Proton-knockout (p, 2p) reactions from C-12 with normal and inverse kinematics

Abstract

The feasibility of studying the (p, 2p) reaction with inverse kinematics in experiments using secondary nuclear beams was evaluated by comparing the following reactions: (1) C-12(p, 2p) reaction with a proton beam on a C-12 target at 210 MeV; and (2) p(C-12, 2p) reaction with a C-12 beam on a proton target at 230 A MeV. A two-arm detector system consisting of drift chambers, a thin plastic scintillator and NaI that stops protons was used. The energy resolution for a 100 MeV proton was 0.6 MeV in the C-12(p, p) reaction. The C-12(p, 2p) reaction directing proton beams on CH2 was studied at 135 and 210 MeV. A sharp peak at 16 MeV (pi-p(sub 3/2)) and a broad peak around 35 MeV (pi-s(sub 1/2)) were observed. In the p(C-12, 2p) reaction with inverse kinematics that was performed using a 230 A MeV C-12 beam, the fragments with Z = 5 and Z = 3, 4 were produced at the peaks of pi-p(sub 3/2) and pi-s(sub 1/2), respectively. The separation-energy resolution was 1.9 MeV. Thus, the momentum distributions of proton knockout were similar to those of the C-12(p, 2p) reaction.

2次核ビームを用いた実験における(p, 2p)反応の逆運動学の実現可能性を、210MeV陽子ビームをC-12標的に照射するC-12(p, 2p)反応、および230AMeVのC-12ビームを陽子標的に照射するp(C-12, 2p)反応により調べた。ドリフトチェンバ、薄いプラスチック・シンチレータ、および陽子を止めるNaIからなる2アーム検出システムを用いた。100MeVの陽子のエネルギー分解能は、C-12(p, p)反応では0.6MeVであった。陽子ビームをCH2に照射したC-12(p,2p)反応を135MeVと210MeVで調べた。鋭い16MeVでのピーク(πp(sub 3/2))と35MeV付近に広がったピーク(πs(sub 1/2))を観測した。逆運動である230AMeVのC-12ビームを用いたp(C-12, 2p)反応では、πp(sub 3/2)とπs(sub 1/2)のピークでZ=5とZ=3、4のフラグメントが生じた。分離エネルギー分解は1.9MeVであった。ノックアウト陽子の運動量分布は、C-12(p, 2p)反応と同様であった。