Does semen come out without a man's control or his sensing it during arousal?

Semen necessitates ghusl (definition) (ritual bath) if it exits forcefully with pleasure, whether that occurs through intercourse, direct contact, masturbation, looking, or thinking. As for its exit without pleasure due to illness or cold, there is a difference of opinion regarding whether it necessitates ghusl. A person usually feels the exit of semen, but if they do not feel it, such as during sleep, then ghusl is required upon waking if they find it.