cross section

Japanese: cross section（英語表記）crosssection

…This type of reaction is called a heavy ion reaction (heavy ion collision). The likelihood of a nuclear reaction occurring, or the probability of it occurring, is expressed by a quantity called the cross section. If there is one target nucleus A in a cylinder with a cutout of 1 cm2, and one particle a enters and collides with it, the probability is σ, then σ is the cross section. …

From [Scattering cross section]

…In the collision of quantum mechanical particles, there are reactions in which the number and type of particles change before and after the collision, and scattering in which the number and type of particles do not change. The quantity that represents the probability of these quantum mechanical particles colliding is called the cross section, or collision cross section. If the collision is scattering, it is called the scattering cross section, and if it is a reaction, it is called the reaction cross section. In either case, when a single incident particle is incident on a target material consisting of many scatterers, the number of scatterers per unit area of the target is N , and the probability that the incident particle will collide with the scatterer is Nα , where α is defined as the cross section. …

*Some terminology explanations that mention "cross section" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

Japanese:

…この種の反応は重イオン反応(重イオン衝突)と呼ばれる。　核反応の起こりやすさ，すなわち起こる確率は断面積cross sectionという量で表される。切口1cm2の筒の中に1個の標的核Aがあるとき，1個の粒子aが入射し，衝突する確率がσであれば，σを断面積という。…

【散乱断面積】より

…量子力学的粒子の衝突には，衝突の前後で粒子の数や種類の変わる反応と変わらない散乱とがある。これらの量子力学的粒子が衝突を起こす確率を表す量を断面積cross section，または衝突断面積collision cross sectionといい，その衝突が散乱である場合を散乱断面積，反応である場合を反応断面積と呼ぶ。いずれの場合も，1個の入射粒子が多数の散乱体からなる標的物質に入射したとき，標的の単位面積当りの散乱体の数をN，入射粒子が散乱体と衝突を起こす確率をNαとして，αを断面積と定義する。…

※「cross section」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典第２版について | 情報

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