Must the prayer be repeated if the worshiper discovers a tear between the thighs in his transparent pants after the prayer, or if he prayed while aware of the existence of this tear?

If the garment does not reveal the skin color, then there is nothing upon you, by agreement. However, if it describes the color and what is exposed is considered little by custom, then there is nothing upon you, according to the more preponderant opinion, regarding what you prayed before knowing. The same applies if it is much in quantity but little in time. The criterion for little and much is custom. If it is much in quantity and time, then repetition is obligatory if you are certain about the exposure of the awrah. However, if concealment is possible, then there is no repetition.