High-resolution study of Gamow-Teller excitations in thê {42}Ca(^{3}He,t)^{42}Sc reaction and the observation of a "low-energy super-Gamow-Teller state"Phys. Rev. C 91, 064316
This paper reports the first measurement of the tensor polarization t 2 o ine-d elastic scattering. The polarization of the recoil deuterons was measured for two values of momentum transfer, # = 1.74 and 2.03 fm" 1 , with a high-efficiency polarimeter. The results are in good agreement with reasonable models for the deuteron.PACS numbers: 25.30.Bf, 24.70,+ s, 25.10.+ S A complete experimental determination 1 ' 2 of the electromagnetic current of the deuteron requires the measurement of at least one polarization observable, in addition to the differential cross section. Here we report the first measurement of t 20 in elastic e-d scattering. Measurements of t 20 have previously not been feasible because of the absence of high-efficiency deuteron tensor polarimeters or tensor-polarized targets, and the lack of high-intensity electron beams and large-acceptance magnetic spectrometers. The results are found to be in good agreement with the predictions of t 20 for "reasonable" models of the deuteron, but in disagreement with those of separable-potential models.Electron elastic scattering from the deuteron can be described by three form factors: charge (F c ), quadrupole (FQ), and magnetic (F M ). Thus far, only F M has been isolated 3 in measurements of the cross section. The form factors F c and F Q have not been isolated previously from measurements of the structure function. 4 A determination of these form factors separately would discriminate further among different deuteron wave functions. The sensitivity of t 20 to the deuteron wave function arises from the fact that the leading term in t 2Q is proportional to the ratio of F Q to F c . in this ratio, the poorly known isoscalar electric nucleon form factor drops out. The expression for t 2Q is given 2 by t 20 2 , and/(6>) = i + (l+77)tan 2 (6i/2). Here, q is the four-momentum transfer, M d is the rest mass of the deuteron, and 6 is the angle of the scattered electron. The terms involving powers of X in the numerator are dominant in the momentum transfer region of 1-5 fm" 1 . Thus, t 20 is sensitive to the ratio of F Q to F c . The quantity F Q is sensitive to the tensor part of the N-N interaction, while F c is dominated by the S-wave part of the deuteron wave function at these values of low momentum transfer. Additionally, recent work 1 ' 2 has shown that t 2Q is also sensitive to the isoscalar meson exchange current (MEC) and relativistic corrections, about which there is much controversy. 5 The experiment was performed at the South Experimental Hall of the Massachusetts Institute of Technology-Bates Linear Accelerator Center. A schematic diagram of the experimental arrangement is given in Fig. 1. The electrons from the linac were focused on a windowless D 2 0 target which consisted of a 0.38-or 0.64-mm-thick laminar flow of heavy water. The incident electron energies were 371 ±2 MeVfor ^r=2.03fm" 1 , and 310± 1.8 MeVfor #=1.74 fm" 1 . During the experiment the average current and duty factor of the electron beam varied from 15 to 50 /iA and 0.3% to 0.4%, respec...
The ( He, t) charge-exchange reaction has been studied at E( He)=200 MeV and angles near 0 on targets of "Sn and Sn. Fragmentation of the giant Gamow-Teller resonance into separate components of the particle-hole type has been observed in good agreement with theoretical predictions. These components are connected with what is usually referred to in the literature as direct-, core-poLarization-, and back-spin-Bip Gamow-Teller strength. The observed cross sections near 0 = 0' suggest contributions from the isovector spin-Hip interaction as well as the isovector tensor interaction. A theoretically predicted configuration splitting of the main Gamow-Teller component into two components involving the lhiii2 neutron orbital could not uniquely be identified. The data are compatible, though, with such a splitting since the observed widths of the main Gamow-Teller components in Sb and Sb exceed the predicted splittings. PACS number(s): 25.55.Kr, 24.30.Cz, 27.60. +j
Observables in elastic proton-deuteron scattering are sensitive probes of the nucleon-nucleon interaction and three-nucleon force effects. The present experimental data base for this reaction is large, but contains a large discrepancy between data sets for the differential cross section taken at 135 MeV/nucleon by two experimental research groups. This paper reviews the background of this problem and presents new data taken at KVI. The nucleon-nucleon potential (NNP) has been studied extensively by investigating the properties of bound nuclear systems, and, in more detail, via a comparison of high-precision two-nucleon scattering data with modern potentials based on the exchange of bosons [1,2,3]. A few of the modern NNPs were facilitated by a partialwave analysis (PWA), that provides a nearly modelindependent analysis of the available scattering data [4]. The modern NNPs reproduce the world data base with a reduced chi-square close to one and have, therefore, been accepted as high-quality benchmark potentials. The precision of modern NNPs has given confidence to study in detail the three-nucleon potential (3NP) which was already predicted in 1939 by Primakoff and Wilson [5]. Compelling evidence of 3NP effects came from various recent theoretical and experimental studies. For example, for light nuclei, Green's function Monte-Carlo calculations employing the high-quality NNPs clearly underestimate the experimental binding energies [2], and, therefore, show that NNPs are not sufficient to describe the three-nucleon and heavier systems accurately. In the last decade, high-precision data at intermediate energies in elastic Nd and dN scattering [6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23] for a large energy range together with rigorous Faddeev calculations [24] * Electronic address: ramazani@kvi.nl † Electronic address: messchendorp@kvi.nl for the three-nucleon system have proven to be a sensitive tool to study the 3NP. In particular, a large sensitivity to 3NP effects exists in the minimum of the differential cross section [25,26]. Precision data for a large energy interval for the differential cross section and analyzing power came from recent experimental studies at KVI [7,8,9], RIKEN [10] and RCNP [12]. All these experiments had one common energy of 135 MeV/nucleon. Strikingly, the cross sections obtained at KVI were found to be significantly larger than those measured at RIKEN and at RCNP. The KVI data show significant deviation from predictions of state-of-the-art Faddeev calculations incorporating modern NNPs and 3NPs at this energy, whereas the results obtained at RIKEN and RCNP imply that the cross section can be described reasonably well exploiting the same potentials.This paper presents the results of a new measurement of the differential cross sections of the reaction 2 H( p, d)p at a proton-beam energy of 135 MeV, taken to provide additional data at 135 MeV/nucleon. These results are compared with the previously published data taken at intermediate energies. The data are obtained at KVI using a ne...
The 28 Si͑a, 8 He͒ 24 Si reaction has been used to measure the energies of the first two excited states in 24 Si. The excitation energies were found to be 1.879 6 0.011 and 3.441 6 0.010 MeV. These data allow for the first time the calculation of the stellar reaction rate of 23 Al͑ p, g͒ 24 Si on the basis of experimental information. This reaction is of considerable interest, since it might lead to a decrease of the 22 Na production in nova explosions, and solve the discrepancy between the 22 Na yield predictions of nova models and recent COMPTEL observations. We show, however, that the temperatures and densities required for a significantly reduced 22 Na yield are not reached in current nova models. [S0031-9007(97)04602-4]
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.