Transverse momentum distribution of fragments in reaction Ar-40 + Be-9

Abstract

The momentum distribution for projectile fragments in the transverse direction was observed systematically in order to get information on the nuclear reaction. The projectile fragments were produced by the reaction Be-9(Ar-40,X)Z-A at the beam energy E(Ar-40) = 90A MeV. The produced fragments were analyzed with a RIPS (RI Projectile-fragment Separator) spectrometer. Particle identification was performed by measuring the time-of-flight and the energy loss. The time-of-flight of each fragment was determined by the scintillation counter timing and the radio frequency timing of RIKEN Ring Cyclotron. The energy loss was measured by scintillation counters. As the result, the transverse momentum distribution of fragments observed is well reproducible by a Gaussian distribution, and its dispersion can be derived by fitting. The correlation between the dispersion and the longitudinal momentum suggests the contribution of multi step process in the nuclear reaction at the intermediate beam energy, E = 90A MeV.

核反応についての情報を得るために、横方向における発射体分裂片の運動量分布を系統的に調べた。発射体分裂片はビームエネルギーE(Ar-40)=90AMeVにおいて反応Be-9(Ar-40,X)Z-Aで作った。作られた分裂片をRIPS(RIビーム発生装置)分光計で分析した。粒子の識別は飛行時間とエネルギー損失を測定して行った。各分裂片の飛行時間は理研リングサイクロトロンのシンチレーション計数器と高周波の両タイミングで求めた。結果として、観測された分裂片の横運動量分布はガウス分布でよく再現され、その分散は適合によって導かれる。分散と縦運動量との相関性から、多段プロセスが中間ビームエネルギーE=90AMeVにおける核反応に寄与していると推定される。