = 0+ isobaric analog transitions. By testing proportionality relationship between the (p,n) cross section andthe corresponding β-decay rate, previously unknown GT matrix elements have been obtained.

sup 14 C( p , n ) sup 14 N reaction at E sub p =35 MeV

Differential cross sections for the {sup 14}C({ital p},{ital n}){sup 14}N reaction were measured at {ital E}{sub {ital p}}=35 MeV. A number of spin-isospin excitations have been observed including Gamow-Teller-type 0{sup +}{r arrow}1{sup +} and 0{h bar}{omega} and 1{h bar}{omega} jump stretched transitions. Distorted-wave Born-approximation calculations using shell-model wave functions have successfully reproduced the experimental results. Renormalization factors of about 0.5 were required for the spin-flip transitions leading to the 3.947-MeV 1{sup +} state and to the 7.026-MeV 2{sup +} state, where {Delta}{ital J}({Delta}{ital L},{Delta}{ital S})=1(0,1) and 2(2,1), respectively. Proton and neutron optical-potential parameters were derived in the course of the present work.

Energy dependence of the analyzing power for the pp → π+d reaction in the energy region 500–800 MeV

Abstract The energy dependence of the analyzing power A y for the pp → π + d reaction was measured during polarized beam acceleration from 500 to 800 MeV, using an internal target inserted into the beam every acceleration cycle. The measurements were made with the pion laboratory angle fixed at 68° and with incident proton energy bins varying from 10 to 30 MeV in width. The statistical accuracy per bin is ΔA y ⋍ 0.06 .

Neutron decay from the giant resonance via the {sup 10}B(e,e{sup '}n) reaction

The cross sections and angular correlations for neutron decay into various states in the residual nucleus following the {sup 10}B(e,e{sup }n) reaction have been measured over the excitation energy range of 18-33 MeV at an effective momentum transfer of 0.56 fm{sup -1}. In the giant resonance, neutron emission leads to the population of two higher excited states in addition to the ground-state transition: 6.97 MeV 7/2{sup -}(n{sub 5}) and 11.70 MeV 7/2{sup -}+12.06 MeV 3/2{sup -}(n{sub 6,7}). This is the first observation of the neutron population of these states. The angular correlations for n{sub 0} show a strong forward-backward asymmetry, which suggests interference from a transition with the opposite parity to E1. The angular correlations for n{sub 5} and n{sub 6,7} have a peak shift of about 50 deg. at lower excitation energy and recover above about 24 and 25 MeV for n{sub 5} and n{sub 6,7}, respectively. Their patterns are considerably different from that for n{sub 0}. The angular correlations for each transition were fitted with a Legendre polynomial. The longitudinal-transverse interference coefficient C{sub 2}/A{sub 0} is negligible for all populations. For n{sub 0} decay, all Legendre coefficients b{sub i} are positive, but b{sub 2} and b{sub 3} formorexa0» the n{sub 5} and n{sub 6,7} decays are negative at lower excitation energy, and the latter causes a shift of the forward peak. The negative values may come from the signs of the phase differences of cos{delta}{sub 21} and cos{delta}{sub 20}. The {sup 10}B(e,e{sup }n) cross section measured up to E{sub x}{approx}32 MeV agrees well with that of {sup 10}B({gamma},n), except for a peak at 23 MeV of the giant resonance. In comparison with shell-model calculations, the partial cross section for n{sub 0} is sizable up to higher excitation energy, and predicted large partial cross sections populating the 6.97 MeV 7/2{sup -} and 11.70 MeV 7/2{sup -}+12.06 MeV 3/2{sup -} states in the giant resonance were not observed.«xa0less