A study of complementary reactions: Single-proton knockout and single-proton pickup

Knockout reactions using fast, exotic beams in inverse kinematics are an established tool for probing the ground state wave function of the incident projectile and studying the spectroscopy of the projectile-like knockout residue. In a knockout reaction, the removal of a nucleon from the projectile populates single-hole states in the residue. Measured partial cross sections and longitudinal momentum distributions to final states of the residue, as tagged by the detection of gamma rays emitted in-flight and correlated event-by-event to the residue, are used to quantify the single-particle composition of the projectile wave function.;Recently, pickup reactions using fast, exotic beams in inverse kinematics have emerged as a complementary tool to single-nucleon knockout reactions by populating single-particle states in the residue. Recent analyeses have shown qualitative agreement between theoretical and measured strengths and population patterns to final states in the residue. This agreement suggests that pickup reactions can provide similar information about the ground state wavefunction of the projectile and the spectroscopy of the residue.;Two experiments were run at the NSCL that show the power and highlight the differences of these two complementary reactions. The one-proton knockout experiment 9Be(54Ti,53Sc+ gamma)X at 72 MeV/u was performed to probe the single-proton configurations of the N = 32 nuclei 54Ti and 53Sc and test the validity of the nuclear shell model and valance space in this interesting neutron-rich mass region. An unexpectedly large spectro-scopic strength to excited states was observed. The magnitude of strength observed was incompatible with shell model calculations using the f p model space only, and was therefore attributed to the knockout of deeply-bound sd-shell protons outside the calculation valance space. This interpretation was substantiated through a comparison to previous experimental work, the analogous 50Ti(d,3He)49Sc transfer reaction and the two-proton knockout reaction 9Be(54Ti, 52Ca + gamma)X, and through the comparison of the inclusive momentum distribution to a theoretical distribution that assumes sd-shell contributions. The results highlight the need for proton cross-shell interactions for the sdpf valance space.;Three different one-proton pickup reactions on proton-rich nuclei centered around 50Fe were studied on two different targets, 9Be and 12C: 9Be(48Cr, 49Mn+ )X, 9Be(49Mn,50Fe+ gamma)X, 9Be(50Fe,51Co+ gamma)X, 12 C(48Cr,49Mn+ gamma)X, 12C( 49Mn,50Fe+ gamma)X, and 12C( 50Fe,51Co + gamma)X. The investigation of these reactions, through the comparison of the experimentally measured and theoretically predicted partial cross sections and population pattern to final states in the pickup residue, was done with the goal of further developing pickup reactions as a spectroscopic tool. The theoretical partial cross sections were calculated using shell-model spectroscopic factors and single-particle cross sections calculated in a post-form Coupled Channels Born Approximation (CCBA ) framework assuming twobody final states. The reaction mechanism was further probed by measured longitudinal momentum distributions whose comparison to calculated distributions that assume the two-body character of the final reaction product tests the direct nature of the reaction processes, and by the use of the two different targets, through which the importance of including only a subset of target final states can be judged. We report the results for the first fast beam, inverse-kinematics, proton pickup reactions in the f p-shell, and the first proton pickup reactions from a 12C target.