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Register a new userNuclear-matter distribution in the proton-rich nuclei $^7$Be and $^8$B from intermediate energy proton elastic scattering in inverse kinematics
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Absolute differential cross sections for elastic $p^7$Be and $p^8$B small-angle scattering were measured in inverse kinematics at an energy of 0.7 GeV/u at GSI Darmstadt. The hydrogen-filled ionization chamber IKAR was used as an active target to detect the recoil protons. The projectile tracking and isotope identification were performed with multi-wire proportional chambers and scintillation detectors. The measured cross sections were analysed using the Glauber multiple-scattering theory. The root-mean-square (rms) nuclear matter radii $R_{rm m} = 2.42 (4)$ fm for $^7$Be and $R_{rm m} = 2.58 (6)$ fm for $^8$B were obtained. The radial density distribution deduced for $^8$B exhibits a proton halo structure with the rms halo radius $R_{rm h} = 4.24 (25)$ fm. A comparison of the deduced experimental radii is displayed with existing experimental and theoretical data.
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The absolute differential cross sections for small-angle proton elastic scattering off the nuclei $^{12,14-17}$C have been measured in inverse kinematics at energies near 700 MeV/u at GSI Darmstadt. The hydrogen-filled ionization chamber IKAR served simultaneously as a gas target and a detector for the recoil protons. The projectile scattering angles were measured with multi-wire tracking detectors. The radial nuclear matter density distributions and the root-mean-square nuclear matter radii were deduced from the measured cross sections using the Glauber multiple-scattering theory. A possible neutron halo structure in $^{15}$C, $^{16}$C and $^{17}$C is discussed. The obtained data show evidence for a halo structure in the $^{15}$C nucleus.
Background: Thick-target-induced nucleon-adding transfer reactions onto energetic rare-isotope beams are an emerging spectroscopic tool. Their sensitivity to single-particle structure complements one-nucleon removal reaction capabilities in the quest to reveal the evolution of nuclear shell structure in very exotic nuclei. Purpose: To add intermediate-energy, carbon-target-induced one-proton pickup reactions to the arsenal of $gamma$-ray tagged direct reactions applicable in the regime of low beam intensities and to apply these for the first time to $fp$-shell nuclei. Methods: Inclusive and partial cross sections were measured for the $ uc{12}{C}( uc{48}{Cr}, uc{49}{Mn}+gamma)$X and $ uc{12}{C}( uc{50}{Fe}, uc{51}{Co}+gamma)$X proton pickup reactions at 56.7 and 61.2 MeV/nucleon, respectively, using coincident particle-$gamma$ spectroscopy at the NSCL. The results are compared to reaction theory calculations using $fp$-shell-model nuclear structure input. For comparison with our previous work, the same reactions were measured on uc{9}{Be} targets. Results: The measured partial cross sections confirm the specific population pattern predicted by theory, with pickup into high-$ell$ orbitals being strongly favored; driven by linear and angular momentum matching. Conclusion: Carbon target-induced pickup reactions are well-suited, in the regime of modest beam intensity, to study the evolution of nuclear structure, with specific sensitivities that are well described by theory.
We present a precise measurement of the cross section, proton and $rm ^3He$ analyzing powers, and spin correlation coefficient $C_{y,y}$ for $p$-$rm ^3He$ elastic scattering near 65 MeV, and a comparison with rigorous four-nucleon scattering calculations based on realistic nuclear potentials and a model with $Delta$-isobar excitation. Clear discrepancies are seen in some of the measured observables in the regime around the cross section minimum. Theoretical predictions using scaling relations between the calculated cross section and the $rm ^3 He$ binding energy are not successful in reproducing the data. Large sensitivity to the $NN$ potentials and rather small $Delta$-isobar effects in the calculated cross section are noticed as different features from those in the deuteron-proton elastic scattering. The results obtained above indicate that $p$-$rm ^3He$ scattering at intermediate energies is an excellent tool to explore nuclear interactions not accessible by three-nucleon scattering.
Vector analyzing power for the proton-6He elastic scattering at 71 MeV/nucleon has been measured for the first time, with a newly developed polarized proton solid target working at low magnetic field of 0.09 T. The results are found to be incompatible with a t-matrix folding model prediction. Comparisons of the data with g-matrix folding analyses clearly show that the vector analyzing power is sensitive to the nuclear structure model used in the reaction analysis. The alpha-core distribution in 6He is suggested to be a possible key to understand the nuclear structure sensitivity.
Two-proton relative momentum ($q_{pp}$) and opening angle ($theta_{pp}$) distributions from the three-body decay of two excited proton-rich nuclei, namely $^{23}$Al $rightarrow$ p + p + $^{21}$Na and $^{22}$Mg $rightarrow$ p + p + $^{20}$Ne, have been measured with the projectile fragment separator (RIPS) at the RIKEN RI Beam Factory. An evident peak at $q_{pp}sim20$ MeV/c as well as a peak in $theta_{pp}$ around 30$^circ$ are seen in the two-proton break-up channel from a highly-excited $^{22}$Mg. In contrast, such peaks are absent for the $^{23}$Al case. It is concluded that the two-proton emission mechanism of excited $^{22}$Mg is quite different from the $^{23}$Al case, with the former having a favorable diproton emission component at a highly excited state and the latter dominated by the sequential decay process.
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